PETRONAS TECHNICAL STANDARDS DESIGN AND ENGINEERING PRACTICE
INSTRUMENT SIGNAL LINES
PTS 32.37.20.10 SEPTEMBER 2008
© 2010 PETROLIAM NASIONAL BERHAD (PETRONAS) All rights reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the permission of the copyright owner
PTS Circular 2009 - 001 PTS No: Publication Title: Base PTS Version:
32.37.20.10 Instrument Signal Lines
This revision of PTS 32.37.20.10 - Instrument Signal Lines has been updated incorporating PETRONAS Lessons Learnt, Best Practice and new information issued by relevant industry code and standards. All updates in the document are highlighted in italic font.
The previous version of this PTS will be removed from PTS binder/ e-repository from herein onwards.
Document Approval
Revision History Date Version
Description of Updates
Author
Summary of Changes Section Standards 2.1
Description of Changes “MESC” standards remove and replaced with other International Standards and/or PTS standard whichever deemed relevant Additional clause added as follows: “The selection of instrument signal cables shall be governed by the specific electrical application and by the areas through which the cable is to run. The physical construction of the cable shall be dependent upon the electrical application, the intended service and the type of signals. The locality in which the cable is installed determines whether armouring is necessary and what resistance to environmental elements is required. Locality can also dictate the fire performance of materials used for insulation and sheathing since the acceptability of smoke and toxic gas emission during fire depends on ventilation and accessibility of areas concerned and on the normal manning levels in these areas. However, it is important to note that in all locations, resistance to fire propagation by cable material is of paramount importance. Hence, the minimum requirement for all cables for normal service shall be of reduced flame propagation type conforming to IEC-332 part 3 cat. A. Cables for vital services (where service must be maintained during or after exposure to fire condition) shall be of fire-resistant type conforming to IEC-331.”
2.2 Fundamental Requirements
New clauses and written as follows: “All cables used shall be minimum flame retardant. Fire resistant cables shall be used whenever required. All cable insulation, filler and sheathing material must add a minimum of fuel to any fire. Mud resistant cables shall be used where cables are routed into or through areas exposed to mud/oil. Material used in cables for manned or confined areas e.g. accommodation should produce minimum levels of smoke and acid gas under fire conditions. Installation of cables in hazardous areas must conform to BS 5345 and BS 5501. All field cables shall be armoured. Braided armour is preferred to single wire armour where there is an option since it is lighter, more flexible and easier to install. However for trench and underground cables, single wire armour shall be used. (Note: Braided and single wire armoured cables require different types of cable glands) The capacitance, inductance and L/R ratio must not exceed certain values for intrinsically safe circuits depending on the hazardous area classification and equipment parameters. Reference should be made to the equipment hazardous area certification. Cables for switched signals (e.g. alarm and indication) should be twisted multi-core type whereas cable for analogue signals should be twisted multi-pair with overall screen and drain wire.
Section
Description of Changes Multicore cables with collective screen shall be standard, individual screens shall be used only when required. Cable without armour may be used in indoor installation 2.2.1
Cable Specifications - Normal Service Selection of electrical signal cables for control and monitoring shall take account of service, environment and circuit conditions. Mineral Insulated (Ml) cables shall only be used on those applications where cables are permanently exposed to intense heat e.g. flare tip thermocouples (Exception to PTS 33.64.10.10 Electrical Engineering Guidelines). In all locations, resistance to fire propagation by cable material is of paramount importance. Hence the minimum requirement for all cables for normal service shall be of reduced flame propagation-type conforming to IEC-332 part 3 cat. A.
2.2.2
Cable Specifications - Emergency Service On all applications where an instrument connection or signal must be maintained for a limited period during or after exposure to a condition, the design shall specify fire-resistant cables (other than MI cables) which conform to IEC 331.”
2.3
Additional clause as follows: “The following systems shall have separate multicore cables: -
Table 1, 2, 3, 4, 5, 6, 7 3.1
General instrumentation. Fire and Gas. ESD. Telecommunication. DCS. Foundation Fieldbus. General Electrical (control) Powered Outputs”
New table - Incorporate and revised from 20.078. Added new clause as follows “Multi-core cables between junction boxes and control rooms shall be laid without splices. Cables entering junction boxes, consoles, cross panels or the like, shall be fastened by means of a cable gland, suitably sized and classified for the area of operation. The design shall incorporate right of way and cable channeling for instrument and electrical signal cables. Instrument signal cables, shall be separated at a distance of at least 0.3 m from electric power cables when laid underground in cable trenches, or be on separate channels with metal separation when laid above ground.
Section
Description of Changes Routing of cables shall take account of any risk of damage or deterioration due to high temperature lines, corrosive fluids, hydrocarbons or radiation (including UV radiation from direct sunlight). In any process-connected instrument where rupture of the sensing element may subject the instrument case to process pressure and where the cable used has interstices which would permit the migration of gas or liquid to a control room, a "Barrier Type" gland with sealing compound shall be specified. All cables for intrinsically-safe circuits must consist of groups of conductors twisted for each independent circuit with screen and drain wires over the cable as a whole. The capacitance, inductance and L/R ratio must not exceed values for intrinsically-safe circuits, depending on the hazardous area classification and equipment parameters. Reference should be made to the equipment hazardous area certification.”
3.2
Added new clause as follows: “The preferred method of cable protection is single-wire armouring for onshore and braided for offshore, in accordance with the relevant. Conduit will not normally be approved, except for use inside buildings in non-hazardous areas. All conduits shall be rigid steel, heavy wall, minimum 20 mm diameter, electro galvanised, and shall be supported with appropriate straps, saddles or hangers. See BS 31, BS 4568 and BS 4607 for conduit requirements. Unarmoured single-pair thermocouple cable shall be protected by U-channel conduits or 1/2" galvanised pipe. Where cables require support or protection from mechanical damage, they shall be run on purpose-made proprietary ladder-rack, U-channel or cable tray, ladder-rack being specified for widths of 300 mm or greater. All components and accessories used with such proprietary systems should be of 316L SS materials. The appropriate proprietary fittings shall be specified for branch connections from tray or channel to individual field instruments. Cable support systems shall not be attached to process lines. Design of the cable support system shall specify minimum clearance from any lines or equipment where close proximity due to heat, chemicals or vibration may adversely affect the cables. Supports for cable trays or cable ladders shall be suitable painted as per PTS 30.48.00.31 and firmly fastened or welded. For underground or trench cables where there is extensive oil contamination in the soil or sand, only then lead sheathed cables shall be used. Horizontal cable trays shall be situated above air supply lines. Vertical cable trays shall be situated behind or by the side of air supply lines unless space is limited by major equipment layout or piping arrangements. Cable trays shall be mounted in such a way as to allow access for maintenance or removal of equipment without undue disturbance to the installation.
Section
Description of Changes
Cable trays and conduits shall be designed to be supported by steel structures or have their own supports at every 2 meters lengths. Pipes for other services e.g. gas, steam, water etc. shall not be used to support cable trays. When a cable tray is designed for branching out, a flanged section shall be provided on the cable tray leading to at each instrument. The tray shall be extended to the furthest instruments. For cables lying in the cable channel, tray or underground trench, a marking strip (with tag no.) of nylon-covered stainless steel or lead shall be fitted around the cable at every 5 meters length, at both the starting and terminating points of the cable and at where the cable is fed into the control room or auxiliary room. All marking strips for cables in cable channels shall be fastened by stainless steel cable ties. Cables entering junction boxes, consoles, cross panels or the like shall be designed to be fastened by means of a cable clamp, Instrument signal cables shall be designed to be situated at least 300 mm from electric power cables shall be entirely clear of hot process lines. Separate trays shall be used for l.S. and non I.S. cables as far as possible as per BS 5345. Whenever this is a constraint, a barrier shall be provided for cable segregation. Cable trays, conduits and cable ladders shall be galvanized iron or stainless steel. 3.3
Added clause as follows: “The Cable Network shall be separated into: System 1: High voltage systems (above 1000V). System 2: Low voltage power supply and control cables for electrical systems (1000V and below) System 3: Instrumentation and Telecommunication systems. Where the cable support systems are installed horizontally one above the other, the cable network shall be arranged from top to bottom, system 1, system 2 and system 3. Cable ladders installed horizontally shall have sufficient space to facilitate cable pulling and cleating/strapping. Instrument and telecommunication cables shall be separated from low voltage power cables and high voltage cables by minimum 300 mm. Instrumentation and telecommunication cables may be routed on system 2 cable support systems when the defined distance between the individual systems can be kept. When separation of the cable systems specified above is not possible or practical, a metal segregation barrier shall be installed to avoid induced disturbances on the instrument/telecommunication cables. However, crossing at right angles is acceptable without further segregation.
Section
Description of Changes Non IS, IS instrument cables and Foundation Fieldbus can be routed on the same cable ladders/trays provided segregation/separation is done.”
3.4
Added new clause as follows: “All above ground cables shall be routed on cable ladders and trays. Underground cables shall be routed through dedicated cable trenches. Trunking or conduits may be used for special mechanical protection of single field routed cables for shorter distances (approximately 5 m). Where conduits are used, they shall be installed with open ends. A computer based cable routing system reflecting the layout of the main cable support system (i.e. cable ladders with width 300 mm and above) represented by ladder segment references, transit numbers, etc. and necessary describing information related to the individual cable including its route, shall be used in the design. Field cables may utilise the main cable support system provided the route of the individual cable is being registered in the routing system and the filing and loading of the main cable support system is acceptable. The cable ladders shall not be filled so the height of the cable ladder side rail is exceeded. Redundant cable systems shall be routed separately. 3.4.1
Cable Bending Radius The minimum permissible bending radius specified by Supplier shall be adhered to.
3.4.2
Cable Strapping PVC coated stainless steel AISI 316L straps shall be used for vertical runs and for horizontal runs in the vertical plane. For strapping of fibre-optical and coaxial cables, Supplier guidelines shall be adhered to. The distance between cable straps shall not exceed the distance between the horizontal and vertical runs on the cable tray. Therefore each cable shall be strapped on each horizontal and vertical run on the cable tray.
3.4.3
Cable Splicing Cable splicing is not allowed. In the event of damage, temporary cable splicing is allowed (non standard repair) provided the necessary risk assessment has been carried out. Temporary cable splicing shall have a time limit before permanent cable repair takes place. Temporary cable splicing shall be reported to Plant Management and tracking for permanent repair shall be in place.”
Section 3.5
Description of Changes Added new clause as follows: “All junction boxes shall be ingress-protected to IP-65(IEC-529/BS 5490) as a minimum. The dimensions of the boxes should be as close as possible to PETRONAS standard drawing S37.603. Junction boxes for terminating fire-resistant cables (IEC 331) shall be of 316 SS material and also suitably certified for use in the classified area. Separate multi-element cables as well as separate junction boxes, shall be provided for I.S. and non l.S. signals. Signal segregation shall be observed for digital and analogue transmissions with due regard being given to the above mentioned l.S. and non l.S. circuitry segregation. All junction boxes shall be complete with sufficient number of insulated earthing rails to terminate all cable armour (SWA or SWB). All junction boxes shall be sized to terminate all cores of cables and screens with a minimum of 20% spare terminals and cable entries. Spare cable entries shall be plugged with certified plugs. All spare cores shall be terminated at both ends.”
3.6
Added clause as follows: 3.6.1 Cable Glands and Multi Cable Transits (MCT) Cables shall be terminated into enclosures using mechanical type compression glands Glands shall be suitable for the reception of all strands of the wire armouring which shall be securely clamped in a permanent manner. Glands shall be provided with clamping rings for cables with wire braids When MCT are used on panels, cables have to be earthed with the braided earth wire under the armour to the earthing bar. MCT shall be installed such that the integrity of the bulkhead or wall is maintained. Contractor shall locate and install MCT. MCT shall be provided with 20% spare entries. When preparing cables prior to fitting glands, the gland manufacturer's instructions shall be followed. In all cases, care shall be taken to ensure that the lay of the armour is maintained after the gland is completely fitted. All spare multicore cable ends which are not terminated, immediately after cutting, shall be sealed effectively to prevent ingress of moisture and shall be protected from damage until termination is complete. Spare and unused glands or MCT frame openings shall be properly blinded (certified plug where applicable) or sealed. 3.6.2
Cable Glands Selection Cable glands/blanking and drain plugs shall be selected as follows: • •
Metal enclosures (except aluminium) - stainless steel (AISI 316L) Aluminium enclosures - stainless steel/nickel plated brass
Section
Description of Changes The certification of the cable glands, blanking and drain plugs shall comply with the certification of the equipment in which the glands/plugs are connected. Ex d gland shall have clamping of braid armour and sealing of inner and outer sheath. Only to be used on Ex d direct entry equipment. Dual certified glands, Ex d and Ex e (flameproof and increased safety) to be used and installed according to Supplier specifications.
3.7
New clause 3.7 CABLE TERMINATIONS All cable conductors shall be terminated by use of compression lugs or ferrules dependent upon the type of termination. The compression ferrule shall be the type where the conductor strands are inserted through the whole ferrule and reach the bottom of the terminal.
Support for cleating of cables when entering panels shall be provided. All cables shall enter field junction boxes via suitably sized and certified cable glands Cable entries shall be from bottom and side of the box only. Terminations in field junction boxes shall NOT be of quick disconnect (e.g. knife-edge) type. Terminals shall be industry proven. The number of terminals in a junction box shall be sufficient to terminate all wires of the cables and screens including a minimum of 20% spare terminals. Signal wires shall be terminated with crimped insulated bootlace ferrules and identified by using colour-coded core markers. Terminal blocks shall be non-hygroscopic vibration-proof and shall use captive screws for terminals. Hinged knife-blade switches/terminals may be used in control room or FAR for isolation and testing purposes. Consideration should be given to the use of ceramic high temperature terminals for the terminations of fire-resistant cables. Where the screens shall be left disconnected (applicable for field instruments), it shall be sealed and isolated with an isolating cap which allows for insulation testing without any disconnecting. Only one conductor is allowed in each terminal of a terminal block/row for external connections. This is not related to terminals as an integrated part of internal components (e.g. relays, contactors) of the equipment. 3.11
Added following Para: “3.11.1 MARSHALLING CABINETS Marshalling cabinets in the control room and equipment room (nonhazardous area) for signal distribution should be fitted with quick disconnecting type terminals and ELCO interconnecting boards for interconnection to system cabinets via system cables.
