Table of Contents
1. General
2. Mechanical Design
3. Instrument Piping
4. Electrical Systems
5. Earthing
Symbol Explanation
o Feature required
o Feature not required
o Vendor to advise
1. General
1.1 Scope
This general specifications modified by the requisition and drawings, specifies the requirements for the design, construction, installation and testing of shop fabricated instrument panels, consoles, desks, racks, etc. in this specification referred to as “panel”.
The panel fabricator shall complete the design package provided by the purchaser and shall supply a panel ready for installation at the site.
Type of panel, quantities and scope details are covered by the applicable requisitions.
1.2 Applicable Conditions and Regulations
1.2.1 The installation shall be in accordance with the following basic codes and all other related documents.
o Local codes applicable at plant site
o (Germany) VDE 0100
o (UK) IEE wiring regulation
o (USA) NEC
o ....
1.2.2 Panels installed in a hazardous area shall be in accordance with:
o European standard (Cenelec) EN 50014 with supplements or related national standards as applicable in country of installation
o (Germany) EXVO regulations including VDE-0105/0165/0171
o (UK) BS 4683, 5345
o (USA) NEC, NFPA, FM, UL and ISA (RP 12) documents.
o ....
1.2.3 Where required by local codes vendor to supply installation certificates to confirm compliance with regulations.
1.2.4 The construction methods, painting and materials supplied shall be suitable for use in:
o Petrochemical and refinery atmosphere ambient temperature -25 to 55°C Relative humidity 5-90%
o Coastal conditions
o Tropical climate (intensive solar radiation, high humidity).
Control room installed equipment shall be suitable for use in industrial areas with an ambient temperature of 5 to 40°C, relative humidity 75%.
1.3 Conflicting Requirements
In case of contradiction between this specification and any of the documents referred to in the requisition or purchase order, the Purchaser shall be consulted for a ruling in writing.
1.4 Procurement and Storage of Material
1.4.1 Material and equipment to be furnished by vendor, shall be procured in time by his own purchasing services. The makes and model numbers if specified in the requisition, are preferred.
Alternate makes or model numbers are subject to purchaser’s approval.
1.4.2 Material and equipment furnished by the purchaser shall be stored by the panel manufacturer. Manufacturer shall be responsible that it will not be damaged or lost during storage.
Instrument accessories such as charts, ink, spares, instruction manuals and warning stickers shall be delivered to purchaser in good order.
Shipping clamps shall be left in place or reused for shipment.
The vendor shall inform purchaser in time of any shortage or damage of this material. Vendor to indicate latest acceptable delivery consistent with panel construction completion.
Material furnished by purchaser will be specified in the requisition.
1.4.3 Material supplied by panel manufacturer as extra (loose) items, are to be properly packed for transport and secured to panel.
To facilitate identification in the field, vendor to provide for adequate item descriptions.
1.5 Panel Installation at Site
When panel installation is included in vendors scope (see requistion) the following services shall be provided:
- Erection of panels, and other equipment in his scope, on the panel base in the control room, using his own unloading equipment and tools
- Installation of filler plates, doors etc. and lining-up of panel sections
- Supply and erection of interconnecting cable tray/trunking at back of panel
- Reinstallation of all temporary disconnected wiring, tubing and headers
- Touch-up of damaged paint work.
Vendor has to meet following site requirements:
- Site rules and safety regulation for sub concontractors
- Terms and conditions applicable to field labour.
1.6 Drawings
1.6.1 Approval of Construction Drawings
Using purchaser’s drawings as a guide, vendor shall prepare detailed construction drawings for approval showing:
- Sections of panels complete with supporting strips, cable ducting, doors, and terminal arrangements
- Layouts of sections not detailed by the purchaser, such as mounting plates
- Air connection and piping layout details.
1.6.2 Photographs
At time of shipment of panel, vendor shall photograph both front and back of panel and forward (2) prints of each view.
1.6.3 Literature
Vendor shall provide specification sheets of all components procured via his own services.
1.6.4 Job Progress Reports
During the first week of each second month after receipt of order vendor shall furnish the following job progress information:
- List of vendor drawings with status
- Procurement status of materials
- Updated fabrication schedule.
1.7 Nameplates
1.7.1 Nameplates to be provided for each device on the panel front except for instruments having an integral nameplate.
1.7.2 Instruments, switches, fuses, sockets, isolating valves, bulkhead unions, etc. mounted in the panels shall be identified behind the panel by permanent tags, attached to the rears of the cases and marked with tagnumber or identifying letters only.
