ASME BPE (Bioprocessing Equipment) is the American standard for hygienic process systems in biopharmaceutical, pharmaceutical and personal-care manufacturing. For tubing buyers, three parts matter most: Part DT (dimensions and tolerances), Part SF (process contact surface finishes) and Part MM (metallic materials). This guide summarises what they require for stainless steel tubing, based on ASME BPE-2026 (issued 1 May 2026, effective six months after issuance; ASME BPE-2024 applies until then).
1. BPE tube sizes (Part DT)
BPE tubing is specified by nominal outside diameter in inches — the OD is the actual size, unlike NPS pipe. Metric values are soft conversions for reference only; for true metric tubing, BPE refers buyers to the appropriate international standards (for example DIN 11850 or ISO 2037).
| Nominal size, in | Tube OD, in (mm) | Wall, in (mm) |
|---|---|---|
| ¼ | 0.250 (6.35) | 0.035 (0.89) |
| ⅜ | 0.375 (9.53) | 0.035 (0.89) |
| ½ | 0.500 (12.70) | 0.065 (1.65) |
| ¾ | 0.750 (19.05) | 0.065 (1.65) |
| 1 | 1.000 (25.40) | 0.065 (1.65) |
| 1½ | 1.500 (38.10) | 0.065 (1.65) |
| 2 | 2.000 (50.80) | 0.065 (1.65) |
| 2½ | 2.500 (63.50) | 0.065 (1.65) |
| 3 | 3.000 (76.20) | 0.065 (1.65) |
| 4 | 4.000 (101.60) | 0.083 (2.11) |
| 6 | 6.000 (152.40) | 0.109 (2.77) |
Source: ASME BPE-2026, Table DT-4-1.
Tolerances
- Tubing tolerances are not tabulated in BPE itself: DT-7.2 refers to ASTM A270, including Supplementary Requirement S2 (the pharmaceutical-quality supplement). Order tube to “ASTM A270 S2 / ASME BPE”.
- Tables DT-3-1 and DT-3-2 give tolerances for fittings and process components, excluding tube, after polishing or electropolishing.
ASTM A270/A270M-24, Table 2 sets the outside diameter tolerances for the tube itself:
| Tube OD, in [mm] | OD tolerance, in [mm] |
|---|---|
| 1.000 [25] and under | ±0.005 [0.13] |
| Over 1 to 2 [25–50] | ±0.008 [0.20] |
| Over 2 to 3 [50–75] | ±0.010 [0.25] |
| Over 3 to 5½ [75–140], excl. | ±0.015 [0.38] |
| 5½ to 8 [140–200], excl. | ±0.030 [0.75] |
Source: ASTM A270/A270M-24, Table 2. Cut-length tolerances in that table do not apply to S2 pharmaceutical tubing.
What Supplementary Requirement S2 (Pharmaceutical Quality Tubing) adds, per ASTM A270/A270M-24:
- Sulphur 0.005–0.017% when S31600 or S31603 (316/316L) is ordered — plain A270 allows up to 0.030%.
- Wall thickness ±10% of the specified wall.
- Cut length +2 in (50 mm) / −0.
- Tensile and Rockwell hardness tests per lot — 316L: tensile 70 ksi (485 MPa) min, yield 25 ksi (170 MPa) min, elongation 35% min, hardness B90 max; plus flattening and flange tests from each lot.
- Surface finish requirements must be stated on the purchase order.
- Default packaging: end capped, plastic sleeved and boxed.
- At weld ends, wall thickness and OD tolerances are held over a control portion of 0.75 in (19 mm) from the welding end.
- Fittings must match the wall of the tube they are welded to; after forming and finishing, wall thickness in any formed part may not fall below 65% of nominal.
2. Surface finish designations SF0–SF6 (Part SF)
| Designation | Finish | Ra max, µin | Ra max, µm |
|---|---|---|---|
| SF0 | Mechanically polished* | No Ra max. | |
| SF1 | Mechanically polished* | 20 | 0.51 |
| SF2 | Mechanically polished* | 25 | 0.64 |
| SF3 | Mechanically polished* | 32 | 0.80 |
| SF4 | Electropolished | 15 | 0.38 |
| SF5 | Electropolished | 20 | 0.51 |
| SF6 | Electropolished | 25 | 0.64 |
Source: ASME BPE-2026, Table SF-2.4.1-1. *Or any other finishing method that meets the Ra max. Ra readings follow ASME B46.1 and are taken across the lay wherever possible.
Ra is only part of acceptance. Table SF-2.2-1 also sets visual criteria for mechanically polished surfaces — for example, no dents, nicks, surface cracks, residuals or blistering; pits only below 0.020 in (0.51 mm) diameter with a shiny bottom and no more than four relevant pits in a 0.5 × 0.5 in window; scratches on tubing limited in cumulative length and to under 0.003 in (0.08 mm) depth. Electropolished surfaces (SF4–SF6) may show haze, orange peel or luster variation if the Ra max is met. Mechanical buffing as a final finish is not acceptable, and flash electropolishing is not permitted.
3. Cleaning and passivation
- Process contact surfaces must be cleaned before service, and stainless surfaces should be passivated after cleaning.
- Electropolished surfaces do not need passivation unless they have been altered (welded, mechanically polished) or contaminated after electropolishing.
- Pickling is not accepted as a substitute for passivation.
- Passivated surfaces must show no particles, stains, construction debris or oils under visual inspection (Table SF-2.5-1).
- Mechanical polishing, electropolishing and passivation providers must work to written procedures under a quality management system.
