This article is about Stainless Steel Tubing and Accessories Installation Checklist and Commissioning & Requirements of Instrumentation and Control Systems as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.
Stainless Steel Tubing and Accessories Installation Checklist and Commissioning
Material Receiving General Checklist for Instrumentation & Control
General – Routing & Supports
No process or service medium, except air, shall be connected into or routed through control rooms, instrument or electrical control buildings, or enclosed field panels. Comment: Sample systems and process analyzers that require a shelter or enclosure are an exception, provided that the requirements for appropriate electrical area classifications are followed. [PIP PCCIP001 Sec 3.1.1]
“Tubes and tube bundles that handle process fluids shall not be installed in channel or cable trays that contain electrical cabling.
[PIP PCCIP001 Sec 3.1.2] ”
Tubing shall not be routed along or supported from handrails. [PIP PCCIP001 Sec 3.1.3]
Tubing shall be installed in a manner that allows for calibration of instruments and removal of adjacent instruments, equipment, and tubing. [PIP PCCIP001 Sec 3.1.4]
Interconnecting instrument piping (tubing) between the primary metering element and the measuring instrument shall be 0.5 inch AISI Series 300 stainless steel tubing minimum. Tubing wall thickness shall be 0.89 mm (0.035 inch) minimum. Applicable piping code and process requirements shall prevail. [PIP PCCFL 001 Sec 3.1.3.10.1]
Interconnecting impulse tubing between a differential flow element and a transmitter shall be limited to a maximum length of 6 m (20 ft) for flowmeters used in control loops. Interconnecting impulse tubing between a differential flow element and a transmitter in compressor suction service shall be kept as close as possible or close coupled. [PIP PCCFL 001 Sec 3.1.3.10.2]
Seal liquids shall not be miscible with nor react with the process fluid being measured. Seal liquids shall be selected so that their potential for contamination of the process fluid is acceptable.[ PIP PCCFL 001 Sec 3.1.3.10.3]
“Supports: All tubing shall be supported to avoid vibration, sags, and vapor/liquid traps. Comment: Tubing supports should be spaced not more than four feet apart. Comment: In locations where mechanical damage is likely, tubing may be installed in structural channel, angle, or in trays, even though not required for normal support. Comment: Tubing should be supported on walls or structural steel whenever possible.
[PIP PCCIP 001 Sec 3.2.1 – Lib drawing DC 950040, 41& 42]”
“When tube bundles or preinsulated/traced tubing are used, the manufacturer’s recommendations for bend radius, support methods, spacing and thermal expansion allowances shall be used as the basis for design and installation.
[PIP PCCIP 001 Sec 3.2.2 – Lib drawing DC 950040, 41& 42]”
Tubes and tube bundles and their support channels and trays shall not be supported from process or utility piping. Tubing channels or trays shall not be supported by bolting to transmitter brackets or control valves. Comment: Tubing may be supported from structural members and instrument stands.[ PIP PCCIP 001 Sec 3.2.3- Lib drawing DC 950040, 41& 42]
“Stainless steel straps or clamps shall be used to attach bare metal tubing to structural angle, channel and cable trays. Tube bundles shall be secured with metal straps and clamps or plastic tie-down straps. Plastic tie-down straps shall be ultraviolet resistant and of a suitable material for the ambient conditions. Comment: Tubing installed in raceways shall be firmly attached to the support at intervals not exceeding 10 feet.