Section
Description of Changes However, special care and attention must be given to the requirements of signal separation of l.S. and non-l.S. type of signal in the selection and application of ELCO interconnecting boards. ELCO interconnecting boards shall not be required for applications where system cables are not used. Cable glands are, however, not required for cables or wires usually of small diameter, entering via rubber grommets in the enclosures of equipment installed in the control rooms and cables entering in the bottom of system cabinets or marshalling cabinets via false floors in the control room. In cases like this, it would be appropriate to install arrangements for cable clamping of the bottom of cabinets to avoid possible strain on terminations. The cabinet shall be executed as a complete enclosure and shall be provided with internal iron angle or channel frame work of sufficient strength to support the internal system. The cabinet shall be constructed as follows: 3.11.1.1
Outdoor installation The panels shall be made of 316L stainless steel plate, thickness minimum 3 mm. The carbon steel framing, supports and other construction parts shall be anti-corrosion treated and painted in accordance with Buyer’s Painting and Coating Specification The enclosure classification shall be minimum IP-65. Generally, all material shall be selected suitable for the environment conditions as described in section 4 of this specification
3.11.1.2
Indoor installation: The panels shall be made of mild steel plate, thickness minimum 3 mm for the front plate to receive panel mounted instruments. The panels shall be reinforced against buckling. The enclosure classification shall be IP-44 as a minimum. The cabinet(s) shall be provided with front and/or back access door(s) mounted on hinges. The door(s) shall have "T" type door handles without locks. The cabinet(s) shall be furnished with proper mounting assembly suitable for mounting in the specified area/location. A plinth, minimum 100 mm, shall be provided for free-standing type cabinet(s). For wall mounting type, the cabinet(s) shall be provided with the suitable mounting brackets assembly. The cabinet(s) shall also be provided with lifting eyes on the top of the cabinet for lifting purposes. Cable entries, such as MCT's (multi cable transit), Ex'd' cable glands and bulkhead connectors, etc. for interfaces with other systems, shall also be part of this system cabinet.
Section
Description of Changes Buyer will advise the size and numbers of the entries which have interfaces with Buyer's systems. Before shipment all cable entries shall be covered, providing IP-44 degree of protection. 3.11.1.3
Power Supply For electrical services, the cabinet shall be provided with terminals to receive the required power supplies. This power distribution system shall be furnished with a lockable main switch. If required, sub-distribution by means of circuit breakers shall be incorporated. The cabinet shall also be provided with a service lighting fixture and socket outlet connected to 110 VAC power supply. Furthermore a drawing pocket shall be installed. Details of the power consumption of the cabinet shall be provided to enable Buyer to calculate the required size of the power supply cables and fuses.
3.11.1.4
Cooling Cooling shall be adequate for the installed environment. It is Supplier's responsibility to provide heat dissipation calculations showing that the temperature inside the cabinet does not exceed 40°C under the maximum load conditions at maximum ambient temperature. When applicable, Supplier shall supply a forced redundant cooling ventilation fan system to be installed in the system. Any cooling fan installed in the cabinet shall be maintainable and replaceable online. Critical cabinets shall be provided with fan failure alarm.
3.11.1.5
Sparage Wire and cable trunking and/or supporting shall have a minimum of 20% spare capacity on completion, including known future installations
3.11.1.6
Painting and Nameplates The cabinet shall have standard finish and painted 'grey' (RAL 3032). Painting shall be in accordance with Manufacturer's Standard. Stainless steel cabinet for outdoor use shall be painted in compliance with Buyer’s Painting ad Coating specification Supplier shall furnish one white nameplate, fixed to the cabinet, in black letters, stating the tag number of the cabinet, description, manufacturer, year, power supply, order number, name Supplier. Instrument nameplates shall be made of corrosion resistant weatherproof material with black letters with a minimum height of 5 mm on a white background. Inscription shall be in the English language.
Section
Description of Changes Permanent nameplates shall also be provided identifying each instrument, instrument switch, meter, relays, control switch, indication lights, etc. in accordance with IEC regulations. 3.11.1.7
Wiring and Terminations Input/output terminals shall be of proven industrial made and shall be fitted to terminal rails located on a mounting plate in the cabinet. I.S. terminals shall be colored blue. There shall be a physical segregation between the I.S. circuits and the non-I.S. circuits in the cabinet in accordance with the applicable standards. All terminals shall be elevated at least 30 mm from the terminal rails. Terminals for voltage levels >50V AC or 120V AC shall be physically segregated from all other terminals and shall be fitted with a personnel protection cover clearly labeled. Terminals shall be of the non-self loosening type, shall be nickel plated and only accept one wire. Terminals to accommodate wiring by others shall be sized to accept 1.5 mm² wires for signal cables and wires of a minimum 4 mm² for power cables. The terminals shall be of a separation type whereby the input circuit can be separated from the other circuit without shutdown the system. Sockets and terminals for input/output connections shall be arranged and labeled according to the documents and drawings provided by Buyer with Purchase Order. Each shall be identified by a securely fixed label which is clearly visible after site cabling is complete. Cable screens of instrument cables are to be connected to the instrument earth bar which shall be supplied and installed by the cabinet Supplier. All earth connections within Supplier's scope of responsibility shall be made and shall be suitable and in accordance with the system requirements. Note that earth bars for I.S. and non-I.S. earth connections shall be separately installed within the cabinet All powered outputs to solenoid valves, indicating lamps and the like shall be fused on the positive side of the power supply. For AC solenoid, only live conductor shall be fused (neutral shall not be fused).
Section
Description of Changes All wires within the panel that are connected to terminal strips used for convenience in internal wiring, or wires terminating on device terminals not otherwise marked, and wires terminating on terminal strips for external connections shall be marked with permanent type wire markers bearing the number of the terminal row and/or the device terminal to which it is connected. Wire markers shall be of the interlockable type. All control wiring within the panel shall be of stranded wire 0.5 mm² with an insulation rating of 500V and a minimum of 2.5 mm² for power busses. Bootlace ferrules shall be used. Systems operating at different voltage levels are to be fully segregated. Wiring to the swing-out rack(s) and door(s) shall be properly secured in wire looms by using spiral lacing or equal. All intrinsically safe equipment and wiring shall be segregated. Overall insulating sheath of intrinsically safe wiring shall be blue. Trunking shall also be segregated and colored blue. Internal wiring shall be by single core, insulated wires, with the following colors: - black colour - AC/DC wiring, power supplies - grey colour - electronic signal, incoming and outgoing contacts - Blue colour - intrinsically safe wiring. Wiring shall be housed in a system of plastic wire ducts. A separate duct is required for the following: - AC wiring, power supply, incoming and outgoing contacts (grey colour) - Electronics signal wiring (grey colour) - Intrinsically safe wiring (blue colour). A 50 mm distance is required between the intrinsically safe wiring and the other wiring types.
4.1
Additional clause added: “All equipment for electric signal transmission, including the enclosures, as well as the armouring, lead sheathing and screening of cables, shall be properly earthed for personnel safety reasons and for obtaining the maximum possible rejection of interference. The instrument 'clean' earth shall be physically separated from the electrical or plant earth. On offshore structures, the instrument 'clean' earth shall be taken to a leg separate from this electrical earth and this earth connection shall be thermic welded. For onshore locations, in addition to the instrument 'clean' earth, a separate 'clean' earth shall be provided for intrinsically-safe system if shunt diode barriers are specified (total loop impedance shall not exceed 1 ohm). The normal instrument earth may be used to ground l.S. systems if opto- or transformer-isolation is used.
Section
Description of Changes For EMC plants, single ground is applicable. The cable armouring at each junction box shall be connected to earth via cable gland. Armour shall not be connected to the screen earth at any point in the systems. All screen earthing shall be earthed at the control room end only. All cable screens including spares shall be earthed at one point only (usually in the marshalling cabinet at the control centre except for tip grounded thermocouples) and shall be kept isolated from cable armouring, instrument enclosures, steel structures and any other electric conductors. Instrument equipment installed in control rooms shall be provided with insulated earth busbars, which are interconnected with 6 sq. mm. single core green insulated wire. To form a ring circuit, both ends shall be connected to a suitable earth point below the support frame by using 70 sq. mm. single core green/yellow insulated cables. To facilitate maintenance, two connection bolts shall be provided on the earth point. To ensure high integrity earthing of cabinets and panels, all moving metallic parts including hinged doors, swing frames, slide out racks, etc. shall be permanently bonded or earthed on an individual basis to the main body of the enclosure using flexible earth bonding straps. Ex 'i' or Ex 'd' solenoid valve, switches, etc., which do not have integral junction boxes shall be connected to the signal cable by means of an appropriate connecting box. The thread of the Ex 'd' enclosure cover shall be applied with a thin smear of approved grease before it is installed. To ensure a good earthing via the frame structure (plant or platform earth), instruments having electric connections shall be fixed by means of Mb, 316L SS bolts having a lock washer each under the nut and under the bolt. In field junction boxes, the individual shields of single pairs and those of multicore cables shall be through connected on insulated terminals. To avoid accidental shorting or grounding of this shield within a terminal box, the shield end and shield drain wire between the end of the cable jacket and the terminal strips shall be insulated. The shield of the ungrounded end of a cable shall be insulated by green/yellow colored PVC sleeve to avoid accidental grounding of any exposed shield or the shield drain wire. The maximum length of an unshielded core at the terminal strips shall be 25 mm. The ring is completed by connecting both ends to a suitable earth point below the support frame by using a 70 mm square single core green/yellow insulated cable. Two M10 316L SS connection bolts shall be provided on this earth point so that each end of the ring, can be connected to an individual bolt, thus allowing maintenance checks that resistance of the ring is less than 1 ohm while the other ring end is still connected and ensures continuous earthing. Where insulated glands are used in metal boxes, the armour shall be throughconnected to other cables and connected to plant (or platform) earth in another junction box. Where insulated boxes are used, the armour shall be through connected to a separate earth source. A separate earth bar should be specified for this purpose in all junction boxes.”
Section
Description of Changes
6.0
This is new clause: “6. PNEUMATIC TUBING All instrument tubing shall be seamless, soft annealed 316 stainless steel. Recommended tubing hardness shall not exceed ROCKWELL No. Rb 80. . All compression fittings shall be 316 Stainless steel of Swagelok make or equal in order to ensure compatibility with existing facilities and minimise stock holding. It is stressed that metric size tubing and fittings are not compatible with their imperial size counterpart. The Company makes extensive use of hydrocarbon gas as an alternative to instrument air on offshore platforms, particularly unmanned platforms. The design shall ensure that the instrument system is compatible with the expected gas composition. Where the length of pneumatic signal-transmission tubing exceeds 60 m, signal booster relays shall be used. Where the tubing length exceeds 90 m, design consideration shall be given to the use of electronic instrumentation. 316 SS tubing is considered to be self-supporting up to a length of 1 m. For longer lengths, the tubing shall be supported over its full length at every 1 m. Air header layout after the primary block valve shall be in accordance with Company practice as shown in the PTS standard drawings. The branch lines shall be connected to the main header with a shut-off valve. All branch line connections shall be made on the top of the line. (Instrument scope commences at the downstream flange of the shut-off valve). Instrument air mains shall be provided with a 316 SS valved branch connection (of one size smaller than the main) at least every 5 m, complete with union coupling, and a 10% spare capacity provision shall be made for future extensions. All future tie-in points shall be valved and plugged. From the main branch lines, all further connections to manifolds and individual air filter/regulators shall be made via 12 mm or ½" O.D. 316L SS tubing. Areas where the carbon steel pipe meets stainless steel piping/fittings, a sacrificial carbon steel nipple shall be installed to cater for galvanic corrosion. The rating of instrument air mains and branch air lines shall be in accordance with Table 4 below unless otherwise specified.
Section
Description of Changes Table 4: Instrument Air Mains and Branch Air Lines Nominal Pipe Pipe/tubing & Maximum Size (OD) fitting Material Number of Users DN 15 (½ inch) 316L SS 5 DN 25 (1 inch) 316L SS 25 DN 50 (2 inch) 316L SS 100 Air supply lines shall be sloped towards drain points. A sufficient number of filters, regulators, drain and bleeders shall be provided in the instrument air system. A filter regulator shall be provided for each individual air user and shall be complete with an output gauge. Filter regulators shall be stainless steel to minimise life cycle costs. Instrument air supply lines from the nearest block valve to the air user and the pneumatic signal line shall consist of 12 mm O.D. x 1.0 mm WT or 1/2" OD x 0.035" WT 316 SS tubing and compression fittings. Instrument air receivers/headers capacity primarily depends on a summed tabulation of all the known users, instruments and instrument system, and their respective consumption rates, which can be obtained from the manufacturers. It also depends on the availability of alternative air sources and has to match other back-up requirements such as UPS, batteries etc.”
Tubing shall be joined by compression type fittings only. Tubing shall be selected for the applicable pressure ratings specified and sized adequately for the required capacity and duty. Tubing material shall be 316 SS as per ASTM A269, with the exception of Molybdenum (Mo) content which shall be 2.5% minimum. Mill certificates of tubing shall be required for every batch of tubing ordered or supplied by fabricators and suppliers. For offshore installation, tubing material shall be either Tungum, 254 SMO, Super duplex Stainless Steel and Alloy 625 to avoid crevice and pitting corrosion caused by chloride attack. For reasons of variety control, fast delivery and to minimise life cycle costs, 317 SS tubing (Mo content of between 3% and 4%) shall not be used unless the process conditions and field conditions warrants their use. With the exception of hydraulic lines, all SS 316 instrument tubing shall have the following dimensions:
Section
Description of Changes
OD
Table 5: SS316 Instrument Tubing Dimensions Thickness Applications
¼” 3/8”
0.035” 0.065”
½” 6 mm 10 mm 12 mm
0.035” 1.0 mm 1.5 mm 1.0 mm
Signal Lines Fusible Loops, Impulse Lines, Supply Lines Supply Lines, Drain Lines Signal Lines Fusible Loops, Impulse Lines, Supply Lines Supply Lines, Drain Lines
316L Stainless steel compression type fittings shall be selected for the applicable pressure ratings specified and sized for the tubing described above and shall be installed in strict accordance with the manufacturer's recommendations. Fittings shall be manufactured by Swagelok. Only NPT type threads shall be used for screwed connections. The thread cutting shall be in accordance with API Code for threading. The number of joints in piping and tubing shall be kept to a minimum, consistent with good practice. All shall be made with the aid of approved tubing benders, correct for the size of tube being worked, to ensure neat serviceable bends. Pipes and tubes shall be run in vertical and horizontal planes as far as possible and shall be run with the minimum number of changes of direction consistent with the good practice and neat appearance. Horizontal runs shall have the pipes or tubes mounted one above the other. Where pipes or tubes run parallel to each other, joints shall be systematically staggered and neatly off-set. Isolation valves shall be located as close to the source as practical. No piping or tubing shall be installed in such a way that it is subject to vibration or any other mechanical stress. All piping and tubing shall be de-burred properly after cutting (preferably with a de-burring drill on a drilling machine). After de-burring process, all piping and tubing shall be cleaned by blowing through with filtered dry and oil-free compressed air before connection to instrument. The installed, but not connected, pipes and tubes shall have their ends capped to prevent the entry of foreign material. All instrument piping connected to process piping shall be run with a slope of not less than 1 to 12, except where otherwise specified. The slope shall be down from the tapping points for liquids and up from the tapping points for gas service. The Contractor must pay special attention to the correct location of vents and drains to ensure that they are respectively at the highest and lowest point of piping runs. All drains shall be connected to the closed drain systems or plugged by an isolation valve.
