Engineering procedure for the preparation of process flow diagrams P-T profiles engineering flow diagrams utility flow diagrams interconnecting flow diagrams process safeguarding flow diagrams revamping flow diagrams and line tables


Table of content

  1. Introduction
    1.1 Purpose
    1.2 Concept
    1.3 Use
    1.4 Types of Diagrams
    1.5 Notes

  2. Scope

  3. General procedure for flow diagram preparation

    3.1 Layout and Format
    3.2 Symbols and Identification
    3.3 Diagram Issues

  4. The process flow diagram
    4.1 General
    4.2 Initial Process flow diagram
    4.3 Kickoff Meeting
    4.4 Process flow diagram drafting
    4.5 Reissues of process flow diagrams
    4.6 Computer vision diagram systems

  5. The Pressure (p) – Temperature (T) profile
    5.1 General

    5.2 Purpose
    5.3 Reissues of P-T Profile
    5.4 Computer Vision Diagram Systems

  6. The Engineering flow diagrams

    6.1 General
    6.2 Initial Engineering flow diagram
    6.3 Pipelines and pipelines referencing
    6.4 Initial flow diagram check
    6.5 Diagram review meeting
    6.6 Engineering flow diagram drafting

    6.7 Reissues of Engineering flow diagrams
    6.8 Computer vision diagram systems

  7. The utility flow diagrams
    7.1 Purpose
    7.2 Preparation
    7.3 Layout
    7.4 Control systems, valves, etc.

    7.5 Equipment
    7.6 Example diagram
    7.7 Example diagram

  8. The interconnecting flow diagrams
    8.1 Purpose

    8.2 Split of work
    8.3 Layout
    8.4 Example diagram

  9. The process safeguarding flow diagrams
    9.1 Introduction
    9.2 General consideration
    9.3 Purpose
    9.4 Timing and preparation of process safeguarding flow diagram
    9.5 Presentation

  10. The revamping flow diagram
    10.1 General
    10.2 Updating and Marking engineering flow diagrams

    10.3 Example diagram

  11. Check list

  12. preparation of line tables

    12.1 Responsibility
    12.2 Format
    12.3 Description of Columns
    12.4 Procedure
    12.5 Computer vision systems
    12.6 Sample forms

  13. List of related Company standards

  14. List of standards other than Company

    14.1 General
    14.2 U.S.A.
    14.3 West Germany
    14.4 Great Britain
    14.5 France
    14.6 The Netherlands
    14.7 S.I.P.M.

    14.8 Aramco

  15. Typical arrangements of equipment installation

    15.1 General
    15.2 Vessels and columns
    15.3 Shell & Tube heat exchangers
    15.4 Aircoolers
    15.5 Pumps
    15.6 Turbines
    15.7 Ejectors
    15.8 API
    15.9 Control stations

    15.10 Utility tie-ins into process lines
    15.11 Battery limits installations
    15.12 Sample stations
    15.13 Safety relief valves
    15.14 Burner installations

    15.15 Steam trap assemblies
    15.16 Instrument purges
    15.17 External seal flush and purge
    15.18 Cooling rotating equipment

    15.19 Flushing oil
    15.20 Blowdown systems
    15.21 Level instruments and stand pipes
    15.22 Instrumentation compressors
    15.23 Valve type selection
    15.24 General instrument requirements

    15.25 Utility header valve requirements


1. Introduction

1.1 Purpose
The purpose of this document is to outline the procedures for the preparation of process flow diagrams, pressure-temperature profile diagrams, engineering, utility and interconnecting flow diagrams and special diagrams as revamp flow diagrams and pressure safeguarding flow diagrams.


1.2 Concept

Flow diagrams are highly specialized “language” for information transfer. They represent the engineer's concept of how plant equipment should be interconnected. The diagram is almost physical in a sense, since every piece of equipment, every pipeline, valve and instrument is shown. Diagrams are used to convey information between groups working on the project and translate the plant design into “real” piping and equipment.


1.3 Use

By preparing the diagrams properly, the engineer can convey a great deal of technical information, quickly and accurately, with a limited amount of paper work.

1.4 Types of diagrams
There are 7 types of flow diagrams:
1.4.1 The process flow diagram (PFD)
The PFD is developed by the process engineering department. Final drafting by the flow diagram squad.

On this document are given the main process equipment., fluid flows, main control loops and critical valves. It is a tool for the process engineer(s) to convey information to project and specialist engineers to design the installation in detail (see fig: 6)

1.4.2 The Pressure Temperature Profile Diagram (PTP)
The PTP diagram is a document prepared by the Process Engineering Department with the purpose of providing project, control systems and piping engineers with the correct pressure and temperature correlations between the various piping systems, vessels, exchangers, etc.

The document ensures that proper values are being used for preparation of data sheets, line tables and other documents as, e.g. painting systems, insulation, etc.


For PTP preparation procedures refer to Standard Specification BN-EG-UE-1 (Design guide for Pressure and Temperature profile).


1.4.3 The Engineering Flow Diagram (EFD)
On this document are shown all equipment connecting piping, utility piping, complete with control loops and all other instrumentation, all valves and safety measures. It is the main tool for the project engineer to convey information to the piping design office and control systems engineering group for the detailed piping and control systems design (see fig:13)

1.4.4 The Utilities Flow Diagram (UFD)
This document shows how utilities are generated and distributed from the source or supply point to the various parts of an installation. The diagram shows common control loops, additional equipment that is deemed necessary to supply the utility as required and the safety measures necessary (see fig: 18). The diagram shall be drawn in accordance with the geographical layout of the plant.


The diagrams are generally divided per generation activity, e.g. steam generation, instrument air, cooling water, fuel oil, etc. The utility equipment shall be shown. Packaged units to be shown within heavy dotted line.


1.4.5 The Interconnecting Flow Diagram (IFD)
These diagram are prepared to show the interconnecting lines between various plant units and, e.g. tank farms, etc.

1.4.6 The Process Safeguarding Flow Diagram (PSFD)
This document shows the correlation of safety devices installed but indicated on separate EFD's. It “highlights” the final level of protection provided by the safety systems installed.

This document will be produced on client's request only, e.g. SIPM.


1.4.7 Revamp Flow Diagram (RFD)
“Revamping Flow Diagram” shall be prepared to indicate which equipment, lines, control loops, etc. must be demolished, modified, removed or relocated, etc. in a revamping project. The existing engineering flow diagrams of a plant or unit to be revamped shall be used.

In general two sets of diagrams are to be prepared:
a. An updated existing EFD's version for demolishing purposes RFD's.
b. New “as built” EFD's
For more details refer to chapter 10


1.5 Notes:
1.5.1 It must be noted that particular instructions given by client or licensor with respect to his requirements or special requirements covered by any authority decrees shall be observed.

1.5.2 If any of such rules, decrees or instructions exist, these must be mentioned in the “Project Specification”.

1.5.3 When these instructions have not been incorporated, the documents produced will be unacceptable to the client or licensor and/or authorities.

1.5.4 Where in the following text of this Engineering Procedures has been referred to other Company procedures or standards, this is only true where the Company standards are not conflicting with those mentioned under par 1.5.1.


1.5.5 To obtain maximum uniformity with regard to line thickness, lettering, symbols, etc. the drafting on vellums shall be executed by the Flow Diagram Squad.

1.5.6 There is still another flow diagram, prepared by the control systems engineering group, exclusively for use by process and control systems engineers. This flow diagram is principally a PFD on which the control system engineer indicates specific instrument physical data: the document is called: “Instrument Data Flow Sheet”. It is not further mentioned in this “Engineering Procedures”.

1.5.7 The examples presented in this Engineering Procedure are taken from actual jobs and include general Client's requirement. Therefore, the symbols used will not always be identical to the symbols shown on the legend sheet fig:22

1.5.8 On an EFD, a package unit, e.g. compressor, can be indicated with a heavy drawn block with reference to one or more vendor flow diagram (process, lube oil, seal oil, water cooling, etc.) which can be adopted.

2. Scope

2.1 This Engineering Procedure shall be used as a standard for the preparation of precess and engineering flow diagrams as outlined in para 1.4 of the introduction.

2.2 It shall also be used to edit systematically the text for the project specification on the subject of flow diagram preparation.

2.3 The purpose of this Engineering Procedure is to provide the engineers with all necessary information to generate the various diagrams needed with the greatest consistency and efficiency possible.


3. General Procedure for flow Diagram Preparation

3.1 Layout and Format

3.1.1 Vellums
All formal diagrams shall be drawn on standard A-1 size vellums (vellum size 594x841mm, including 10mm edge). In those cases where the project specifications ask for drafting on client's standard forms, the size may be different from the A-1 size.

3.1.2 Title block
The PFD, EFD and other diagrams shall bear in the right hand bottom corner of the diagram the standard Company title block. In cases where project specifications ask for specific use of client's vellums with client's title block, a standard Company drawing number sticker shall be added to the drawing for use of Company drawing record (see figure 1a).

Fig. 1a

In cases where client forbids the use of Company drawing number sticker, the Company drawing number shall be outside the drawing boundary line (see fig:1b).

The title block shall be completed with information as unit number unit name, unit section, drawing number, and all other information that is necessary to give all drawing-related information.

3.2 Symbols and Identification

3.2.1 For each project the engineering and utility flow diagrams will use the Company standards, if not overruled by client's licensor's or authority's requirements. These technical documents are:
BN-DS-C1 General information and Explanation of the Company symbols
BN-ES-C1 Standard symbols for Process and Engineering Flow Diagrams

BN-ES-K1 Standard for Identification of Instruments.

3.2.2 All symbols, instrument identifications and abbreviations used must be conform to those shown in above given standards, unless otherwise noted in the project specification.