1.7.3 Name and tag plates shall be laminated plastic black with white lettering.
Dimensions and engraving of nameplates on the front of the panel shall be in accordance with the nameplate schedule provided by the purchaser.
1.7.4 Nameplates on the front of the panel be fixed with double side sticking tape. Tagplates behind the panel shall be fixed with screws.
1.8 Testing and Inspection
1.8.1 Complete testing of pneumatic and electrical systems shall be performed by vendor following the completion of panel.
When testing is completed, vendor, shall notify purchaser and offer panel for inspection at vendor’s work shop. Vendor shall have available the required test equipment to perform acceptance tests.
1.8.2 Following tests/checks shall be carried out prior to delivery:
- Completion check against drawings
- Continuity check of all electrical circuits
- All wiring to be tested for short circuits and grounds. Insulation resistance shall be at least two (2) megohms at 500 volts DC
Sensitive electronic circuitry shall be protected from damage
- The panel to be inspected to ensure that connections to earth have been made in accordance with the requirements
- Labels to be inspected to ensure that these are installed, legible and comply with the requirements
- Leak testing of air tubing and piping, as per ISA RP 7.1
- Heat/soak test (only when specified)
The equipment is to be subjected to a test during 48 hours in fully operational conditions under an ambient temperature of 40°C.
Temperature record of the test period to be provided. Vendor shall agree in writing to this test and support it with full warranty for any subsequent failure
- Functional test (only when specified)
The complete functional performance to be verified by an operating test
Test set-up and procedure must enable the inspector to simulate the inputs, verify the status of the outputs and observe system performance. Any restrictions have to be clearly indicated in vendors quotation
- Integrated systems, making use of solid state components, shall receive a burn-in period of minimum two weeks with all loads energized.
2. Mechanical Design
2.1 General
2.1.1 The panel is to be of dimensions, shape and construction as per applicable design drawings.
A tolerance of plus or minus 4 mm is allowed in the width of the individual panel section. Tolerances are to be compensated, so that the overall tolerance of the complete panel does not exceed plus or minus 8 mm.
For panel height, a tolerance of plus or minus 8 mm is allowed when deviation is the same for all sections.
2.1.2 Panels shall be fabricated from steel plate stiffened as necessary to support instruments and other devices.
The steel plate shall be flat within a tolerance of 3 mm in 2.5 meters of length.
There shall be no bend or slope on the plate greater than 1 mm in 0.5 meters.
Panel must be flat, free from surface flaws and blemishes before finishing.
2.1.3 The panel plates shall conform to the following requirements:
Quality
Indoor panels :
o Cold rolled, stretcher leveled steel
Outdoor panels :
o As for indoor
o Galvanized
o Stainless steel
o ....
Thickness
Panel fronts :
o 4 mm
Other plates :
o 2.5 mm (minimum)
o ....
2.1.4 Panel sections shall be made self-supporting by a box-like frame work and be designed so as to permit bolting together into a composite panel in the field. Adjacent sections shall assemble flush with return type joints as per panel drawing, or hairline type joints where required.
The top and end corners at the front shall be ground off to provide a smooth radius.
Control panel will be bolted to a panel base which will be supplied by others.
Front and rear base frame to be 100 mm wide so that panel may overlap the panel base 50 mm front and rear.
2.1.5 Frame work shall be suitable for support of front plate mounted instruments, cabling, trunking and other devices which must be installed in the panel.
Reinforcing ribs shall be welded to the back of the front plate in any location where cut-outs may weaken the plate excessively.
2.1.6 Suitable mounting plates, clips and supports shall be installed for back of panel mounted equipment. Dimensions shall be determined by panel manufacturer.
2.1.7 Cut-outs shall be machine-cut in accordance with purchasers drawings. Flame cutting is not permitted.
The panel manufacturer shall check that the dimensions are true to the shape.
When spare cut-outs are specified, a blanking plate shall be provided.
2.1.8 Design drawings will state the entry location of incoming field cabling and/or tubing.
Provisions for cable clamping will be made by purchaser outside the panel unless otherwise specified.
2.1.9 Panel doors shall be fitted with gaskets, a lockable espagnolet type closure and heavy duty hinges permitting complete removal of doors, etc. during installation.