Section
Description of Changes Handling and storage of Tubing Tubing shall be stored and transported in dedicated plastic boxed/tubes, to prevent tubing corrosion before installation. The transport and storage in dedicated plastic boxed/tubes applies for offshore locations and any onshore location, including construction sites. Multi-core Tubing Where indicated on the hook-up drawings, multi-core tubing shall be used. Multi-core tubing shall be routed, supported and secured in a similar manner to that of the electrical cable. All entries to junction boxes shall be made weatherproof, using suitable cable glands and/or bulkhead fittings. Piping and Tubing Support All piping and tubing shall be adequately supported and/or braced so as to provide maximum protection against mechanical damage and vibration. The distance between supports shall not exceed those in the following table: Table 6: Distance Requirement for Tubing Support Line Size Maximum Distance ¾ inch 1.0 m 1 inch 1.5 m 1½ - 2 inch 2.0 m Multi-core tube shall be supported each 0.25 m. Single tube size 1/2 inch or less shall be supported continuously. For continuously supporting five or more single tubes, one 316L SS cable tray shall be used. For continuously supporting four or less single tubes, 316L SS angle bar (50 x 50), or 316L SS Unistrut channel shall be used. The tubing shall be secured to the tray with fastening blocks at (maximum) 0.6 meters intervals. Blocks with stainless steel cover plates, bolts and nuts shall be delivered and supplied by the Contractor. The supports shall be fabricated by the Contractor (or supports to be made of SS 316L), including coating in accordance with the Painting and Coating Specification 525. Coating shall be finished before installation supporting materials. The required small mounting materials and consumable items shall be delivered and supplied by the Contractor. Capillaries of filled systems shall run independently of all other lines and shall be continuously supported using 316L SS angle bar 316L SS Unistrut channel with adequate fastening clamps or tie-wraps at 0.25mintervals. Adequate means of protecting capillaries from damage shall be employed. Special care shall be taken against kinks in the capillaries on bends or changes of direction. Cable trays shall be run with the width of the tray in a horizontal plane. A short section may be run with the width in a vertical plane after Company's approval. In this case, additional support shall be provided to prevent sagging.
Section
Description of Changes Under certain circumstances and with Company's approval, trunking or conduits may be used instead of cable trays. The required materials shall be delivered and supplied by the Contractor. Unless otherwise specified, the process pipelines and handrails shall not be used to support instrument pressure and air piping and tubing. Process equipment, rotating equipment and electric motors which are liable to vibration shall not be used to support instrument pressure and air piping and tubing. Multi-core transit, insert frames and blocks, supplied by the Contractor, shall be provided after piping or tubing installation, in accordance with the drawings or when required by Company.
7.1
7.1
CABLE IDENTIFICATIONS Quads or pairs shall be identified by black numbers on each individual core of the quads or pairs, no greater than 50 mm apart. If the dimension of a core does not permit this, other means of identifying the cores shall be used. A purpose-made identification method shall be specified for cables in the cable channel, at every 5 meters. In addition, similar identification markings/bands shall be specified for the starting and terminating points of the cable, and on both sides of any wall or bulkhead penetration. The identification markings/bands shall be blue for I.S. cables, green for non I.S. cables and red for F&G cables. Cable identification numbers shall be permanent, character size being 10 mm. Cable numbers shall be as per PTS 32.37.20.31. All cables, whether I.S. or non l.S., shall have black outer sheath regardless of type of cable and conform to BS 5308.
PREFACE PETRONAS Technical Standards (PTS) publications reflect the views, at the time of publication, of PETRONAS OPUs/Divisions. They are based on the experience acquired during the involvement with the design, construction, operation and maintenance of processing units and facilities. Where appropriate they are based on, or reference is made to, national and international standards and codes of practice. The objective is to set the recommended standard for good technical practice to be applied by PETRONAS' OPUs in oil and gas production facilities, refineries, gas processing plants, chemical plants, marketing facilities or any other such facility, and thereby to achieve maximum technical and economic benefit from standardisation. The information set forth in these publications is provided to users for their consideration and decision to implement. This is of particular importance where PTS may not cover every requirement or diversity of condition at each locality. The system of PTS is expected to be sufficiently flexible to allow individual operating units to adapt the information set forth in PTS to their own environment and requirements. When Contractors or Manufacturers/Suppliers use PTS they shall be solely responsible for the quality of work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, it is expected of them to follow those design and engineering practices which will achieve the same level of integrity as reflected in the PTS. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the owner. The right to use PTS rests with three categories of users: 1) 2) 3)
PETRONAS and its affiliates. Other parties who are authorised to use PTS subject to appropriate contractual arrangements. Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) and 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards.
Subject to any particular terms and conditions as may be set forth in specific agreements with users, PETRONAS disclaims any liability of whatsoever nature for any damage (including injury or death) suffered by any company or person whomsoever as a result of or in connection with the use, application or implementation of any PTS, combination of PTS or any part thereof. The benefit of this disclaimer shall inure in all respects to PETRONAS and/or any company affiliated to PETRONAS that may issue PTS or require the use of PTS. Without prejudice to any specific terms in respect of confidentiality under relevant contractual arrangements, PTS shall not, without the prior written consent of PETRONAS, be disclosed by users to any company or person whomsoever and the PTS shall be used exclusively for the purpose they have been provided to the user. They shall be returned after use, including any copies which shall only be made by users with the express prior written consent of PETRONAS. The copyright of PTS vests in PETRONAS. Users shall arrange for PTS to be held in safe custody and PETRONAS may at any time require information satisfactory to PETRONAS in order to ascertain how users implement this requirement.
TABLE OF CONTENTS 1. 1.1 1.2 1.3 1.4 2. 2.1 2.2 2.3 2.4 2.5 2.6 2.7 3. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 4. 4.1 4.2 4.3 4.4 5. 5.1 5.2 6. 6.1 6.2 6.3 6.4 7. 7.1 7.2 7.3 7.4 7.5 8.
INTRODUCTION............................................................................................................................... 1 SCOPE .............................................................................................................................................. 1 DISTRIBUTION, APPLICABILITY AND REGULATORY CONSIDERATIONS ................................ 1 DEFINITIONS AND ABBREVIATIONS............................................................................................. 1 CROSS REFERENCES .................................................................................................................... 2 ELECTRICAL CABLING ................................................................................................................... 3 GENERAL ......................................................................................................................................... 3 FUNDAMENTAL REQUIREMENTS ................................................................................................. 3 SIGNAL SEGREGATION IN MULTICORE CABLES ....................................................................... 4 SELECTION AND SPECIFICATION OF INSTRUMENT CABLES................................................... 5 CABLES FOR DIGITAL AND VIDEO SIGNALS ............................................................................... 7 CABLES FOR SPECIAL APPLICATIONS ........................................................................................ 7 PROTECTION OF CABLES AGAINST FIRE DAMAGE................................................................... 8 CABLE SEGREGATION, ROUTING AND INSTALLATION ............................................................. 9 INSTALLATION ASPECTS ............................................................................................................... 9 MOUNTING AND PROTECTION OF CABLES ................................................................................ 9 CABLE SEGREGATION ................................................................................................................. 10 ROUTING ........................................................................................................................................ 11 JUNCTION BOXES FOR MULTICORE CABLES .......................................................................... 13 CABLE GLANDS............................................................................................................................. 14 CABLE TERMINATIONS ................................................................................................................ 15 TRUNKING AND TRAYS ................................................................................................................ 16 TRENCHES..................................................................................................................................... 17 CABLE PULLING AND INSTALLATION ASPECTS....................................................................... 18 CONTROL ROOM/AUXILIARY AREAS ......................................................................................... 18 EARTHING AND BONDING ........................................................................................................... 23 GENERAL ....................................................................................................................................... 23 CONNECTIONS TO THE EARTHING SYSTEMS ......................................................................... 24 EARTHING OF INTRINSICALLY SAFE CIRCUITRY..................................................................... 25 EARTHING OF CAVITY FLOORS.................................................................................................. 25 LIGHTNING PROTECTION OF INSTRUMENTATION .................................................................. 26 GENERAL ....................................................................................................................................... 26 INSTRUMENTATION AND CABLING IN THE FIELD .................................................................... 26 PNEUMATIC TUBING..................................................................................................................... 27 GENERAL ....................................................................................................................................... 28 SELECTION AND SPECIFICATION OF TUBING.......................................................................... 31 JUNCTION BOXES FOR MULTICORE TUBING ........................................................................... 31 INSTALLATION...............................................................................................................................31 IDENTIFICATION AND MARKING ................................................................................................. 32 CABLE IDENTIFICATIONS............................................................................................................. 32 IDENTIFICATION OF SYSTEM CABLES....................................................................................... 32 IDENTIFICATION OF SINGLE CABLES/TUBING ......................................................................... 32 IDENTIFICATION OF MULTICORES AND JUNCTION BOXES.................................................... 32 MARKING........................................................................................................................................ 33 REFERENCES................................................................................................................................ 34
APPENDICES APPENDIX 1
DISTANCE BETWEEN CABLE TRENCHES
APPENDIX 2
ARRANGEMENT OF CABLE TRENCHES
APPENDIX 3
TYPICAL EARTHING AT FAR/CCR
APPENDIX 4
TYPICAL EARTHING OF INSTRUMENT SIGNAL CABLES IN THE FIELD
APPENDIX 5
TYPICAL EARTHING OF INSTRUMENT SIGNAL CABLES IN THE MDF
32.37.20.10 January 2009 Page 1
1.
INTRODUCTION
1.1
SCOPE This PTS specifies requirements and gives recommendations for the design and engineering of instrument signal lines, with immunity from electromagnetic interference as appropriate. It covers design, material selection and installation methods for cabling the signal lines of the different systems. Cabling for transmitting digital and video signals is also covered in this PTS. In the context of this PTS, instrument signal lines include: a) Electric signal lines (paths), including thermo-electric voltage lines from thermocouples; lines from transmitters to their receiving instruments, auxiliaries, logic systems, controllers etc. and the lines from these to the relevant actuating elements such as solenoid valves, converters, transducers or control valves. b) Pneumatic signal lines (paths) from pneumatic transmitters to their receiving instruments, auxiliaries, controllers and the lines from these to the relevant final control elements. Signal lines for similar applications such as fire and gas detection and protection systems, plant communication systems, CCTV systems, plant information systems, maintenance management systems and plant security systems are also within the scope of this PTS. This PTS is a revision of the PTS of the same number dated October 1990.
1.2
DISTRIBUTION, APPLICABILITY AND REGULATORY CONSIDERATIONS Unless otherwise authorised by PE TRONAS, the distribution of this PTS is confined to companies forming part of PETRONAS Group, and to contractors nominated by them. This PTS is intended for use in oil refineries, chemical plants, gas plants, exploration and production facilities and supply/marketing installations. If national and/or local regulations exist in which some of the requirements are more stringent than in this PTS, the contractor shall determine by careful scrutiny which of the requirements are the more stringent and which combination of requirements will be acceptable as regards safety, economic and legal aspects. In all cases the contractor shall inform the Principal of any deviation from the requirements of this document which is considered to be necessary in order to comply with national and/or local regulations. The Principal may then negotiate with the authorities concerned with the object of obtaining agreement to follow this document as closely as possible.
1.3
DEFINITIONS AND ABBREVIATIONS
1.3.1
General definitions The Contractor is the party which carries out all or part of the design, engineering, procurement, construction, commissioning or management of a project or operation of a facility. The Principal may undertake all or part of the duties of the Contractor. The Manufacturer/Supplier is the party which manufactures or supplies equipment and services to perform the duties specified by the Contractor. The Principal is the party which initiates the project and ultimately pays for its design and construction. The Principal will generally specify the technical requirements. The Principal may also include an agent or consultant authorised to act for, and on behalf of, the Principal.
32.37.20.10 January 2009 Page 2 The word shall indicate a requirement. The word should indicate a recommendation. 1.3.2
1.3.3
Specific definitions Bonding
The act of connecting together exposed conductive parts and extraneous conductive parts of apparatus, systems or installations that are at essentially the same potential (IEC TR 61000-5-2).
Cable ladder
Above-ground, ladder-type cable tray without cover.
Cavity floor
Computer floor or false floor.
Instrument earth
Dedicated earth for instrument systems.
Safety earth
Plant safety earth.
Sealing fitting
Conduit fitting which, when filled with a suitable sealing compound, prevents transportation of flammable substances through the conduit.
System cabling
A wiring concept, consisting of cables, plugs and sockets, as detailed in PTS 32.37.20.31.
Tray
Above-ground, open cable support system, such as U-shaped flatbottomed or ladder type.
Trench
Underground cable routing system provided with a mechanical protection on top of the cables.
Trunking
Above-ground, U-shaped cable support system with cover. It is flatbottomed and has a top cover secured by cover clips/fasteners.
Abbreviations AL/HDPE/PA CCR CCTV DCS EM EMC EMI FAR IPF MDF ROV SWA SWB
1.4
Aluminium/High Density Polyethylene/Polyamide (nylon) Central Control Room Closed Circuit Television Distributed Control System Electro magnetic Electro magnetic compatibility Electro magnetic interference Field Auxiliary Room Instrumented protective function Main Distribution Frame Remote operated valve Steel wire armouring Steel wire braiding
CROSS REFERENCES Where cross references to other parts of this PTS are made, the referenced section number is shown in brackets. Other documents referenced in this PTS are listed in (8).
