1. PURPOSE – This article is about technical requirements for representing instrumentation information on tubing hookup details, more will be discussed about Process Tubing, Instrument Air System Technical Requirements, Pneumatic Tubing, Analyzer Tubing Technical Requirement.
2. SCOPE
This general technical requirement applies to all instrument packages in all petrochemical and other plants.
3. RELATED DOCUMENTS
3.1 Engineering Documents
Worldwide:
3PS05005 Process Analytical System Pressure Regulation and Relief
3PS05010 Analyzer Systems Design Guideline for Hazardous Applications (Including Analyzer Houses)
Oxygen Clean (Class AA) Inspection and Acceptance Requirements
Tubing for Instrumentation Service
Copper Tubing, Brass Fittings, and Valves for Instrument Service
Stainless Steel Tubing, Fittings, and Valves for Instrument Service 70 bar g (2500 psig) Maximum
Bundled Tubing for Instrument Service
Electrically Traced Tubing for Instrument Service
Analyzer Vent Systems
Instrument Tubing Hook-Up Detail Analyzer Sample Moisture Removal Enclosure
- GENERAL
4.1 All instrument hookup diagrams shall be per standard instrument design details. Any special diagrams shall be generated using the standard format.
4.2 A cover sheet and general notes shall be released with all instrument hookup detail packages.
4.3 Each hookup diagram shall be shown schematically with all fittings, valves, and tubing, referred to by the bill of material item number.
4.4 Instruments with similar hookup details shall be included on one diagram to eliminate multiple diagrams containing identical content.
5. PROCESS TUBING
5.1 All instrument process tubing sizes, wall thicknesses, pressure ratings, fittings, and valves shall be selected from the information in Tubing for Instrumentation Service, Copper Tubing, Brass Fittings, and Valves for Instrument Service, Stainless Steel Tubing, Fittings, and Valves for Instrument Service 170 bar g (2500 psig) Maximum, Bundled Tubing for Instrument Service, and Electrically Traced Tubing for Instrument Service.
5.2 Tubing for oxygen or ultrahigh-purity (UHP) service shall be hydrocarbon decontaminated (Class AA clean) as defined by Oxygen Clean (Class AA) Inspection and Acceptance Requirements.
5.3 All process tubing to a Gage pressure-measuring instrument shall include a two-valve manifold installed between the process root valve and the instrument, located at the instrument. All two- valve manifolds shall be cleaned per Oxygen Clean (Class AA) Inspection and Acceptance Requirements.
5.4 Differential-pressure instruments shall include a 3-valve manifold when used on pressures of 10 bar g (150 psig) and below, and a 5-valve manifold for pressures over 10 bar g (150 psig). All manifolds shall be cleaned per Oxygen Clean (Class AA) Inspection and Acceptance Requirements.
5.5 For critical circuits when the flowsheet identifies a “lock open” (LO) or “lock closed” (LC) valve within the instrument connection tap, the manifold valve must be specified with removable Anti- Tamper bonnet that can be locked into position. Single isolation valves should have a mechanical locking device.
5.6 For projects that have a pressure and flow transmitter in a condensable vapor line and the instruments are mounted below the piping process connection, the instrument tubing shall be electrically heat traced and the instruments shall be mounted in a heated enclosure or an insulated covering. Heat tracing and enclosures shall be used only when freeze protection is required by ambient conditions. Check with Project Engineering for site conditions.
5.7 When instruments can be mounted above a condensable-vapor line, the tubing must be sloped to the process line, avoiding any low points. Depending on site location, insulation and/or heat- tracing may be eliminated. Consult with Project Engineering for heat-tracing requirements.
5.8 Any process tubing which might accumulate condensation in the line, requires condensate traps at the low point of the tubing run to the instrument. Heat-tracing might be required to avoid freezing (see paragraph 5.7).
5.9 In most steam process applications, avoid mount instruments above the process connection. If above mounting can’t be avoided, a siphon shall be installed at the process connection with the instrument mounted above the tap to keep live steam from overheating the instrument.
5.10 For instruments mounted below a process line containing steam, a fill tee shall be installed in the tubing so that the line can be filled with water for protection of the instruments. Check heat tracing requirements.
5.11 When mounting instruments for liquid service (for example, cooling water), the instrument shall be mounted below the tap with the tubing sloping toward the instrument. Check heat tracing requirements.
5.12 Process tubing for hydrocarbon gases shall be designed with no threaded joints. The connection to the field instrument shall be threaded unless otherwise indicated by the instrument specification. All root valves will have socket weld connections for installation of a “male pipe weld connector.”
5.13 Tubing containing combustible or toxic gases shall have welded connections, whenever possible. A male pipe weld connector shall be used at all socket-welded valves.
6. PNEUMATIC TUBING
- For pneumatic-signal outputs on field instruments, a tubing tee with a fitting plug shall be installed, for calibration purposes, as close as possible to the instrument.
- When a single pneumatic signal is controlling two or more process variables, an isolating block valve must be installed on each circuit for service and maintenance purposes.