Doors shall have a cylinder lock with identical replaceable cylinders (Lips Euro-format or equal) and key.
For smaller doors, alternative means may be selected with fixed lock construction.
For panels with a width of 700 mm one door is acceptable, for wider enclosures two doors shall be provided.
2.1.10 All devices installed back of panel or on the panel front shall be easy accessible and protected from accidential operation.
2.1.11 Vendor is to supply all nuts and bolts to secure panels to each other and to the panel base.
2.1.12 Removable eye bolts for transport shall be fitted to all panels. Wall mounted panels shall have mounting lugs.
2.1.13 The maximum temperature rise inside panel enclosures shall not exceed 15°C above ambient, proper functioning of equipment however shall be warranted.
2.1.14 In tropical/subtropical climates, outdoor panels shall be provided with sunshades to prevent exposure to direct sunshine (refer drawings).
2.1.15 The width of panel sections, as shipped, shall not exceed 3.00 meters
Each separate section shall have a complete, self-supporting frame work.
2.1.16 Exact dimensions for critical closing filler plates will be determined after installation of the panel.
2.1.17 The panel shall be supplied with an adequate number of any special tools e. g. for mounting and/or removal of lamp, switches or special covers etc.
2.2 Painting
2.2.1 Surface Preparation
All grease, oil and foreign particles are to be removed before painting.
The edges and exterior surfaces shall be free of rust, scale, burrs, sharp edges, deep scratches, weld and tooling marks or any other imperfections.
Possible deep marks in front of panel, which cannot be sanded-out shall be filled with a suitable compound. The quality of surface preparation shall be in accordance with the methods described in the Swedish Standard SIS 055900 gritblasting to Sa 2 1/2 (near white).
Blast cleaning shall not be used on thin plates when deformation can be expected, phosphating shall be considered as an alternative.
The abrasive used shall be such as to produce a maximum roughness of 25 microns.
2.2.2 Application
Paints and other materials shall be applied in accordance with manufacturers instructions. Vendor shall be responsible for the application of the correct painting system and shall submit full details of his painting practice.
Painting system shall provide a scratch free surface and withstand high impact loads.
2.2.3 Painting System
The painting system shall be:
Indoor panels:
o Conventional four coat system
o Manufacturers standard
Outdoor panels:
o As for indoor panel
o Two-component Polyurethane
The four coat painting system, if specified, shall consists of :
- Two coats anti corrosive primer
- One under coat
- One finish paint, oil resistant.
The dry-film thickness of each coast shall not be less than 30 microns with a total of 125 microns for the four coat system.
In the event that total dry-film thickness has not been obtained, an additional coat shall be applied.
Finish paint to be semi-gloss with a low reflectance factor.
Manufacturer shall provide 2 kg of spare paint for each colour.
2.2.4 Colour Schedule
Control room panels : ....
Panel exterior :....
Interior : white.
Auxiliary panels installed back of panel or in the basement :
Panel exterior : ....
Interior : white.
System cabinets :
o As for auxiliary panels
o MFR standard
Outdoor panels : ....
Panel exterior : ....
Interior : ....
2.3 Conventional Panels
2.3.1 Conventional panels consist of free standing panel sections with instruments mounted in horizontal and vertical rows on a vertical flat faced or inclined panel front.
2.3.2 Miniature instruments are mounted a maximum of four positions high.
The top instrument row shall not exceed an elevation of 1650 mm whereas switches shall not be installed below 650 mm.
2.3.3 The top section above the instruments shall be available for the display of alarm indicators or semigraphic sections.
2.3.4 Conventional panels shall have an open rear frame with hinges for future installation of rear panel doors, unless otherwise specified
2.3.5 Panel sections to be open at the bottom. Roof and side panels shall be removable.
2.4 Consoles
2.4.1 The consoles type panel shall have a free standing enclosure incorporating a desk or bench board section for mounting of keyboards, instruments and manually operated switches, etc.
2.4.2 The bench board section (sloping area on the front of the console ) shall be designed for use by operators in a seated position.
2.4.3 Consoles with desk sections shall be designed for use in seated position and incorporate a writing space.
2.4.4 Console type panels to be fitted with rear panel doors, removable front panels underneath the desk section, removable side panels and have an open frame work at the bottom.
2.5 Desks
2.5.1 The construction of control desks shall be similar to office type desks and be designed for use by one operator.
Sufficient leg clearance (650 mm minimum) shall be provided.