32.37.20.10 January 2009 Page 3
2.
ELECTRICAL CABLING
2.1
GENERAL Single pair cables are used for signal transmission from field instruments to field mounted junction boxes. Multicore cabling will subsequently transmit the signals from the junction box to an MDF in the CCR or FAR. Wherever possible and consistent with the design of other plant facilities, multicore cabling should be routed underground because it then has inherent protection against fire and mechanical damage. However, above-ground cabling is acceptable, subject to the Principal's approval, provided a definite cost advantage can be demonstrated, or where it is the standard local practice. Outdoor, above-ground and underground cabling shall be provided with steel wire braiding (SWB) or steel wire armouring (SWA) to protect them against mechanical damage and for EMC reasons, even if these cables are installed in trenches / trunking or on cable trays. Underground cabling shall additionally be provided with a chemical/moisture barrier. The selection of instrument signal cables shall be governed by the specific electrical application and by the areas through which the cable is to run. The physical construction of the cable shall be dependent upon the electrical application, the intended service and the type of signals. The locality in which the cable is installed determines whether armouring is necessary and what resistance to environmental elements is required. Locality can also dictate the fire performance of materials used for insulation and sheathing since the acceptability of smoke and toxic gas emission during fire depends on ventilation and accessibility of areas concerned and on the normal manning levels in these areas. However, it is important to note that in all locations, resistance to fire propagation by cable material is of paramount importance. Hence, the minimum requirement for all cables for normal service shall be of reduced flame propagation type conforming to IEC-332 part 3 cat. A. Cables for vital services (where service must be maintained during or after exposure to fire condition) shall be of fire-resistant type conforming to IEC-331.
2.2
FUNDAMENTAL REQUIREMENTS All cables used shall be minimum flame retardant. Fire resistant cables shall be used whenever required. All cable insulation, filler and sheathing material must add a minimum of fuel to any fire. Mud resistant cables shall be used where cables are routed into or through areas exposed to mud/oil. Material used in cables for manned or confined areas e.g. accommodation should produce minimum levels of smoke and acid gas under fire conditions. Installation of cables in hazardous areas must conform to BS 5345 and BS 5501. All field cables shall be armoured. Braided armour is preferred to single wire armour where there is an option since it is lighter, more flexible and easier to install. However for trench and underground cables, single wire armour shall be used. (Note: Braided and single wire armoured cables require different types of cable glands)
32.37.20.10 January 2009 Page 4 The capacitance, inductance and L/R ratio must not exceed certain values for intrinsically safe circuits depending on the hazardous area classification and equipment parameters. Reference should be made to the equipment hazardous area certification. Cables for switched signals (e.g. alarm and indication) should be twisted multi-core type whereas cable for analogue signals should be twisted multi-pair with overall screen and drain wire. Multicore cables with collective screen shall be standard, individual screens shall be used only when required. Cable without armour may be used in indoor installation 2.2.1
Cable Specifications - Normal Service Selection of electrical signal cables for control and monitoring shall take account of service, environment and circuit conditions. Mineral Insulated (Ml) cables shall only be used on those applications where cables are permanently exposed to intense heat e.g. flare tip thermocouples (Exception to PTS 33.64.10.10 Electrical Engineering Guidelines). In all locations, resistance to fire propagation by cable material is of paramount importance. Hence the minimum requirement for all cables for normal service shall be of reduced flame propagationtype conforming to IEC-332 part 3 cat. A.
2.2.2
Cable Specifications - Emergency Service On all applications where an instrument connection or signal must be maintained for a limited period during or after exposure to a condition, the design shall specify fire-resistant cables (other than MI cables) which conform to IEC 331.
2.3
SIGNAL SEGREGATION IN MULTICORE CABLES When electrical signals are assigned to multicore cables, the following signal segregation rules shall be followed: •
Intrinsically safe and non-intrinsically safe signals shall be segregated as required by IEC 60079-14.
•
Segregation on the basis of cabling requirements may be required. Example: Thermocouple signals require extension cabling and thus can only be combined in one cable with signals from thermocouples of the same type.
•
For practical reasons, segregation between disciplines is recommended (e.g. no signal cabling for Instrumentation and Electrical in one multicore cable). The following systems shall have separate multicore cables: -
General instrumentation. Fire and Gas. ESD. Telecommunication. DCS. Foundation Fieldbus. General Electrical (control) Powered Outputs
• •
32.37.20.10 January 2009 Page 5 The supply and return conductor of a signal shall be contained in the same cable pair. Segregation on the basis of signal level classes shall be applied as shown in Table 1 to achieve EMC.
Table 1: Classification of Instrument Signal Levels SIGNAL LEVEL CLASS
SIGNAL TYPE
EXAMPLES
1
• • •
Low energy digital systems Analogue low level (mV signals) Analogue medium level (approx, 1V)
• • •
2
•
Analogue high level (e.g. 1-10 VDC, 420 mA Binary low level (below 24 VDC and below 0.5 VA) Digital low level (pulse train) Digital high level (pulse train) Proximitors for machine monitoring On-Off medium level (< 50 V or > 0.5 VA, > 40 VA) High level signals > 50 VAC and DC power signals higher than Class 4 Power supply cables
• • •
Computer bus signals Thermocouples Resistance temperature measurements, analysers Electronic instrumentation loops Digital and analogue IS Actuating logic systems, annunciators
• • • •
Turbine meter, proximity sensors Tank gauging system Vibration sensors 24 VDC solenoids (note 2)
•
110 VDC solenoids (note 2)
•
Power supply cables to instrument cabinets and field instruments
•
4
• • • •
5
•
3
•
NOTES:
1. 2.
The classification is based on the use of cables with metal screen for signal level classes 1, 2 and 3. The classification is based on de-coupled solenoids to limit induction. DC solenoids shall be decoupled with shunt diodes and AC solenoids with RC networks, connected directly across the solenoid terminals.
In addition to the above segregation rules for multicore cabling, functional segregation may be desirable for operability and maintainability reasons (e.g. segregation between process units or segregated cabling for fire and gas systems). The design shall cater for spare capacity in multicore cabling. When the design is finalised, 1015% of the installed cabling capacity shall be available in each signal level class and plant area to accommodate unforeseen future plant modifications.
2.4
SELECTION AND SPECIFICATION OF INSTRUMENT CABLES
2.4.1
Conductors Solid insulated conductors should be used for instrument field cables. The minimum conductor diameter shall be 1.13 mm for single signal cables and 0.8 mm for multicore signal cables. The maximum permissible current rating and allowable voltage drop criteria shall be observed in selecting signal cables and larger conductor diameters may be required to reduce the voltage drop. Stranded wires are permitted for internal wiring inside cabinets; for connections in screw type terminals, wire crimp pins/lugs shall be applied NOTES: 1. Cables having conductors of 0.8 mm diameter (cross section approx. 0.5 mm2) have a maximum continuous current rating of 1 A per core. The fuse rating for these cables shall not exceed 4 A. The voltage drop in signal cabling shall be calculated and the available voltage at the terminals of field instruments shall be checked against the minimum requirements. If the allowable voltage drop is exceeded, a larger conductor diameter and/or a higher supply voltage shall be selected. 2. Crimped-on wire pins/lugs shall provide a gas-tight (corrosion free) connection between the crimp pin/lug and conductor in the signal cable. 3. Solid conductors should not be provided with crimp-on wire pins/lugs.
32.37.20.10 January 2009 Page 6 For thermocouple signals, the conductors shall consist of pairs of dissimilar materials with the correct thermo-electric voltage as a function of temperature, based on IEC 60584-3. For all other signals, the conductor material shall be copper. For resistance thermometer elements, the conductor resistance shall be compatible with the requirements as specified by the Manufacturer of the resistance thermometer elements and/or the instrument. Signal wires shall be twisted in pairs. The use of quad cables requires approval by the Principal. 2.4.2
Cable Construction
2.4.2.1 Cable construction for signal level classes 1/2/3 Instrument signal cabling for signal level classes 1, 2 and 3 of Table 1 (2.2) shall be specified with a metal screen and drain wire. Multicore cabling shall be provided with a collective screen; individual pair screening should only be applied if specifically needed for the application. Where possible, underground cabling shall be provided with an AL/HDPE/PA inner sheathing as a moisture/chemical barrier in preference to lead sheathing.
Cable capacitance and inductance shall not invalidate the requirements for intrinsically safe or non-incendive (switched) circuits. Unless special cabling construction requirements apply, the following cables types are recommended:
Table 2: Recommended Cable Types for Signals Level Classes 1/2/3 (Note 1) Type ID (Note 1) Application Conductor Screen Inner Sheath Mechanical Protection Oversheath
Type-1 PE-MS-PVC
Type-2 PE-MS-PE-SWB-PVC
Type-3 PE-AL/HDPE/PA-SWAHDPE Underground cabling
Indoor use in a protected EM PE (note 2) MS -
Above ground cabling in a plant PE (note 2) MS PE
-
SWB
SWA
PVC
PVC
HDPE
PE (note 2) AL/HDPE/PA
NOTES: 1. Identification of cable construction is from the centre to the outside. 2. Cross linked polyethylene (XLPE) may be used as alternative insulation material. 3. Cables of table 2 are not suitable for direct connection to a low impedance source, e.g. the public mains electricity supply. 4. For multicore cellular PE-insulated telecommunication cables, based on BS 3573.
32.37.20.10 January 2009 Page 7 Background to and abbreviations used, in Table 2: AL/HDPE/PA
HDPE HDPE
MS PE PVC PVC SWA SWB
Aluminium / high density polyethylene / polyamide (nylon), that combines overall, metal screening with inner sheathing. The aluminium acts as metal screen and moisture barrier. HDPE and PA act as chemical barriers, while PA provides also protection against termite attacks. AL/HDPE/PA is a low cost and light weight alternative for lead sheathing. High density polyethylene used as outer sheathing. as outer sheathing has a good chemical resistance and water tightness, but is inflammable (acts as torch) and stiff. Furthermore, HDPE is only UV-resistant, if it is of black colour and containing carbon black. Metal screen with drain wire. Polyethylene, used as conductor insulation or inner sheathing. Polyvinyl chloride used as outer sheathing. as outer sheathing is UV-resistant, flame retardant and commercially attractive. Steel wire armouring by a single layer of round galvanised steel wire. Steel wire braiding.
2.4.2.2 Cable construction for signal level classes 4 and 5. Cables for signal level classes 4 and 5 of Table 1 (2.2) shall follow the requirements for low voltage cables, as defined in PTS 33.64.10.10. The conductor cross section for signal level classes 4 and 5 shall be at least 2.5 mm2.
2.5
CABLES FOR DIGITAL AND VIDEO SIGNALS Microprocessor-based digital instrumentation and CCTV systems may require special cables to transmit the associated digital and video signal paths. Digital signals can be carried by screened twisted pair cables, coaxial cables or fibre optic cables, depending on the system requirements. The choice is usually dictated by bandwidth and layout requirements. Wherever relevant (e.g. long cable runs via lightning-unprotected areas), fibre optic cabling shall be considered for digital and video signal paths (e.g. between a CCR and FAR) to take advantage of the large bandwidth capability, inherent EM immunity and inherent intrinsic safety offered by such cabling.
2.6
CABLES FOR SPECIAL APPLICATIONS Special cabling and/or earthing requirements may apply for signal transmission outside the standard 4-20 mA range. This may be the case with inline flow meters with remote electronics, machine monitoring devices, analyzer systems, systems for fire and gas detection & protection and other devices with non-standard output signals. Manufacturer’s instructions with regard to cable selection, routing, termination and earthing shall be followed. The routing of special cabling in one unbroken length from the transmitting to the receiving instrument, i.e. bypassing the junction box and MDF, should be considered.
32.37.20.10 January 2009 Page 8
2.7
PROTECTION OF CABLES AGAINST FIRE DAMAGE In general, above-ground cabling shall be routed via low fire risk areas. However, some cabling may be exposed to fires. The cabling for certain critical duties, such as cabling in fire protection, process isolation (ROVs) and depressuring duty, shall maintain circuit integrity for a limited period of time after commencement of a fire to reduce or limit the consequences of the fire. For cabling associated with fire safety and fire protection, see PTS 80.47.10.12., PTS 80.47.10.30. and PTS 80.47.10.31. For cabling associated with hydraulic systems for remote operation of shut-off valves, see PTS 31.36.10.30. For cabling associated with depressuring systems, see PTS 32.45.10.10. Protection against fire damage may be achieved by special cabling or by fire resistant covering. For the selection of cabling requiring protection against fire damage, reference is made to PTS 33.64.10.10. If chemical spillage is likely to occur during fire conditions, fire resistant cabling shall also be resistant to chemical attack.
32.37.20.10 January 2009 Page 9
3.
CABLE SEGREGATION, ROUTING AND INSTALLATION
3.1
INSTALLATION ASPECTS Multi-core cables between junction boxes and control rooms shall be laid without splices. Cables entering junction boxes, consoles, cross panels or the like, shall be fastened by means of a cable gland, suitably sized and classified for the area of operation. The design shall incorporate right of way and cable channeling for instrument and electrical signal cables. Instrument signal cables, shall be separated at a distance of at least 0.3 m from electric power cables when laid underground in cable trenches, or be on separate channels with metal separation when laid above ground. Routing of cables shall take account of any risk of damage or deterioration due to high temperature lines, corrosive fluids, hydrocarbons or radiation (including UV radiation from direct sunlight). In any process-connected instrument where rupture of the sensing element may subject the instrument case to process pressure and where the cable used has interstices which would permit the migration of gas or liquid to a control room, a "Barrier Type" gland with sealing compound shall be specified. All cables for intrinsically-safe circuits must consist of groups of conductors twisted for each independent circuit with screen and drain wires over the cable as a whole. The capacitance, inductance and L/R ratio must not exceed values for intrinsically-safe circuits, depending on the hazardous area classification and equipment parameters. Reference should be made to the equipment hazardous area certification.