In other cases a new legend sheet is to be prepared, which includes the required symbols and abbreviations. Project shall decide, in consultation with client or licensor, which system has to be used.

3.2.3 All equipment shown on the process and engineering flow diagram shall be identified with both name and number as listed on the equipment list.
Placement of titles shall be as follows:
a) Towers, tanks, tubulars, general equipment and other items on or above the upper base line shall be identified with titles placed across the top of the diagram. In some cases a space shall be provided to indicate design and/or operating conditions.
b) Pumps, compressors, etc. on the lower base line. Space shall also be provided to give design/operating conditions, if required.
3.2.4 To save drafting time, the flow diagram squad may make use of preprinted self-adhesive stickers to be stuck to the front or the back of the flow diagrams. These stickers can be adapted to any project an requirement.

3.2.5 Sticker samples


3.3 Diagram Issues

3.3.1 Issue numbering
It is of utmost importance that flow diagrams are kept up to date continuously and are regularly to keep all disciplines informed of the change during the engineering stage.

A release for design issue of flow diagrams shall be made directly after incorporation of Client's comments. Any further change after this issue mad by the Client shall be a subject for a change order.

The reissues shall be distributed in accordance with the job document distribution schedule.

All issues shall be numbered, dated and provided with a short description of the reason for reissue in accordance with QA procedure 006.

Typical example

The issue number shall be in accordance with the required numbering system as given in the job project procedure.

3.3.2 Revision list

All issues distributed after the “preliminary piping materials B.T.O.” shall be accompanied by a “revision list” on standard form BN-UD-101 “List of Revisions”.

This list of revisions (change) shall be issued as an addendum to the revised flow dagram. Each new diagram issue shall be accompanied by such a list of revisions.


3.3.3 Internal Issues
In some cases it may be required to distribute a diagram exclusively for the use within the BBV organization only.

It shall be clear that the number of such “Internal Issues” shall be kept to an absolute minimum. It is even better to have none at all.


In the case however, that an internal issue is necessary, the numbering procedure is as follows:


A circle of 16 mm diameter shall be drawn at the left hand side of the diagram title block and on the backside of the vellum. The circle shall be divided in two parts by a horizontal line.


An index capital A, B,etc. shall be pencilled in the top half of the circle and the issue date in the bottom half. Both capital and date on the front side of the vellum. The first internal issue shall be numbered. A. At the next internal issue the A and date are removed and a B together with the new issue date shall be written in the reserved places.


To keep properly track of these internal issues, the Project Engineer shall keep a record of the internal issues. This record is a very important document and can be a key document with regard to, e.g. material takeoffs.




3.3.4 The revisions shall be indicated by a “cloud” around the change and with the corresponding issue number within that cloud. The clouds shall be drawn with an orange colored pencil, e.g. color code 415, and on the BACK of the vellum. The clouds of previous issues shall be erased before new revision clouds are drawn on the vellum.

For changes/revisions on prints a standard BBV practice is to use the following color codes:
a. Equipment, lines, instruments, etc. removed from the drawing indicated with “red”, color code 426
b. Equipment lines, etc to be incorporated on the drawing indicated with “blue”, color code 443
c. Equipment lines, etc which are correct may be checked off with “yellow”, color code 407.
d. Remarks and additional notes which are not to be drawn on the vellum, “green”, color code 463.

Above color codes refer to the code numbers used by pencil manufacturer Faber-Castell, Gold Faber pencils. Other manufacturers have not necessarily the same code number system.

Instead of a red color for removing equipment, lines, etc a flesh-colored pencil may be used, which permits to draw new equipment and lines over the removed equipment. Use for this purpose pencil Faber-Castell Polychromos, code number 131.


Engineers are instructed to follow above system very consistently.


3.3.5 All changes on the diagrams shall be recorded on a “project Master” print of the last issue and kept at hand by the project engineer. All changes and/or additions made by others shall be passed through the project engineering department. It is the project engineer's responsibility to see that the diagrams are reissued every one, or at the most, every 2 months to keep all disciplines informed about latest revisions and changes.

3.3.6 All superseded “Project Masters” should be kept in the project file to provide a record of events.

3.4 Coordination
3.4.1 Copies of all correspondence, all specifications, all equipment vendor drawings and other pertinent job documents should be sent to the project engineer so that he may keep abreast of any and all changes which would affect the diagram. The project engineer shall forward all the relevant information to the different disciplines.

3.4.2 Any department, when making revisions or additions, which will affect a diagram, is required to notify the project engineer immediately, preferably in writing or to send hem his “master”. The project engineer will pass this information to the process engineer involved and update his master diagram accordingly for inclusion in the next diagram issue.

3.4.3 Revisions to precess flow diagrams must be brought to the attention of the project engineer. In this manner the project engineer will keep abreast of all process changes and will be able immediately to incorporate the changes into the engineering flow diagrams. After this updating by project, the process engineer will sent his “Master Copy” directly to the flow diagram squad.

It is necessarily for the process engineer to discuss contemplated changes with the project manger/engineer before changing the process flow diagram. The effect on fabrication and deliveries of equipment and/or materials, the client's or licensor's desires and construction schedule should be carefully considered and increasingly so as the job progresses.


4. The Process Flow Diagram (PFD)

4.1 General
After a project has been awarded the Process Department shall provide all special information required to commence engineering.


Process shall prepare a hand-sketched draft Process Flow Diagram which can be used for informing the various disciplines about the work to be performed. This normally is done at a formal kickoff meeting.
4.2 Initial Process Flow Diagram
The Process Department will prepare a had-sketched initial process flow diagram on preparinted standard vellums provided especially for this purpose (Form number E-B-UD15) (see example fig:5.)

The use of this sketch is two-fold. The sketch shall be used as a visual aid during the kickoff meeting and is the basis for the flow diagram squad to start drawing the process flow diagram proper. See example fig:6

4.3 Kick-off Meeting

4.3.1 Before engineering is started, a conference shall be called by the project manager to discuss the process and mechanical aspects of the job. This meeting should be attended by the job process engineer(s), project engineer(s), manager design engineering operations, design engineering supervisor, lead control systems engineer, lead piping engineer and other lead specialist engineers, as required.


4.3.2 A detailed explanation of the process shall be given by the process engineer. He outlines special considerations required for the location of related equipment, both in plan and elevation and calls attention to pipelines which must be arranged for gravity flow, tow-phase flow, self draining, etc.


At this meeting, the general philosophy of the control systems shall be discussed, particularly what types of instruments are to be local or remote, which indicators will be trend-recorded, the number of special analytic instruments, data loggers or other unusual requirements.


The process engineer should emphasize anticipated corrosion or erosion problems, explain the basis for the selection of materials of construction and review any special problems which must be considered in the mechanical design of the plant.


It is essential that the project engineer be given a thorough understanding of all process and operating problems at the project outset. In this way the information given on the initial diagram Layout will be as complete and accurate as possible.

4.4. Process Flow Diagram Drafting
4.4.1 Before the job starts, the project manager, in consultation with client or licensor, has to decide which system has to be followed, i.e. all process data, material balance, etc. should be shown on the process flow diagram proper, or that a separate set of material balance sheet will be prepared.


This information is necessary for the equipment layout on the diagram.

4.4.1 The flow diagram squad starts with the hand-sketched process flow diagram, from which the process engineer has given the explanations described in para 4.3.1, to make the process flow diagram on the proper format and with the standard symbols given in BN-ES-CI-1 and BN-ES-KI-1, or, if necessary, translate the Company symbols into symbols required by the client. This flow diagram will only be issued to the process engineer in charge to give on a print more information, such as heat duties, capacities, pressures, temperatures, equipment sizes on towers and drums, and capacities and P's for pumps.

4.4.3 It is essential to show a process flow diagram as simple as possible as far as mechanical details are concerned. It has to be avoided to show too many valves, etc. , and only the main instruments have to be given when laying out a process flow diagram. Ample space shall be provided for process data such as capacities, pressures and temperatures and instrument data on IDF sheet (see 1.5.6).

4.4.4 When all this information is shown on the process flow diagram, this will be officially issued by the project manager.

4.5 Reissues of Process Flow Diagrams
During the progress of the project the process flow diagram shall be reissued when necessary with the purpose of keeping all disciplines properly informed about the changes and corrections forthcoming during the engineering stage. For issue frequency and numbering see para 3.3 Issues are distributed in accordance with the job distribution schedule by the Project Department.

4.6 Computer Vision Diagram System
At the time this guide was updated and reissued plans to incorporate the means of producing flow diagrams by a computerized system were approved. In due time the guide will be updated to include the necessary information for generating computerized process flow diagrams and pressure-temperature profile diagrams. For example of such diagram see fig: 7

5. The Pressure-Temperature Profile Diagram (PTP)

5.1 General
The PT profile prepared by the Process Department is basically the process flow diagram on which for all critical flows through control valves and lines the following data may be given as deemed necessary for the project.

- Normal operating pressure
- Maximum operating pressure
- Normal operating temperature
- Maximum operating temperature
- Molecular weight
- Design pressure
- Design temperature
- Density
- Viscosity
- Normal flow
- Maximum flow
- Maximum temperature thermal stress
- Maximum shutoff pressure for pumps
- Set pressure of relief valves/break plates
- Differential pressure of pumps.

5.2 Purpose

The PT profile shall be used by all disciplines in order that the use the proper values of pressures and temperatures applicable to their specific requirements, e.g. pipe stress engineers, control system engineers, etc.

5.3 Reissues of PT Profile
The process engineer shall keep the data on the PT profile up to data and have the diagram reissued when necessary by the project manager.

The data on the PT profile must be “Certified Final” as early as possible, in order to minimize extra work because of process data changes.


