General Instrumentation Installation Practice in Refinery

Here we are going to discuss General Instrumentation Installation inspection points and Instrument installation practice (For Engineers only)to be checked in plants and industrial instrumentation for Electrical and Instrumentation QC Engineers. Main keywords for this article are General Instrumentation Installation Practice in Refinery.

What is Instrument Installation basic requirement for Instrumentation Engineers? Explain precaution prior and after installation.

Installation: It is very hard to explain or define Installation all together at same time but in simple way we can explain standard instrument hook-up the parameter with process, sub-system or any system as per approved drawing is called Installation. Usually there are two types of installation: inline and offline or remote.

They basic precaution for instrumentation Installation could be as following:

Material: Ensure that material is as per spec and suitable to use.

Calibration: Ensure that parameter is functioning fine prior to take it for site to install.

Location: Ensure the location is as per P&ID and elevation is per approved Layout: All instrument remote type should be mounted as close as possible to the process connection, consistent with required accessibility, operability, maintainability, visibility and not be subject to vibration, invisible and obstacle to walkway etc.

Instrument Height: Instrument should be mounted as closer to grade than 1.2 to 1.5 meter unless specified or approved.

Nozzle orientation: for Gas must be vertical or 45o below vertical, for Liquid must be horizontal or 45o below horizontal, for steam must be horizontal or 45 above horizontal in normal cases for exceptional it may vary upon mutual agreement only.

Instrument: instrument must above tape for Gas, below tape for liquid and steam.

Instrument Installation: most instruments are susceptible to damage, abnormal wear, or malfunction if mounted in a location where the are subject to vibration. If any part of the flow system or equipment is subject to vibration, the affected instrument should be provided with vibration free stanchion/support/bracket etc.

Impulse Line: Tubing for remote devices should be as short as possible, 3 feet for close-coupled transmitters and preferably not more than 20 feet (6mtrs). Slope should be at least 1 inch per foot (12:1) for liquid /steam services towards instrument and for gas towards process.

Impulse Tubing for Gas service: Instrument and impulse line for gas service must be free from liquid pocketing and slope should be towards process since instrument is mounted above process taping.

Impulse Tubing for Liquid service: Instrument and impulse line for liquid service must be free from air trapping and slope should be towards instrument since instrument is mounted below process taping.

Impulse tubing for Steam service: Instrument and impulse line for steam service must be provided with Seal-pot (condensate port) to avoid damage of device by heat and slope should be towards instrument since instrument is mounted below process.

Access Field mounted: for maintenance purpose all locally mounted devices shall be easily accessible, operable, maintainable, and removable from grade, platform, fixed walkway or fixed ladder etc.

Local Panel mounted: Where several instruments are installed within a small area, consideration shall be given to mounting them on a common local panel / board and sunshade shall be provided to avoid calibration drift if they are in open area.

Differential type Instrument: Should not be installed in a service where the measured liquid gravity will vary widely and often, magnetic, PDmeter or turbine should be used.

Displacer type Instrument: should be always be installed in a manner to permit removal without disconnecting major process piping, shall be installed in external chamber with block and drain valves. Shall never be considered for vessels which are subject to high vibration.

Indication: Instrument Indicator should always be installed in front means visible for manual station, obstacles to see unacceptable.

Cable way: Tray/Conduit: Cable way must be made of adequate fitting and all standards accessories even site fabricated fitting and Accessories are acceptable as long as they comply to standard bending radius and sharp bending must be avoided.

Cabling: Proper segregation must be maintain for power, signal, control, TC etc cable and slaking, twisting, crossing, and sharp bending must be avoided and loop shall be provided at the end of instrument for easy removal of instrument.

Cable dress: Cable must be dress nicely with cable tie (the approved material)

Transmission: Hydrocarbon or other process fluids should not be piped to any instruments located in a control room. Standard industry practice is to convert the process variable to an electrical or pneumatic signal and transmit the signal to remote receiving instruments.

Seal / Gland: If cable is being run through conduit then seal fitting must be provide for Zone 0 and zone 1 area, if Tray is used then cable should be connected to instrument through gland.

Wiring: Wiring must be done in such a manner that shrinkable ferrules shall be provided with from/To address (cross ferruling) for easy maintenance.

Name plate: Name plate must be provided of Stainless steel as well as Phenolic with clear alpha-numeric number as per approved drawing and must be readable.

Purging Sealing : When viscous liquids or pressure of corrosive, slurry, or freezing process fluids are measured or when plugging is possible where solid exist, an instrument may be sealed, purged, or protected by a diaphragm seal or protector.