3.2
MOUNTING AND PROTECTION OF CABLES The preferred method of cable protection is single-wire armouring for onshore and braided for offshore, in accordance with the relevant. Conduit will not normally be approved, except for use inside buildings in non-hazardous areas. All conduits shall be rigid steel, heavy wall, minimum 20 mm diameter, electro - galvanised, and shall be supported with appropriate straps, saddles or hangers. See BS 31, BS 4568 and BS 4607 for conduit requirements. Unarmoured single-pair thermocouple cable shall be protected by U-channel conduits or 1/2" galvanised pipe. Where cables require support or protection from mechanical damage, they shall be run on purpose-made proprietary ladder-rack, U-channel or cable tray, ladder-rack being specified for widths of 300 mm or greater. All components and accessories used with such proprietary systems should be of 316L SS materials. The appropriate proprietary fittings shall be specified for branch connections from tray or channel to individual field instruments. Cable support systems shall not be attached to process lines. Design of the cable support system shall specify minimum clearance from any lines or equipment where close proximity due to heat, chemicals or vibration may adversely affect the cables. Supports for cable trays or cable ladders shall be suitable painted as per PTS 30.48.00.31 and firmly fastened or welded.
32.37.20.10 January 2009 Page 10 For underground or trench cables where there is extensive oil contamination in the soil or sand, only then lead sheathed cables shall be used. Horizontal cable trays shall be situated above air supply lines. Vertical cable trays shall be situated behind or by the side of air supply lines unless space is limited by major equipment layout or piping arrangements. Cable trays shall be mounted in such a way as to allow access for maintenance or removal of equipment without undue disturbance to the installation. Cable trays and conduits shall be designed to be supported by steel structures or have their own supports at every 2 meters lengths. Pipes for other services e.g. gas, steam, water etc. shall not be used to support cable trays. When a cable tray is designed for branching out, a flanged section shall be provided on the cable tray leading to at each instrument. The tray shall be extended to the furthest instruments. For cables lying in the cable channel, tray or underground trench, a marking strip (with tag no.) of nylon-covered stainless steel or lead shall be fitted around the cable at every 5 meters length, at both the starting and terminating points of the cable and at where the cable is fed into the control room or auxiliary room. All marking strips for cables in cable channels shall be fastened by stainless steel cable ties. Cables entering junction boxes, consoles, cross panels or the like shall be designed to be fastened by means of a cable clamp, Instrument signal cables shall be designed to be situated at least 300 mm from electric power cables shall be entirely clear of hot process lines. Separate trays shall be used for l.S. and non I.S. cables as far as possible as per BS 5345. Whenever this is a constraint, a barrier shall be provided for cable segregation. Cable trays, conduits and cable ladders shall be galvanized iron or stainless steel.
3.3
CABLE SEGREGATION The Cable Network shall be separated into: System 1: High voltage systems (above 1000V). System 2: Low voltage power supply and control cables for electrical systems (1000V and below) System 3: Instrumentation and Telecommunication systems. Where the cable support systems are installed horizontally one above the other, the cable network shall be arranged from top to bottom, system 1, system 2 and system 3. Cable ladders installed horizontally shall have sufficient space to facilitate cable pulling and cleating/strapping. Instrument and telecommunication cables shall be separated from low voltage power cables and high voltage cables by minimum 300 mm. Instrumentation and telecommunication cables may be routed on system 2 cable support systems when the defined distance between the individual systems can be kept.
32.37.20.10 January 2009 Page 11 When separation of the cable systems specified above is not possible or practical, a metal segregation barrier shall be installed to avoid induced disturbances on the instrument/telecommunication cables. However, crossing at right angles is acceptable without further segregation. Non IS, IS instrument cables and Foundation Fieldbus can be routed on the same cable ladders/trays provided segregation/separation is done. When combining instrument cables for electrical signals in trenches/trunking and on cable trays, the following cable segregation rules shall apply: −
Redundant cabling for critical services shall be physically segregated and follow separate cable routes in the field and in the CCR/FAR (e.g. redundant highways for the DCS and redundant signal cabling for normally de-energised IPF functions, such as depressuring systems).
−
Intrinsically safe and non-intrinsically safe cabling shall only be segregated if so dictated by IEC 60079-14.
−
Cables of signal level class 5 (Table 1) shall be segregated from cables for signal level classes 1 through 4. Cables for signal level classes 1 through 4 inclusive may be combined in the same trench/trunking and on the same cable tray without physical separation. NOTE: Cables of signal level class 5 are to be considered as electrical cables.
−
3.4
Pneumatic tubing and fibre optic cables may be combined with any type of instrument signal cable.
ROUTING All above ground cables shall be routed on cable ladders and trays. Underground cables shall be routed through dedicated cable trenches. Trunking or conduits may be used for special mechanical protection of single field routed cables for shorter distances (approximately 5 m). Where conduits are used, they shall be installed with open ends. A computer based cable routing system reflecting the layout of the main cable support system (i.e. cable ladders with width 300 mm and above) represented by ladder segment references, transit numbers, etc. and necessary describing information related to the individual cable including its route, shall be used in the design. Field cables may utilise the main cable support system provided the route of the individual cable is being registered in the routing system and the filing and loading of the main cable support system is acceptable. The cable ladders shall not be filled so the height of the cable ladder side rail is exceeded. Redundant cable systems shall be routed separately.
3.4.1
Cable Bending Radius The minimum permissible bending radius specified by Supplier shall be adhered to.
32.37.20.10 January 2009 Page 12 3.4.2
Cable Strapping PVC coated stainless steel AISI 316L straps shall be used for vertical runs and for horizontal runs in the vertical plane. For strapping of fibre-optical and coaxial cables, Supplier guidelines shall be adhered to. The distance between cable straps shall not exceed the distance between the horizontal and vertical runs on the cable tray. Therefore each cable shall be strapped on each horizontal and vertical run on the cable tray.
3.4.3
Cable Splicing Cable splicing is not allowed. In the event of damage, temporary cable splicing is allowed (non standard repair) provided the necessary risk assessment has been carried out. Temporary cable splicing shall have a time limit before permanent cable repair takes place. Temporary cable splicing shall be reported to Plant Management and tracking for permanent repair shall be in place. The optimum cable routing and junction box locations are related to plant layout and can only be determined after equipment and piping layouts have been finalised. Single cables connect field instruments to junction boxes and shall be supported and protected against mechanical damage by cable trunking, cable trays, steel angles, beams etc. as appropriate. Use of conduits is not favored. Cables shall not be supported from process equipment or piping. When selecting the above-ground routing for cables, the following aspects shall be considered: − − −
− − −
Constructability and cost: make optimum use of structures for process equipment, pipe racks etc. The need for special passages/ducts and crossings will also affect the route selection. Required cable length and associated cost. EMC aspects: apply cable segregation (3.1) and do not route cabling through areas classified as severe EM environments; if feasible, route cabling through areas that are protected against direct lightning strikes. Cable routing along and in the direct vicinity of earthed steel structures and piping will reduce electromagnetic interference. Avoid obstructing other users: layout shall not obstruct traffic or interfere with the accessibility of process equipment (pumps, compressors, motors, heat exchanger bundles, etc.). Accessibility: layout shall guarantee sufficient access for cable pulling and maintenance. Prevent cable damage: the layout shall be selected so that the cables are not prone to damage.
This involves at least the following: -
Cabling shall be routed through low fire risk areas.
-
Cabling shall not be routed in the vicinity of sample points, drains, vents, hot pipes and hot surfaces.
-
Where riser points are liable to damage by traffic, they shall be protected by free standing, sturdy mechanical structures.
32.37.20.10 January 2009 Page 13 For multicore cabling, underground routing is preferred as it provides excellent protection against mechanical and fire damage. The route selection for underground cable trenches shall take the following rules into consideration: -
Maintain a safe distance from power and lighting cables. For separation distances, see Appendix 1. When power cables intersect instrument signal cables, the crossing shall be at right angles, with a minimum separation distance of 0.3 m.
-
Trenches shall be kept away from buried hot surfaces (e.g. pipes) so that the properties of the cable shall not be adversely affected. The minimum separation distance shall be 0.2 m plus 0.1 m for every 100 °C temperature of the non-insulated surface.
The conceptual design for the cable routing shall be submitted to the Principal for approval.
3.5
JUNCTION BOXES FOR MULTICORE CABLES Junction boxes shall be located in low fire risk locations that are either electrically safe or classified as Zone 2. Furthermore, they shall be located close to the instruments they serve, to keep the single cable runs short (typically 15 to 20 m). In the plant, stainless steel junction boxes should be applied. For signal levels classes 1, 2 and 3 of Table 1 (2.2), see Standard Drawing S 37.603. Junction boxes should be supplied complete with terminals and accessories such as mounting rails, end plates, earth bolts, drain plug, gland plates, glands etc. All cables shall be provided with metallic glands located at the bottom of the junction box. All terminals in junction boxes shall have facilities to protect them from accidental loosening. Terminals in intrinsically safe circuits shall be of light blue colour, terminals in non-intrinsically safe circuits shall be of the Ex ’e’ type and shall not be of blue colour. The minimum degree of protection for junction boxes (containing terminals only) shall be IP 65 as specified in IEC 60529. All junction boxes shall be ingress-protected to IP-65(IEC-529/BS 5490) as a minimum. The dimensions of the boxes should be as close as possible to PETRONAS standard drawing S37.603. Junction boxes for terminating fire-resistant cables (IEC 331) shall be of 316 SS material and also suitably certified for use in the classified area. Separate multi-element cables as well as separate junction boxes, shall be provided for I.S. and non l.S. signals. Signal segregation shall be observed for digital and analogue transmissions with due regard being given to the above mentioned l.S. and non l.S. circuitry segregation. All junction boxes shall be complete with sufficient number of insulated earthing rails to terminate all cable armour (SWA or SWB). All junction boxes shall be sized to terminate all cores of cables and screens with a minimum of 20% spare terminals and cable entries. Spare cable entries shall be plugged with certified plugs. All spare cores shall be terminated at both ends.
32.37.20.10 January 2009 Page 14
3.6
CABLE GLANDS
3.6.1
Cable Glands and Multi Cable Transits (MCT) Cables shall be terminated into enclosures using mechanical type compression glands Glands shall be suitable for the reception of all strands of the wire armouring which shall be securely clamped in a permanent manner. Glands shall be provided with clamping rings for cables with wire braids When MCT are used on panels, cables have to be earthed with the braided earth wire under the armour to the earthing bar. MCT shall be installed such that the integrity of the bulkhead or wall is maintained. Contractor shall locate and install MCT. MCT shall be provided with 20% spare entries. When preparing cables prior to fitting glands, the gland manufacturer's instructions shall be followed. In all cases, care shall be taken to ensure that the lay of the armour is maintained after the gland is completely fitted. All spare multicore cable ends which are not terminated, immediately after cutting, shall be sealed effectively to prevent ingress of moisture and shall be protected from damage until termination is complete. Spare and unused glands or MCT frame openings shall be properly blinded (certified plug where applicable) or sealed.
3.6.2
Cable Glands Selection Cable glands/blanking and drain plugs shall be selected as follows: • •
Metal enclosures (except aluminium) Aluminium enclosures
- stainless steel (AISI 316L) - stainless steel/nickel plated brass
The certification of the cable glands, blanking and drain plugs shall comply with the certification of the equipment in which the glands/plugs are connected. Ex d gland shall have clamping of braid armour and sealing of inner and outer sheath. Only to be used on Ex d direct entry equipment. Dual certified glands, Ex d and Ex e (flameproof and increased safety) to be used and installed according to Supplier specifications.
Metallic cable glands shall be used for electric signal cabling entering the housing of field instruments and junction boxes, to provide: − a means to attach and secure the cable end; − the type of protection to avoid ignition of a surrounding explosive atmosphere, as appropriate, according to the requirements of IEC 60079-14 or EN 50014 (if applicable), e.g. Ex ‘d’ glands are required for Ex ‘d’ enclosures; − the required degree of ingress protection (IP code according to IEC 60529) of the instrument or junction box enclosure; − an earthing connection for cable armouring/braiding and, if applicable, the metallic sheathing.
32.37.20.10 January 2009 Page 15 EMC requires the cable armouring/braiding to be earthed onto the instrument/junction box housing via the metal gland by a robust, circumferential (360 degrees) connection at low impedance. Glands constructed in accordance with BS 6121-1 types C/D/E or BS 6121-3 types CK/EK provide such an earthing connection. NOTE:
1. 2.
3.
4. 5.
For instruments that are not designed for cable entry by a metal cable gland (e.g. proximitors with flying leads), the Manufacturer’s installation instructions should be followed. Many cable gland suppliers provide metal glands with dual certification (Ex ‘d’ and Ex ’e’). The use of these types of glands may be considered for all applications for reasons of uniformity and variety control. The practice of using a ‘litze’ wire between the cable armouring/braiding and the safety earth connection of the instrument/junction box should not be adopted as it is not suitable for the large equalising currents in the armouring/braiding. Furthermore, this technique brings magnetic fields inside the cable, instrument and junction box that were intended to be ‘Faraday cages’. Cable glands for SWB cabling shall be constructed so that the grip force cannot be reduced after installation as a result of braiding settling. Where cable glands should grip on steel wire braiding, this shall be specified explicitly, as most clamping rings are designed for steel wire armouring.
Where brass glands are used in atmospheres which attack the brass, the glands shall be provided with shrouds. Cable glands on plant instruments should preferably be located at the bottom, never at the top, to prevent ingress of water. Where cable glands are installed in the side wall of the instruments, the cables shall enter from below. Cables coming from above shall first drop to below the elevation of the gland. The entry thread of the cable glands should preferably be ISO metric. Cables shall be clamped just below the cable glands to prevent excessive force on the cable gland. A special case is if cable glands are used for electric signal cables entering potentially hydrocarbon filled spaces (e.g. flying leads of vibration probes on rotating equipment). In addition to the above requirements, these glands shall be of a blocking type to prevent oil leakage from the inner casing to the outside environment.
3.7
CABLE TERMINATIONS All cable conductors shall be terminated by use of compression lugs or ferrules dependent upon the type of termination. The compression ferrule shall be the type where the conductor strands are inserted through the whole ferrule and reach the bottom of the terminal. Support for cleating of cables when entering panels shall be provided. All cables shall enter field junction boxes via suitably sized and certified cable glands Cable entries shall be from bottom and side of the box only. Terminations in field junction boxes shall NOT be of quick disconnect (e.g. knife-edge) type. Terminals shall be industry proven. The number of terminals in a junction box shall be sufficient to terminate all wires of the cables and screens including a minimum of 20% spare terminals. Signal wires shall be terminated with crimped insulated bootlace ferrules and identified by using colour-coded core markers. Terminal blocks shall be non-hygroscopic vibration-proof and shall use captive screws for terminals. Hinged knife-blade switches/terminals may be used in control room or FAR for isolation and testing purposes. Consideration should be given to the use of ceramic high temperature terminals for the terminations of fire-resistant cables.