5.5 Computer Vision Diagram Systems
When the computer vision diagram becomes operational (refer to para 4.6) the PT profile shall be made using the available info to produce a process flow diagram and the required PT profile data (see example fig: 7)


6. The Engineering Flow Diagrams (EFD)

6.1 General
A simplified block diagram showing the key elements of a systematic approach to flow diagram preparation is given in figure 8.

6.2. Initial Engineering Flow Diagram
6.2.1 The project engineer shall make the initial diagram layout for the engineering flow diagrams based on the process flow diagram. He should make the layout free hand and to full scale on the standard flow diagram vellum E-B-UD15 (see fig 5). The free hand edition should be initialed and dated by the project engineer and black and white prints distributed to the process and control systems engineers. See attached example, figure 9.

6.2.2 EFD General Layout
The EFD's shall be laid out with three horizontal zones across the sheet. Across the lower middle portion of the drawing is the “pipe alley” containing lines which enter and leave the sheet to other EFD's in the same unit plus lines running between pumps and other pieces of equipement on the drawing. Pumps and pump stations shall be located along a line below the “pipe alley”. All pump valving shall be lined up. All other equipment shall be located above a base line above the “pipe alley”. The general flow scheme shall be read from left to right. Unnecessary line crossing should be avoided. All line numbers and flow arrow shall line up as far as practical.

General notes for each unit are to be indicated on only the first sheet of the unit. The area above the title block on this sheet shall be completely left open for notes. Diagrams showing special equipment such as burner and compressor controls, etc shall have the related special notes on the same diagram.

6.2.3 Equipment
To be shown on the EFD:
a) Each piece of equipment including spares on the EFD of that particular unit. When an item is to be physically located inside the area of another unit it shall be so noted, exception may be made for situations where a large number of identical trains exist.

b) Pump item numbers and titles below the pumps “base line”. Indicate pump train designation only under each pump base (e.g. A.B.C.). When spares are required, the last pump of a train shall always be considered spare.
c) The other equipment item numbers and titles across the top of the flow scheme with the item number duplicated on or near the piece of equipment at its location on the diagram.
d) The equipment outline as simply as practical, but including all essentials and outlines, e.g. body flanges, domes, etc.
e) All connections and instruments on equipment. All connections whose purpose is not readily evident shall have the purpose indicated (examples: spare inlet, UC etc.), and the piping class to be used for the trim of the equipment.
f) Essential internals shall be shown in phantom so as to clarify the laction of connections relative to the internals. Vortex breakers are also to be indicated.
h) Motors on pumps only when connected to an interlock.
h) The support for columns and vessels supported by legs or a skirt.
j) A gap in the vessel support where a bottom outlet line crosses a vessel support.
k) Exchangers in side profile, with indication of expansion joints, tube side distribution baffles, etc., if any. Each shell te be shown and in relative position if stacked.
l) Bundles and fans on airfin coolers shall be shown simplified, but details on louvres, winterizing, running lights, temperature regulations and piping connections are to be shown if necessary on separate sketches.
m) A list next to the left hand side of the title block indicating the item numbers of equipment contained on the particular flow diagram.

n) Vendor-supplied packages only as a dashed/dot “box” with an outline of the main component(s) inside. At a proper time the reference drawing numbers are to be added.
o) The relative size of equipment – although no to scale.
p) The relative elevation of equipment – although not to scale.
q) Critical elevation notes as required.
r) Nozzle size when line size is different, reducers where applicable.
s) Existing equipment, when required, shall be shown with a dash-dot line, and marked “EXISTING”.

t) Manholes on columns/vessels.
u) Flushing/seal oil systems.
v) Start-up/shutdown lines.

6.3 Pipelines and pipeline referencing
6.3.1 All pipeline branching should be shown in proper sequence.

6.3.2 When lines cross one another, preference should be given to horizontal line, i.e. all horizontal lines should be continuous and vertical lines broken to cross them.
6.3.3 The procedure for cross referencing of pipelines going from sheet to sheet is as follows:

a) All main and process lines should enter and leave the diagram right or left (see figure 10) . An exception has to be made for lines coming or going to another unit. Those lines are coming in or leaving the sheet in a block (2x5cm) below the lowest pump base line (see figure 11).
b) Lines should enter and leave a diagram in a manner consistent with the actual process, where possible.
c) Whenever possible a line should match its continuation on a following diagram where possible. Line crossings as shown in fig 10 shall be kept to a minimum.
d) On each side of the flow diagram a dashed line shall be drawn to show from which diagram a line comes or to which one it goes. References and line numbers should also be added to lines where they enter or leave the sheet (see fig. 10).

e) A line shall not run across a sheet unless it ties into another line or piece of equipment on that sheet. It is permitted to skip one or more intervening sheets when running a line from one sheer to another.

f) All utility lines should be shown on the engineering flow diagram terminating in a diamond which shows the abbreviation as indicated on the legend sheet (see fig.12). The utility lines shown on EFD's shall only show instrument, valves, etc. directly related to the connected equipment (see fit. 13). The utility header valves and instruments will be shown on the utility flow diagram (see fig. 16). Example of legend, see fig:22.
g) The size of control valves shall be noted, e.g. 2”. If equipped with reduced size trim, body and trim size shall be noted, e.g. 2”x1,5”.

h) The size of relief valve inlet and outlet connections shall be noted, e.g. 3”x4” and must be shown below the relief valve number, including the set pressure, e.g:

j) The size of any valve not line size shall be noted. Reducers etc. shall be shown.
k) Any valve specified by the project engineer which must be other than a standard type identifiable by symbols and piping class specification, shall be identified by an “MM” number assigned by the material control section.

l) For line numbering refer to section 12.
m) For some instruments, like flow or temperature instruments, a pipeline shall, over a short distance, be enlarged or reduced as indicated by the instrument engineer.

m) For some instruments, like flow or temperature instruments, a pipeline shall, over a short distance, be enlarged or reduced as indicated by the instrument engineer.

n) All lines and connections shall show their respective size. In case the actual size is not yet known, the indicated size shall bear a note 'assumed'.

6.4 Initial Flow Diagram Check
The process and control systems engineer should each review this initial layout and should note on their copies all corrections and additional information available to them at this phase of development. Each reviewing engineer should return his copy to the project engineer. The project engineer has to take over all comments and additional information on the project master copy and return the process and instrument copies to the engineers concerned, as the keep a record for their own references.

6.5 Diagram Review Meeting
6.5.1 After the process and control system engineer's additions and/or corrections have been incorporated on the project master copy, the project engineer should hold a conference to discuss these additions and corrections.

6.5.2 It is important that the diagram be as complete as possible at this stage, however, the progress should not be retarded by incomplete details which can be added later.
6.6 Engineering Flow Diagram Drafting
The up to date project master copy is then sent to the flow diagram squad of the design engineering group. The vellum(s) will be updated in accordance with the marked up master copy and prepared for Issue I (or O or A; according to the project specification) “For Client's Comments” or “For Client's Approval”. A check print of this diagram will be sent to the project engineer for a last review. When comments of this review have been incorporated, the vellum will be signed and dated in accordance with procedure QA-006 and released for issue.

6.7 Reissues of Engineering Flow Diagrams
During the progress of the project, the EFD's shall be reissued when necessary with the purpose of keeping all disciplines properly informed about the changes and corrections forthcoming during the engineering stage. For issue frequency and numbering , refer tot para 3.3.

6.8 Computer Vision Engineering Flow Diagram System
At the time this guide was updated and reissued, plans to incorporate the means of producing EFD's by a computerized system were approved. In due time the guide will be updated to include the necessary information for generating EFD's by computer. For example of such diagrams see fig. 14

and 15.

7. The Utility Flow Diagrams (UFD)
7.1 Purpose
The primary purpose of the utility flow diagrams is to facilitate correct utility line sizing and to give this information to the piping designer as soon as possible.

7.2 Preparation
The utility flow diagram shall be prepared by the project engineer. A careful check must be made with the piping squad leader to ensure that the utility flow diagram is consistent with the piping design.

7.7 Layout
Utility flow diagrams are laid out suing format E-BN-UD2. The pipe rack(s) on the vellum should be shown as a “landmark” which must be the same on all drawings with the various groups of utilities. This vellum does not need to be on scale but it must present the various areas items in their relative geographical locations.


One sheet should be used for each utility system although several services could be shown on the same sheet if there are few users for each utility. Avoid overcrowding these diagrams, but be sure that every utility connection and branch is shown.

Additional equipment, if being serviced by any particular utility, should be added to the sheet. Remember that at a later date a number of service stations (SS …..) have to be added at the following utility flow diagrams:

Water System Diagram
(see fig. 16&17)
- Steam System Diagram
- Plant Air System Diagram.

Sometimes nitrogen or inert gas Lines are also incorporated in utility stations for purging purposes (reactors or compressors).

7.4 Control Systems, Valves, etc.

Only piping riot already shown on the engineering flow diagram should be shown on the utility flow diagram. Instruments and. valves should not be shown on a flow diagram, unless they apply directly to the utility and are independent of the process (see also 6.3.3, para f).

As an example of this type of exception might be a pressure-reducing controller and its valves from a high pressure to a low pressure steam header. Care shall be taken that valves are not shown twice, e.g. on the EFD and on the UFD.

7.5 Equipment

Process equipment shown on the utility flow diagram should be represented by squares of 2 x 2 cm with the information given as in figure 17. More detail than this is not wanted nor required. The only equipment to be shown in detail on a utility flow diagram is special utility equipment such as a steam boiler, a cooling tower, instrument air drier, etc. Packaged units as a part of a complete offsite utility system, may require a separate utility engineering flow diagram.

