Standards explainer

ASME B16.34 valve ratings: what it covers and what to check in a vendor datasheet

A plain-English overview of ASME B16.34 for bid engineers and proposal engineers: pressure classes, material groups, rating class types, tests, and where it sits beside the API valve standards.

By Ademola Afolabi, Founder, New Odyssey Ltd · Last reviewed: 2026-10-23

The short answer

ASME B16.34 is the standard for flanged, threaded and welding-end valves. It sets pressure-temperature ratings by class and material group, minimum wall thicknesses, materials, examination, testing and marking. Product standards such as API 600 build on it. Check every pressure-containing material's rating at the design temperatures on your datasheet.

Key Takeaways

ASME B16.34 is a general valve standard, not a product standard for one valve type.
A pressure class points to a rating table; the allowable pressure depends on material group and temperature.
Special Class gives higher ratings only with extra non-destructive examination.
Seats and seals can limit a valve below its B16.34 body rating; state the real limits.

What ASME B16.34 covers

ASME B16.34 applies to new cast, forged and fabricated valves with flanged, threaded or welding ends. Tenders usually bring it in through the piping class or through a product standard, such as API 600 for gate valves, that relies on it (ASME).

What ASME B16.34 addresses (own summary)
Area	What it covers in outline
Pressure-temperature ratings	Allowable working pressure by pressure class, material group and temperature
Materials	Acceptable material specifications, sorted into numbered material groups
Design	Minimum body wall thickness by class and inside diameter, and dimensional tolerances
Examination	Non-destructive examination, including the extra examination needed for Special Class
Testing	A shell test of the pressure boundary and a closure test of the seat on each valve
Marking	What must be marked on the valve body and identification plate

Pressure classes and rating class types

ASME B16.34 uses pressure classes 150, 300, 600, 900, 1500, 2500 and 4500; Class 4500 applies to welding-end valves only. A class is not a pressure. It points to a rating table whose allowable pressure falls as temperature rises, and each material group has its own tables.

Rating class types (own summary)
Class type	What it means	What to check in a tender
Standard Class	The base rating	Rating at the design temperatures for the body material
Special Class	Higher allowable pressures, only with extra non-destructive examination of the pressure boundary	Whether Special Class is asked for, and whether the NDE and its records are priced
Limited Class	A rating option for small threaded and welding-end valves, with its own conditions	The size limit and conditions in the edition named

Where ASME B16.34 sits beside the API valve standards

Product standards add to ASME B16.34 rather than replace it. API 600 sets heavier minimum walls than B16.34 for refinery gate valves and uses the B16.34 material groups. Sour service, fire testing and fugitive emissions come from their own standards, such as NACE MR0175 / ISO 15156, API 607 or API 6FA, and ISO 15848-1. Flanged ends follow the flange standard, butt-welding ends follow ASME B16.25, and many tenders name ASME B16.10 for face-to-face dimensions. See the API valve standards hub and API 6D.

What to check in a vendor datasheet against ASME B16.34

Datasheet checks against an ASME B16.34 requirement
Datasheet item	Check against	Typical deviation source
Pressure class	Piping class and datasheet	Class shown does not match the piping class
Body and bonnet materials	Material groups and rating tables	Material not listed, or not rated at the design temperature
Rating at design conditions	Rating table for the group and class, at the highest and lowest design temperatures	Allowable pressure below the design pressure
Rating class type	Spec and datasheet	Special Class asked for but extra NDE not offered or priced
Seat and seal limits	Design pressure and temperature	Non-metallic seats limit the valve below the body rating
Wall thickness basis	Spec and product standard	B16.34 minimum offered where a heavier product-standard wall is asked
End connections and dimensions	Piping class, flange and butt-weld end standards, face-to-face standard	Facing, bore or face-to-face does not match
Tests	B16.34 shell and closure tests, plus any test standard the spec names	Extra tests or tighter leakage limits not priced
Marking and documents	Spec and VDRL	Marking or certificate type differs from the spec

Write each gap as a row in your technical deviation list, and use the datasheet vs specification checklist and free templates for the rest of the offer. OdysseyGPT drafts these rows from the tender package with a quote and page for each, for an engineer to check; see OdysseyGPT for manufacturing and valve manufacturers.

Buyer questions

20 questions bid engineers, proposal engineers and buyers ask. Last reviewed: 2026-10-23

What does ASME B16.34 cover?

ASME B16.34 is the US standard for flanged, threaded and welding-end valves. It sets pressure-temperature ratings, minimum wall thicknesses, dimensions and tolerances, materials, non-destructive examination, testing and marking for new valves. It is not a product standard for one valve type. Product standards such as API 600 and API 608 sit on top of it and rely on it.

Which valves does ASME B16.34 apply to?

It applies to cast, forged and fabricated valves with flanged, threaded or welding ends, across the common valve types such as gate, globe, check, ball, plug and butterfly. What brings it into a tender is usually the piping class or a product standard that calls it up. Check the scope of the edition named if your valve type is unusual.

What pressure classes does ASME B16.34 use?

ASME B16.34 uses pressure classes 150, 300, 600, 900, 1500, 2500 and 4500. A class is not a pressure. It points to a table of allowable working pressures that fall as temperature rises, for each material group. So a Class 600 valve in one material can have a different rating at the same temperature from another material.

Can a flanged valve be Class 4500 under ASME B16.34?

No. Class 4500 applies only to welding-end valves, because standard flange tables do not go above Class 2500. If a datasheet shows a flanged valve at Class 4500, query it before you price. Ask whether the buyer means a welding-end valve or a different design basis, and record the answer as a clarification in your offer.

What is the difference between Standard Class and Special Class in ASME B16.34?