32.37.20.10 January 2009 Page 16 Where the screens shall be left disconnected (applicable for field instruments), it shall be sealed and isolated with an isolating cap which allows for insulation testing without any disconnecting. Only one conductor is allowed in each terminal of a terminal block/row for external connections. This is not related to terminals as an integrated part of internal components (e.g. relays, contactors) of the equipment.
3.8
TRUNKING AND TRAYS Cable trunking and cable trays are intended to provide a protected routing for multicore cables from the trenches to the junction boxes. They may also contain single cables, running from an instrument to a junction box. The trunking/tray shall be of metal construction and the sections shall be connected to each other and to instruments/junction boxes/structures by short connections at low impedance. For EMC purposes, closed metal trunking has preference over open, U-shaped cable trays. Cable trays of the ladder type have limited EMC quality. For guidance on this subject, see IEC TR 61000-5-2, clause 7. NOTE:
The shielding capability of metal trunking is, amongst other things, used to achieve the required level of EMC. Non-metal trunking does not contribute towards EMC and is therefore not recommended. The trunking design shall be in accordance with the latest downstream/upstream requirements. The Principal will inform the Contractor of the applicable requirements.
Trunking/trays shall be firmly supported by structures. The strength and spacing of the supports shall take into account the weight of the cables they are designed to carry. The trunking shall be internally smooth, bolts shall be installed with the head inside and the nut outside. The cable exits from trunking should be protected by plastic or metal bushings. Trunking constructions shall be in accordance with standard drawing S 37.604. Trunking/trays can be made of stainless steel, galvanised mild steel or painted mild steel. Galvanized steel shall not be used for cable trunking/trays or other supporting materials in the vicinity of stainless steel process equipment or piping in a fire risk area. Note: In the event of a fire, molten zinc from galvanized metal parts may drop on stainless steel process equipment or piping, thus causing liquid metal embrittlement.
In order to prevent galvanic corrosion, non-ferrous metals shall not be in direct contact with trunking, supports etc. EMC requirements do not allow the use of insulating methods. Welding of trunking/tray supports to structures may be considered. The trunking/trays shall be positioned so that cables can be laid from the side of the run, instead of pulling them through consecutive holes. The free space above the trunking/tray shall be at least 0.3 m for small trays (maximum nominal width of 100 mm if accessible from one side, and 200 mm if accessible from both sides) and 0.5 m for wide trays. To minimise mechanical stress, cabling shall be suitably fixed to trunking/trays with UV-resistant ties, especially in the vertical runs. Trunking and trays shall be suitably sized for the number of cables they are required to carry. The final design shall cater for a minimum spare space of 30%. Based on an average cable overall diameter of 25 mm for SWA multicore cables, Table 3 below gives the number of cables that can be accommodated by the trunking, leaving 30% spare space for the installation of future cables.
32.37.20.10 January 2009 Page 17 Table 3: Number of Multicore Cables in Trunking, Leaving 30% spare space Nominal width (mm) 50 100 150 200 250 300 Nominal height (mm) 50 100 100 100 100 100 Number of multicore cables 1 8 14 19 25 30 The curvature of trunking/tray bends and branches shall be selected so that the permissible bending radius of the cables is not exceeded. Where trunking/trays entering the buildings, special measures should be taken to support the cables and to prevent ingress of water or gas. Trunking/tray design shall be submitted to the Principal for approval.
3.9
TRENCHES Underground instrument signal cables shall be laid in dedicated trenches and their routing shall be indicated by above-ground markers. Cross-sectional drawings of trenches shall show the location and laying pattern of each group of cables. The trenches shall have such a depth that the signal cables are not damaged by traffic passing over them. Where possible, the bottom of the trench shall be kept above the ground water level, to avoid cable deterioration. For general construction details for trenches in paved and unpaved areas, refer to Appendix 2 and Standard Drawings S 19.001, S 19.002 and S 68.009. The distance between cables, as indicated on Standard Drawing S 68.009, does not apply to instrument cables of signal level classes 1 through 4: they may be laid without spacing. The bottom of the trench shall not have a slope of more than 10 degrees and the transition of horizontal surfaces shall have a smooth curvature. Where trenches for signal cables pass under roads or below other cable trenches or pipes, protective DN 100 or DN 150 pipes or concrete ducting shall be provided to facilitate future cable laying. Such pipes/ducting shall be capped or plugged at the ends. Particularly for cables entering buildings, a detailed proposal shall be made by the Contractor with respect to supporting the cables to prevent cable damage by soil settlement over a prolonged period. NOTES:
1. 2.
3.
Backfilling of the trenches shall be carried out with sand, free of stones to grade 2-5 mm, and shall contain no contaminants which may cause deterioration of the cable. The top cable layer shall be covered with protective material, such as tiles, to provide mechanical protection. Alternatively plastic cover plates may be applied, provided the same degree of protection is obtained. The procedure for jointing cables underground shall be submitted for approval to the Principal, detailing as a minimum the materials to be used, work method, supervision, inspection, testing and labeling.
Where large quantities of signal cables cross or branch off, the trench depth shall be increased locally. The curvature of the corners in trenches shall be selected so that the permissible bending radius of the cables is not exceeded.
32.37.20.10 January 2009 Page 18
3.10
CABLE PULLING AND INSTALLATION ASPECTS To prevent cable damage, cables shall not be pulled at ambient temperatures below 5 °C. All cables in a particular trench shall be pulled in one consecutive and uninterrupted operation. When interruption is unavoidable, the trench shall be covered temporarily with steel plates. Cables shall be installed in one unbroken length between two termination points. NOTE: For optimum cable usage and to prevent wastage, a cable drum and cable number take-off schedule shall be prepared. This is best prepared by the construction Contractor during the construction phase.
The cables shall be laid with sufficient slack (especially at rising points) to prevent stress, in particular where trenches are made in soft soil. All above-ground cables not installed in trunking or on trays shall be suitably supported and clamped, especially at the end. Instrument cables shall not be clamped to equipment, process piping, handrails, access ladders, structural steel etc. Near the plant mounted instrument, a cable slack of at least 0.5 m shall be provided to facilitate termination/disconnection. Cables connected to instruments in which there may be an internal release of flammable medium shall be sealed off with a fitting to prevent liquid/gas transport. During plant welding operations, the electronics of adjacent instruments will be damaged if all or part of the welding current flows through the instrument. During plant construction, electric cabling should only be connected to instruments after completion of welding activities, preferably just prior to loop testing. For fibre optic cables, the Manufacturer's instructions shall be followed with respect to termination, allowable bending radius and pulling force. Cable trunking, trays and trenches shall be designed so that cable laying and cable pulling is possible within the allowable mechanical properties of the cable. Cable Manufacturer’s specifications shall be followed with respect to the minimum bending radius and pulling force of the cables.
3.11
CONTROL ROOM/AUXILIARY AREAS
3.11.1 MARSHALLING CABINETS Marshalling cabinets in the control room and equipment room (non-hazardous area) for signal distribution should be fitted with quick disconnecting type terminals and ELCO interconnecting boards for interconnection to system cabinets via system cables. However, special care and attention must be given to the requirements of signal separation of l.S. and non-l.S. type of signal in the selection and application of ELCO interconnecting boards. ELCO interconnecting boards shall not be required for applications where system cables are not used. Cable glands are, however, not required for cables or wires usually of small diameter, entering via rubber grommets in the enclosures of equipment installed in the control rooms and cables entering in the bottom of system cabinets or marshalling cabinets via false floors in the control room. In cases like this, it would be appropriate to install arrangements for cable clamping of the bottom of cabinets to avoid possible strain on terminations. The cabinet shall be executed as a complete enclosure and shall be provided with internal iron angle or channel frame work of sufficient strength to support the internal system.
32.37.20.10 January 2009 Page 19 The cabinet shall be constructed as follows: 3.11.1.1
Outdoor installation The panels shall be made of 316L stainless steel plate, thickness minimum 3 mm. The carbon steel framing, supports and other construction parts shall be anticorrosion treated and painted in accordance with Buyer’s Painting and Coating Specification The enclosure classification shall be minimum IP-65. Generally, all material shall be selected suitable for the environment conditions as described in section 4 of this specification
3.11.1.2
Indoor installation: The panels shall be made of mild steel plate, thickness minimum 3 mm for the front plate to receive panel mounted instruments. The panels shall be reinforced against buckling. The enclosure classification shall be IP-44 as a minimum. The cabinet(s) shall be provided with front and/or back access door(s) mounted on hinges. The door(s) shall have "T" type door handles without locks. The cabinet(s) shall be furnished with proper mounting assembly suitable for mounting in the specified area/location. A plinth, minimum 100 mm, shall be provided for free-standing type cabinet(s). For wall mounting type, the cabinet(s) shall be provided with the suitable mounting brackets assembly. The cabinet(s) shall also be provided with lifting eyes on the top of the cabinet for lifting purposes. Cable entries, such as MCT's (multi cable transit), Ex'd' cable glands and bulkhead connectors, etc. for interfaces with other systems, shall also be part of this system cabinet. Buyers will advise the size and numbers of the entries which have interfaces with Buyer's systems. Before shipment all cable entries shall be covered, providing IP-44 degree of protection.
3.11.1.3
Power Supply For electrical services, the cabinet shall be provided with terminals to receive the required power supplies. This power distribution system shall be furnished with a lockable main switch. If required, sub-distribution by means of circuit breakers shall be incorporated. The cabinet shall also be provided with a service lighting fixture and socket outlet connected to 110 VAC power supply. Furthermore a drawing pocket shall be installed. Details of the power consumption of the cabinet shall be provided to enable Buyer to calculate the required size of the power supply cables and fuses.
32.37.20.10 January 2009 Page 20 3.11.1.4
Cooling Cooling shall be adequate for the installed environment. It is Supplier's responsibility to provide heat dissipation calculations showing that the temperature inside the cabinet does not exceed 40°C under the maximum load conditions at maximum ambient temperature. When applicable, Supplier shall supply a forced redundant cooling ventilation fan system to be installed in the system. Any cooling fan installed in the cabinet shall be maintainable and replaceable online. Critical cabinets shall be provided with fan failure alarm.
3.11.1.5
Sparage Wire and cable trunking and/or supporting shall have a minimum of 20% spare capacity on completion, including known future installations
3.11.1.6
Painting and Nameplates The cabinet shall have standard finish and painted 'grey' (RAL 3032).. Painting shall be in accordance with Manufacturer's Standard. Stainless steel cabinet for outdoor use shall be painted in compliance with Buyer’s Painting ad Coating specification Supplier shall furnish one white nameplate, fixed to the cabinet, in black letters, stating the tag number of the cabinet, description, manufacturer, year, power supply, order number, name Supplier. Instrument nameplates shall be made of corrosion resistant weatherproof material with black letters with a minimum height of 5 mm on a white background. Inscription shall be in the English language. Permanent nameplates shall also be provided identifying each instrument, instrument switch, meter, relays, control switch, indication lights, etc. in accordance with IEC regulations.
3.11.1.7
Wiring and Terminations Input/output terminals shall be of proven industrial made and shall be fitted to terminal rails located on a mounting plate in the cabinet. I.S. terminals shall be colored blue. There shall be a physical segregation between the I.S. circuits and the non-I.S. circuits in the cabinet in accordance with the applicable standards. All terminals shall be elevated at least 30 mm from the terminal rails. Terminals for voltage levels >50V AC or 120V AC shall be physically segregated from all other terminals and shall be fitted with a personnel protection cover clearly labeled. Terminals shall be of the non-self loosening type, shall be nickel plated and only accept one wire. Terminals to accommodate wiring by others shall be sized to accept 1.5 mm² wires for signal cables and wires of a minimum 4 mm² for power cables. The terminals shall be of a separation type whereby the input circuit can be separated from the other circuit without shutdown the system.
32.37.20.10 January 2009 Page 21 Sockets and terminals for input/output connections shall be arranged and labeled according to the documents and drawings provided by Buyer with Purchase Order. Each shall be identified by a securely fixed label which is clearly visible after site cabling is complete. Cable screens of instrument cables are to be connected to the instrument earth bar which shall be supplied and installed by the cabinet Supplier. All earth connections within Supplier's scope of responsibility shall be made and shall be suitable and in accordance with the system requirements. Note that earth bars for I.S. and non-I.S. earth connections shall be separately installed within the cabinet All powered outputs to solenoid valves, indicating lamps and the like shall be fused on the positive side of the power supply. For AC solenoid, only live conductor shall be fused (neutral shall not be fused). All wires within the panel that are connected to terminal strips used for convenience in internal wiring, or wires terminating on device terminals not otherwise marked, and wires terminating on terminal strips for external connections shall be marked with permanent type wire markers bearing the number of the terminal row and/or the device terminal to which it is connected. Wire markers shall be of the interlockable type. All control wiring within the panel shall be of stranded wire 0.5 mm² with an insulation rating of 500V and a minimum of 2.5 mm² for power busses. Bootlace ferrules shall be used. Systems operating at different voltage levels are to be fully segregated. Wiring to the swing-out rack(s) and door(s) shall be properly secured in wire looms by using spiral lacing or equal. All intrinsically safe equipment and wiring shall be segregated. Overall insulating sheath of intrinsically safe wiring shall be blue. Trunking shall also be segregated and colored blue. Internal wiring shall be by single core, insulated wires, with the following colors: - black colour - AC/DC wiring, power supplies - grey colour - electronic signal, incoming and outgoing contacts - blue colour - intrinsically safe wiring. Wiring shall be housed in a system of plastic wire ducts. A separate duct is required for the following: - AC wiring, power supply, incoming and outgoing contacts (grey colour) - Electronics signal wiring (grey colour) - Intrinsically safe wiring (blue colour). A 50 mm distance is required between the intrinsically safe wiring and the other wiring types. The control room and auxiliary areas shall be fitted with cavity floors, designed to allow for cable segregation. The cabling shall enter the buildings through proper sleeves that are made fire resistant and waterproof and are in compliance with EMC requirements. NOTE: The limited access under the cavity floor makes the installation of cable trays impractical. Cables should be segregated in bundles on the basis of the segregation rules given in (3.1).
