1 · Dimensional Standards by Product
The dimensional standard fixes the geometry — centre-to-end, bend radius, bolt circle, face-to-face. Naming exactly one on the purchase order removes most of the ambiguity in a fitting order.
| Product | ASME / ASTM | EN / DIN | JIS | GOST | GB / HG |
|---|---|---|---|---|---|
| Butt-weld elbow | ASME B16.9 | EN 10253-1/-2/-4 | JIS B2311 / B2312 | GOST 17375 | GB/T 12459 |
| Butt-weld tee | ASME B16.9 | EN 10253 | JIS B2311 | GOST 17376 | GB/T 12459 |
| Reducer | ASME B16.9 | EN 10253 | JIS B2311 | GOST 17378 | GB/T 12459 |
| Cap | ASME B16.9 | EN 10253 | JIS B2311 | GOST 17379 | GB/T 12459 |
| Plate-fabricated fitting | MSS SP-75 (large OD) | EN 10253-2 | — | — | GB/T 13401 |
| Forged socket-weld & threaded | ASME B16.11 | BS 3799 | JIS B2316 | — | GB/T 14383 |
| Flange ≤ NPS 24 | ASME B16.5 | EN 1092-1 | JIS B2220 | GOST 12820 / 12821 | GB/T 9112–9124 · HG/T 20592 |
| Flange > NPS 24 | ASME B16.47 Series A / B | EN 1092-1 | JIS B2220 | GOST 12821 | HG/T 20615 |
| Valve — rating & testing | ASME B16.34 · API 600 / 602 / 594 / 6D | EN 12516 · ISO 15761 | JIS B2071 | GOST 5762 | GB/T 12224 / 12234 |
| Pipe — dimensions | ASME B36.10M (CS) · B36.19M (SS) | EN 10220 · ISO 4200 | JIS G3454 / G3459 | GOST 8732 / 8734 | GB/T 17395 |
| Marking & traceability | MSS SP-25 | EN 10253 §marking | — | — | GB/T 12459 §marking |
Buyer note. Standards in the same row are counterparts, not drop-in substitutes.
A GOST 17375 elbow and an ASME B16.9 elbow of nominally the same size can differ in outside diameter
and wall thickness, because GOST works from metric OD series while ASME works from NPS. Mixing them
inside one weld joint is the single most common cause of site rework.
2 · Material Grade Equivalents
Nearest counterparts across the five systems. Chemistry and mechanical envelopes overlap but are not identical — where a design code names a grade, order that grade rather than an equivalent.
| Family | ASME / ASTM | EN / DIN | JIS | GOST | GB |
|---|---|---|---|---|---|
| CS fittings | A234 WPB | P235GH (1.0345) | STPT370 / PT370 | Ст20 | 20# |
| CS forgings | A105 | P250GH (1.0460) | SF440A | Ст25 | 25# |
| CS low-temp | A420 WPL6 · A350 LF2 | P275NL1 (1.0491) | STPL380 | 09Г2С | 16Mn / Q345 |
| SS 304 / 304L | A403 WP304 / WP304L | 1.4301 / 1.4307 | SUS304 / SUS304L | 08Х18Н10 | 06Cr19Ni10 |
| SS 316 / 316L | A403 WP316 / WP316L | 1.4401 / 1.4404 | SUS316 / SUS316L | 03Х17Н14М3 | 022Cr17Ni12Mo2 |
| SS 321 / 347 | A403 WP321 / WP347 | 1.4541 / 1.4550 | SUS321 / SUS347 | 12Х18Н10Т | 06Cr18Ni11Ti |
| Duplex / super duplex | A815 UNS S31803 / S32750 | 1.4462 / 1.4410 | SUS329J3L | — | 022Cr23Ni5Mo3N |
| Cr-Mo alloy | A234 WP11 / WP22 / WP91 | 13CrMo4-5 · 10CrMo9-10 · X10CrMoVNb9-1 | STPA23 / STPA24 | 15ХМ / 12Х1МФ | 15CrMo / 12Cr1MoV |
| Line pipe | API 5L Gr.B / X42–X70 · A106 Gr.B | L245–L485 (EN 10208) | STPG370 / STPG410 | Ст20 / 09Г2С | L245–L485 (GB/T 9711) |
Each ASME/ASTM grade above links to a dedicated page — cross-system equivalents, where the grade belongs and where it does not, the forms and sizes we supply in it, and the documentation available.