Standard Class is the base rating. Special Class gives higher allowable pressures for the same class and material, but only if the valve passes extra non-destructive examination of the pressure boundary. A tender that asks for Special Class is asking for that extra examination and its records. Price the NDE, and do not mark a valve Special Class without it.

What is Limited Class in ASME B16.34?

Limited Class is a rating option for small threaded and welding-end valves. It has its own rules and rating tables that differ from Standard and Special Class. Check the size limit and conditions in the edition named before you apply it. If a tender names Limited Class, make sure your design and records meet those conditions, or declare the difference.

What are material groups in ASME B16.34?

ASME B16.34 sorts acceptable material specifications into numbered groups, such as Group 1.1 for common carbon steels. Each group has its own pressure-temperature rating tables. So the material you choose sets the rating, not just the class. Check that every body and bonnet material on your datasheet is listed in a group and rated for the design temperature.

How do I check a valve's rating against the design conditions in ASME B16.34?

Find the material group of the body material, open the rating table for that group and the right class, and read the allowable pressure at the design temperature. It must be at least the design pressure. Do this at both the highest and lowest design temperatures in the datasheet. If the rating falls short, you need a higher class or another material.

Can soft seats limit a valve below its ASME B16.34 rating?

Yes. The B16.34 rating covers the metal pressure boundary. Seats, seals and other non-metallic parts can have lower pressure or temperature limits, and they then limit the valve. State the real limits of your valve on the datasheet. If the tender's design conditions exceed your seat limits, declare a deviation even when the body rating is fine.

How does ASME B16.34 set valve wall thickness?

ASME B16.34 gives minimum wall thicknesses for the valve body by pressure class and inside diameter. Product standards can ask for more. For example, API 600 sets heavier walls for refinery gate valves. Check which wall basis the tender asks for and which your design meets. A design that meets the B16.34 minimum may still fall short of a heavier product-standard wall.

What pressure tests does ASME B16.34 require?

ASME B16.34 requires a shell test of the pressure boundary and a closure test of the seat on each valve. The shell test is a hydrostatic test at a pressure set from the valve's room-temperature rating. Many tenders call up API 598 or an owner standard for testing as well. Check which test standard and leakage limits govern, then price them.

What is the difference between ASME B16.34 and API 600?

ASME B16.34 is a general valve standard for ratings, walls, materials, testing and marking. API 600 is a product standard for bolted-bonnet steel gate valves, with heavier walls and gate-valve details such as trim and wedge. An API 600 tender will normally also bring in B16.34. See the API valve standards hub for the product standards.

How does ASME B16.34 relate to ASME B16.5?

ASME B16.5 covers pipe flanges and flanged fittings. ASME B16.34 covers valves, and flanged valve ends follow the flange standard for their dimensions. Butt-welding ends follow ASME B16.25, and many tenders name ASME B16.10 for face-to-face dimensions. Check each end connection and dimension on your datasheet against the standard the piping class names.

What are common ASME B16.34 deviations in valve tenders?

Common ones are a body material whose rating falls short at the design temperature, seat limits below the design conditions, and Special Class asked for but not priced. Wall thickness to a heavier standard and end dimensions that do not match the piping class come up too. Record each one in a technical deviation list with the clause and page.

What do EPCs ask for to show ASME B16.34 compliance?

Expect a datasheet stating the class, rating basis and materials, material certificates for pressure-containing parts, shell and closure test records, and any NDE reports for Special Class. Marking details and a general arrangement drawing are common. The vendor data requirements list sets each document and its due date. Certificates are often asked to EN 10204 3.1.

How do I check a valve datasheet against ASME B16.34?

Check the class, then each pressure-containing material against its material group and rating at the design temperatures. Then check rating class type, seat and seal limits, wall basis, end connections, tests and marking. Mark each line complies, deviates or needs clarification. The datasheet vs specification checklist covers the rest of the datasheet.

What if a material is not rated at the design temperature in ASME B16.34?

Then you cannot claim a B16.34 rating for it at that temperature. Choose a material that is rated, or raise a clarification with the buyer before you price. Do not extrapolate a rating table. Low temperatures can also bring impact-test requirements from the project specification, so check those at the same time as the rating.

Does ASME B16.34 cover sour service or fire testing?

No. Sour service materials usually come from NACE MR0175 / ISO 15156, and fire testing from standards such as API 607, API 6FA or ISO 10497. Fugitive emissions come from standards such as ISO 15848-1. A tender will call these up separately. Treat each one as its own requirement row in your compliance matrix.

How does OdysseyGPT check ASME B16.34 requirements in a tender?

OdysseyGPT reads the whole tender package and lists each requirement, including the class, rating and test clauses that bring in B16.34. It checks each one against your own datasheets, standard specifications and test procedures, with a quote and page from the source. You export an editable compliance matrix and a deviations and clarifications list for an engineer to review.

Can OdysseyGPT check a valve rating against the ASME B16.34 tables?

Not unless the rating data is in the documents you upload. OdysseyGPT does not ship copies of ASME standards and does not certify compliance. It compares the tender's requirements with what your own documents say, such as the class and rating on your datasheet, with the source quoted. Your engineers confirm ratings and decide every open item.

Frequently asked questions

Is ASME B16.34 a valve product standard?

Not for one valve type. It is a general standard for ratings, walls, materials, examination, testing and marking that product standards such as API 600 rely on.

Does a higher pressure class always mean a higher rating?

For the same material group and temperature, yes. Between different materials, no: each material group has its own rating tables, so compare ratings, not class numbers.

References

ASME B16.34: Valves, Flanged, Threaded, and Welding End

ASME

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API standards catalogue

American Petroleum Institute