7. Figure 16 is an illustration of a utility flow diagram (draft).

7.7 Figure 18 is an illustration of a utility flow diagram when drafted by the flow diagram’ squad.

7.8 A separate UPD shall be prepared showing detailed sketches for miscellaneous pump piping with all valves, instruments and safeguarding requirements.

7.9 All Lines and branches shall be sized. U the final size cannot yet be determined, an ‘assumed’ size shall be shown and marked as such.

8. The Interconnecting Flow Diagram (IFD)

8.1 Purpose
The purpose of the interconnecting flow diagram is to show how and where various units, that make up the process plant, are connected with each other. This includes also possible tank farms, loading areas, other process plants, etc.

The lines that connect the units are normally located on pipe bridges and in trenches. These pipe bridges and trenches are to be used on the diagram(s) as landmarks and to obtain, as in the case for utility flow diagrams, a geographical layout. The diagrams shall indicate where at battery limits valve manifolds are located for distribution, bypass or shutoff purposes.

Also instruments physically located on pipe bridges, in trenches, and at valve manifolds, for as far as not shown elsewhere on EFD’s, shall be indicated.

8.2 Split of Work

Where a project is split in an “onsites” and an “offsites” part by others, the diagrams shall also be used to indicate clearly the location of the split in scope of work.

Standard Company indications on the diagrams under notes:

8.3 Layout

As already mentioned in para 8.1, the layout of the diagram(s) shall follow the geographical layout of the process plant.

The individual plant units for which a set of ETD’s have been prepared, shall be represented by a block on the drawing. Within this block the name and reference number of the unit shall be given. Each connecting line to or from this plant unit, either coming from other plant units, tank farm, other process plants, etc. shall be clearly identified, giving following data as minimum requirement:

a) Fluid name.

b) The pipeline number complete with. index capital, size and line class.

c) A reference to the EFD, UFD, etc. on which the continuation of the pipeline can be found.

All lines shown on the diagram shall be numbered in accordance with Company standards (see section 12) or in accordance with instruct given in the project specification.

8.4 Fig. 19 is an example of an interconnecting flow diagram.

9. The Process Safeguarding Flow Diagram (PSFD)
9.1 Introduction
Process Safeguarding Flow Diagrams shall only be prepared when asked for in the job project specification.

Since the Process Safeguarding Flow Diagrams are presently required by only one client, this Engineering Procedure does not include detailed instructions for the preparation of these diagrams. Refer to client’s instructions when these diagrams are required.

9.2 General Considerations

The PSTD of a process is intended to assist concerned parties in understanding the influence of safeguarding: protective instrumentation systems on equipment operation and process variables

When PSFD’ s are prepared, they shall be included in the design book and in the operating manuals of new units. The diagrams are to be included for instruction purposes in the chapter on “Safeguarding”.

9.3 Purpose

The PSFD is NOT a substitute for an Engineering Flow Diagram (EFD) of a particular unit. Often there are quite a number of EFD's per processing complex and the influence of operational upsets between one unit and another are not always readily recognized.

The PSPD should therefore clearly show the interrelation between various units and with processing plants outside battery limit including utilities, relief and blowdown systems, etc. It should high1ight the effect of one process on another from an equipment protection point of view, as far as potential loss of containment is concerned.

9.4 Timing and Pre of Process Safeguarding Flow Diagram

The PSFD shall be prepared from the Engineering Flow Diagram by the project engineer.

Modifications to the design automatically mean reassessment of the final level of protection of plant equipment. It is for this reason that alter modifications it is vitally important that also the PSFD is kept up to date..

The PSPD is a tool for checking that the unit is adequately protected. In order to save duplication of work the PSFD should be prepared after the EFD’s have been APPROVED, i.e. when the comments and modifications in the design have been incorporated. However, the PSFD should be correct at the time the EPD is issued as FINAL.

9.5 Presentation

If possible the PSFD of a unit including its relevant tie-ins with other units, should be confined to one sheet per unit. Tie-ins with other units nay figure twice, i.e. on the PSFD of each unit.

The same symbols should be used as for a Process Flow Diagram (PTD).

Equipment (vessels, pumps, etc.) and instruments shown should carry their tag-number.

A PSFD of furnaces need not be prepared. Furnace firing control and safeguarding should be on separate EFD which are adequate in themselves. Only if fuel Tight Shut Off valves are shut by process signals the TSO valve and the fuel Line may be shown.

10. Revamping Flow Diagrams (RFD)

10.1. General

Before updating of EFD’s for a revamp project can be started it must be made absolutely certain that diagrams are fully in accordance with actual installed equipment and relevant piping systems.

It is therefore necessary that a piping system squad visits the plant area for a site verification. During such a visit existing EFD’s are updated for the involved areas.

10.2 Updating and Marking EFD’s

10.2.2. After the site verification has been made the EFD vellums are corrected and handed to project.

10.2.2 Project is responsible for the preparation of a set of RfD’ s indicating which pipelines shall be removed, equipment to be removed, reinstalled, modified, etc.

Prints of the marked up vellums are distributed to inform all disciplines what has to be modified.

A set of piping arrangement drawings can with this information be modified to demolishing drawings.

2.0.3 Marking-up Cede

To obtain uniformity in the marking-up of RFD’s the following has been standard practice with Company.

10.3.1 Pipelines that shall be removed from the existing installation will be crossed out on the RFD as follows:

10.3.2 Cutting point and tie-in locations are to be indicated by an ellipse with the corresponding cutting or tie-in number written in it.

New equipment shall be marked “X”

Modified equipment shall be marked “Y”

Modified and relocated equipment shall be marked “Z”

Relocated equipment shall be marked “V”

10.3.3 The marked up diagrams shall be accompanied by a “mark-up list on which all cutting/tie-in points as well as all equipment shall be noted and numbered.

10.3.4 It shall be noted that the marked up RFD’s are to be used for preparation of various basic documents.

Depending on the complexity of the revamp, new EFD’s may be required.

New PFD’s and/or EFD’s are to be prepared in accordance with guidelines given in chapters 4 and 6.

Care shall. be taken that when new PFD s and EFD’s are to be prepared, the old PFD’ s and EFD’s shall be reissued in full d including that of client, as Deleted.

Note on the diagram: This diagram has been replaced by drawing no.

Marked up RFD’s for demolishing purposes shall be marked

For demolishing only

10.3.5 No information on demolishing drawings shall be removed by erasing Only crossing out as described in para 10.3.1 is permitted.

10.4 Example of Typical Demolishing Diagram Fig: 20.

10.5 Complicated Revamps

For highly complicated revamps, the foregoing procedure may not lead to satisfactory results as the marked-up RFD’s will become unreadable.

In such cases, the following procedure may be considered:

- New EFD’s to be prepared from the PFD’s in accordance chapter 6.

These EFD’S should reflect the situation after the revamp as if a new plant is being built.

- These EFD’s will be carefully compared to the EFD’s that reflect the existing situation and marked-up to show which lines, nozzles, instruments etc. can be re-used and which will have to be new.

New equipment and lines will be shown in heavy contours brought on the vellum at the backside to facilitate removal after the plant has been started-up.

- Demolishing RFD’s will be prepared on a reproducible of the existing EFD’s by comparing New EFD’s to Existing EFD’s. (refer para 10.3.1.)

An example of such new EFD’s is given in fig: 21.

- Indicate size of relief valves (control systems engineer).

- Show all valving (excluding sample and. bleeder valves, of instruments).

- Always date any flow diagram when printing, it for issue in accordance with para 3 3.

- Check which lines require steam tracing and select type of steam tracing

- Give equipment numbers shown on diagram in alphabetical order at the lefthand side of drawing title block.

- Ensure that all lines, branches and equipment connections are sized and shown

11. Check List

- Make all flow diagrams on standard flow diagram vellums (E-BN—U15) (fig. 5).

- Provide ample room around all equipment for instrument details, auxiliary piping.

- Use the standard legend sheet 00107A as cover sheet for all flow diagrams on a job (SN-ES-C1-1, sheet 28-30).

- Use symbols in accordance with instructions in project specification.

- Show equipment in outline form only except internals essential to external piping.

- Show all connections on equipment with size, including spare and blank connections, irrespective of line size.

- Indicate nozzles on equipment as per vessel sketches, e.g. N1; N2; Kl; K2, etc.

- Check the diagram versus the Company vessel drawing to be sure that all connections are shown in proper relative location.

- Show important equipment internals in phantom.

- Check correct connections on exchangers versus Company specification and drawing.

- Give sizes of valves which are not line size, show reducers where applicable.

- Show flows entering and leaving equipment as the process engineer intends.

- Put line number and title on each line as it enters or leaves a diagram.

- Number and size all lines on the diagrams as soon as possible. (All process line sizing by process engineering; all utility, tankfarm, etc. line sizing by project engineering, in consultation with process where necessary.) An assumption is to be made for lines not yet firm.

- Prepare the line table as the diagrams are being prepared and issue simultaneously.

- Show all instrumentation on the engineering flow diagram that is shown on the process flow diagram.

- Indicate sizes of all control valves and the size of the bypass, where required.

12. Preparation of line tables

12.1. Responsibility

The project engineer assigned to make the EFD’s shall also prepare the line tables required for these diagrams. He shall obtain all needed information from, e.g. the engineer who prepares the diagrams for utilities, etc. The project engineer is responsible for the completion of all co1mns on the line tables with the exception of line sizes for process and flare lines (see pars 12.3.5). Note that some clients have their own line tables which differ from Company standards.

The operating and maximum service conditions, requirement of tracing and insulation temperature are filled in by the project engineer and checked by the process engineer.

12.2 Form

The Company standard form BN-UE-l07 will be used for the line table.