Color schedule shall be as follows:
Frame :
o As for main panel
o Manufacturers standard
Writing space :
o Dark grey
o Manufacturers standard
2.5.2 When the desk is used as an operating terminal for centralized control or display systems, provisions have to be incorporated to install terminals, route and support of system cables and integrated electronic subsystems.
To accomplish this, separate extension wings may be added (refer drawings).
Display and selection terminals shall not obstruct operator view on the main panel.
2.6 Semigraphic Sections
2.6.1 Semigraphic sections shall be executed on a separate base plate.
The base plate shall be fastened machanically to the panel board in a neat fashion.
2.6.2 Construction of semigraphic section shall be as follows:
o Raised symbols, plastic faced, Plastic base plate with cemented plastic symbols.
o Flat front symbols, photoprint on aluminium base plate.
Alternative methods to be approved by purchaser.
All inscriptions shall be engraved directly on symbols or base plate and filled with contrasting colours. When cementing plastic symbols to a plastic base an adhesive shall be used which can be loosened by a special solvent.
2.6.3 Symbol dimensions and colours are to be in accordance with the applicable drawings.
2.6.4 The drawings are to be used for guidance only.
Vendor shall prepare his own detailed fabrication drawings with all relevant details.
2.6.5 General guide lines for the design of the semigraphic sections are as follows:
- Panels mounted instruments and temperature indicator points will be shown by instruments symbols with tag number
- Local instruments will be shown only where they are necessary for understanding the process
- Alarm functions be shown as:
o Blind symbol with alarm window display on conventional panel
o Back lighted symbols for process alarms with window display for alarms not associated with the process.
- Semigraphic sections will be installed above the associated instrumentation for that unit.
2.7 Mosaic Panels
2.7.1 Mosaic panels shall consist of a conventional panel frame with building block type panel front.
Building block dimensions :
o 48 x 48 mm
o Manufacturers standard
Mosaic Material :
o Aluminium
o Plastic
o Manufacturers standard.
2.7.2 The mosaic panel front to be self-supporting requiring fixing to the steel panel frame at the sides only.
2.7.3 Lines and symbols to be engraved in the tiles and filled with a constrasting colour.
Colour schedule to be in accordance with the applicable drawings.
2.7.4 Back lighted signal lights to have a coloured translucent insert.
All devices installed in the mosaic panel front to be connected to rearrangement terminal blocks at the back of panel.
Cables to be sufficiently long to allow for possible mosaic panel front rearrangements after start-up.
2.8 Cabinets and Racks
2.8.1 Cabinets shall have a self-supporting frame with sheet steel panels.
The rack construction normally consists of a freestanding construction steel box like frame with open bottom.
Wall-mounted cabinets (box) shall have front doors only.
2.8.2 Cabinets shall have provisions to install front and back doors. In general, electrical equipment shall be accessible from the front and internal wiring and terminations from the back side.
2.8.3 When specified, the electrical equipment shall be mounted on a swing-out rack allowing free access to all terminations.
Swing-out racks shall be of heavy duty construction adequate for the weight of installed equipment without risk for distortion and fitted with detachable hinges.
In closed position the rack weight shall be relieved from the hinges by additional supports.
Swing-out racks shall open at least 90 degrees.
2.8.4 The side panels shall not be used for ventilation openings or cable entries, unless asked for by the drawings.
2.8.5 Multiple racks shall be of uniform modular construction with identical dimensions allowing the installation of mounting plates, etc. on either side. Racks will be bolted to a steel panel base provided by others.
2.8.6 Cabinet/rack internals shall not be attached to walls but be mounted on removable mounting plates.
2.8.7 Cabinets with internal heat dissipation to have ventilation louvers with dust filters in the top plate or door.
2.8.8 System cabinets may be of manufacturers standard constructions and dimensions. The following dimensions, however are preferred (approximately) 2000 mm high, 600 mm wide and 600 mm deep.
2.8.9 Cabinet doors shall be provided with a plastic map(s) for the safe keeping of drawings, and system documentation
2.9 Local Panels
2.9.1 Enclosed local panels shall be of a self-supporting sheet steel cubicle construction with door(s) and internal lighting fixture.
2.9.2 Gauge board type local panels will consist of a flat panel plate supported by construction steel. Electric terminations, if any, to be housed in a suitable junction box.