Density basis for weight calculation: carbon and alloy steel 7.85 kg/dm³, austenitic 304 7.93 kg/dm³, 316L 7.98 kg/dm³, duplex 7.80 kg/dm³.
3 · Pressure Ratings & Pipe Schedules
Two independent questions: how much pressure the joint is rated for, and how thick the pipe wall is.
3.1 Rating systems — nearest comparison
| ASME Class | Nearest EN PN | Nearest JIS | Typical service |
|---|---|---|---|
| Class 150 | PN 20 (often cross-listed PN 16) | 10K | Utilities, low-pressure process, water |
| Class 300 | PN 50 (often cross-listed PN 40) | 20K | General refinery and chemical process |
| Class 600 | PN 100 | 40K | High-pressure steam, hydrocarbon |
| Class 900 | PN 150 | — | High-pressure gas, wellhead |
| Class 1500 | PN 250 | — | Boiler feed, high-pressure injection |
| Class 2500 | PN 420 | — | Extreme pressure, small bore |
These are comparisons, not equivalents. Bolt circle diameter, bolt count, bolt size,
flange thickness and raised-face dimensions differ between systems. Two flanges in the same row will
not bolt together. Pick one system per flanged joint and carry it through gaskets and bolting.
3.2 Pipe schedule basics
| Designation | Source standard | Applies to | Behaviour |
|---|---|---|---|
| SCH 10 / 20 / 30 / 40 / 60 / 80 / 100 / 120 / 140 / 160 | ASME B36.10M | Carbon & alloy steel | Wall thickness increases with schedule number at a given NPS |
| SCH 5S / 10S / 40S / 80S | ASME B36.19M | Stainless steel | Thinner than the plain-number series at larger diameters |
| STD | ASME B36.10M | All | Equal to SCH 40 up to NPS 10; fixed at 9.53 mm from NPS 12 upward |
| XS | ASME B36.10M | All | Equal to SCH 80 up to NPS 8; fixed at 12.70 mm from NPS 10 upward |
| XXS | ASME B36.10M | All | Heaviest wall in the series; no fixed relation to a schedule number |
Butt-weld fittings are ordered to match the pipe they join: the fitting wall must be specified to the same schedule as the connecting pipe, otherwise the bores will not line up at the weld root.
4 · Weight Calculation Formulas
Theoretical weights at carbon steel density 7.85 kg/dm³. D = outer diameter (mm), S = wall thickness (mm), all results in kilograms.
| Item | Formula | Variables |
|---|---|---|
| Steel pipe | W = 0.02466 × S × (D − S) | Result in kg per metre |
| 90° elbow | W = 0.0387 × S × (D − S) × R / 1000 | R = bend radius; LR R = 1.5 × DN. × 0.5 for 45°, × 2 for 180° |
| Equal tee | W ≈ 0.02466 × S × (D − S) × (2C + M) / 1000 | C = centre-to-end run, M = centre-to-end branch |
| Cross | W ≈ 0.02466 × S × (D − S) × (2C + 2M) / 1000 | Approximation |
| Reducer | W ≈ 0.02466 × S × ((D₁ + D₂)/2 − S) × H / 1000 | D₁ / D₂ = large / small OD, H = end-to-end length |
| Cap | W ≈ 0.02466 × S × (D − S) × H / 1000 | H = cap height |
| Flange & valve | No closed formula | Masses from ASME B16.5 / B16.47 / EN 1092-1 tables |
Rather not do this by hand? Use the weight calculator — pick a size and schedule and the outside diameter and wall thickness are looked up from ASME B36.10M for you.
