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Seamless Stainless Steel Pipe [CO:wp/v2/product/title]

Seamless stainless steel pipe is produced by piercing a solid billet and then extruding or cold drawing it to size, so the finished pipe has no longitudinal weld. Walmay supplies seamless pipe to ASTM A312 and ASME SA312 in 304, 304L, 316, 316L, 321, 316Ti and 310S, and to ASTM A790 in 2205 and 2507 duplex, covering NPS 1/2 to NPS 24 in schedules 5S through 160. Every length ships hydrostatically or eddy current tested with an EN 10204 3.1 mill test certificate, cut to your length list and bevelled if required.

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Industrial stainless steel product. [CO:wp/v2/product/excerpt]

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  • Hygiene Certification [CO:fe/b216/product_advantage/strong]

    Certified compliant with FDA 21 CFR & GB 4806.9. Meets rigorous food-safety standards, ensuring zero lead/cadmium migration for your production lines. [CO:fe/b216/product_advantage/p]

  • Superior Inner Surface [CO:fe/b216/product_advantage/strong]

    Advanced internal polishing (Ra ≤0.6μm) eliminates bacterial trap zones, increasing CIP (Cleaning-in-Place) efficiency by 30% and reducing cleaning downtime. [CO:fe/b216/product_advantage/p]

  • Enhanced Corrosion Resistance [CO:fe/b216/product_advantage/strong]

    Survives 1000-hour salt spray testing. Our 304 pipe resists organic acids in food/beverage processes, extending service life by 2x vs. standard industrial grades. [CO:fe/b216/product_advantage/p]

Product Specifications

Specification [CO:theme-meta/product0_title]
ItemDetail
ProductSeamless stainless steel pipe
StandardsASTM A312 / ASME SA312, ASTM A213 for boiler tube, ASTM A790 for duplex
Grades304, 304L, 316, 316L, 316Ti, 321, 310S, 904L, 2205, 2507
Nominal pipe sizeNPS 1/2 to NPS 24
Outside diameter6 mm to 630 mm
Wall thickness1.0 mm to 30 mm
Schedules5S, 10S, 20, 40S, 80S, 120, 160, XXS on request
Lengths6 m, 6.096 m for 20 ft, random 4-7 m, or cut to length
SurfacePickled, annealed, bright annealed, 180 or 320 grit polished
EndsPlain, bevelled 30 degrees, threaded
TestingHydrostatic or eddy current, plus ultrasonic and dye penetrant on request
CertificationEN 10204 3.1 with heat number and full analysis
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Dimensions to ASME B36.19M

Wall thickness in millimetres. The S suffix denotes the stainless series, which is thinner than the equivalent carbon steel schedule at the same nominal size. Schedules 120 and 160 are carried over from ASME B36.10M and are used for high-pressure work.

NPSOutside diameterSCH 5SSCH 10SSCH 40SSCH 80SSCH 160
1/2 in21.3 mm1.652.112.773.734.78
3/4 in26.7 mm1.652.112.873.915.56
1 in33.4 mm1.652.773.384.556.35
1-1/2 in48.3 mm1.652.773.685.087.14
2 in60.3 mm1.652.773.915.548.74
3 in88.9 mm2.113.055.497.6211.13
4 in114.3 mm2.113.056.028.5613.49
6 in168.3 mm2.773.407.1110.9718.26
8 in219.1 mm2.773.768.1812.7023.01
10 in273.1 mm3.404.199.2715.0928.58
12 in323.9 mm3.964.579.5317.4833.32
Seamless or Welded
CriterionSeamlessWelded
ManufacturePierced from a billet, then extruded or cold drawnFormed from strip and longitudinally welded
Weld seamNoneOne longitudinal seam
Quality factor E in ASME B31.31.00.85 without radiography
Wall thickness tolerancePlus or minus 12.5 percentFollows the strip, typically plus or minus 5 percent
ConcentricityLess uniform, eccentricity is inherent to piercingVery uniform
Availability above NPS 12Limited and expensiveGood
Cost30 to 60 percent higher at the same scheduleLower
Typical specification driverCode requirement, cyclic or high pressure, sour serviceCost, availability, large diameter

Both routes are covered by ASTM A312, so the standard alone does not tell you which you are getting; the purchase order has to state it. Reach for seamless when the design code requires it, when the service is high pressure or cyclic, when the medium is sour and NACE MR0175 applies, or when a weld seam would interfere with downstream bending or forming. Where none of those apply, welded pipe is the economically correct answer, particularly above NPS 12.