2.9.3 Outdoor local panels shall have airtight and weather proof gasketed doors and a rain canopy with provisions to install a lighting fixture (by others).
2.9.4 Process fluids shall not be piped to (enclosed) instrument cubicles containing electric circuits.
2.9.5 The location of the local panels, usually not in a safe area, shall be taken into consideration when selecting electrical equipment.
2.9.6 When purging is required to assure protection of electrically operated devices in hazardous areas, preference is given to the purging of individual instrument enclosures above the purging of the complete cubicle.
When individual purging of enclosures is applied or when other means of protection have been utilized, the cubicle is to be provided with louvre openings for adequate natural draft ventilation.
3. Instrument Piping
3.1 Air Headers
3.1.1 The air supply lines to panel mounted instruments shall be from a 2 inch nominal low pressure brass, hard tempered air header. Where possible, the main air header will be routed on top or underneath the panel sections.
Instrument take-offs shall be connected to subheaders, installed within the panel section, via isolating valves fitted to 1/4 inch brazed nipples. Subheaders shall be 1 inch nominal (minimum). Supply lines to the individual instruments shall be taken from the top or side of the subheader.
The isolating valves shall be:
o Diaphragm type valves with aluminium body and neoprene diaphragm
o Self-sealing quick disconnectors, connections to be 1/4 inch NPT female.
3.1.2 Where the main air header can not be routed outside the panel the header may be installed inside the panel.
3.1.3 Spare take-off points with isolating valve shall be provided for each spare cut-out and an additional 5% per panel section
Spare panel sections shall be supplied with subairheader complete with isolating valves. The number of take-off points shall be determined with respect to the theoretical number of cut-outs.
3.1.4 The air header shall be sufficiently supported and clamped. An expension joint shall be installed in the air header for long panels to facilitate lining-up.
A blind flange to be provided at the end of the main air header.
Interconnections between the main header and the subheader shall be made by flexible hoses.
Branches from the main air header shall be flanged. Drain valves, 1/4 inch, shall be installed at low points and at the end of each header.
The main air header shall have flanged connections at the points where the panel is to be separated for transport.
3.2 Instrument Air Piping
3.2.1 All pneumatic tubing in the control panel shall be:
|
Pneumatic Tubing |
: |
o |
High density polyethylene tubing. ASTM-D-1248 type III, gr. 5, class C. |
| o |
Copper tubing as per ASTM-B 68, soft annealed. |
||
|
Size |
: |
o |
1/4” OD |
| o |
6 mm OD |
||
|
Colour |
: |
o |
Black |
| o |
Colour scheme as per ISA RP 7.2” "colour code for panel tubing”. |
3.2.2 All pneumatic tubing inside the panel shall be supported and routed in plastic trunking.
Where the use of trunking is not appropriate, bundles of tubing may be laced to rigid pipes or structural members by plastic straps. Tubing shall not be routed behind instruments or spare cut-outs.
All trunking to have adequate size allowing for 40% expansion.
3.2.3 Tubing shall be installed with sufficient slack to prevent bending with too small a radius. Elbow connectors shall be used to connect tubing to instruments.
3.2.4 All pneumatic tubing shall be coded at instrument connections and bulkheads using adhesive tags or plastic ferrules.
3.2.5 Pneumatic lines, leaving or entering the panel sections, shall terminate in bulkhead or clip-on fittings.
Bulkhead fittings to accept following type of tubing from field:
|
Type |
: |
o |
Polyethylene |
| o |
Copper |
||
|
Size |
: |
o |
6 mm OD |
| o |
1/4{“ NPT OD |
3.2.6 The arrangement of bulkhead fitting shall be in accordance with drawings.
Vendor to provide two spare bulkhead fittings for each spare cut-out and three additional spare bulkhead fittings per section.
Spare sections without cut-outs or instruments shall have bulkhead plate fitted and drilled, but no bulkhead fittings to be provided.
3.3 Process Piping
3.3.1 Instrument lead lines in prefabricated gauge board type local panels shall be in accordance with the process piping hook-up details.
Material shall be selected consistent with temperature, pressure, and corrosion requirements.
Standard material for instrument process piping inside local panels up to 125 barg will be:
o Type 316 stainless steel tubing 12 mm OD X 10 mm with compression type tube fitting.
4. Electrical Systems
4.1 Power Supplies
4.1.1 There shall be a power distribution system per section, cabinet or rack to distribute power to the various instruments mounted in that section.