[ PIP PCCIP 001 Sec 3.2.4- Lib drawing DC 950040, 41& 42]”
All instrument piping and tubing to equipment or process piping shall be properly supported to avoid strain on equipment, piping connections, and instruments. Thermal expansion and vibration of the process piping or equipment to which an instrument is connected shall be considered in designing and installing the supports. [ PIP PCCIP 001 Sec 3.2.5 – Lib drawing DC 950040, 41& 42]
Materials of construction for instrument piping supports shall be appropriate for the ambient conditions and shall be consistent with the materials used for other piping supports in the facility. [PIP PCCIP001 Sec 3.2.6]
Tubing Installation
All tubing shall be installed in a neat manner with no signs of crimping, flattening, or bends with radius too small. Tubing shall not be marked or scored. On offshore facilities, scratches may lead to corrosion of 316SS tubing from salt water pitting. [HOKE instrument tube manufacturers manual- PIP PCCIP 001 Sec 3.3.1 – Lib drawing DC 950040, 41& 42]
Tube-bending tools shall be used to form tubes. The minimum bend radius shall be in accordance with directions and recommendations of tube-bender manufacturer. Hand bending of tubes without the use of tube-bending tools is not permitted. [PIP PCCIP001 Sec 3.3.2]
All open tubing shall be capped to keep out dust, dirt, moisture, and other foreign matter.[PIP PCCIP001 Sec 3.3.3]
Tube ends shall be cut square and deburred after cutting. [PIP PCCIP001 Sec 3.3.4]
Tubing shall be assembled with the specified compression fittings in accordance with the manufacturer’s instructions. The proper tools, recommended by the manufacturer, shall be used to assure adequate engagement and tightness. [PIP PCCIP001 Sec 3.3.5]
Tube fittings (for example, unions and tees) installed in individual or parallel tube runs shall be staggered and raised to allow tube removal or reinstallation without distorting or damaging the individual tube or adjacent tubes. [PIP PCCIP001 Sec 3.3.6]
Tubing must have a minimum length of straight run adjacent to bends to allow correct installation of fittings. [PIP PCCIP001 Sec 3.3.7]
Threaded Pipe Connections: All threaded pipe connections shall be tapered and comply with ASME B1.20.1. [PIP PCCIP001 Sec 3.4.1]
Sealant/lubricant for threaded instrument piping connections shall meet the requirements of the process service. [PIP PCCIP001 Sec 3.4.2]
Polyfluorethylene (PTFE) tape shall not be used as a thread lubricant on pipe threads for pneumatic signal or instrument air pipelines that are downstream of the filter regulator, except with owner approval.[PIP PCCIP001 Sec 3.4.3]
Instrument connections for process service shall be in accordance with Appendix 1( Attachment 1) . Threaded connections shall be tapered per ASME B1.20.1.
Instrument air branch lines shall originate from the top of the header. [PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.1]
Block valves are required for branch connections less than NPS 2 and shall be located at the header. [PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.2]
The main instrument air header size shall be 2 inches minimum.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.3]
A 1-inch-size line shall supply no more than 15 instruments.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.4]
Minimum size of takeoffs to individual users shall be 1/2 inch.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.5]
A maximum of four users (single pneumatic instruments or valves) may be connected to one 1/2-inch takeoff.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.6]
Threaded joints in instrument air service shall be made using Teflon dispersion sealant. Teflon tape as a substitute shall be used only with owner approval. Comment: When installed improperly, small pieces of Teflon tape can flake off, enter the air stream, and create a potential plugging hazard for the internal components of pneumatic devices.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.7]
Materials for pipe for instrument air systems shall conform to PIP PN12CS2T01.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.9]
Materials for tubing for instrument air systems shall conform to PIP PCCIP001.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.10]
Spare taps complete with valve and plug shall be installed on instrument air sub-headers to allow for future instrument installations that require air.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.7.11]
Building penetrations for instrument pneumatic piping and tubing shall be consistent with the building requirements. The intended use and location of the building may require pressure-tight and flame-retardant penetrations. [PIP PCCIP001 Sec 4.2.1]
Instrument air tubes, tube bundles, and tube trays shall be routed to avoid excess heat or damaging hot spots. Avoid routing directly above pumps handling flammable materials, near furnaces, or air-cooled exchangers, except when routed to final instrument air users. [PIP PCCIP001 Sec 4.2.2]
As a minimum, brass tube fittings shall be used to connect instrument air or pneumatic signal lines. Plastic tubing fittings or brass fittings with plastic ferrules shall not be used.[PIP PCCIP001 Sec 4.2.3 ]
All main and branch headers shall be sloped {minimum 64 mm per 30 m (2.5 inches per 100 feet)} and provided with low point drains.