Fig: 24

In the Company organization exists also a standard form BN-UE-108A which is a special Line table used for Dutch projects subject to Stoomwezen” (Dutch Boiler and Pressure Vessels Authorities) approval. This form will not be discussed in this paper. Refer to example Line table fig. 26.

12.3 Description of Columns

12.3.1 Form Head

In the “Form Head” the Company project number, title, unit number for Company and client, drawing and sheet numbers, shall be properly filled out on each sheet.

Issue and date to be filled in every time the line table is issued (refer to para 3.3.1 for descriptions).

The issue of the line table shall be simultaneous with the issue of EFD’s. and UFD’s.

12.3.2 Fluid – column A

The name of the fluid being handled should correspond to one of the fluids Listed in the job piping specification BN-SP-C2 so that a suitable class specification can be selected. The same name should be used consistently throughout all the lines in the same service. Names should be abbreviated t letters whenever possible, e.g. CW, STM. These abbreviations must e the same as used on the P&I Legend Sheet (see fig; 22).

12.3.From and To columns B and C

Origin and destination of a line should be simple but clear, e.g.



Line P10112



Line P10122



East B.L.


12.3.4 Line number – column D

The project engineer shall assign basic numbers according to the following procedure.

A Line number shall consist of a letter followed by a five-digit number. The first two digits shall be the unit number followed by a sequence number.

Process unit lines shall be assigned in sequence number blocks wherever possible, and referenced as a block on the Line table cover sheet. For example, reactor area lines might be numbered. . 101 to 200.

Process line numbers shall, have the letter prefix “P”.

Utility Line numbers and other non-process lines shall have a letter prefix according to the following code, with further sequence number block assignments preferable for different levels of steam, etc.

A001 to A999 – Air
C001 to C999 – Condensate
D001 to D999 – Drains, Blowdown, etc.
F001 to F999 – Fuel Oil, Gas
G001 to G999 – Inert Gas or Nitrogen
K001 to K999 – Chemicals
R001 to R999 – Refrigerant
S001 to S999 – Steam (all levels)
V001 to V999 – Vent and Relief Headers
W001 to W999 – Waters (cooling, tempered, potable, boiler, feed, etc.

Each Line shall in principle have only one origin and one destination. A pump and spare require a total of four Line numbers, one to each suction, and one from each discharge, however, one should take into account that, where possible, a minimum of isometrics drawings by APD system shall be obtained. By giving line numbers, the project engineer shall take into account which system for isometric drawing production is applicable.

It is riot necessary to have a separate number for control valve bypasses, or when a line changes class, per the Latest APD system.


On some projects it is permitted to have after every 10 or 15 line numbers some spare line numbers reserved. This to obtain maximum continuity in the line numbering when during the engineering phase of the project lines have to be added..

12.3.5 Line size column E

Sizes for process and flare system Lines are determined by the responsible process engineer. Sizes for utility and other non-process lines are determined by the responsible project engineer who in some cases may consult the process engineer and request to review or even assume complete responsibility for some non-process lines..

Whenever such a split of work is desired it shall always be at the discretion of the project manager.

Line sizing shall be done in accordance with the criteria given in the Process Standard Data Book.

The process and project engineers shall carefully check, their calculations after the actual piping configuration has been determined.

12.3.6 Material class - column F

Classes shall be assigned for each lines depending on the fluid being carried, and its required design pressure and temperature. The selection of a suitable piping material for corrosive fluids is made by the piping engineer after consultation with project and/or process engineer. Consideration of conditions other than maximum service as enumerated in 12.3.10 below must be undertaken to properly classify lines.

12.3.7 Schedule number - column G

The wall thickness is the thickness indicated in the piping specifications, as a pipe schedule. For “standard pipe classes” it is not necessary to fill in this column. However, the wall thickness should be included for all special services such as:

Boiler code piping
Special high temperature or high pressure piping
Services requiring unusual corrosion allowances.

12.3.8 Operating temperature - column H

This is the temperature of the fluid during normal continuous operation. This temperature will be the basis for setting the insulation thickness, unless a special note is included in the remarks column, by the process engineer or project engineer.

12.3.9 Operating pressure – column H

This is the pressure occurring simultaneously with the. stated operating temperature.

12.3.10 Maximum service temperature and pressure - column J

These are the most severe temperature and pressure conditions occurring simultaneously during continuous operation of the plant. If there are more severe conditions not occurring simultaneously or not associated with plant operation, they should be stated separately as different design conditions (see 12.3.10 (a) below)

The maximum service temperature and pressure are used in the selection of the piping class. In all situations where the conditions are close to the upper limits of a class or force the use of a higher class than that required by the operating conditions, the conditions and class selection should be reviewed by the process engineer and forwarded to the piping engineer.

The maximum service temperature is and pressure are used in the design for the pipe expansion and for painting, unless a higher, non-simultaneous temperature controls.. In this case, the higher temperature should be stated separately per paragraph. above. Special attention shall be given to flare lines, which may become very hot over short periods.

(a) Other maximum conditions

The conditions affecting design of lines other than normal operating temperature and pressure must be recorded, if they affect design or insulating of lines in the remarks columns or in an addendum to the line table. This applies to emergency conditions, start-up, shut-down, steam-out, preconditioning decoking, reactivation, pump shut off head, thermal expansion of fluids, steam tracing, or evacuating by vacuum, heat conservation dictated by process and oat economics.

The acceptable temperature for steam-out temperature at nearly atmospheric pressure is 120°C. This applies to any supply steam temperature.

When steam tracing is used, a differential temperature of 25°C can be allowed between steam condensate temperature and pipe wall temperature.

(b) Code statement on operating and maximum service conditions

(Excerpt from American National Standard Code for Pressure Piping - Petroleum Refinery Piping ANSI B31 .3.)

302.2. Normal Operating Conditions

For normal operation, the design pressure and. temperature shall not be greater than the pressure-temperature rating of the components. In the absence of such rating, the design pressure shall not result in stress exceeding the allowable stress for the material, at the temperature.

302.2.4 Allowances for Variations from Normal Operating Conditions

Variations in the temperature and pressure, or both, from normal operating conditions are characteristics of certain services. If these variations are infrequent and of short duration, the pressure-temperature ratings (or the allowable stresses) of the piping components may be adjusted as follows:

(a) If the increased operating condition will riot exceed 10 hours at any one time or 100 hours per year, it is permissible to increase the pressure rating (or the allowable stress) at the temperature existing during the increased operating conditions, by a maximum of 33%.

(b) If the increased operating condition will not exceed 50 hours, at any one time or 500 hours per year, it is permissible to increase the pressure rating (or the allowable stress) at the temperature existing during the increased operating condition by a maximum of 20%

Special consideration should be given to the above allowances when setting maximum service conditions.

Cyclic operation

In many chemical processes, lines and equipment are subject to planned cyclic changes in pressure and/or temperature. Frequently these operations are controlled by means of elaborate cycle timers.

The selection of line materials and the design of the whole piping system demands a full and accurate description of the cyclic operation in terms of times, temperatures and pressures of all equipment and piping elements,

To provide this information to all concerned, a full set of explanatory notes and time-sequence diagrams should be incorporated into the line table as an addendum and issued with it. The maximum service conditions will be shown n the addendum rather than in the line table for the lines affected.

12.3.11 Testing – column L

The test pressure shall be calculated according to ANSI B31.3 requirements, except for non-critical, non-hazardous services, where service testing is acceptable. Typical examples of lines that may be accepted with service tests are low pressure, large diameter ducts; low pressure steam, cooling water; condensate; and instrument air. The project engineer shall complete this section, adding the test media and obtaining client approval for service test plans.

12.3.12 Tracing type - column L

The type of tracing or jacketing should be added according to the symbols defined on the P&I Legend Sheet, Drawing No. BN-. . . -00107A (fig: 22). On jobs requiring extensive tracing, additional columns should be added to the applicable line table sheets to indicate Thermon Grade and Steam Pressure.

12.3.13 Insulation and paint code – columns M and N

Insulation thickness and painting code shall be filled in in accordance with applicable job number and R specification.

12.3.14 Flow diagram number - column 0

The flow diagram number on which the corresponding line appears (originates) shall be filled in.

12.3.15 Remarks - column P

Space reserved for additional information

12.4 Procedure

12.4.1 The project engineer prepares the line table in accordance with paragraph 12.3.2, 12.3.3 and 12.3.4 above. He then issues the format to the process engineer.

12.4.2 The process engineer adds the line size and checks the operating temperature, operating pressure, and maximum service temperature and pressure on the Line table prints and returns the forms to project for interim use by project or design.

12.4.3 The Project engineer adds the material class based on the maximum service conditions.

When high pressure and/or temperature indicate the selection of alloy materials the project engineer is expected to recheck line velocities and maximum operating conditions and governing design conditions with process to assure the most economical line size and class specification. Sometimes a small extra pump head is cheaper t an increase in line size. Sometimes maximum service conditions or governing design conditions are at first set too much above operating conditions resulting in unnecessarily high pipe class specification ratings.

12.4.4 Project completes the table for issue, according to QA-O06.

12.4.5 Revisions are made according to 12.3.1.

12.4.6 For revamp jobs, the project engineer must include all lines affected by the revamp on the LDT.

12.5 Computer Vision System

At the time of reissue of this procedure the plans to incorporate the computer vision system has been approved.

When the system becomes operational then also the line tables are to be produced by using the information stored in the computer memories.

Detailed instructions will be incorporated in this procedure in due time when more information becomes available.

For example of such computer produced line table see fig. 27.

Sample Forms

Figure 23 is a sample line table cover sheet with notes

Figure 24 is a sample line table sheet. Form BN-UE-107A.