4.1.2 Each instrument shall have an individual disconnect switch.
4.1.3 All circuits shall be provide with fuses or magnetic circuit breakers as specified, rayed such that a selective protection is ensured.
4.1.4 Commom DC power supply systems shall not supply more than one rack or 12 users per circuit disconnect switch.
DC power supply circuits shall have enough terminals or facilitate a plug-in (bus bar) system so that one device may be disconnected without interrupting the power to the other devices.
4.2 Wiring Methods
4.2.1 All wiring within the panel shall be run in plastic wire ways with break-out openings and covering lid, trunking or conduits.
Open wiring, splicing of wires and terminal strips in wire ways shall not be accepted.
Wire ways shall be located so that they will not interfere with the access to any equipment.
Where trunking is not practical, the use of open bundles is permitted provided that adequate mechanical protection is available.
Armoured cable and heavy field cables, shall be routed on cable trays.
Vendor shall include sufficient space in conduits, trunking and ducts to allow for a 40% expansion or at least rated for a maximum of 80% filling when all engineered spare positions have been wire.
4.2.2 The following wiring shall be kept separate:
- AC power wiring exceeding 48 Volt, 3 Watt
- Electronic signal wiring including DC power supply and annuciator wiring
- Thermocouple and computer signal wiring
- Intrinsically safe wiring
Trays, ducting, wiring and terminal blocks for different voltages shall be separated by at least 50 mm and also be clearly identified.
4.2.3 All external wiring to panels shall be connected to terminals with a bank of terminals or multipin socket(s) assigned to each cable.
Interconnection wiring between shipped panel sections and auxiliary panels shall be brought to terminal strips.
Terminal rows shall have adequate spacing for easy connecting of cables. There shall be sufficient room left for spreading multicore cables.
A minimum distance of 30 mm between terminals and ducting shall be observed.
4.2.4 Vendor to install at least 10% spare terminals for each service or that spare quantity as required by wiring diagrams, whichever is greater.
Spare wiring shall be terminated on terminals up to a quantity of 30% overall spare. Above 30% the drawing may indicate that spare wiring shall be bundled and left in the trunking.
4.2.5 Terminations of internal panel wiring shall be screwed. Alternative means such as soldering, crimping and wire wrapping may only be considered for low power circuits in pre-wired and factory tested system cabinets.
No more than one wire shall be connected to a single terminal.
Wiring may be looped by the use of linked terminals or by joining two wires in a suitable crimp connector at a termination point.
Wiring connected to terminals, switches, instruments etc. shall have adequate slack but minimum 50 mm.
All flexible stranded wire ends shall be terminated in “insulated” type crimp connectors, make AMP or Burndy.
4.2.6 All panel wiring shall be number-coded at all terminals using adhesive tags or plastic ferrules in accordance with the typical numbering system. Terminal blocks shall have terminal numbering as specified.
Wire identification tags shall be:
o Weidmüller or approved equal.
o ....
4.2.7 All exposed terminals with live voltage over 24 volts shall be enclosed for personnel protection.
4.2.8 Cable entry to the equipment shall minimize the risk of damage. If the cable enters through a hole a grommet or cable gland shall be fitted. The cable to be firmly fixed at its point of entry to prevent stress on the conductors
Cable glands in general shall be applied where a firm mechanical grip on the cable is required. Rubber grommets may be used in the control room to achieve a dust tight cable entry.
All entries made in the roof sheet of panels shall be dust sealed.
Unusually shaped cable bundles or plug coupled cabling may be dust sealed by properly cut rubber flaps pr specially designed brushes.
Cable glands are not required for cables entering panels via false floors (open bottom frames).
4.2.9 Wiring for panels installed in hazardous areas shall be in accordance with the local codes.
Particular attention shoud be given to:
a. The use of approved flame proof cable glands when connecting cables to flame proof housings
b. The use of increased safety, spring loaded terminals when connecting wiring to electrical equipment of the nonsparking design
c. Segregation of instrinsically safe wiring.
4.2.10 Wiring shall be connected to spring loaded terminal blocks of the clip-on type suitable for DIN-46277 channel mounting. Following types or equivalents shall be selected:
General applications:
o Weidmüller SAKD 2.5N PA, flexible polyamide, width 5 mm
Hazardous areas:
o Weidmüller SAK 2.5 Ex(e) width 6 mm
Instrinsically safe signals:
o Weidmüller SAKD 2.5N PA blue.
