Instrumentation Tubes
Giriraj Impex stocks, supplies and exports instrumentation tubes – seamless and welded stainless steel tubing to ASTM A269 and ASTM A213 in 316/316L and 304/304L, with duplex, super duplex, 6Mo and nickel alloy tubing on request. We supply instrumentation tubes from approved mills from ⅛" to 1" OD and in metric sizes from 3 mm to 25 mm, bright annealed, with controlled hardness for compression fittings, in straight lengths or coils, with mill test certificates.
Instrumentation tubes connect pressure gauges, transmitters, analysers and control valves to process lines, and carry hydraulic, pneumatic, sample and chemical-injection fluids in plants, offshore platforms and skids.
Specifications
| Item | Details |
|---|---|
| Standards | ASTM A269 (seamless and welded, general service); ASTM A213 (seamless); ASTM A789 (duplex); ASTM B444 / B167 (nickel alloys) |
| Grades | 316/316L (most common), 304/304L; duplex 2205, super duplex 2507, 6Mo, Incoloy 825, Inconel 625 on request |
| Sizes | ⅛" to 1" OD; metric 3 mm to 25 mm OD |
| Condition | Bright annealed, or annealed and pickled |
| Hardness | Controlled for compression-fitting use – see below |
| Form | Straight lengths, typically 6 m; coils for small sizes |
| Tests | Hydrostatic or eddy-current test, flare and flattening tests |
| Documents | Mill test certificate (MTC); third-party inspection on request |
Common sizes
| OD | Common wall | Heavier walls |
|---|---|---|
| ⅛" | 0.028" (0.71 mm) | 0.035" (0.89 mm) |
| ¼" | 0.035" (0.89 mm) | 0.049" (1.24 mm), 0.065" (1.65 mm) |
| ⅜" | 0.035" (0.89 mm) | 0.049" (1.24 mm), 0.065" (1.65 mm) |
| ½" | 0.049" (1.24 mm) | 0.065" (1.65 mm), 0.083" (2.11 mm) |
| ¾" | 0.065" (1.65 mm) | 0.083" (2.11 mm) |
| 1" | 0.083" (2.11 mm) | 0.109" (2.77 mm) |
| 6 mm | 1.0 mm | 1.5 mm |
| 10 mm | 1.0 mm | 1.5 mm, 2.0 mm |
| 12 mm | 1.5 mm | 2.0 mm |
Wall thickness is chosen for the working pressure, the tube material and the fitting maker's recommendations. Other sizes are available on request.
Hardness for compression fittings
Compression fittings seal by the ferrule biting into the tube surface, so the tube must be softer than the ferrule. ASTM A269 allows a maximum hardness of 90 HRB for austenitic stainless tubing, but fitting manufacturers generally recommend tubing of 80 HRB or less for reliable sealing. Bright-annealed, fully annealed tubing is supplied to meet this, and the hardness is reported on the mill test certificate. A smooth, scratch-free outer surface and close OD tolerance are equally important for leak-tight joints.
Seamless or welded instrument tube
Seamless tubing is preferred for high-pressure hydraulic, chemical-injection and gas lines and is specified by most oil and gas operators. Welded and redrawn tubing, with the weld bead cold worked and annealed, offers excellent concentricity and surface finish and is widely used for general instrument air and low-pressure service. The project specification normally states which is acceptable.
Choosing the material
316/316L is the standard material for instrument tubing in most plants. Offshore and in coastal plants, 316L tubing can suffer pitting and crevice corrosion under clamps and supports in salt spray, so 6Mo (UNS S31254), super duplex or Incoloy 825 tubing is increasingly specified. For sour service and hydraulic control lines in subsea systems, Inconel 625 and super duplex tubing are used. Tubing should be supported with clamps that do not trap water against the tube.
Bending and installation
Annealed instrument tubing bends easily with hand or bench benders to a radius suited to its size, without kinking. Tubes are cut square with a tube cutter, deburred inside and out, and inserted fully into the fitting before tightening to the manufacturer's instructions. Keep tube ends capped until use to prevent contamination.
Cleanliness
For oxygen, analyser and high-purity service, tubes can be supplied cleaned and capped at both ends so that no oil or particles enter the instrument system.
Ordering and related products
Please give the material, specification, seamless or welded, OD and wall thickness, hardness limit, length or coil, quantity and any testing or inspection requirement. Tubes are packed in wooden boxes with end caps. Related pages: stainless steel seamless pipes, stainless steel tubes, carbon steel seamless pipes, alloy steel pipes and tubes, duplex steel pipes and tubes, super duplex pipes and tubes and the weight calculator. All materials are on the seamless pipes and tubes page.
Frequently Asked Questions
ASTM A269 covers seamless and welded austenitic stainless tubing for general service; ASTM A213 covers seamless tubing.
Fitting makers generally recommend 80 HRB or less for stainless tubing; ASTM A269 allows up to 90 HRB.
Imperial ⅛" to 1" OD, especially ¼", ⅜" and ½", and metric 6, 8, 10 and 12 mm.
It resists pitting and crevice corrosion under clamps in salt spray, where 316L tubing can fail.
Seamless is preferred for high-pressure and critical lines; welded and redrawn tubing is widely used for general service.
Small sizes can be supplied in coils; larger sizes in straight lengths.
Request a Quote for Instrumentation Tubes
Tell us the product, grade, size, standard, quantity and delivery location, and our sales team will reply with a quotation.
Inconel® and Incoloy® are trademarks of Special Metals Corporation.