4. Materials and weld ends (Part MM)
Austenitic stainless steels such as 316L are the usual BPE tube material. Weld ends that will be autogenously (orbitally) welded must meet the chemical composition requirements of MM-5.2.1.1(a), which control sulphur so that automatic welds penetrate consistently; non-automatic weld ends follow the applicable ASTM specification. Specify the sulphur-controlled condition on the order when tube will be orbitally welded.
BPE’s weldability table (Table MM-5.2.1.1-1) distinguishes wrought product with sulphur below 0.005% (expected ferrite number 0.5–4) from wrought product in the 0.005–0.017% sulphur range (FN 1.0–6); GTAW welds with ER316L filler are expected at FN 4–12. Mixing low-sulphur and controlled-sulphur heats in one orbital weld can shift the weld pool, so keep sulphur consistent within a system. For duplex grades, BPE sets a maximum service temperature of 600 °F (315 °C).
Material cross-references in BPE (Table MM-2.1-1)
BPE lists UNS, EN and JIS grades side by side, but notes that grades grouped together are comparable, not equivalent, and that the values are primary elements only — the product specification governs. Selected nominal limits (wt.%, single values are maximums):
| Grade | C | Cr | Ni | Mo |
|---|---|---|---|---|
| UNS S31603 (316L) | 0.030 | 16.0–18.0 | 10.0–14.0 | 2.00–3.00 |
| EN 1.4404 | 0.030 | 16.5–18.5 | 10.0–14.5 | 2.00–2.50 |
| EN 1.4435 | 0.030 | 17.0–19.0 | 12.5–15.0 | 2.50–3.00 |
| JIS SUS316L | 0.030 | 16.0–18.0 | 12.0–15.0 | 2.0–3.0 |
| UNS S30403 (304L) | 0.030 | 18.0–20.0 | 8.0–12.0 | – |
| EN 1.4307 | 0.030 | 17.5–19.5 | 8.0–10.5 | – |
Source: ASME BPE-2026, Table MM-2.1-1. The higher-Mo 1.4435 is often preferred in European pharma specifications; if you need 316L and 1.4404/1.4435 at the same time, ask for a heat that meets all the grades you list.
5. Inspection, marking and packaging
- Visual inspection on receipt: manufacturer, material type, size and configuration, heat number, process contact surface finish designation and reference to ASME BPE — verifiable without unpacking.
- Physical examination (when required by the owner/user): a percentage of each lot checked for weld-end wall and OD, surface finish and visual condition; if a defect is found, a further 10% is examined, then 100% or rejection of the balance. Results are recorded on a Material Examination Log.
- Marking: traceability to the MTR (heat number or code), material type, manufacturer, reference to ASME BPE and only one SF designation. Only ASME BPE Certificate of Authorization holders may apply the ASME Certification Mark with BPE designator; others may only mark “BPE”.
- Packaging: all end connections protected with end caps; fittings sealed in transparent bags or shrink-wrapped.
6. How to order BPE tubing
Example: “Electropolished tube, ASTM A270 S2 / ASME BPE, 316L (sulphur-controlled for orbital welding), 2 in OD × 0.065 in wall, SF4 inside, 20 ft lengths, end caps and individual sleeves, EN 10204 3.1 certificate with Ra report.”
Always state the BPE edition your project works to, the SF designation and whether it applies to the inside or outside surface, and the inspection documents required.
How TeCarve supplies hygienic tubing
TeCarve is the sole export arm of two stainless steel tube factories in Foshan and Wenzhou, China. We supply sanitary stainless steel tube in ASME BPE sizes and in metric ISO 2037 and DIN 11850 sizes, in 304L and 316L, mechanically polished or electropolished, with Ra profilometer reports and an EN 10204 3.1 certificate. TeCarve is not an ASME BPE Certificate of Authorization holder; tube is supplied to the dimensional and surface-finish requirements you specify. Trial orders start from 100–300 kg; in-stock sizes ship in 7–10 days and custom production in 10–25 days. Contact sales@tecarve.com.
Frequently asked questions
What is the Ra of SF1 and SF4?
SF1 is mechanically polished to Ra max 20 µin (0.51 µm); SF4 is electropolished to Ra max 15 µin (0.38 µm), per ASME BPE Table SF-2.4.1-1.
What wall thickness is 2 inch BPE tubing?
2 in nominal BPE tube is 2.000 in (50.80 mm) OD with a 0.065 in (1.65 mm) wall.
Where are BPE tubing tolerances specified?
ASME BPE DT-7.2 refers to ASTM A270 including Supplementary Requirement S2 for tubing tolerances; A270 Table 2 gives ±0.005 in for tube up to 1 in OD, ±0.008 in up to 2 in and ±0.010 in up to 3 in, and S2 limits wall thickness to ±10%. BPE’s own tolerance tables DT-3-1 and DT-3-2 apply to fittings and process components, excluding tube.
What sulphur content is used for orbitally welded BPE tube?
0.005–0.017%. ASTM A270 Supplementary Requirement S2 restricts sulphur to this range for 316 and 316L, and BPE’s weldability table uses the same range for orbitally welded wrought product. Ordering “ASTM A270 S2” covers it; plain A270 allows up to 0.030%.
Is BPE tubing the same as DIN 11850 or ISO 2037?
No. BPE uses inch OD sizes; DIN 11850 and ISO 2037 are metric series. The sizes are close but not interchangeable — see our ISO 2037 tubing guide.
Which edition of ASME BPE applies?
ASME BPE-2026 was issued on 1 May 2026 and becomes effective six months after issuance. Use the edition named in your project specification.
Related reading: DIN 11850 tube sizes · How to specify sanitary stainless steel tubing · ISO 2037 tubing guide · EN 10204 3.1 certificates · Pharmaceutical & medical industry