Steam Heat tracing: The need for heating depends on the severity of the winters in the locality to prevent freezing. Since steam is normally available in the plant process unit, steam heating has the advantage of being readily accessible steam. Steam supplies high-density heat from condensation, and large quantities of heat can be obtained from a single tracer line. On the other hand, steam delivers heat at a temperature that corresponds to the saturated steam pressure in the tracer

 Electrical Heat Tracing: Electrical heating selection care must be exercised to ensure that they are not potential source of ignition. Several types of cables are available (mineral Insulated MIC, and self limiting)

Insulation/protective covering: The entire tracing system for impulse lines should be carefully insulated and waterproofed. Particular care should be used at the point of measurement and at the entry into insulated enclosure. A durable protective cover should be used where stainless steel tubing is used, chloride-free insulation must be specified to prevents stress corrosion cracking.

If one Pressure Transmitter is installed at site, how many inspections are related to that one instrument?

  • Cable Tray Installation Inspection.
  • Cable Laying Inspection.
  • Cable IR/Continuity Test Inspection.
  • Cable Glanding &Termination Inspection.
  • Instrument Tubing Installation Inspection.
  • Final Instrument Installation Inspection.


What are the necessary points to be inspected for cable laying?

They shall be as following:

Ø Material inspection as per approved materials specification and Purchase order

Ø Cable Types and size as per spec and cable schedule

Ø Cable meggering and continuity prior to cable pulling and recorded in QVD

Ø Updated Cable routing drawing shall be available prior to cable laying

Ø Completion of cable route (tray, conduit or trench etc.) prior to cable laying

Ø Segregation and separation shall be maintain after cable laying (dressing)

Ø Cable bending radius should be as per spec and vendor recommendation

Ø Proper tools and accessories should be used to avoid cable damage

Ø Cable dressing shall be done in good workmanship to avoid slaking, twisting etc.

Ø Cable numbering (tags) shall be provided as per spec and Drawing.


What is the basic requirement for cabling?

Instrument cable shall be routed separately from electrical cables, details are below:

separation of signal and power cable on parallel run shall be as below:

Power Cable Instrument signal / control / power cable etc

125VAC or 10A              250 mm

250VAC or 50A              500 mm

440VAC or 200A            750 mm

3.3KVAC or 500A           1250 mm

11KVAC or 800A            4000 mm

-Separation of signal and power cable for crossover should be 250mm as minimum.

What are the inspection points of cable tray installation inspection?

First Required IFC drawing (cable tray lay out diagram).

Check material: aluminum free of cooper or SS316 for classified areas. Follow the

NEMA VE-2 standard for cable tray installation.

What are the checks you will perform for a cable tray installation?

Supports prefabrication, Installation & layout as per approved drawings, Supports & hangers installed properly, Clamps & fixings properly installed ,

Expansion joints, splice plates and fittings correctly located, Midspan deflection acceptable, Clearances from other structures and components, Cable tray without roughness.

Cable tray Inspection Notes

First I will check cable tray routing as per drawing.

I will check support as per standard.

I will check nut bolt as per Steen less steel and proper tight.

I will check bonding jumper as per with 25m

I will check expiation joint with in 20m..

I will check all support tray made steel or iron either hot-dip-galvanized or zinc electroplated.

I will check tray to tray distance. 

Cable Tray Inspection Documents

  • Cable laying drawing and IPL or location drawaing.
  • The elevation of the bottom of the lowest interior cable tray shall be a minimum of 2.67 m above the main substation floor. SAES-P-119 Sec. 6.3.3.
  • All cable trays shall have a minimum of 300 mm clear space above the tray. (NEMA VE 2 Sec. 4) SAES-P-104 Sec. 3.2.
  • A minimum of 200 mm of vertical clearance shall be provided between cable trays. SAES-P-119 Sec. 6.3.2.
  • Supports should be located within 2 ft. (600 mm) of each side of vertical adjustable splice plates. (NEC 110.3, NEMA VE-2 Sec.4.3.3).
  • Place horizontal tee supports within 2 ft. (600 mm) of each of the three openings connected to other cable tray items for the 12 in.
  • All fasteners (i.e., nuts, bolts, washers, etc.) used to connect and assemble the cable tray system shall be 304 SS. In severe corrosive environments, 316 SS fasteners shall be used.
  • Channel erector system components (Unistrut or similar) used to support cable tray shall be made of steel or iron, either hot-dip galvanized (preferably), or zinc electroplated as supplied by the manufacturer.
  • Cables are fastened a minimum of every 18 in. (450 mm) on vertical runs. (NEC 110.3, NEMA VE-2 Sec.5.6) SAES-P-104 Sec. 4.1.
  • Cable trays shall not have sharp edges, burrs, or projections that could damage the insulation or jackets of the wiring. [NEC 392.5 (B)]
  • Minimum thickness of covers shall be 1 mm. SAES-P-104 Sec. 9.2.
  • Cable tray installed outdoors shall have ventilated covers. SAES-P-104 Sec. 9.1
  • Cable trays run vertically in outdoor areas shall have covers on both sides. SAES-P-104 Sec. 9.1
  • Flanged type covers shall be secured with stainless steel banding, one band per ½ m of cover length, with a minimum of six bands per cover. SAES-P-104 Sec. 9.1.