Tolerances to ASTM A312
DimensionTolerance
Outside diameter, NPS 1/8 to 1-1/2Plus 0.40 mm, minus 0.79 mm
Outside diameter, NPS 2 to 4Plus 0.79 mm, minus 0.79 mm
Outside diameter, NPS 5 to 8Plus 1.59 mm, minus 0.79 mm
Outside diameter, NPS 10 to 18Plus 2.37 mm, minus 0.79 mm
Wall thicknessMinus 12.5 percent of nominal
Length, cut to sizePlus 3.2 mm, minus 0
Straightness1.0 mm per metre
Grade Selection
GradeStandardChoose it for
304 / 304LASTM A312General process, water and structural service
316 / 316LASTM A312Chlorides, marine, chemical transfer, sanitary lines
321ASTM A312Cycling between 500 and 800 C, exhaust and superheater duty
316TiASTM A312Welded assemblies held hot with chloride exposure
310SASTM A312Furnace and kiln service to about 1,150 C
904LASTM B677Sulphuric and phosphoric acid lines
2205 duplexASTM A790High strength plus chloride resistance, offshore and brine
Ordering
ItemDetail
Minimum order1 tonne from stock, 3-5 tonnes for a mill run
Lead time from stock7-12 days to loading
Lead time mill run30-45 days
IncotermsFOB, CIF, DAP
PackingWooden crate or strapped bundle, plastic end caps

Send the grade, NPS or outside diameter, schedule or wall thickness, length, quantity, end preparation and destination port. Where the line is code designed, send the design pressure and temperature too and we will confirm the schedule rather than quoting what the enquiry states.

Related products: pipe and tube overview, square tube, rectangular tube and precision bright tube. Background on the company is on our about us page.

Pricing Calculation

Workshop & Manufacturing Machine

Stainless Steel Tubes Packed in Truck

Wooden Crate Packaging in Factory

Neo-Mac Machine with Stainless Steel Tubes

Factory Tube Packaging Process

Industrial Manufacturing Equipment

Stainless Steel Composition Analyzer

Bundled stainless steel pipes of varying diameters racked in a mill warehouse
Close-up of a stainless steel pipe end showing the weld seam and polished bore

Seamless stainless steel pipe is produced by piercing a solid billet and then extruding or cold drawing it to size, so the finished pipe has no longitudinal weld. Walmay supplies seamless pipe to ASTM A312 and ASME SA312 in 304, 304L, 316, 316L, 321, 316Ti and 310S, and to ASTM A790 in 2205 and 2507 duplex, covering NPS 1/2 to NPS 24 in schedules 5S through 160. Every length ships hydrostatically or eddy current tested with an EN 10204 3.1 mill test certificate, cut to your length list and bevelled if required. [CO:fe/b216/about_intro/p]

Weight per Metre and per 20 ft Length [CO:fe/b216/application_advantages/h2]

Calculated for austenitic grades at 8.0 g/cm3 in schedule 40S and 80S, the two most commonly ordered walls. [CO:fe/b216/application_advantages/p]

NPSSCH 40S per metreSCH 40S per 20 ftSCH 80S per metreSCH 80S per 20 ft
1/2 in1.29 kg7.9 kg1.64 kg10.0 kg
3/4 in1.72 kg10.5 kg2.24 kg13.7 kg
1 in2.55 kg15.5 kg3.30 kg20.1 kg
1-1/2 in4.13 kg25.2 kg5.52 kg33.6 kg
2 in5.54 kg33.8 kg7.62 kg46.5 kg
3 in11.51 kg70.1 kg15.58 kg95.0 kg
4 in16.38 kg99.9 kg22.75 kg138.7 kg
6 in28.80 kg175.6 kg43.42 kg264.7 kg
8 in43.36 kg264.3 kg65.90 kg401.7 kg

For any size, weight in kilograms per metre equals 0.025133 multiplied by the wall thickness multiplied by the outside diameter minus the wall thickness, both in millimetres. [CO:fe/b216/application_advantages/p]

Bundled stainless steel pipes strapped and tagged for export shipment on a warehouse dock

Known Limitations of Seamless Pipe [CO:fe/b216/application_intro/h2]

Seamless is not automatically the better product, and knowing where it is weak prevents the wrong specification. [CO:fe/b216/application_intro/p]