Material factor: × 1.01 for SS304, × 1.02 for SS316L, × 0.994 for duplex. Theoretical weight is for planning, freight estimating and quotation only — invoicing follows actual weight recorded on the material test certificate.
Live calculators for every product type are built into each product page.
5 · Certification & Inspection Documents
What each document actually proves — and what it does not.
| Document | What it certifies | Typically required for |
|---|---|---|
| EN 10204 2.1 | Declaration of compliance with the order; no test results | Non-critical, low-pressure items |
| EN 10204 2.2 | Test report from non-specific inspection | General commercial supply |
| EN 10204 3.1 | Actual test results on delivered material, validated by an inspector independent of production | Standard for pressure equipment |
| EN 10204 3.2 | Jointly signed by manufacturer and purchaser's representative or official inspector | Nuclear, marine class, high-consequence vessels |
| PED 2014/68/EU | Conformity route for pressure equipment placed on the EU market; material needs 4.3 appraisal or harmonised standard | Any delivery into the European Union |
| NACE MR0175 / ISO 15156 | Material suitability for wet H₂S service — chemistry, hardness limits, HIC / SSC testing | Sour oil and gas production |
| NORSOK M-650 | Manufacturer qualification for duplex and super duplex production routes | North Sea and offshore projects |
| API 607 / API 6FA | Fire type test of a specific valve design, size range and class | Hydrocarbon service isolation valves |
| ISO 15848-1 | Fugitive emission classification of valve stem sealing | Volatile organic compound containment |
| MSS SP-25 | Marking and identification of fittings and valves | Traceability on all shipments |
| ABS · DNV · LR · BV · CCS | Marine classification society approval | Shipbuilding and offshore structures |
On reading certificates. A mill certificate proves what a heat of steel was,
not that the fitting in your hand came from it. Traceability depends on heat number marking surviving
from the mill through forming, heat treatment and marking. Ask how heat numbers are transferred —
it is the question that separates a real quality system from a paperwork exercise.
6 · Procurement FAQ
The questions that come up most often in a fittings enquiry.
What is the difference between long radius (LR) and short radius (SR) elbows?
A long radius elbow has a centreline bend radius of 1.5 times the nominal diameter (1.5D);
a short radius elbow is 1.0D. LR is the default in process piping because the gentler bend causes lower
pressure drop and less erosion. SR is used only where space is restricted, and many specifications
restrict it to lower-velocity or non-critical service.
Are ASME Class and EN PN pressure ratings interchangeable?
No. They are different rating systems with different bolt circles, bolt counts, flange
thicknesses and facing dimensions. A Class 150 flange and a PN 20 flange carry a comparable
pressure-temperature rating but are not dimensionally interchangeable and must not be bolted together.
Specify one system for a complete flanged joint, including gaskets and bolting.
What does EN 10204 3.1 mean, and when do I need 3.2 instead?
3.1 is an inspection certificate with actual test results on the delivered material,
validated by an inspection representative independent of the manufacturing department — the normal
requirement for pressure equipment. 3.2 is jointly signed by the manufacturer and either your
representative or an official inspector, and is usually reserved for nuclear, marine class or
high-consequence pressure vessel work.
What is the difference between SCH 40 and SCH 40S?
SCH 40 is ASME B36.10M and applies to carbon and alloy steel. SCH 40S is ASME B36.19M
and applies to stainless steel. Many smaller sizes share the same wall thickness, but they diverge at
larger diameters — from NPS 12 upward SCH 40S is thinner. The S suffix changes both wall thickness and
weight, so it belongs on the purchase order.
Seamless or welded — when does it actually matter?