What are the inspection points for duct bank inspection?

First we check survey report.

  1. Type of conduit material
  2. It should be- PVC gray color conduit. Schedule 40 as per NEMA TC-6/8
  3. Size:- 3” to 6”
  4. Separation between conduits
  5. 50mm or 150mm from the conduit centre to centre.
  6. separation between reinforced to conduit
  7. 75mm minimum.
  8. Separators should be provided every 2.4 meter
  9. Bell end to be provide very end point of conduit.

How to check the installation of inst. panels?

  • The complete assembly shall be checked to ensure alignment and level after the tightening the bolts.
  • The instrument shall be checked against identifying labels d and tags are installed as per the layout drawing.
  • Earthling of the panel shall be checked to ensure it is as per detailed drawing.
  • The installation shall be rigid.
  • Panel doors and detachable cover shall be checked to ensure proper closure and sealing .

Connections at Field Junction Boxes:

  • First I will check all instrument cable entries to field junction boxes shall be through the bottom.
  • The outer jacket Twisted, multi-pair/triad cables shall be cut to the appropriate length to minimize looping and flexing of the cable within the junction box.
  • The outer jacket of shielded twisted single pair/triad cables shall be left intact up to the point of termination. (Approximately three to four inches from terminal blocks).
  • The shield drain wire shall be insulated from jacket end to terminal. Approximately, one inch of heat shrink tubing shall be applied over the jacket end.
  • Drain wires and Mylar shields on shielded cables shall be cut and insulated with heat shrink sleeve.
  • Spare pairs/triads in multi-pair/triad cables shall be labeled “Spare” in addition to the destination and source terminal numbers.
  • For individually shielded twisted multi-pair/triad cables each pair/triad shall be heat shrink sleeve insulated from the cable-jacket-end up to the point-of-termination to keep the foil shielding intact and free from accidental grounds. The shield drain wire shall be insulated from foil end to terminal. Approximately, two inches of heat shrink tubing shall be applied over the jacket end.
  • All wiring shall be tagged at each end. Each wire tag shall have two labels. The first label (closest to the end of the wire) shall identify the terminal number to which the wire is physically connected. The other label shall be the terminal number of the connection of the opposite end of the wire.
  • Wire tag information shall be permanently marked in block alpha numeric or typed on tubular, heat-shrinkable, slip-on sleeves. Wrap-around, snap-on or self-adhesive wire markers shall not be used. Handwritten wire tags are not acceptable.
  • A clear heat shrink sleeve shall be installed over the wire tag for all instruments that use rust preventive grease on its threaded wiring access cover.

Cable Tagging Inspection:

  • All cables shall be tagged, at each end, with a cable-tag.
  • Homerun cables shall be tagged with the assigned “IC” cable number.
  • Cable tags outside junction boxes and marshaling cabinets shall be 316 SS with permanently marked alphanumeric characters i.e., raised or stamped characters.
  • Outside junction box The cable tag shall be securely attached to the cable with stainless-steel cable ties. Terminal Reference: Each row of terminals shall be uniquely identified alphanumerically, e.g., TS-101, TS-102, etc.
  • The terminals in each row shall be sequentially numbered starting at number one (1). The number of conduit entries shall be kept to a minimum.
  • All unused entry ports shall be fitted with approved plugs.
  • How to check the instrument installation?
  • Check the identification tag)
  • Check the elevation if it is above or below the process tapping point
  • The support shall be rigid
  • The instrument shall be accessible.

What are the checks you will perform for installation of JB?