Figure 25 is a sample line table sheet. Form BN-UE-107B (for other than ISO units)

Figure 26 is a sample line table sheet. Form BN-UE-108A (for use by Dutch Boiler and Pressure Vessel authorities).

Figure 27 is a sample line table produced by “Computer Vision” method.

List of Related Company Standards

BN- EG –UE-1 Pressure ad Temperature Profile

BN-EG-UE-2 General Rules to Establish Mechanical Design Pressures and Temperatures.

BL-EP-206 Equipment Numbering

BC-EP-210 Preparation of P&I and Utility Diagrams

BL-EP -210A Preparation of Flow Diagrams (PFD, P&I, UDD)

BL-EP-210B Preparation of Flow Diagrams (P&I, PFD, UFD)

BL-EP-210C Preparation of Flow Diagrams (line numbering and tables)

BL-EP-210D Preparation of Flow Diagrams (determination mechanical design conditions)
BA-EP-377 Instrumentation Symbols and Identification


14.1 General

This list does not pretend to be complete. It only serves to guide the project engineer through the maze of many documents issued by government authorities and companies.

Before any drafting shall be started it is good practice to check which documents are applicable and that the latest issues of these are at hand.

14.2. U.S.A.

ANSI Z-32.2.3 Graphic. Symbols for Pipe Fittings, Valves and Piping
ANSI Y-32.11 - 1961 Graphic Symbols for Process Flow Diagrams in
ASME K40 Petroleum and Chemical Industries
ISA SS.1. Instrumentation Symbols and Identification.

14.3 West Germany

DIN 19227 Blatt 1- Graphic Symbols and Identifying Letters for Process Measurement and Control Functions.

Part 2 Measurement and Control, Graphical Symbols and Identifying Letters for Process Measurement and Control Functions; Symbols for Instruments.

Part 3 Measurement and Control, Graphical Symbols and Identifying Letter for Process Measurement and Control Functions; Symbols for Basic Functions.

DIN 28004 Part 1 Flow Sheets and Diagrams for Process Plants, Types of Flow Sheets, Informative Content.

Part 2 Flow Sheets and Diagrams for Process Plants, Drawing Instructions.

Part 3 Flow Sheets and Diagrams for Process Plants, Graphic Symbols.

Part 4 Flow Sheets and Diagrams for Process Plants, Assignments of Item Numbers and Piping

14.4 Great Britain

BS 1553 Specification for Graphic Symbols for General Engineering
Part 1 Piping Systems and Plants

BS 1646 Symbolic Representation for Process Measurement Control Functions and Instrumentation
Part 1 Basic Requirements (equal to ISO 3511/1)

BS 5536 Specification for Preparation of Technical Drawings and Diagrams for Microfilming

14.5 France

AFNOR Z-09-0l0 Engineering and Design Documents, General User’s Guide

NF X 02-105 Symbols for Liquid Mechanics

NF E 04-202 Graphic Symbols for Chemical Engineering


There are a lot more French standards issued. Before starting drafting the diagrams check which standards are applicable.

14.6 The Netherlands

Ontw. 2195 Technical Drawing Symbols for Process and Engineering Flow Diagrams

NEN 3157 Technical Drawing Instrument Symbols. Basic Symbols for the Process Instrumentation

NEN 3347 Technical Drawing Instrument Symbols Advanced Symbols for Process Instrumentation

14.7 S.I.P.M.

DEP Symbols and Identification System Mechanical
DEP Symbols and Identification System Instrumentation

14.8 Aramco

AE5-J.4 Identification and Symbols, Section IV, Index A, Drafting Manual

DA-299407 Symbols and Abbreviations

DA-299408 Instrument Symbols

DA-299409 Instrument Identification.


15.1 General
In this addendum a number of typical equipment installations are given which are common in many industrial plants.

It does not pretend to be 100% complete and only serves as a guide to obtain maximum uniformity.

For each project this addendum needs to be updated in accordance with client’s, licensor’s or authority’s requirements.

The updated version of this addendum may be made part of the chapter on flow diagram preparation in the project specification.

It should be noted that some clients use the word ‘Scheme’ instead of ‘Diagram’. The latter being the indication used by Company.

If the word ‘Scheme’ is standard for a particular client, then the text of the addendum must be adapted accordingly before it shall be used in the project specification.

15.2 Typical Installations for Vessels and Columns


(1) Indicate all nozzles shown on the equipment data sheet.

(2) Provide spectacle blinds at nozzles

(a) 10 inches and larger
(b) where piping is obviously rigid.


Add spectacle blinds in other lines which are designed rigid, during detailed engineering phase).

The general philosophy is to blind at equipment nozzles for maintenance operations. Spectacle blinds are not required for reboiler/column connections where operation is not possible without the reboiler.

(3) Provide a valved drain for all columns and vessels. Generally this valve is to be located on the bottom line outside the skirt and between the vessel and the first pipeline shutoff location (valve or blinding flange). The drain valve shall be located on the bottom of the vessel when:

(a) No bottom line is present, or

(b) The bottom line is not flush with the lowest point of the vessel.

(4) Provide a valved vent for all columns and vessels on the top of the vessel.

(5) Vessel/column TI shall be located on the top outlet line.

(6) Vessel/column PI shall be located on the piping if no upstream block valve is provided on the piping.

(7) Relief valves shall be generally located on the top outlet line downstream of the vessel blinding location.

(8) Provide utility connections on all vessels/columns.


During detailed engineering, size per Project Specification.

(9) Legs shall be indicated by drawing one leg

(10) Skirts shall be indicated by drawing two such lines.

(11) Indicate, all nozzle sizes and show piping class to be used for trimming.


(1) Exchanger symbol (a floating head exchanger is shown here).

(2) Generally direction of flow - cooled media downflow, heated media upflow.

(3) Isolation valves shall be provided on inlet and outlet lines where maintenance can be performed on the exchanger with the unit operating.

(4) Provide spectacle blinds at inlets and outlets where maintenance valves have been provided in process and steam services, and the line is l0’ or larger. Provide no spectacle blinds for cooling water services.

(5) Provide thermal expansion protection (generally in the outlet line) of liquid-fiiled services with heating media on the opposite side, when the stream can be blocked in by valves.

(6) Shell and channel piping shall be provided with a valved vent connection and a drain connection unless venting and draining can be done via other equipment.

(7) Indicate exchanger vent and drain connections per equipment data sheets and provide valves.

(8) Valved utility connections shall be provided where requested by the client for fouling process services. (Valved utility connections may be also required for cooling water services). The utility connections may also serve as the pipeline vent and drain. Flushing oil shall not be hard-piped to these connections.

(9) Consider to provide an inlet and outlet multipoint TI to monitor the process side of each exchanger service. If, in order to perform one service multiple bundles are used in series or parallel arrangement, provide TW’s on the outlet of each bundle (except for the last bundle in a series arrangement). For water-cooled exchangers provide in the water outlet a TW where manual control exists, or a multipoint TI where automatic control exists. Where practical, locate temperature instruments between the exchanger bundle and its isolation valves. Do not duplicate with TI’s required for other reasons.

(10) Provide PI on process streams entering and leaving exchangers or groups of exchangers as required (Non-fouling services will generally not require the PI). Provide a local PI in steam services between the control valve and the exchanger inlet, facing the control valve.

(II) Route thermal expansion discharges to grade, funnel, or closed system as required.

(12) Backwash connections are not required in any service.

(13) At exchangers with circulating heat transfer media (CW, TW, SW, etc.), indicate the outlet valve as a throttling valve with the basic symbol. During detailed engineering, select appropriate valve, depending upon size and actual pressure drop requirements to balance the system flows.

(14) Provide permanent flush oil supply and return lines on all exchangers handling crude, long residue, short residue, light waxy distillate and heavy waxy distillate. Utility connections shall be replaced by flushing oil connections for above exchangers.

(15) For each case the execution of the exchanger installation is subject to instructions from the process group. e.g. the application of a kettletype exchanger for reboiler or the use of a thermssyphon type reboiler. Also special considerations to be given for two phase flow exchangers. As well as the location of the equipment with regard to selfdraining, accessibility etc., etc.

(16) Indicate all nozzle sizes and show piping class to be used for trimming.

15.4 Typical Air Cooler Installation


(1) If possible, indicate only one bundle and one fan for each air-cooled exchanger service, but make sure that details on winterizing, running lights, temperature regulations, etc. are clearly shown. Use the forced draft s when the configuration is unknown.

(2) When multiple bundles are anticipated, indicate headers in the lines and all inline items and instruments required for each individual bundle between the piping header and the bundle nozzle(s).

(3) Provide isolation valves in corrosive and fouling services where individual bundles can be repaired and maintained with the unit operating.

(4) Indicate valved vents and valved drain connections for each bundle header. Number of vents/drains in accordance with client’s requirements. Often 2 valved vents and 2 valved drains are provided on each headerbox for complete venting and draining. Same valves are used for flushing, chemical cleaning etc.

(5) Provide spectacle blinds at inlets and outlets where maintenance valves have been provided and the line is 10” or larger, or where piping is obviously rigid.

(6) Provide an inlet and an outlet multipoint TI to monitor the process side of each airfin service. Do not duplicate with TI’s required for other reasons. If in one service multiple bundles are used provide TW’s on the outlet of each bundle.

(7) Indicate auto variable hub as shown. Write the air failure position on the signal line when applicable (e.g. ‘max. pitch during air failure’).

(8) Indicate louvres when required. Show hand control unless otherwise specified.

15.5 Typical Pump Installation


(1) Provide an isolation valve in the suction line of each pump – normally a manual valve (see note 13 for remote operated valve). Rating of suction valve shall be indentical to the rating of the discharge valve, except in the case of multi-stage pumps.