32.37.20.10 January 2009 Page 22 When the design is finalised, the cable entry in buildings shall have at least 20% spare space to accommodate additional cables for unforeseen future plant modifications.
When a cellar type of auxiliary room is used with the control room above it, the interconnecting cabling shall be routed through riser cabinets, connecting the cavity floors of these rooms. All signal, power and earthing cables shall be routed and connected via the cavity floor and shall enter cabinets from the bottom. Cabinets/racks shall not be placed against the walls of auxiliary rooms. The bottom of the cabinets shall be sealed to prevent dust entry from the cavity floor into the cabinets. Signal marshalling shall take place in MDF cabinets only; system cabling (see PTS 32.37.20.31.) shall interconnect MDFs and instrument cabinets. An MDF cabinet typically consists of: -
rows of test/disconnect terminals for termination of field cables; rows of socket boards into which auxiliary room wiring is connected via system cables; cross wiring between field terminals and socket board terminals for signal marshalling.
Remote input/output cards of systems, such as DCS, may also be located in MDFs. Thermocouple compensation cable shall be used up to the device where the cold junction compensation resides (usually the input card). Instrument cabinets shall be designed to terminate the full capacity (including spare capacity) of the cabinet on system cables, organised in a logical fashion (input/output card channels modularly into system cables). Thus any input or output from any instrument cabinet shall be marshalled at the MDFs only. The final design of instrument cabinets shall provide a minimum of 20% spare capacity. Cable glands are not required for cable terminations in control/auxiliary room cabinets. Cables shall be suitably anchored with clamps and fixtures to take their weight and for EMC purposes, before connecting them to terminals or sockets.
32.37.20.10 January 2009 Page 23
4.
EARTHING AND BONDING
4.1
GENERAL Earthing systems are the responsibility of the Electrical Engineering discipline and provisions for earthing are covered by PTS 33.64.10.10. This Section identifies aspects affecting personnel safety and proper functioning of instruments and instrument systems. The number of earthing types should be limited to two, i.e.: - Safety earth - Instrument earth For a typical configuration of a safety earth and instrument earth system at the FAR/CCR, refer to standard drawing S 68.030 and Appendix 3. Instrument earth cables shall connect the instrument earth bar to MDFs and instrument cabinets, using one cable for each MDF/cabinet. The crosssectional area of these cables shall be at least 6 mm2 and the terminal insulation colour shall be yellow/black. Each instrument earth cable shall be properly identified at the side of the instrument earth bar, showing the MDF/cabinet number it is connected to. NOTE: Earthing bolts shall have a diameter of at least 10 mm.
Some Manufacturers require a dedicated earth: Manufacturers' recommendations on the arrangement of earthing and maximum allowable resistance to earth should be followed. Requirements for earthing and bonding of enclosures containing electric and electronic components may be dictated by local regulations (e.g. European standards associated with CEmarking). Where this is not the case, international standards such as IEC TR 61000-5-2 should be followed. All equipment for electric signal transmission, including the enclosures, as well as the armouring, lead sheathing and screening of cables, shall be properly earthed for personnel safety reasons and for obtaining the maximum possible rejection of interference. The instrument 'clean' earth shall be physically separated from the electrical or plant earth. On offshore structures, the instrument 'clean' earth shall be taken to a leg separate from this electrical earth and this earth connection shall be thermic welded. For onshore locations, in addition to the instrument 'clean' earth, a separate 'clean' earth shall be provided for intrinsically-safe system if shunt diode barriers are specified (total loop impedance shall not exceed 1 ohm). The normal instrument earth may be used to ground l.S. systems if opto- or transformer-isolation is used. For EMC plants, single ground is applicable. The cable armouring at each junction box shall be connected to earth via cable gland. Armour shall not be connected to the screen earth at any point in the systems. All screen earthing shall be earthed at the control room end only. All cable screens including spares shall be earthed at one point only (usually in the marshalling cabinet at the control centre except for tip grounded thermocouples) and shall be kept isolated from cable armouring, instrument enclosures, steel structures and any other electric conductors. Instrument equipment installed in control rooms shall be provided with insulated earth busbars, which are interconnected with 6 sq. mm. single core green insulated wire. To form a ring circuit, both ends shall be connected to a suitable earth point below the support frame by using 70 sq. mm. single core green/yellow insulated cables. To facilitate maintenance, two connection bolts shall be provided on the earth point.
32.37.20.10 January 2009 Page 24 To ensure high integrity earthing of cabinets and panels, all moving metallic parts including hinged doors, swing frames, slide out racks, etc. shall be permanently bonded or earthed on an individual basis to the main body of the enclosure using flexible earth bonding straps. Ex 'i' or Ex 'd' solenoid valve, switches, etc., which do not have integral junction boxes shall be connected to the signal cable by means of an appropriate connecting box. The thread of the Ex 'd' enclosure cover shall be applied with a thin smear of approved grease before it is installed. To ensure a good earthing via the frame structure (plant or platform earth), instruments having electric connections shall be fixed by means of Mb, 316L SS bolts having a lock washer each under the nut and under the bolt. In field junction boxes, the individual shields of single pairs and those of multi-core cables shall be through connected on insulated terminals. To avoid accidental shorting or grounding of this shield within a terminal box, the shield end and shield drain wire between the end of the cable jacket and the terminal strips shall be insulated. The shield of the ungrounded end of a cable shall be insulated by green/yellow colored PVC sleeve to avoid accidental grounding of any exposed shield or the shield drain wire. The maximum length of an unshielded core at the terminal strips shall be 25 mm. The ring is completed by connecting both ends to a suitable earth point below the support frame by using a 70 mm square single core green/yellow insulated cable. Two M10 316L SS connection bolts shall be provided on this earth point so that each end of the ring, can be connected to an individual bolt, thus allowing maintenance checks that resistance of the ring is less than 1 ohm while the other ring end is still connected and ensures continuous earthing. Where insulated glands are used in metal boxes, the armour shall be through-connected to other cables and connected to plant (or platform) earth in another junction box. Where insulated boxes are used, the armour shall be through connected to a separate earth source. A separate earth bar should be specified for this purpose in all junction boxes.
4.2
CONNECTIONS TO THE EARTHING SYSTEMS
4.2.1
Connections to instrument earth Screens of instrument signal cables shall be connected to the instrument earth by the 'star' method. Screens shall be insulated from cable armouring/braiding/metal sheathing, instrument enclosures and metal structures. Refer to Appendices 3 through 5. Screens shall be earthed at one point only: −
for screened cables between the field and the CCR or FAR, the screens shall be earthed at the MDF in the CCR/FAT. The screen shall be insulated at the field instrument side. Dedicated terminals in junction boxes shall connect the screens of single and multicore cables. These terminals shall be insulated from safety earth. NOTE:
1.
2.
−
Most field instruments do not have insulated connection facilities for the screen. The screen shall be insulated with a protective sleeve and left unconnected, with the same length as the signal wires. This creates the possibility for checking interconnections between the two earth systems. for (special) screened cabling running directly from the field instrument to the receiving instrument (i.e. bypassing junction box and MDF), the screen shall be earthed at the receiving instrument end only.
for screened cables between the CCR and FAR, the screens shall be earthed at the MDF in the CCR.
− −
4.2.2
32.37.20.10 January 2009 Page 25 for screened system cabling running inside the FAR or CCR, the screens shall be earthed at the MDF. if screened cabling is run between two MDFs or between two instrument cabinets, the 'star' method requires the screen to be earthed at one of the MDFs/cabinets only.
Connections to safety earth Steel wire armouring, steel wire braiding and metal sheathing of cables shall be connected to safety earth, at least at both ends. For typical safety earthing installation details, refer to Appendices 3 through 5. Instrument housings, junction boxes, local panels and local cabinets shall be bonded to cable trunking/steel angles etc. In addition, earthing or mounting bolts of instrument housings shall be fitted with two shark rings to allow low resistance bonding to plant structures/safety earth. Junction boxes, local panels and local cabinets shall be provided with an earthing bolt to enable a proper earthing connection to plant structures/safety earth. Any outside earthing connection shall comply with IEC 60079-0.
4.3
EARTHING OF INTRINSICALLY SAFE CIRCUITRY Safety barriers should preferably be connected to safety earth or alternatively to a dedicated earth bar, connected to safety earth.
4.4
EARTHING OF CAVITY FLOORS A 1.20 x 1.20 m safety earth grid is required for cavity floors, consisting of bare copper stranded wires with a minimum cross section of 16 mm2, connected to the cavity floor construction. The grid shall be connected to the safety earth ring at a maximum spacing of 5 m.
32.37.20.10 January 2009 Page 26
5.
LIGHTNING PROTECTION OF INSTRUMENTATION
5.1
GENERAL The lightning protection for instruments described in this Section assumes that plants are equipped with lightning protection as specified in PTS 33.64.10.10. Protective measures shall not adversely affect the protection of the instrument or instrument system against ignition of a surrounding explosive atmosphere. Protective measures against lightning are subject to the approval of the Principal.
5.2
INSTRUMENTATION AND CABLING IN THE FIELD
5.2.1
Instruments and cabling inside "Protected" areas. Where feasible, instruments and cables should be located/routed so that some degree of protection is obtained from earthed structural steel and dedicated lightning conductors. Instruments and cabling installed in such a "protected" area are protected against direct discharges to earth. Together with common installation practices such as the use of twisted conductor pairs, screening, armouring/braiding and proper earthing, no additional protection should be required to abate the induction effect.
5.2.2
Instruments and cabling outside "Protected" areas. During detailed engineering, instruments and cabling located outside protected areas (5.2.1) shall be identified, as lightning protection is required in addition to the common installation practices mentioned in (5.2.1). This may include instruments and cabling located at high points (e.g. instruments on the top of process equipment, cabling installed on top of pipe racks) or in open areas (e.g. tank farms). Instruments located outside protected areas and instruments connected to cables that are routed outside protected areas shall be provided with protective lightning arrestors at both ends of the transmission line. NOTES:
1. 2.
A lightning arrestor shall consist of a gas tube/varistor/zener diode combination approved by the Principal. Devices with fuses shall not be applied. For field instruments such as tank level gauges, telemetry systems, local multiplexers, etc. advice on lightning protection should be obtained from the instrument Manufacturer.
Long communication lines should preferably use fibre optic cabling. If coaxial or twisted pair cabling is applied, galvanic isolation should be used.
32.37.20.10 January 2009 Page 27
6.
PNEUMATIC TUBING All instrument tubing shall be seamless, soft annealed 316 stainless steel. Recommended tubing hardness shall not exceed ROCKWELL No. Rb 80. . All compression fittings shall be 316 Stainless steel of Swagelok make or equal in order to ensure compatibility with existing facilities and minimise stock holding. It is stressed that metric size tubing and fittings are not compatible with their imperial size counterpart. The Company makes extensive use of hydrocarbon gas as an alternative to instrument air on offshore platforms, particularly unmanned platforms. The design shall ensure that the instrument system is compatible with the expected gas composition. Where the length of pneumatic signal-transmission tubing exceeds 60 m, signal booster relays shall be used. Where the tubing length exceeds 90 m, design consideration shall be given to the use of electronic instrumentation. 316 SS tubing is considered to be self-supporting up to a length of 1 m. For longer lengths, the tubing shall be supported over its full length at every 1 m. Air header layout after the primary block valve shall be in accordance with Company practice as shown in the PTS standard drawings. The branch lines shall be connected to the main header with a shut-off valve. All branch line connections shall be made on the top of the line. (Instrument scope commences at the downstream flange of the shut-off valve). Instrument air mains shall be provided with a 316 SS valved branch connection (of one size smaller than the main) at least every 5 m, complete with union coupling, and a 10% spare capacity provision shall be made for future extensions. All future tie-in points shall be valved and plugged. From the main branch lines, all further connections to manifolds and individual air filter/regulators shall be made via 12 mm or ½" O.D. 316L SS tubing. Areas where the carbon steel pipe meets stainless steel piping/fittings, a sacrificial carbon steel nipple shall be installed to cater for galvanic corrosion. The rating of instrument air mains and branch air lines shall be in accordance with Table 4 below unless otherwise specified. Table 4: Instrument Air Mains and Branch Air Lines Nominal Pipe Size Pipe/tubing & Maximum (OD) fitting Material Number of Users DN 15 (½ inch) 316L SS 5 DN 25 (1 inch) 316L SS 25 DN 50 (2 inch) 316L SS 100 Air supply lines shall be sloped towards drain points. A sufficient number of filters, regulators, drain and bleeders shall be provided in the instrument air system. A filter regulator shall be provided for each individual air user and shall be complete with an output gauge. Filter regulators shall be stainless steel to minimise life cycle costs. Instrument air supply lines from the nearest block valve to the air user and the pneumatic signal line shall consist of 12 mm O.D. x 1.0 mm WT or 1/2" OD x 0.035" WT 316 SS tubing and compression fittings.
32.37.20.10 January 2009 Page 28 Instrument air receivers/headers capacity primarily depends on a summed tabulation of all the known users, instruments and instrument system, and their respective consumption rates, which can be obtained from the manufacturers. It also depends on the availability of alternative air sources and has to match other back-up requirements such as UPS, batteries etc.
