Valve Standards Overview: API, ASME, ISO, EN, JIS & GB

A lookup matrix, not an essay. Find the standard that governs the property you care about, then find its equivalent in the other system.

Key Takeaways

Standards divide by function, not by valve type. One valve is normally governed by four or five at once: a design standard, a rating standard, a face-to-face standard, a test standard and a marking standard.
PN and Class are different rating systems and cannot be converted by arithmetic. PN 16 is not "Class 100" and there is no formula that makes it so.
Face-to-face length is the most common cause of a replacement valve not fitting. ASME B16.10, EN 558 and GB/T 12221 do not always agree for the same DN and rating.
"Pressure tested and passed" is meaningless without naming the standard. API 598, ISO 5208 and EN 12266 use different allowable leakage rates and different hold times.
Chinese GB/T standards map closely onto ISO and EN structure, while API and ASME come from a separate lineage — which is why GB-to-API substitution needs a clause-level check, not a title match.

Standards Divide by Function, Not by Valve Type

The most common misconception is that a valve "complies with API 600" and that this is the specification. API 600 governs design and construction of one family of gate valves. It does not set the pressure-temperature rating, the face-to-face length, the flange drilling, the test acceptance or the marking — each of those comes from a different document.

Use the matrix below the way you would use an index: identify the property in dispute, then read across to find which standard governs it in each system.

Matrix 1 — By Function and Region

Governed function	US (API / ASME / MSS)	ISO	Europe (EN / BS)	China (GB/T, HG/T)
Ball valve design	API 608, API 6D	ISO 17292	EN 1983	GB/T 12237
Gate valve design	API 600, API 602, API 603	ISO 10434	EN 1984	GB/T 12234
Globe valve design	API 623, API 602	—	EN 13709	GB/T 12235
Check valve design	API 594, API 6D	—	EN 13709	GB/T 12235
Butterfly valve design	API 609, MSS SP-67	—	EN 593	GB/T 12238
Pressure-temperature rating	ASME B16.34	—	EN 12516	GB/T 12224
Face-to-face dimensions	ASME B16.10	ISO 5752	EN 558	GB/T 12221
Pipe flanges	ASME B16.5, B16.47	ISO 7005	EN 1092-1	GB/T 9124, HG/T 20592, HG/T 20615
Pressure testing	API 598	ISO 5208	EN 12266	GB/T 13927
Marking	MSS SP-25	ISO 5209	EN 19	GB/T 12220
Fire type test	API 607, API 6FA	ISO 10497	—	—
Cryogenic type test	MSS SP-134	ISO 28921	BS 6364	GB/T 24925

Chinese sector-level JB/T standards sit underneath GB/T and appear constantly on domestic vendor datasheets — our JB/T valve standards map explains which ones matter and how they relate to the GB/T layer.

Matrix 2 — Who Issues What

Body	Full name	Scope in valve work
API	American Petroleum Institute	Valve design, testing and pipeline practice for oil, gas and petrochemical.
ASME	American Society of Mechanical Engineers	Pressure-temperature ratings, flanges and dimensions — the B16 series.
MSS	Manufacturers Standardization Society	Supplementary US practice (SP series) covering marking, cryogenic testing, butterfly valves.
ISO	International Organization for Standardization	International consensus standards, often the base document EN and GB align to.
EN	European Committee for Standardization (CEN)	Harmonised European standards supporting the Pressure Equipment Directive.
BS	British Standards Institution	Legacy UK standards; several remain the live reference, notably BS 6364 for cryogenic.
DIN	Deutsches Institut für Normung	Historic German standards, now largely superseded by EN but still cited on older specs.
JIS	Japanese Industrial Standards	Japanese practice; its own K-series pressure ratings and flange dimensions.
GB/T	Guobiao (Chinese national, recommended)	Chinese national valve standards, structurally aligned with ISO and EN.
JB/T	Chinese machinery industry standard	Sector-level detail standards below GB/T; common on Chinese vendor datasheets.