(2) Provide an isolation valve in the discharge line of each pump.

(3) Provide a check valve in the discharge line unless there is no possibility of reverse flow (check valve, SB and isolation valve to be mounted without spool piece).

(4) Provide a ¾" bypass/drain from the check valve to the pump discharge line when:

(a) The design temperature exceeds 230°C.

(b) The process fluid solidifies at ambient conditions.

(c) The process fluid is corrosive or toxic (to drain downstream of check valve).

(5) Provide a PI on the discharge of each pump between the pump and the discharge check valve. Locate on the check valve bypass line when possible.

(6) Provide for removal of solids from process stream a strainer in the suction line of each pump. (Y type is preferred)
For coarse or plentiful solids during start-up, a temporary cone type strainer is installed instead.


Strainers 6” and larger shall have a one inch drain valve indicated during detailed engineering.

(7) Provide spectacle blinds at the pump isolation valves when more than one pump is installed on a common suction and/or discharge line.

(8) Valve the casing drain only on pumps requiring casing flushing or where connection to a closed drain system is required. For all other pumps do not valve casing drains - provide blind/blank at casing drain.

(9) Provide a valved discharge line vent on pumps:

(a) Container butane or lighter process fluid (see note 15). Pipe vent line to flare (liquefied gases).

(b) When the pump operates with fluid-temperature close to boiling point. Pipe vent Line back to suction vessel with valves at each end of the line, or piped to blowdown system.

(c) When the suction vessel operates under vacuum.
Pipe vent Line back to the suction vessel with a valve at each end of the Line.

(10) Indicate flushing oil supply and return as shown to pumps requiring flushing oil (refer to section 15.19 for hook-up details).

(11) Indicate external seal. flushing fluid as shown to pumps requiring external sea flushing (refer to section 15.17 for hock-up details). Internal seal and/or cooling systems provided by pump vendor are not to be shown.

(12) Indicate water cooling supply and return as shown to pumps requiring water cooling (refer to section 15.13), either for bearings, seals or pedestal.

(13) Provide a remotely operated shutdown system on pumps where required. This remotely operated shutdown system includes an ROVon the pump suction, and a shutdown signal to the pump motor. No board mounted running light is required for the motor. For automatic starting standby equipment a running ‘alarm’ light is required.

(14) Indicate the local emergency shutdown station. During detailed engineering this may be located on a local panel at a safe distance. In case of a local alarm panel with a common alarm in the control room, the common alarm should not be blocked by the standby equipment but should have the possibility to be cleared by pushing the local reset and the control room reset.

(15) For LPG pumps the vent to the flare shall have block, bleed, blind and thermal expansion protection as indicated. A note for detailed engineering will require that a flanged valve be provided downstream of the thermal expansion valve to allow for blinding. During detailed engineering, only when essential, locate vent line on pump casing for positive fillling before the pump is started.

(16) For pumps handling hot products which will oxidize when brought into contact with the atmosphere, indicate a steam quench on the mechanical seal as shown. The steam let down system will be shown on Utility Flow Diagrams.

(17) Consider a typical pump piping hock-up diagram, showing repeating details, to simplify the general diagrams.


Typical Turbine Installation (Special Purpose Turbine with Manual Startup)


(1) Indicate turbine symbol with normally supplied governor (SC) system, trip (SX) system and inlet strainer. Do not indicate normally supplied sentinel relief valve.

(2) Provide a relief valve between the turbine exhaust and the outlet isolation valve.

(3) Provide an isolation valve on all turbines exhausting to a steam header.

(4) Provide an isolation valve on all turbine inlet lines (to be provided in addition to the turbine trip/throttle valve).

(5) A second isolation valve and spectacle blind is to be provided in the inlet line at the header (upstream of the FR).

(6.) Provide a spectacle blind at the isolation valve in the exhaust line in all cases (a second valve is not to be provided at the header).

(7) Provide a warming bypass around the inlet isolation valve with one isolation valve and one throttling valve as indicated.

(8) Provide inlet and outlet PT on all turbines in the location shown.

(9) Provide inlet and outlet TI on all turbines in the location shown.

(10) Consider an inlet FR on all turbines in the location shown. Do not duplicate with unit limits FRQ in the case of a single consumer inside one unit.

(11) A casing trap station is not required for manual startup turbines.

(12) Indicate the existence of valved drains and leak-off lines from turbines.

(13) Inlet separators are not required in the inlet line because a warming bypass is being included around the inlet isolation valve for startup.

(14) Indicate requirements for an inlet line steam trap station (with drain) upstream of the isolation valve by use of a note as shown.

(15) When required, indicate remote shutdown.

(16) For automatic starting turbines indicate the on/off startup valve at this location and include a steam trap assembly for the casing drain.

(17) Manual shutdown functions to be shown as HSA with alarms on main and local panel (also applicable to compressors).

(18) For compressors, show temperature indication on local panel(s) with remote (main) panel alarm on compressor discharge applications as high temperature alarm only. No indication on local panels.

(19) Additional instrumentation may be required to be shown, according to the equipment actually supplied.


The final EFD shall show instrumentation and all appurtenances as supplied by equipment vendor and Company. e.g. vibration/proximeter instruments hooked up to shut down system etc.

(20) For complicated systems a separate diagram for the turbine control may be considered with a block shown on the normal EFD or UFD.

15.7 Typical Ejector Installation


(1) Large ejectors shall normally be provided as two units (e.g. 1/3 and 2/3 capacity).

(2) Provide isolation valves on the inlet but not the outlet of each jet. Spectacle blinds are not required.

(3) Provide a PI on the process common inlet line.

(4) Provide an isolation valve on the steam inlet to each jet - not a throttling valve.

(5) For the intercondensers and aftercondensers apply the requirements of section 11.3 with the following exceptions

(a) No multipoint TI is required on the process inlet.

(b) No multipoint TI is provided on the process vapor outlet.

(6) Provide a dual Y strainer station in the common steam line supplying a group of jets.

(7) Provide a check valve in the co steam line supplying a group of jets.

(8) Provide a PI on the con steam inlet manifold.

(9.) For each ejector system (intercondensers and aftercondenser) only one common inlet valve and thermal e valve is required. Individual outlet valves are required.

(10) Provide an FE on the common steam inlet manifold. During detailed engineering, provision of an FR or FRS to be considered, as required, depending upon steam balance considerations.


Special attention shall be given to ejector sets with special requirements. Such as recycle line, or when combined with a vacuum pump, etc. Also consider the safety requirements with regard to flame arrestor, seals, flashback, etc.

15.8 Typical API Tank Installation


(1) Individual tank requirements will be determined by the process and the contents, and by the requirements of the refinery operation.

(2) Single temperature measurement only if required.

(3) Averaging temperature measurement if required.

(4) For slops tanks special arrangements to be made.

(5) Large storage tanks (e.g. floating roof) and LPG tanks shall be carefully equipped with required instrumentation, fire protection systems or sprinkler systems.


Each tank shall be analyzed carefully for the characteristics of the product being stored. Special requirements may be required such as:

a. Heating cost (heavy stock)

b. Wall tracing (Sulphur storage)

c. Pressure tanks (LPG spheres)

d. Vapour recovery systems (Benzene)

e. Hazardous products. (VCM, Acryl)

15.9 Typical Control Station
Sequence of preference:


(1) Provide an upstream isolation valve for all control valves unless the upstream system is to be shutdown on control valve failure.

(2) Provide a downstream isolation valve whenever the downstream side of the control valve cannot be isolated from other continuously operating pressure sources.

(3) Provide a drain valve upstream of all control valves.

(4) Provide a drain valve downstream of the control valve only when the process fluid is toxic or corrosive.

(5) Provide block and bypass arrangement per “B”, above, when:

(a) Line size is obviously 2” and less, unless high pressure service requirements dictate otherwise.

(b) Unsafe conditions, undue loss of efficiency, or unacceptable plant disturbance would be caused by loss of the control valve.
(c) In services that are flashing, corrosive, at high temperature, or at high differential pressure.

(6) Provide a handwheel on all control valves not having a bypass except where undesirable (e.g. solenoid shutdown of the control valve is provided).

(7) Bypass valves shall be indicated as a globe valve unless the line is 8” or larger. Size not to be larger than control valve capacity.


Where a control valve is smaller than line size, the line reducers shall also be shown on the EPD. (Refer j)
Drains in liquefied gas service shall be executed with 2 drainvalves approx. 0.5m apart to prevent hydration.

15.10 Typical Utility Tie-in to Process ( for Steam and Nitrogen only)


(1) The isolation valve may be omitted if the process line is open to the atmosphere.

(2) A check valve is to be provided.

(3) Provide a drain upstream of the check valve.

(4) Indicate branch header block valves (ref. Section 15.25).

Control facilities or equipment, if any, shall be located between this block valve and the downstream check valve.

(5) Provide spectacle blind and block valve for N2 service.

(6) In vacuum service provide a blind flange at the drain valve.

(7) Tie-in details for other utilities to be determined as required.


15.11 Typical Unit Battery Limits Installation


(1) Provide for each process line an isolation valve, spectacle blind, drain and pressure indicator as shown above.

(2) Consider a flow recorder integrator (FRQ) for each process stream entering and leaving each unit. Do not duplicate measuring elements in the same stream within one Block area.

(3) Provide a multipoint TI on all process streams leaving a unit and where a flow integrator is provided. Do not duplicate with TI’s required for other purposes. Generally locate the TI downstream of the FRQ.

(4) Requirements for utility headers (including steam bypass valves) are as indicated on the Utility System UFD (above installation is for process lines).