Terminals to be suitable for solid/flexible wiring of 0.5-2.5 sq. mm. Where appropriate, special purpose terminals such as knife-type, test, fuse, resistor and diode terminals shall be used.
4.3 Wiring for Relay and Power Supply Systems
4.3.1 Panels wiring shall be minimum 250 volts grade suitable for voltage and climate conditions.
Cross section shall be determined by the current conducting capacity, or be as specified on the design drawings but minimum:
o 1 1/2 sq. mm for mains operated devices
o 1 sq mm for other services.
Conductor type : Flexible, stranded copper, PVC insulated.
Colour code : Mains (phase, neutral ground) and DC power supply (plus, minus) wiring shall be colour coded as per local standards.
All other wiring shall be black.
If permitted by local standards, following is preferred:
|
Mains |
: |
brown, blue, green/yellow |
|
DC |
: |
red, green. |
4.3.2 Live termination points of electrical devices operated above 50 volts such as push buttons, switches etc. shall be preotected by a plastic cover.
Instruments of so called free issue to manufacturer shall be checked for adequate protection.
4.4 Signal Wiring (24 volts, 3 watt)
4.4.1 For signal wiring, following cable/wiring shall be used:
|
Grade |
: |
250 volts nominal |
||
|
Conductors |
: |
0.75 sq.mm strand thinned copper |
||
|
Insulation |
: |
(70ºC PVC |
||
|
Colour code |
: |
Single core Two core Tripe core Quad Interinstrincally safe |
: : : : : |
black black/white black/white/red black/white/red/blue blue or blue jacket. |
|
Shield (if required) |
: |
Metalized tape with 1.0 mm solid thinned copper drain wire. |
||
|
Twisting (if required) |
: |
Lay of twist approximately 50 mm. |
||
|
Outer jacket |
: |
For multi conductor cable : black PVC |
||
Execution
|
General purpose |
: |
Single core |
|
Alarm wiring |
: |
Single core |
|
Electronic wiring |
: |
Twisted pairs |
|
Resistance elements |
: |
Twisted triples/quads |
|
Thermocouple wiring |
: |
Twisted pairs with pair shield and overall jackets |
|
Digital signal wiring (low level) |
: |
Twisted pairs with pair shield and overall jacket |
|
Plus/frequency signals |
: |
Twisted pairs with pair shield and overall jacket |
5. Earthing
5.1 Safety Earthing
5.1.1 All electric devices shall be mounted in such a way that positive earthing is assured by metal to metal contact to the panel.
5.1.2 Panel sections and doors shall be electrically bonded by a flexible copper strap.
Each panel section shall be provided with a M 8 earthing bolt for the connection of an external earthing conductor.
5.1.3 Mains operated equipment shall be connected to a 6 mm x 20 mm minimum, soft copper bar by means of earthing wires.
Provisions shall be made to connect armouring or lead sheating of field cables to a isolated soft copper bar.
5.1.4 All earth connectors should be protected against corrosion and shall have a very low resistance to earth.
5.1.5 Shunt diode safety barriers shall be connected to the safety earthing system.
5.1.6 Where earth connections are necessary to preserve the integrity of an intrinsically safe system, a high integrity earth system shall be provided.
The impedance from the point of connection to the system earth points shall be less than 1 Ohm.
The conductor used for the connection shall be of 4 mm2 minimum cross sectional area.
5.2 Shielding
5.2.1 Shielding for electronic systems shall be earthed to obtain the maximum possible rejection of interference.
5.2.2 The earthing shall be such that multiple ground loops do not occur.
5.2.3 For electronic system a separate earthing star point, close to the control room, will be provided by others. The distance between the electronic system earthing electrodes and (any) plant earthing electrode will be at least five (5) meters.
Resistance to earth of the electronic system earthing electrode will be less than 2 ohms.
5.2.4 To avoid any other path to earth the electronic earthing system inside the system panels shall not make galvanic contact with the building structure, steel frames, etc.
The insulation resistance shall be at least 10 megohm.
5.2.5 All cable screens shall be earthed at one point only. Screening shall be electrically continuous.
A separate terminal shall be provided to maintain screen continuity.
5.2.6 Each panel, containing electronic circuitry, shall have an isolated earth bar.
5.2.7 Single cable armouring shall be kept isolated from the screens.