The Four Traps That Cost Real Money

Trap 1 — Treating PN and Class as convertible

PN and Class are independent rating systems with different derating curves and different flange drilling. Approximate pairings are useful shorthand in a conversation and dangerous in a purchase order. The full explanation and the actual comparison tables are in PN vs ASME Class conversion, and the Chinese Class-series flange standard is covered in HG/T 20615.

Trap 2 — Ignoring the face-to-face series

EN 558 defines multiple basic series for the same nominal size, and they do not all agree with ASME B16.10 or GB/T 12221. The symptom appears on site, when the replacement valve is dimensionally wrong and the pipework has to be cut. Specify the series explicitly — see face-to-face dimensions under GB/T 12221.

Trap 3 — Accepting an unqualified test certificate

API 598, ISO 5208 and EN 12266 permit different leakage and different hold times, and ISO 5208 further lets the buyer select an acceptance rate from A to G. A certificate must state the standard and the rate. Background in leakage classes and sealing standards and, for the Chinese test regime, GB/T 13927 test pressure calculation.

Trap 4 — Matching material grades by name

CF8M, 316, 06Cr17Ni12Mo2 and SUS316 are related but not identical designations with differing composition tolerances and test requirements. Substituting on the strength of a familiar-looking name is how a corrosion failure gets specified in. The full mapping is in Chinese valve material grades cross-reference.

Building a Complete Specification

A defensible valve line item names all of the following:

Design standard — e.g. API 600, ISO 17292, GB/T 12237.
Pressure class or PN, plus the rating standard it derives from.
Design temperature range, minimum and maximum.
Face-to-face standard and series.
End connection standard and flange facing.
Body, trim, seat and packing materials by grade designation.
Test standard and acceptance rate.
Any type-test certification required — fire, cryogenic, fugitive emission.
Marking standard.

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Frequently Asked Questions

How many standards apply to a single valve?

Usually four or five simultaneously. A flanged steel gate valve for a refinery might be designed to API 600, rated to ASME B16.34, dimensioned to ASME B16.10 face-to-face and ASME B16.5 flanges, pressure-tested to API 598, and marked to MSS SP-25. Each governs a different property, so citing only the design standard leaves most of the specification undefined.

Can I convert PN to ASME Class with a formula?

No. PN is a dimensionless designation loosely tied to bar at ambient temperature, while ASME Class ratings come from tabulated pressure-temperature curves that depend on the material group. They are two independent systems with different derating behaviour as temperature rises, and the flange bolt patterns differ as well. Approximate pairings exist for procurement shorthand — PN 16 near Class 150, PN 40 near Class 300 — but they are not interchangeable and must never be used to justify mating a PN flange to a Class flange.

Why does a replacement valve of the same size not fit?

Almost always face-to-face length. ASME B16.10, EN 558 and GB/T 12221 each define lengths for a given DN and rating, and they do not always match — EN 558 in particular offers multiple basic series for the same size. A DN100 PN16 butterfly valve bought against one series can be tens of millimetres different from the one it replaces. Record the face-to-face series on the datasheet, not just the size.

Are API 598 and ISO 5208 leakage acceptances the same?

No. They define different allowable leakage rates, different test durations and, in the case of ISO 5208, a set of lettered rates (Rate A through Rate G) that lets a specification choose how tight is tight enough. EN 12266 is a third variant again. A test certificate that says "passed hydrostatic and seat test" without naming the standard and the acceptance rate tells you very little.

How closely do Chinese GB/T standards match API and ASME?

GB/T valve standards are structurally closer to ISO and EN than to API and ASME, because much of the GB system was harmonised against ISO. That means GB-to-EN substitution is often straightforward, while GB-to-API substitution needs a clause-level comparison of wall thickness, testing and trim requirements rather than a title match. Our GB versus API and ASME cross-reference works through the practical differences.

Which standard governs valve marking?

MSS SP-25 in the US, ISO 5209 internationally, EN 19 in Europe and GB/T 12220 in China. They cover what must appear on the body and the nameplate — size, rating, material, manufacturer, and where applicable the design standard and heat number. Marking is frequently the first thing an inspector checks, and a valve that is otherwise compliant can be rejected on marking alone.