- PURPOSE
1.1 This engineering standard defines the criteria for the selection of stainless steel tubing, fittings, and valves used for high pressure instrument services.
- SCOPE
2.1 This standard applies to all field instrument packages, except instrumentation for ultra-high purity service.
2.2 This engineering standard shall be used for tubing in instrument service at pressures up to
415 bar g (6000 psig) and at temperatures from -30° to +150°C (-20° to +300°F).
- RELATED DOCUMENTS
3.1 American Society for Testing and Materials (ASTM)
A182 Specification for Forged or Rolled Alloy-Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service
A269 Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General
Service
A276 Specification for Stainless Steel Bars and Shapes
3.2 American Society of Mechanical Engineers (ASME)
B31.3 Process Piping
- MATERIAL SELECTION
4.1 Applications exceeding the limitations of this standard shall be referred to the Mechanical
Systems Engineering Group for preparation of a special specification.
5. TUBING 5.1 Tubing sizes shall be as follows:
| • Process tubing
• Pneumatic signal tubing • Analyzer sample tubing • Instrument air supply tubing within 18 inches of user |
3/8″ OD
1/4″ OD, for response speed 1/4″ OD, for response speed
3/8″ OD |
Note: The project team will review customer requested deviations from this standard.
4PS52003A, Rev. 1, Page 2 of 2
5.2 Design pressures have been calculated using ASME B31.3 allowable stress values and A269 manufacturing tolerances.
5.3 Tubing shall be fully annealed seamless Type 304/304L dual-certified stainless steel per ASTM A269, hardness RB80 or less. Type 316/316L dual-certified may be substituted when Type 304/304L is unavailable. Wall thickness shall be per Table 1.
| TABLE 1- STAINLESS STEEL TUBING WALL THICKNESS
OD WALL MAXIMUM PRESSURE (inches) (inches) bar g (psig) |
|||
| 1/4 | .049 | 415 6000 | |
| 3/8 | .065 | 415 6000 | |
- FITTINGS
6.1 Compression fittings shall be Swagelok® as manufactured by the Crawford Thread Fittings Co., Solon, Ohio, or Parker A-Lok® manufactured by Parker Hannifin Corp., Instrumentation Connectors Div., Huntsville, Alabama, and shall be Type 316 stainless steel made from forgings per ASTM A182 or bar stock per ASTM A276.
6.2 Compression fittings shall be supplied and used as complete assemblies.
6.3 Type 316 stainless steel hex nipples, Cajon “HN” Series, as manufactured by the Swagelok company, through 1/2″ National Pipe Thread (NPT), are approved for this service. Otherwise, the use of pipe fittings shall be avoided. Pipe fittings shall be assembled using teflon pipe thread tape or oxygen compatible teflon pipe dope.
6.4 Mixing of compression fittings materials (that is, brass and stainless steel) at a transition joint between copper and stainless steel tubing systems is prohibited. Transitions between tubing materials shall be accomplished by means of screwed fittings.
- VALVES
7.1 Shut-off valves shall be Whitey “NB” Series severe-service, union bonnet valves, as manufactured by the Swagelok company, (Swagelok Catalog Number SS-3NBS4), Type 316 stainless steel, 415 bar g (6000 psig) at 40°C (100°F) stellite ball-tip stem, TFE packing, integral seat, backseat feature, and 1/4″ Swagelok® connections.
7.2 Shut-off valves used in oxygen service shall be specified as oxygen cleaned and with a blue handle by adding the suffix “W1” and “BL” to the model number. (Example: SS-xxxx-W1-BL.)
7.3 Shut-off valves used in critical shutdown applications, as indicated on the flowsheet at the process block valve by LO (Lock Open) or LC (Lock Closed) shall be specified with an orange handle by adding the suffix “OG” to the model number. A Nupro brand “Valve Lokout®” accessory, manufactured by the Swagelok company, shall be installed around the handle and secured with a nylon cable tie to prevent accidental closing or opening of the valve.
7.4 Ball valves shall be specified as Whitey “83” series, with a Kel-F seat material (2-way and 3- way), manufactured by the Swagelok company. Ball valves shall not be used in oxygen service or when the temperature range exceeds -29° to +121°C (-20° to +250°F).