A valve that leaks on the first pressure test of a new line costs far more than the valve. The line is drained, the valve is cut or unbolted, a replacement is found, and the commissioning date moves. Often the cause is not a bad factory. It is an order that named the valve type and size but not the standard it is built to, the standard it is tested to, or the seat leakage the buyer expected.
Valves are bought from manufacturers and stockists across Asia — Japan, China, Taiwan, Korea, India, Vietnam and Thailand all make them — and the same rule applies everywhere: a valve is specified by its design standard, its pressure rating and its test standard, and the three are written separately. This article shows how to write them for the common valve types, and which records to ask for so that the valve is proven before it leaves the supplier.
💬 Have a valve list from a drawing or a maintenance schedule? Send it to us and we will check that each line names a design standard, a rating and a test standard before it goes out for quotation.
Three standards on every valve line
Each valve line needs a design standard (what the valve is), a pressure rating (what it may hold) and a test standard (how that is proven before shipment).
Buyers often write one standard and assume it covers the others. It usually does not. A valve built to one of the API process valve standards that reference API 598 is tested to it because the design standard calls it up; a valve built to a JIS or catalogue design may be tested to JIS B 2003 or to the maker’s own procedure. Write the test standard explicitly, and the end connection standard too (flange to ASME B16.5, JIS B 2220 or EN 1092-1; see pipe fittings and flanges).
| Line on the order | What it fixes | Example |
|---|---|---|
| Valve type and design standard | Construction, wall thickness, materials | API 608 metal ball valve; ISO 17292; JIS B 2071 steel valve |
| Pressure rating | Allowed pressure at temperature | ASME Class 150 / 300; PN 16; JIS 10K |
| Pressure-temperature basis | Where the rating table comes from | ASME B16.34 |
| End connection | Flange, butt-weld, socket-weld, thread | RF flanged to ASME B16.5; wafer; NPT thread |
| Face-to-face dimension | Whether it fits the space in the line | ASME B16.10 or the design standard’s own table |
| Test standard | Shell and seat tests, acceptance | API 598; ISO 5208; JIS B 2003 |
| Materials | Body, trim, seat, seals | Body grade, ball or disc grade, seat material |
| Inspection document | Material and test proof | EN 10204 3.1 certificate; test report |
Design standards by valve type
For process and utility service, the API and ISO valve standards set the construction of each valve type, and ASME B16.34 sets the pressure-temperature basis many of them refer to.
ASME B16.34 (Valves — Flanged, Threaded, and Welding End) is the general standard behind most steel valves in ASME-rated piping. ASME lists the 2025 edition, issued on 30 May 2025. Several API valve standards are written as additional requirements on top of B16.34.
The API standards below are listed in API’s 2025 Publications Catalog with the scope shown. API revises these standards regularly, so name the edition your project specification requires rather than relying on the one in force when this was written.
| Valve type | API standard (2025 catalogue scope) | ISO or JIS counterpart to consider |
|---|---|---|
| Ball | API 608 Metal Ball Valves — flanged and butt-welding ends NPS 1/2 to NPS 20 in Classes 150, 300 and 600; threaded and socket-welding ends NPS 1/4 to NPS 2 up to Class 800; full, single-reduced and double-reduced bore | ISO 17292:2015 metal ball valves, DN 8 to DN 600, Classes 150 to 800 and PN 16 to PN 100 |
| Gate | API 600 heavy-duty bolted-bonnet steel gate valves for refinery service; API 602 compact gate, globe and check valves DN 100 (NPS 4) and smaller; API 603 corrosion-resistant bolted-bonnet gate valves, Classes 150, 300 and 600 | ISO 10434:2020 bolted bonnet steel gate valves; JIS B 2071 steel valves |
| Butterfly | API 609 double-flanged, lug, wafer and butt-welding butterfly valves in iron, bronze, steel and alloys | ISO 10631:2021 metallic butterfly valves; JIS B 2032 wafer-type rubber-seated butterfly valves |
| Check | API 594 flanged, lug, wafer and butt-welding check valves (two types) | Design standard of the maker, tested to ISO 5208 |
| Plug | API 599 metal plug valves, NPS 1/2 to NPS 24 | — |
| Pipeline valves | API Spec 6D (Specification for Valves), 25th edition | — |
For general utility water, air and low-pressure steam, valves are often bought from a maker’s catalogue by part number — for example from Japanese makers such as KITZ or TOYO — and the catalogue itself names the design and test basis. That is a valid way to order, provided the catalogue number is complete (body material, end type, rating and seat material all sit in the code) and you ask for the maker’s test report. On Japanese-designed utilities you will also meet bronze valves to JIS B 2011 and steel valves to JIS B 2071.
If you are replacing a valve with a different brand, compare the face-to-face dimension and the end connection first. A ball valve of the same nominal size and rating from another maker can be longer or shorter, and a wafer butterfly valve’s disc must clear the bore of the adjacent pipe and flange.
Pressure class is not a pressure
A class or PN designation selects a rating table; the permitted pressure depends on body material and temperature and must be read from the standard, not from the class number.
ASME Class 150 valves made of carbon steel and of stainless steel do not have the same permitted pressure, and both fall as temperature rises. JIS “K” ratings and EN PN ratings follow their own tables. When comparing quotations, ask each supplier to state the body material group and the rating at your design temperature, quoted from the edition of the standard they build to.