Fabrication of JB Support as per drawing, support earthed. JB location as per approved drawing. JB shall be free of damage. Type 316 stainless steel Body, door and hardware. Continuously welded seams, finished smooth. Stainless steel captive clamps. Data/Print pocket on inside of door. Ground stud for terminating A/C safety ground wire. A gasket shall be secured with adhesive. Junction boxes having an internal volume exceeding 2,000 cm³ shall be provided with Type 300 Series stainless steel breather and drain fittings, or a combination breather and drain fitting. JB shall conform to all applicable requirements, standards, and specifications. A coding system to indicate the degrees of protection provided by an enclosure against access to hazardous parts, ingress of solid foreign objects, ingress of water and to give additional information in connection with such protection. A designation of the degree of protection provided by an enclosure is indicated by the IP Code arranged. . (IEC 60529 sec. 3.4 and 4). Locations where chlorine or other corrosive chemicals are being handled are also corrosive environments. In these locations, enclosures must be resistant to the chemicals present.In hazardous (classified) areas, General Box that are required by the National Electrical Code (NEC) to be approved) shall be labelled or listed or certified by any of the agencies,

What are inspection points for field instruments with impulse tubing? 

Ans: Materials inspection as per approved spec material, type and size, Installation as per Hook-up, check line route to avoid any obstruction, check tube bending, and check tube support, compression fitting or ferrules, and then pressure test (hydrostatic test) shall be done.

1.I will check taping point as per P&ID. Or high or low as per P&ID

  1. I will check slope

3.I will check tubing support should be spaced not more then 4 feet.

What are the checks you will perform for a field Instruments with impulse tubing? 

Fabrication of Stand as per drawing, Instrument location as per IPL Drawing, Access is unobstructed and clear for maintenance, Stand earthed, Instrument mounted in accordance with hook up drawing, Check instrument is correct in accordance with ISS / P & ID, impulse tubing material used according to specification, Isolation and equalization valves / manifold installed, Vent and drain / manifold installed, Verify Tubing connection to HP & LP sides, Impulse tubing length, tubing slope, Elevation correct relative to process tapping.

For Gas and Vapor Service- For gas and vapour service, transmitters shall be mounted above and as close to pressure taps as possible while still maintaining accessibility. Impulse lines shall slope continuously downward from transmitter to root valve such that they are self-draining (minimum one inch per foot).

For Liquid or Condensing Service- For liquid or condensing service, transmitters shall be mounted below the pressure taps. Impulse lines shall slope continuously upward from transmitter to root valve such that they are self-venting (minimum one inch per foot).

For steam service, the transmitter may be mounted above the pressure taps with a siphon or pigtail or below the taps with correction for static head in the process tap lines.

Leak Test done, Pressure Test of impulse tubing.

What are the checks you will perform for a conduit inspection?

Conduit installation as per approved drawings, Supports installation &support distance, Correct type & size, Conduit bending radius, Internal surface smooth & free of sharp edges, Alignment and straightness, Clearances from other objects, Bodies, fittings, unions, nipples and other components installed properly, low point drain installation, Bushings installation (where applicable), Grounding connection (when applicable)

What are the checks you will perform in a material receiving inspection of received cable?

Review Quality Documentation for Material Receiving- Purchase Order and specification sheet criteria shall be confirmed and compared with stainless steel tags / labels and nameplates, and shipment checked for damage, prior to acceptance of the shipment Cable materials supplied shall be third-party listed as meeting the requirements of UL standards (UL 13, 1277, 1709, 2250, NEC Article727, and NEC Article 725 as applicable, or approved equal standards). (NFPA 70 NEC) – cable materials shall be new and unused-Free of Damage-

What are the checks you will perform for installation of instruments?

1.Instrument location as per IPL Drawing

  1. Instrument mounted in accordance with P&ID hook up drawing,
  2. Check instrument is correct Elevation
  3. Access is unobstructed and clear for maintenance,
  4. Fabrication of Stand as per drawing
  5. Stand earthed,
  6. Instrument Calibrated prior to installation and documentation checked,
  7. I will check instrument securely installed

The most important activities for pre-loop checking inspection are:

  • Check the hook-up and installation of instruments is correct.
  • Check that impulse lines are pressure tested.
  • Check the cable continuity and resistance test are completed.
  • Check that all the instruments involved in the loop are calibrated.
  • Check the correct wiring and tagging of instrumentation cable point to point from marshalling cabinet to instrument at field side, in accordance to wiring diagram loop. All of them

What are inspection points for a cable laying? 

Ans: Material inspection as per approved materials, types and size, meggering, cable routing drawing, completion of cable route ( tray, conduit or trench etc ) and cable numbering (Tag), cable bending, use or proper tools and equipment for cable pulling.

First I will check cable laying as per IPL(instrument point and line ) or location drawing,

  1. I will check cable schedule
  2. I will check specification marking cable outer jacket
  3. I will check cable tag ss both side installed

Document required cable laying RFI

IPL(instrument point and line ) or location drawing, cable schedule.

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