All headers shall terminate with a line-size valve, blind, or plug to facilitate cleaning and plant expansions.
Each branch header shall connect to the top of the Main header through a branch line size full bore isolation valve.
Where there is a general distribution system for more than one plant, the piping shall be connected in a loop to provide two directions of supply to each plant. Isolation valves shall be provided to enable isolation of each plant.
Supply take offs to individual instruments shall connect to the top of the branch header through a takeoff-line-size, full bore isolation valve.
Twenty percent (20%) spare takeoff fittings and block valves shall be installed on the branch header.
For installations in which the instrument air consumers are located more than 600 m (2000 ft) from the instrument air compressor; pipe sizes should be calculated to keep pressure drops within the limit. [The pressure drop for piping between the dryer after filter outlet and the most remotely located user shall not exceed 35 kPa (5 psi) under maximum service flow rate.] Below 600 m (2000 ft) instrument air header pipe size should be selected from Table 2.
Table 2
Number of Users ————– Pipe Size
1 – 4 ————– ½ inch
5 – 9 ————– ¾ inch
10 – 15 ————– 1 inch
16 – 80 ————– 1½ inch
81 – 150 ————– 2 inch
151 – 300 ————— 3 inch
Instrument air piping shall not be pocketed (i.e., shall not contain, U-sections). Instrument air piping shall not be installed underground. Exception: Instrument air branch connections may be buried to cross beneath roadways or fences where there is no existing overhead rack and where the aboveground support would interfere with crane or emergency vehicle movement. Prior approval from the General Supervisor, Process Instrumentation Division, P&CSD is required. Buried branch lines shall have low point drains, stainless steel construction and external coating per SAES-H-002.
Testing
Before energizing the air supply to instruments, instrument air piping shall be inspected and cleaned of trash, particles, and foreign objects by blow down with clean, dry air. [PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.10.1]
Instrument air systems shall be pressure tested pneumatically using dry air or inert gas. Hydrostatic testing shall not be done because of the risk of contamination.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.10.2]
Leak tests shall not be made at pressures higher than the maximum operating pressure of the system.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.10.3]
Liquid leak detector (liquid soap solution) shall be used to check for leaks.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.10.4]
Leaks shall be repaired only after the system is depressurized.[PIP PCCIP001 Sec 4.1 and PIP PCCIA001 Sec. 3.10.5]
Commissioning
“All pneumatic instrumentation shall pass:
a) Leakage test of all piping and tubing”
“All pneumatic instrumentation shall pass:
b) Functional test of all pneumatic instruments”
“All pneumatic instrumentation shall pass:
c) Functional test of all pneumatic control loops”
“All electric/electronic instruments and systems shall undergo:
a) Functional test of all electronic instruments after testing for short circuits, cable continuity, ground insulation with a “”megger””, and ground faults.”
“All electric/electronic instruments and systems shall undergo:
B) Functional test of all electronic control loops verifying a proper response to a simulated input signal.”
“Pneumatic Tests
Instrument process tubing shall be tested pneumatically to 1.1 times design pressure starting at the root valve and ending at the instrument.
International Standard and Codes for Stainless Steel Tubing and Accessories
Copper Tubing, Brass Fittings, and Valves for Instrument Service
3. SAES-J-901 – Instrument Air Supply Systems – 30 June 2003
4. 34 SAMSS 831 – Instrumentation for Packaged Units – 5 April 2008
5. PIP PCSIP001 – Instrument Piping and Tubing Systems Specifications – Oct. 2002
6. PIP PCCIP001 – Instrument Piping and Tubing Systems Criteria – Oct. 2002
7. PIP PCCIA001 – Design of Instrument Air Systems Editorial Revision – March 2003
8. Swagelok Tubing data. Http://www.swagelok.com
1. Attachment 1: Instrument and Process Connections