6.1
GENERAL Single tubing shall be used for signal transmission from field instruments to field mounted junction boxes. They shall be routed above ground through low fire risk regions and shall be provided with some form of protection against mechanical damage. Multicore tubing will subsequently transmit the signals from the junction box to an MDF in the CCR or FAR. Wherever possible and consistent with the design of other plant facilities, multicore tubing should be routed underground because it then has inherent protection against fire and mechanical damage. However, the use of above-ground tubing is acceptable, subject to the Principal's approval, provided a definite cost advantage can be demonstrated, or where it is standard local practice. The design shall cater for spare capacity in multicore tubing. When the design is finalised, 10-15% of the installed tubing capacity shall be available to accommodate unforeseen future plant modifications. Tubing in fire protection and depressuring duties requires protection against fire damage. The design intent of (2.6) and (3) for an electrical signal line applies equally to pneumatic signal lines, except for electrical aspects. Tubing shall be joined by compression type fittings only. Tubing shall be selected for the applicable pressure ratings specified and sized adequately for the required capacity and duty. Tubing material shall be 316 SS as per ASTM A269, with the exception of Molybdenum (Mo) content which shall be 2.5% minimum. Mill certificates of tubing shall be required for every batch of tubing ordered or supplied by fabricators and suppliers. For offshore installation, tubing material shall be either Tungum, 254 SMO, Superduplex Stainless Steel and Alloy 625 to avoid crevice and pitting corrosion caused by chloride attack. For reasons of variety control, fast delivery and to minimise life cycle costs, 317 SS tubing (Mo content of between 3% and 4%) shall not be used unless the process conditions and field conditions warrants their use. With the exception of hydraulic lines, all SS 316 instrument tubing shall have the following dimensions:
OD
Table 5: SS316 Instrument Tubing Dimensions Thickness Applications
¼” 3/8” ½” 6 mm 10 mm 12 mm
0.035” 0.065” 0.035” 1.0 mm 1.5 mm 1.0 mm
Signal Lines Fusible Loops, Impulse Lines, Supply Lines Supply Lines, Drain Lines Signal Lines Fusible Loops, Impulse Lines, Supply Lines Supply Lines, Drain Lines
316L Stainless steel compression type fittings shall be selected for the applicable pressure ratings specified and sized for the tubing described above and shall be installed in strict
32.37.20.10 January 2009 Page 29 accordance with the manufacturer's recommendations. Fittings shall be manufactured by Swagelok. Only NPT type threads shall be used for screwed connections. The thread cutting shall be in accordance with API Code for threading. The number of joints in piping and tubing shall be kept to a minimum, consistent with good practice. All shall be made with the aid of approved tubing benders, correct for the size of tube being worked, to ensure neat serviceable bends. Pipes and tubes shall be run in vertical and horizontal planes as far as possible and shall be run with the minimum number of changes of direction consistent with the good practice and neat appearance. Horizontal runs shall have the pipes or tubes mounted one above the other. Where pipes or tubes run parallel to each other, joints shall be systematically staggered and neatly off-set. Isolation valves shall be located as close to the source as practical. No piping or tubing shall be installed in such a way that it is subject to vibration or any other mechanical stress. All piping and tubing shall be de-burred properly after cutting (preferably with a de-burring drill on a drilling machine). After de-burring process, all piping and tubing shall be cleaned by blowing through with filtered dry and oil-free compressed air before connection to instrument. The installed, but not connected, pipes and tubes shall have their ends capped to prevent the entry of foreign material. All instrument piping connected to process piping shall be run with a slope of not less than 1 to 12, except where otherwise specified. The slope shall be down from the tapping points for liquids and up from the tapping points for gas service. The Contractor must pay special attention to the correct location of vents and drains to ensure that they are respectively at the highest and lowest point of piping runs. All drains shall be connected to the closed drain systems or plugged by an isolation valve. Handling and storage of Tubing Tubing shall be stored and transported in dedicated plastic boxed/tubes, to prevent tubing corrosion before installation. The transport and storage in dedicated plastic boxed/tubes applies for offshore locations and any onshore location, including construction sites. Multi-core Tubing Where indicated on the hook-up drawings, multi-core tubing shall be used. Multi-core tubing shall be routed, supported and secured in a similar manner to that of the electrical cable. All entries to junction boxes shall be made weatherproof, using suitable cable glands and/or bulkhead fittings.
32.37.20.10 January 2009 Page 30 Piping and Tubing Support All piping and tubing shall be adequately supported and/or braced so as to provide maximum protection against mechanical damage and vibration. The distance between supports shall not exceed those in the following table: Table 6: Distance Requirement for Tubing Support Line Size Maximum Distance ¾ inch 1.0 m 1 inch 1.5 m 1½ - 2 inch 2.0 m Multi-core tube shall be supported each 0.25 m. Single tube size 1/2 inch or less shall be supported continuously. For continuously supporting five or more single tubes, one 316L SS cable tray shall be used. For continuously supporting four or less single tubes, 316L SS angle bar (50 x 50), or 316L SS Unistrut channel shall be used. The tubing shall be secured to the tray with fastening blocks at (maximum) 0.6 meters intervals. Blocks with stainless steel cover plates, bolts and nuts shall be delivered and supplied by the Contractor. The supports shall be fabricated by the Contractor (or supports to be made of SS 316L), including coating in accordance with the Painting and Coating Specification 525. Coating shall be finished before installation supporting materials. The required small mounting materials and consumable items shall be delivered and supplied by the Contractor. Capillaries of filled systems shall run independently of all other lines and shall be continuously supported using 316L SS angle bar 316L SS Unistrut channel with adequate fastening clamps or tie-wraps at 0.25mintervals. Adequate means of protecting capillaries from damage shall be employed. Special care shall be taken against kinks in the capillaries on bends or changes of direction. Cable trays shall be run with the width of the tray in a horizontal plane. A short section may be run with the width in a vertical plane after Company's approval. In this case, additional support shall be provided to prevent sagging. Under certain circumstances and with Company's approval, trunking or conduits may be used instead of cable trays. The required materials shall be delivered and supplied by the Contractor. Unless otherwise specified, the process pipelines and handrails shall not be used to support instrument pressure and air piping and tubing. Process equipment, rotating equipment and electric motors which are liable to vibration shall not be used to support instrument pressure and air piping and tubing. Multi-core transit, insert frames and blocks, supplied by the Contractor, shall be provided after piping or tubing installation, in accordance with the drawings or when required by Company.
32.37.20.10 January 2009 Page 31
6.2
SELECTION AND SPECIFICATION OF TUBING All tubing cores shall have an outside diameter of either 6 mm or 0.25 inch, as advised by the Principal. For recommended tubing types, see Table 4 below. Table 7: Recommended tubing types Type Single
Service (note 1) Indoor
7-core
Outdoor above ground only Indoor Outdoor above and underground
Tube Material
Sheath
PE Copper Copper
PVC
PE Copper PE
PVC PVC PVC and lead (note 2)
Outer Colour Black Black
Black Black Black
NOTES: 1. Indoor service includes field cubicles and enclosed field panels. 2. Lead sheathing may be replaced by another type of suitable sheathing.
Background to and abbreviations used, in Table 4: PE Polyethylene, used as tube material. PVC Polyvinyl chloride, used as outer sheathing. PVC as outer sheathing is UV-resistant, flame retardant and commercially attractive.
6.3
JUNCTION BOXES FOR MULTICORE TUBING Pneumatic junction boxes shall be located in low fire risk locations and close to the instruments they serve, to keep the single tubing runs short (typically 15 to 20 m). Tubing shall enter via adapter plates. Any transition from plastic to copper tubing shall be accomplished by means of bulk head connectors mounted on the side walls of the junction box.
6.4
INSTALLATION All fittings shall be brass or plastic, of the compression type and be suitable for the size and material of the tubing. Where air lines leave trunking, bulkhead unions shall be applied. If feasible the bulkhead unions should be of the angle type. If tubing serves instruments without instrument air supply (e.g. to a control valve not having a positioner or booster), the tubing shall be clamped to a 25 mm dummy pipe or angle iron firmly attached to a structure.
32.37.20.10 January 2009 Page 32
7.
IDENTIFICATION AND MARKING
7.1
CABLE IDENTIFICATIONS Quads or pairs shall be identified by black numbers on each individual core of the quads or pairs, no greater than 50 mm apart. If the dimension of a core does not permit this, other means of identifying the cores shall be used. A purpose-made identification method shall be specified for cables in the cable channel, at every 5 meters. In addition, similar identification markings/bands shall be specified for the starting and terminating points of the cable, and on both sides of any wall or bulkhead penetration. The identification markings/bands shall be blue for I.S. cables, green for non I.S. cables and red for F&G cables. Cable identification numbers shall be permanent, character size being 10 mm. Cable numbers shall be as per PTS 32.37.20.31. All cables, whether I.S. or non l.S., shall have black outer sheath regardless of type of cable and conform to BS 5308.
7.2
IDENTIFICATION OF SYSTEM CABLES Each system cable (see PTS 32.37.20.31.) should have a unique identification of the format: c-SC-x whereby 'c' A two-digit number used to identify the relevant MDF. 'SC' Abbreviation for System Cable. ‘x’ A three-digit number used to identify the system cable termination board/block number at the MDF.
7.3
IDENTIFICATION OF SINGLE CABLES/TUBING Each single cable or tube should have a unique identification, linked to the associated instrument, e.g. 120FT-101 and 120FCV-101 are single cables in loop 120F-101 for the transmitter and control valve respectively.
7.4
IDENTIFICATION OF MULTICORES AND JUNCTION BOXES Each instrument multicore signal cable, other than a system cable, and multicore pneumatic tubing should have a unique identification of the format: a-bi-y Junction boxes should have a unique identification of the format: a-Jbi-y whereby: 'a' A two or three digit number is used to identify the process unit. It should be similar to the ‘a’ used for instrument tag number assignment, see PTS 32.31.00.32. ‘J’ Abbreviation for junction box 'b' Letter code to identify the service and/or signal type, as follows: D Cabling for Data transmission, such as telecommunication, data transmission lines, LAN systems, etc. E Electric multicore cabling, except system cabling and cabling covered by one of the other codes. This includes multicore cabling for signals to/from measuring elements, transmitters, transducers, valve Positioners, solenoid operated valves.
32.37.20.10 January 2009 Page 33 P Pneumatic tubing. Q Cabling for Quality measurement signals. S Field cabling for Special applications, such as off-plot cables. T Thermocouple extension cabling. X Special cabling such as fibre optic cables, coaxial cables, etc. ‘i’ Letter ‘I’ , to be used only if the cabling contains intrinsically safe circuits. ‘y’ A three digit serial number, starting from 101 for each unique ‘a-b’/’a-Jb’ combination. The serial number is related to the junction box number. Example: In unit 1200, a junction box is installed with intrinsically safe circuitry. The junction box is identified as 120-JEi-123 and the multicore cable as 120-Ei-123.
7.5
MARKING Signal conductors should be individually marked on each termination side with the corresponding terminal number. NOTE: If multicore cables are fitted which have a colour coding according to BS 5308-1/2 or another standard numbering, e.g. according to IEC 60304, the Principal may waive the requirement for marking the individual conductors.
Instrument tubing shall be marked with the instrument tag number at the point of connection to the multitube. Junction boxes shall be identified with an engraved nameplate of synthetic material. For details of nameplate requirements, refer to PTS 32.31.00.32. and Standard Drawing S 37.601. Cable and tubing markers shall show at least the cable/tubing number. Underground cables and tubing shall be marked at intervals of approximately 5 m by means of lead or stainless steel strips. For long cable stretches (e.g. alongside roads or in tank farms), marking at 10 to 15 m intervals may be sufficient. Above-ground cables and tubing should be marked at their termination points (outside the instrument and junction box) with a suitable label of engraved or embossed material.
32.37.20.10 January 2009 Page 34
8.
REFERENCES In this specification reference is made to the following publications. NOTE: Unless specifically designated by date, the latest edition of each publication shall be used, together with any amendments/supplements/revisions thereto.
PETRONAS STANDARDS Index to PTS publications and standard specifications
PTS 00.00.05.05
Index to standard Drawings
PTS 00.00.06.06
Hydraulic systems for remote operation of shut-off valves
PTS 31.36.10.30
Instruments for measurement and control
PTS 32.31.00.32
System cabling
PTS 32.37.20.31
Instrumentation for depressuring systems
PTS 32.45.10.10
Electrical engineering guidelines
PTS 33.64.10.10
Water-based fire protection systems for offshore facilities
PTS 80.47.10.12
Assessment of the fire safety of onshore installations
PTS 80.47.10.30
Active fire protection systems and equipment for onshore facilities
PTS 80.47.10.31
Painting and Coating of New Equipment
PTS 30.48.00.31
BRITISH STANDARDS Specification for polyolefin copper conductor telecommunication cables
BS 3573
Instrumentation cables Part 1: Specification for polyethylene insulated cables
BS 5308-1
Instrumentation cables Part 2: Specification for PVC insulated cables
BS 5308-2
Mechanical cable glands Part 1: Specification for metallic glands
BS 6121-1
Mechanical cable glands Part 3: Special corrosion resistant glands
BS 6121-3
Code of practice for protection of structures against lightning
BS 6651
Issued by: British Standards Institution 389 Chiswick High Road London W4 4AL England United Kingdom
EUROPEAN STANDARDS Electrical apparatus for potentially explosive atmospheres: General requirements Issued by: CENELEC, European Committee for Electrotechnical Standardization 2 Rue Bréderode, B-1000 Brussels, Belgium
EN 50014
32.37.20.10 January 2009 Page 35 INTERNATIONAL STANDARDS Electrical apparatus for explosive gas atmospheres Part 0 : General requirements
IEC 60079-0
Electrical apparatus for explosive gas atmospheres Part 14: Electrical installations in explosive gas atmosphere (other than mines)
IEC 60079-14
Standard colors for insulation for low-frequency cables and wires
IEC 60304
Degrees of protection provided by enclosures
IP IEC 60529 Code
Thermocouples Part 3: Extension and compensating cables - Tolerances and identification system
IEC 60584-3
Electro Magnetic Compatibility(EMC) Part 5: Installation and mitigation guidelines Section 2: Earthing and cabling
IEC TR 61000-5-2
Issued by: Central Office of the IEC (Sales Dept) 3, Rue de Varembé 1211 Geneva 20 Switzerland. Copies can also be obtained from national standards organizations
STANDARD DRAWINGS Electrical and instrument cable trenches in concrete paved areas
S 19.001
Cable routing in unpaved, brick-paved or tiled areas and crossing roads
S 19.002
Instrument nameplates
S 37.601
Junction box construction
S 37.603
Instrument cable trunking
S 37.604
Typical arrangements of cable trenches in plant areas
S 68.009
Typical earthing arrangements for substations, control buildings and field auxiliary rooms and associated typical mounting details.
S 68.030
NOTE: The latest edition of Standard Drawings can be found in PTS 00.00.06.06.
32.37.20.10 January 2009 Appendix 1 APPENDIX 1 DISTANCE BETWEEN CABLE TRENCHES
32.37.20.10 January 2009 Appendix 2 APPENDIX 2 ARRANGEMENT OF CABLE TRENCHES
32.37.20.10 January 2009 Appendix 3 APPENDIX 3 TYPICAL EARTHING AT FAR/CCR
32.37.20.10 January 2009 Appendix 4 APPENDIX 4 TYPICAL EARTHING OF INSTRUMENT SIGNAL CABLES IN THE FIELD
32.37.20.10 January 2009 Appendix 5 APPENDIX 5 TYPICAL EARTHING OF INSTRUMENT SIGNAL CABLES IN THE MDF
Last Page of this PTS
