Table of contents
- Scope
- Definition and Purpose
- Responsibility
- Data to Be Indicated on a PTP
- The PTP Development
- Distribution and Use of PTP's
1. Scope
Reference: engineering design guide BN-EG-UE002: general rules to establisch mechanical design pressure and temperature. Appendix a to BN-EG-UE002: Applicable rules in various countries.
1.1 This Engineering Design Guide shall be used for the preparation of Pressure Temperature Profiles (PTP). It is not intended as a complete guide to the interpretation of the several codes for the design of pressure vessels or of piping which apply in various countries.
1.2 This Engineering Design Guide shall be used in conjunction with the documents with establish the code and contractual criteria applicable to the design of the plant.These documents are e.g.:
- the project procedure manual with basic engineering design data (including a definition of design pressure and temperature), - applicable codes for pressure parts,
- clients standards,
- clients insurer’s requirements.
2. Definition and Purpose
2.1 A pressure Temperature Profile is a simplified flow diagram on which the various possible process operating and design conditions have been indicated.
2.2 The purpose of a PTP is:
- to serve as internal check device for use by the Process Department to verify pressures and design temperatures for each plant component (equipment and lines) are consistent and in accordance with all applicable code requirements and job specifications under all possible operation conditions during start-up, normal operation, regeneration, on-stream cleaning, planned-or emergency shut-down, malfunctioning or maloperation.
- to established or verify the location, the set-pressures and the relieving temperature of safety valves in order to ensure a safe plant design in accordance with the code requirements and job specifications under all possible conditions.
- to show, if required, to the authorities that the correct design conditions have been established and that adequate protection against overpressure or vacuum and over- temperature has been provided.
- to serve as one of the process documents used by Design Engineering in the execution of the design.
- to assist Project Engineering Department in the preparation of line designation tables.
2.3 As a rule a PTP shall be made for each process unit and complicated utility or off-site facilities for each job.Under special circumstances the Project Manager, together with the Process Supervisor and after consultation of Design Engineering, may decide to deviate from this general rule depending on type of unit, type of contract, Company’s scope of work, etc.
Such a decision shall be laid down in the Project Procedure Manual
3. Responsibility
The Process Engineer is responsible that the data on the PTP correspond with data given on the latest issue of the process data sheets (as governing for Design Engineering); with operating requirements; with Client’s requirements etc.
The Process Supervisor shall have the overall responsibility for consistency and compliance with the job and code requirements.
4. Data to Be Indicated on a PTP
4.1 Process conditions which should correspond to those indicated on Process Flow Diagrams, process data sheets etc.:
- Operating pressures (for different operation cycles if any).
- Operating temperatures (for different operation cycles if any).
- Density (Dens.) (where necessary).
- Pressure drop (D P) over equipment, lines, control valves (where necessary).
- Normal differential pump heads.
4.2 Mechanical design conditions which should correspond to those indicated on process floe diagrams, process data sheets, etc.:
- Design pressures. (Top/Bottom on towers and vertical vessels).
- Design temperatures. (Top/Bottom if applicable).
- Max. differential pump head.
- Relief valve set pressures.
- Max. relieving temperatures.
- Liquid level elevations (LLL, NLL, HLL).
- Hold-up time in minutes between HLL - LLL; with an indication on which stream it is based.
| Note 1: | For definitions, abbreviations, units and the calculation of design pressures and temperatures, reference is made to the engineering design guide BN-EG-UE002, “General rules to establish mechanical design pressures and temperatures”. |
| Note 2: | If not yet available a max. pump differential head of 1.2 x normal differential head shall be used for Electric motor driven pumps. In case of turbine driven pumps, it should be noted that due to high trip speeds the maximum pump differential head can be substantially higher. Here a number of 1.45 x normal differential head can be used as guide. |
| Note 3: | The max. pump shut-off heads shall be rounded off to the next higher 0.1 bar for pressures under 10 bar g and to 0.5 bar for pressures higher than 10 bar g. |
5. The PTP Development
5.1 The PTP shall be made by the process engineer assigned to the subject unit(s).
5.2 The format of the PTP shall be determined for each job. The PTP shall show all pressure equipment, main lines, all valves which might affect the design conditions of equipment or lines, and all safety valves. If too complicated, a separate PTP has to be made for separate operation cases. For instance, a reactor unit might have two different cases: the normal process conditions and the catalyst regeneration conditions. Another example is the heat exchanger train in a crude unit. The definition of system and operation cycles which require separate PTP’s is to be established by the process engineer.
5.3 Within 1 month after job start in Design Engineering, the PTP shall be issued with data as available at that time. Regular updatings must be initiated by the Process Engineer at least at (but not limited to) the following job milestones:
- Upon completion of the major equipment process data sheets and with assumed maximum pump differential heads. This issue shall carry as issue description “Certified for mechanical design”.
- Upon completion of the pump calculations.
- Upon receipt of pump curves from vendors.
- Upon changes in the project affecting the design conditions of equipment, piping etc.
5.4 The Process Engineer shall advise the Project Manager immediately when PTP’s released for Mechanical Design have to be revised.The Project Manager shall then decide, pending the nature of the changes, whether the design work shall be stopped or not. A listing of revisions shall be attached to each issue or the PTP. As an alternate, revisions may be circled.
6. Distribution and Use of PTP’s
6.1 The PTP’s (originals) shall be forwarded to the Project Manager, who shall make the distribution as follows:
- Process Engineer (print plus original)
- Project Engineer
- Instrument Engineer
- Piping Engineer
- Authority Engineer
- Mechanical Engineer
6.2 The Project Engineer checks if the valve shown are in agreement with the EFD’s and used the PTP to fill out the line designation tables.
The Instrument Engineer uses the PTP as one of his sources to fill out the instrument data sheets.
The Piping Engineer uses the PTP to determine pipe classes and as source for data on which stress and flexibility calculations are based.
The Authority Engineer checks compliance with code requirements and uses the PTP for presentation with code Authorities (only when the Authorities require this) and to fill out classification lists (if required by Authorities).
The Mechanical Engineer checks if the actual max. pump differential head is within the estimated max. differential pump head indicated on the PTP. If any of the users has comments on the PTP, he shall direct such comments to the Process Engineer who will incorporate the comments on the PTP diagram.