(5) Generally, provide a sample station for all products leaving and entering a unit. See section 15.12 for sample station arrangements (adjacent units without long transfer lines may not require the station).

(6) Liquid product streams leaving units shall be piped at the unit limits to the dry slops header as shown for start-up (off-spec) operation (Tie-in from the dry slops line to the recirculation header will be indicated on the slops system EFD).

(7) The above are general guidelines only. Consideration shall be given to the possibility of avoiding duplication of some or all of the above hardware on adjacent units.

(8) Unit battery limit abbreviation (UBL) shall not be used at utility/common facility diamonds.

(9) Block battery limit stations shall be shown on “interconnecting lines” diagram (IFD).

15.12 Typical sample stations
Type A (for cold liquids below the boiling point)

Type B ( for liquids above 80°c, or above boiling point, low viscosity, low pour point)

Type C (for liquid above 80°c, high viscosity or high pour point)

Type D ( For LPG and gas up to 30 bars)

Type E ( for LPG and gas above 30 bars)


(1) When valve “A” is accessible from the same location as valve “C”, the valve “B” is not required and for sample system type C the return line is not required.

(2) During detailed engineering select appropriate valve types for isolation and throttling services.

(3) Minimum distance. No bends allowed.


15.13 Typical Safety Relief Valve Installation


(1) A typical relief valve to flare with spare position is indicated. For other installations provide only the following:

(a) Safety Relief to Atmosphere
No Upstream Isolation Valve is required.

(b) Thermal Expansion to Closed System
Provide a Downstream locked open Isolation valve.

(c) Thermal Expansion to Open system
No valves required.

(d) Safety Relief to Flare (without spare position)
Provide a downstream locked open isolation valve.

(2) Indicate only one relief valve even when multiple valves are anticipated.


Actual number and size of relief valves shall be determined during detailed engineering phase.

(3) Provide inlet and outlet isolation valves with ‘Castell lock’ system or similar approved system.

(4) When required provide a spare relief valve location as indicated above.

The inlet and cutlet valves are normally closed but require locked open facilities when the PSV is installed.

(5) Provide a bursting disc in vacuum service or where required in hazardous service (e.g. VCM). The bursting disc shall be provided with a downstream PI. The spare position spool piece shall also be provided with bursting. disc-holder only and a PI. Pressure alarm between the bursting disc and relief valve only when required.

(6) Spare position shall normally not be provided with a safety relief valve

(7) Provide a spool piece with valved bleeder bet the PSV inlet and the upstream isolation valve when a rupture disc is provided. The bleed connection is not required when a PI is provided (can bleed through PI connection).

(8) Process relief valve discharges shall generally be piped to the HC flare. The ADIP and Sulphur unit relief valve discharges shall be piped to the H2S flare. Relief valve discharges from flammable and hazardous liquids s be piped as required.

Thermal e valves in process service shall discharge back to low pressure process when possible. Thermal expansion valves in non-hazardous water service shall discharge to atmosphere at a safe location (grade) and to a funnel when discharge is hot.

(9) Show relief valve number and rupture disc number.

(10) Give relief valve or rupture disc identification number.

(11) Give relief valve or rupture disk size indication.

(12) Show relief valve and rupture disc set pressure.

15.14 Typical Burner Installation
A. Natural Draft Gas Fired Heaters

B. Forced Draft (combined fuel oil and fuel gas fired steam boilers)

B. Forced Draft (combined fuel oil and fuel gas fired steam boilers)


(1) During detailed engineering phase the “trial-for-ignition time” for each furnace shall be determined. If found to be less than 30 seconds special safeguarding measures are to be proposed for review by client’s safety engineer for approval.

(2) During detailed engineering, locate burner control system (PCV and TS0) alongside operating platform of relevant furnace.

(3) Provide a FSA as shown when a waste gas safeguarding system is to be provided.

(4) The given examples on previous sheets are only “typical” and are meant as a general guide. Control engineering depends largely on size of boiler or heater, type of burners, and governmental requirements. In each case the system should be very carefully observed.

(5) The concept of this guide does not permit inclusion of all firing and protection possibilities.


15.15 Typical Steam Trap Assembly


(1) A bypass is required only at heat exchange equipment in continuous service and inside buildings. The bypass is not required in line traps and tracing traps.

(2) Equipment producing condensate shall be provided with a full capacity drain.

(3) This symbol is used here as a basic symbol.

(4) Downstream drain also serves as a test connection.

15.16 Typical Instrument Purge


(1) During detailed engineering, the data for purge instrumentation shall be numbered and specified.

(2) A bleed valve is not provided in the utility line as bleed is provided at impulse line drains or displacer/LG drains.

15.17 Typical Rotating Equipment External Seal Flush and Purge


(1) Omit the FG for services other than water.

(2) During detailed engineering, number and specify the data for seal flush and purge instrumentation not supplied by the pump vendor.

(3) If an oilmist lubrication system is being used, show this with a diamond as a utility. (A utility UFD shall be prepared for this service).

(4) Various details to be combined on a UFD together with other pump piping details.

15.18 Typical Rotating Equipment Cooling System

Indicate a cooling water system detail which is to be generated during detailed engineering. Pump data sheets shall indicate API cooling plans (which may require modification during detailed engineering).


(1) Details of hook-up to be combined on a UFD with other pump piping details.


15.19 Typical Flushing Oil Connections





(1) During detailed engineering:

(a) Size all flush oil lines at 2”

(b) Size the drains above at 1”

(c) Modify the instrumentation standard hook-up to provide a drain line from the pump discharge P1 drain to the pump drain funnel in services where flush oil is provided.

(d) Various details to be combined on a UFD together with other pump piping details.


15.20 Typical Blowdown Systems (Process Waste Heat Boilers)


15.21 Typical Arrangement Level Instruments & Standpipes


A) Systems 3 and 4 preferred.

B) Systems 1 and 2, where standpipes are not considered.

C) For standpipes use separate connections, do not connect to process connections.

Where standpipes are used the following precautions shall be observed

(1) LIC and LA may be combined or separate, on one standpipe.

(2) LA and LSA may not be combined on same nozzle or standpipe.

(3) LIC and LG may not be combined. Independent check facilities to be provided.

(4) LG and LSA may be combined on one standpipe.

(5) Visible length of LG has to cover all instruments.

(6) Standpipes always have a drain, vent and isolating valve. (A general note on legend sheet shall cover this requirement, these will riot be shown on flow schemes.)

(7) If no isolating valves on standpipe each instrument to be provided with drain, vent and isolating valve.

(8) Minimum diameter of standpipe shall be 3” and the connecting nozzle to the vessel shall be 2” nominal.

Typical Instrumentation for Compressors

(1) Pre-alarm signals:

- All process pre-alarms on local, panel. Where required, also on the main panel.

- All machine alarms on local panel, with a common alarm on the main panel.

(2) Trip alarms
- All process and machine trip alarms on the local panel, with a common trip alarm on the main panel. All trips to be included in a first failure system.

(3) Local panel indication
- Suction temperature
- Suction and discharge pressure.
- For centrifugal compressor:
- flow indication.
- surge parameter indication (where applicable)

- Speed indication (where applicable).

(4) Local controls

- Speed control (hand and remote station)

- Surge control valve

- Suction throttling valve

(5) Control panel in main control room

- Surge controller )

- Speed recorder and control ) where applicable

- Suction pressure control )

- High discharge temperature alarm

(6) Hand trips

- Local trip with alarm on local pane (with common alarm on main panel).

- Main panel trip without alarm on main panel, but with alarm on local panel.

- Both alarms included in the first failure system.


Valve Type Selection

15.23.1 Select the actual valve type requirements in accordance with the piping class specifications and any other issued job specification for piping and valves.


Basic symbols shall be used as from the first (I) issue of the EFD‘s.

15.23.2 Specific valve type requirements shall be indicated on the EFD as follows:

(a) Fuel gas valves between manifolds and burners -Ball valves.

(b) main fuel shut-off — Fire Safe ball valves.

(c) Flexible wedge gate valves where tight shut off is required. Differentiate between solid wedge and flexible wedge by using appropriate symbols.

15.23.3 Remote operated valves (ROV’s) shall generally be hydraulically operated. ROV’s will be grouped and served by a combined hydraulic unit and provided with one 1imit switch to shut pump down if valve is 20% closed (Initiating switch to be mounted in a safe area.) For cost saving, pneumatic operated ROV’s may be considered with individual air bottles.

15.24 Instrumentation General Requirements

13.24.1 All process flow meters shall be provided with:

(a) A multipoint TI (downstream of the flow element).

(b) A local PI in gas and steam services only.

15.24.2 All board-mounted temperature instruments shall have a check multipoint TI. All local temperature controllers shall have a local check TI.

15.24.3 For added safety two individually connected level transmitters per equipment will be provided in the following cases:

- Level Control (panel mounted or local) and level alarm.

- Level Control, Pre-Alarm (taken from transmitter serving the control and Emergency Action/Alarm.

15.24.4 A combined nozzle for a pressure controller with backup pressure indicator is only acceptable on vessels/columns.

15.24.5 For quality measuring instruments the differential pressure across a control valve shall not generally be used for the fast loop differential pressure.

15.24.6 Thermal expansion valves and breather valves do riot require a spare position.

1.5 .25 Utility Header Valve Requirements
(shown on UFD only)

Utility/common facility branch line header valves within the Process units are not anticipated as being required and will not be indicated on the UFD. The EFD shall therefore indicate any valves in utility/common facility individual branch lines required for process and maintenance operations even if these valves may be physically located in the pipe rack or the sequence of branches may allow in the future for a single valve to serve several branch lines. Valves are not provided in utility/common facility individual branch lines to allow solely for the repair of piping failures due to mechanical breakage or corrosion.