Seat and seal materials set a second limit. A ball valve with a polymer seat may carry a body rating that its seat cannot achieve at high temperature. Write the design temperature on the order and ask the supplier to confirm that the complete valve, not just the body, is rated for it.
💬 We source valves from manufacturers and stockists across Asia, by standard or by maker’s part number, and check the records before shipment. See pipe fittings, valves and couplings.
Testing: API 598, ISO 5208 and JIS B 2003
Ask for a pressure test record for every valve, made to a named test standard, with the shell test and the seat test reported separately.
API 598 (Valve Inspection and Testing, 11th edition, February 2023 in API’s catalogue) covers inspection, examination, supplementary examinations and pressure test requirements for resilient-seated, non-metallic-seated (for example ceramic) and metal-to-metal-seated gate, globe, plug, ball, check and butterfly valves. It supplements the API standards that reference it and may be applied to other valves by agreement. Its Annex A lists information the purchaser specifies — read it before ordering, because the tests you need may be optional unless you ask.
ISO 5208:2015 (Industrial valves — Pressure testing of metallic valves) specifies the examinations and tests a valve manufacturer performs to confirm the integrity of the pressure boundary, the tightness of the closure and the strength of the closure mechanism. ISO states it is used with a product standard that cites it, and that it does not address the safety of pressure testing. ISO lists the 2015 edition as current, with an amendment (Amd 1) at committee-draft stage.
JIS B 2003 (general rules for inspection of valves) is the Japanese counterpart that JIS valves usually refer to.
| Test | What it proves | What the record should show |
|---|---|---|
| Shell test | Body and bonnet hold pressure without leakage | Test medium, pressure, duration, result per valve |
| Seat (closure) test | The closed valve does not leak beyond the allowed rate | Test medium, pressure, direction, leakage rate or “no visible leakage” as the standard defines |
| Backseat test (where applicable) | Stem backseat seals | Per the test standard |
| Fire test (if specified) | Valve stays pressure-tight after fire exposure | Type-test certificate, e.g. API 607 (8th edition, October 2022) for quarter-turn valves |
| Fugitive emission type test (if specified) | Stem packing performance | Type-test report, e.g. API 622 / API 624 |
Production tests are per valve; type tests (fire, fugitive emissions) are done once on a design and reported by certificate. Do not accept a type-test certificate in place of production test records, and check that the certificate covers the size range and pressure class you are buying.
Materials and documents
For steel valves in pressure service, require a material certificate for the pressure-retaining parts and link it to the valve by heat number and serial number.
The body and bonnet are the pressure-retaining parts. Ask for an inspection certificate type 3.1 under EN 10204 for those, plus the pressure test record per valve. How to read a certificate and check that it belongs to your valve is set out in mill test certificates under EN 10204.
Trim and seats are specified separately. A “stainless ball valve” can have a stainless body with a different ball grade, or a stainless body and ball with a seat that does not suit your fluid. Write each one.
If the valve will be fitted to a line in a regulated plant, ask the end user which marking and documents its inspector expects. In the EU, Directive 2014/68/EU covers stationary pressure equipment with a maximum allowable pressure greater than 0,5 bar, according to the European Commission — how it applies to a valve depends on the fluid, pressure and size; for other countries, confirm the current rule in the country of use.
Inspection before shipment
Witness or review the pressure tests on a sample, and check marking, dimensions and documents against the order before goods are packed.
A practical sequence is: confirm the valve tag or serial numbers match the test records; check the nameplate or body marking against the order line (type, size, rating, body material); measure face-to-face on a sample; check flange facing and drilling; and confirm that end protectors are fitted so the sealing faces arrive undamaged. For high-value or critical valves, witness the shell and seat tests at the supplier.
Inspection sampling and how to record findings are covered in pre-shipment inspection and AQL, and supplier checks are part of our supplier check and inspection service.
💬 Need valves from several makers consolidated with fittings and gaskets in one shipment? Tell us what the project needs.
Frequently asked questions
1. Is an API 598 test the same as an API 6D test?
No. API 598 is the inspection and test standard used with API process valve standards; API Spec 6D has its own requirements for the valves it covers. Name the one your specification requires.
2. Can I buy a valve by brand and part number instead of a standard?
Yes, for catalogue valves this is common. Make sure the full catalogue code is on the order and ask for the maker’s test report and material certificate for each valve.
3. Does a Class 300 valve hold 300 psi?
Not as a rule. The class selects a rating table; the permitted pressure depends on material and temperature. Read it from ASME B16.34 or the design standard for your conditions.
4. Is a fire-safe certificate required for every ball valve?
Only if your specification or the end user requires it. Where it does, ask for the type-test certificate and check it covers your size, class and seat design.
5. What should a valve test record contain?
The valve serial or tag number, the test standard, test medium, pressures, durations, results for shell and seat tests, and the inspector’s signature and date.
Sources: API 2025 Publications Catalog (Refining) entries for Std 594, 598, 599, 600, 602, 603, 607, 608, 609, 622, 624 and RP 578; API announcement page for Spec 6D 25th edition; ASME B16 revision list (B16.34-2025, B16.10-2022); ISO catalogue pages for ISO 5208:2015, ISO 17292:2015, ISO 10434:2020 and ISO 10631:2021; JISC database titles for JIS B 2003, B 2011, B 2032 and B 2071; European Commission page on Directive 2014/68/EU. Checked on 27 October 2026.