- External connections to the reset bellows (ECRB) on local pneumatic controllers are not shown on the flowsheet and must be identified by reviewing the controller specification. Installation details must be reviewed by the Process Control Engineer.
7. INSTRUMENT AIR SYSTEM TECHNICAL REQUIREMENTS
7.1 All instrument air subheaders shall be diagrammed by the instrument designer on the tubing hookup details. Pipe size will range from 1/2 to 11/2 inch with material type determined on a project-by-project basis. The following information shall be used by the instrument designer when sizing sub-headers:
- 7.1.1 For design purposes, instrument air consumptions are:
Transmitter 0.25 SCFM
| • Valve Positioner | 0.5 SCFM |
| • Controller | 0.5 SCFM |
| • I/P | 0.5 SCFM |
| • Solenoid Operated Valve | 1.5 SCFM |
| • Small Booster Relay (see 7.1.3) | 2.0 SCFM |
| • Air Set (see 7.1.3) | 10.0 SCFM |
Critical Solenoid Operated Valves (see paragraph 7.1.4)
- Maximum allowable flows in supply piping are:
- The listed flows are maximum; actual consumption by boosters and air sets is limited by the item supplied.
- Critical solenoid-operated valves are those which must operate in less than 2 seconds when pressurized. Use flow equal to actuator volume (in3) divided by 50.
- Flows listed are for 30 m (100 ft) runs and are based on a 0.34 bar (5 psi) change. For other lengths, multiply flow by 120/(LA+20), with LA equal to actual length in feet. Minimum length is 10 ft.
7.2 All field-mounted pneumatic instruments shall have a filter regulator installed in the instrument air supply tubing unless already furnished with the instrument. Conoflow Model # (See instrument BOM) is the preferred filter regulator. Some regulator gauges may require that kg/cm2 or bar g pressure ranges be shown. Check with Process Controls or Project Engineering for metric pressure identification.
8. ANALYZER TUBING TECHNICAL REQUIREMENT
8.1 Sample lines from the field shall be 1/4 inch copper or stainless steel tubing. Specify Class AA cleaning (Oxygen Clean (Class AA) Inspection and Acceptance Requirements) for sample lines containing oxygen and all sample lines to hydrocarbon analyzers.
8.2 Stainless steel tubing shall be used according to purity requirements, atmospheric conditions, or customer request. Consult Process Controls Engineering for purity requirements. (Welded systems are necessary for certain UHP requirements.) All tubing for oxygen and UHP service shall be cleaned per this article Oxygen Clean (Class AA) Inspection and Acceptance Requirements.
8.3 Whenever possible, sample lines shall be run with no union connections. To avoid sample contamination, continuous tube bundles are preferred. Bundles shall be extended to the analyzer panel connections. Avoid the use of junction boxes.
8.4 Generally, the best way of getting the sample tube bundle(s) to an analyzer room is via cable or tubing tray. In rare cases when underground conduits or direct burial are required, inform the project electrical designer regarding the conduit size and location which will be added to the underground package drawing(s).
8.5 Instrument air might be required inside analyzer panels. If required, run air header and regulate inside the analyzer panel.
8.6 For moisture analyzers, the tubing shall be 1/4 inch from the process connection to the probe enclosure. The enclosure shall be mounted as close as possible (maximum 10 ft) to the process connection to avoid excessive moisture buildup in the tubing. The probe vent tubing shall be vented to a safe location, bent 90 degrees for weather protection and have a Fisher model #Y602-5, 3/8″ or equivalent bug screen installed.
8.7 Sample line pressure control valves (PCV) will be shown on the P&ID.
8.8 Sample lines which normally contain more than 10% combustible or toxic gas shall be equipped with flow restrictors. Note that this includes hydrogen samples. Install the excess flow restrictor outside the analyzer building at an accessible location. The restrictors shall be per guideline 3PS05010, Analyzer Systems Design Guideline For Hazardous Applications, Appendix A. Flow restrictors shall be type of O’Keefe Controls Co., Precision Micro-Orifices.
8.9 For analyzer sample lines that contain excessive moisture, a moisture removal unit should be considered. Use Air Products Standard drawing STD-A060 for the sample line moisture removal enclosure.
8.10 The tubing from all calibration bottle regulators to the related analyzers will be 1/4 inch copper, for low purity applications and 1/4 inch stainless steel for high-purity (HP) and ultrahigh-purity (UHP) applications. Specify hydrocarbon decontamination for all tubing connected to cylinders containing 25 to 100% oxygen and all tubing connected to hydrocarbon analyzers.
8.11 Analyzer manifold regulator assemblies which are used on cylinders containing combustible or toxic gases shall be supplied with a flow restrictor device. For additional manifold regulator assembly information, refer to 3PS05005.
8.12 For all analyzer sample lines that require coiled tubing see the P&ID for tubing coil lengths.
8.13 All root valves installed by piping for hydrocarbon sampling will have a socket weld connection. A “male pipe weld connector” will be indicated on the tubing hookup details.