  • Wall eccentricity. [CO:fe/b216/application_intro/strong] Piercing a billet never produces a perfectly concentric hollow, so wall thickness varies around the circumference. ASTM A312 permits minus 12.5 percent on nominal wall, which must be deducted before any pressure calculation. Welded pipe made from rolled strip is far more uniform.
  • Internal surface quality. [CO:fe/b216/application_intro/strong] The bore is formed by a mandrel rather than by a rolled strip surface, so it is rougher and can carry laps or scores. For sanitary service, specify a bright annealed or mechanically polished bore, or use tube to ASTM A269 instead.
  • Inclusions and laps. [CO:fe/b216/application_intro/strong] Defects in the original billet are elongated by piercing rather than eliminated. Ultrasonic examination is the reason it is routinely specified on seamless pipe for critical service.
  • Cost and availability. [CO:fe/b216/application_intro/strong] Above NPS 12 the extrusion press limits size, and lead times for a mill run reach 30 to 45 days. Large-diameter seamless is often two to three times the price of welded.
  • Ovality on thin wall. [CO:fe/b216/application_intro/strong] Thin-wall seamless in schedule 5S and 10S can go out of round in handling more readily than the equivalent welded pipe.
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Stainless steel pipe being cut to length on a bandsaw in a fabrication shop
Technician checking stainless steel pipe wall thickness with an ultrasonic gauge

Processing Before Dispatch

  • Cut to your length list, including exact 6 m and 20 ft bundles
  • End bevelling to 30 degrees for site welding, or facing for fittings
  • Polishing to 180 or 320 grit, satin or mirror on the outside diameter
  • Bright annealing for a clean bore where the medium is high purity
  • Pickling and passivation, plus surface treatment for sanitary duty
  • Inspection: hydrostatic, eddy current, ultrasonic and dye penetrant with reports
  • Crating with plastic end caps and moisture barrier
Bundled stainless steel pipes strapped and tagged for export shipment on a warehouse dock

Applications

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FAQs [CO:fe/b216/page_faqs/h2]

Is ASTM A312 seamless?
ASTM A312 covers both seamless and welded austenitic pipe, so the specification alone does not tell you which you are buying. The purchase order must state the manufacturing route. In the design calculation the difference shows up as the quality factor E, which is 1.0 for seamless and 0.85 for welded pipe without radiography, so a welded pipe of the same schedule carries roughly 15 percent less pressure.
What are the differences between seamless and welded stainless steel pipe?
Seamless is pierced from a solid billet and has no weld seam, giving it a quality factor of 1.0 and making it the choice for high-pressure, cyclic and sour service. Welded pipe is formed from strip and longitudinally welded, which gives more uniform wall thickness, better availability in large diameters and a materially lower price. Seamless has looser wall tolerance at minus 12.5 percent and a rougher bore; welded follows the strip thickness closely.
What are the common problems with seamless pipe?
Wall eccentricity from the piercing operation, which is why ASTM A312 allows minus 12.5 percent on wall and why that must be deducted before any pressure calculation. A rougher bore than welded pipe, which matters for sanitary and high-purity service. Elongated inclusions or laps carried over from the original billet, which is why ultrasonic examination is normally specified for critical duty. Limited availability and long lead times above NPS 12. And greater susceptibility to ovality in thin walls during handling.
Is seamless stainless steel tubing available?
Yes, and it is a different product from seamless pipe. Tube is specified by actual outside diameter and wall thickness to ASTM A269 or ASTM A213, with tighter dimensional tolerance and a better surface, and it is what compression fittings and heat exchangers require. Pipe is specified by nominal pipe size and schedule to ASTM A312. We supply both; state which one your fittings need.
What is the largest seamless pipe you can supply?
NPS 24, with outside diameters up to 630 mm in metric sizing. Above NPS 12 seamless becomes expensive and lead times lengthen to 30 to 45 days, so welded pipe to the same ASTM A312 specification is usually the better commercial choice unless the code requires seamless.
Do you supply seamless pipe in 20 ft lengths?
Yes. We cut to exactly 6.096 m for 20 ft requirements, and also supply 6 m metric lengths, random 4 to 7 m mill lengths at a lower price, or any cut list you send. Cutting at our end removes both the saw time and the remnant from your yard.
What wall thickness should I order for a given pressure?
Use the ASME B31.3 relationship, remembering to deduct the mill tolerance and any corrosion allowance from the nominal wall before calculating, and to take the allowable stress for the grade at the design temperature rather than at ambient. A nominal 3.91 mm schedule 40S wall must be treated as 3.42 mm in the design case. Send the design pressure, temperature, medium and code and we will confirm the schedule.
Can seamless pipe be supplied to NACE MR0175?
Yes, where the grade and heat treatment condition permit it. Duplex 2205 and 2507 to ASTM A790 are the usual choices for sour service, with hardness and ferrite content verified per heat. State NACE MR0175 on the enquiry so the material is selected and documented accordingly.

Need more details on stainless steel products? Feel free to contact Walmay anytime.

Walmay will help match the right stainless product form and specification for your application, confirm quantities and packing needs, and provide requested documents based on order requirements.

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