Seamless has no longitudinal weld and is normally specified for high-pressure, sour or
cyclic service, and is often mandated by project specification regardless of calculation. Welded
(ERW, LSAW, SSAW) is dimensionally equivalent, considerably cheaper and entirely acceptable in many
utility and structural applications. Above roughly NPS 24 seamless becomes scarce and expensive, and
most large-bore fittings are plate-fabricated by necessity.
When is NACE MR0175 / ISO 15156 compliance required?
Where the line handles wet hydrogen sulphide. Compliance constrains chemistry, hardness
(typically 22 HRC maximum for carbon and low-alloy steel), heat treatment condition and, for some
grades, HIC and SSC testing. It must appear on the purchase order — it cannot be applied retroactively
to material already manufactured.
When does PED 2014/68/EU apply?
To pressure equipment placed on the European Union market above defined pressure and
volume thresholds. For fittings and flanges the practical consequence is that the material needs a
PED 4.3 specific appraisal or a harmonised European material standard, with documentation to match.
Buyers outside the EU rarely need it, though many specify it as a quality benchmark.
What is the difference between weld neck, slip-on and blind flanges?
A weld neck has a tapered hub butt-welded to the pipe, transferring stress smoothly into
the pipe wall — preferred for high pressure, cyclic loading and low temperature. A slip-on slides over
the pipe and is fillet welded inside and out: cheaper, more tolerant of cut-length error, roughly one
third the fatigue life. A blind has no bore and closes off a flanged opening.
What is the difference between API 600 and API 602 gate valves?
API 600 covers bolted bonnet cast steel gate valves, generally NPS 2 and larger, for
refinery and general process service. API 602 covers compact forged gate, globe and check valves,
generally NPS 2 and smaller, at higher pressure classes. Size and cast-versus-forged construction
normally decide which applies.
What makes a valve fire-safe under API 607?
API 607 is a type test, not a construction feature. A representative valve is burned at
defined temperature for a defined period, then seat and atmospheric leakage are measured against
allowable limits. A valve is fire-tested only if it carries a valid certificate covering that specific
design, size range and pressure class.
How do I calculate the weight of a butt-weld fitting?
Start from pipe weight W = 0.02466 × S × (D − S) kg/m. A 90° elbow is approximately
W = 0.0387 × S × (D − S) × R / 1000 kg per piece, where R = 1.5 × DN for long radius; multiply by 0.5
for 45° and by 2 for 180°. Flanges and valves come from standard tables, not formulas. Full formulas
and live calculators are in section 4 and on each product page.
Which standard should I specify when buying from China?
Specify the standard that governs the plant where the material will be installed, not
the country of manufacture. Chinese mills routinely produce to ASME, EN, JIS and GOST as well as GB.
What matters is that the purchase order names one dimensional standard, one material specification and
one certification type — mixing systems is the most common source of dispute at inspection.
What documentation ships with an order?
A standard export shipment carries an EN 10204 3.1 material test certificate traceable to
the heat number, certificate of origin, packing list, commercial invoice and bill of lading. Depending
on scope this can extend to NDE reports, hydrostatic test reports, positive material identification,
hardness reports for sour service, and third-party inspection reports from agencies such as SGS, BV or TÜV.
Can you supply third-party inspection?
Yes — SGS, BV, TÜV, Lloyd's and Intertek inspection can be arranged at your cost, and
witness points can be built into the production schedule. Nominate the agency and the hold points at
order stage so that heat treatment and testing can be scheduled around them.
What are typical lead times?
Common carbon steel items in standard sizes generally ship from stock or within about
15 working days ex-works. Special grades, large diameters, sour-service heat treatment and third-party
witness points extend this. Lead time is confirmed per item on the quotation, not estimated.
Which Incoterms and payment terms do you work with?
Quotations are normally issued FOB Shanghai, with CFR and CIF available on request.
Payment terms are agreed per order and stated on the proforma invoice. Remit only to the beneficiary
name shown on that proforma invoice — see the note in the site footer.