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Pressure Classes and Material Groups under ASME B16.34
| Class | Approx. Max Pressure at 38 °C, Group 2.1 and 2.2 (304, 316) | Typical Use |
|---|---|---|
| Class 150 | About 19 bar (275 psi) | Water, air, low-pressure steam, general process |
| Class 300 | About 50 bar (720 psi) | Higher-pressure process, steam, hydrocarbons |
| Class 600 | About 99 bar (1440 psi) | High-pressure process and steam |
| Class 900 | About 149 bar (2160 psi) | High-pressure gas and injection |
| Class 1500 | About 248 bar (3600 psi) | Very high pressure lines |
| Class 2500 | About 413 bar (6000 psi) | Specialised high-pressure systems |
Material groups for common stainless steels
| Group | Typical Materials | Note |
|---|---|---|
| 2.1 | 304, 304H, CF8, 347 | Higher ratings; for 304 and similar grades |
| 2.2 | 316, 316H, CF8M, 317 | Similar ratings to group 2.1 at moderate temperature |
| 2.3 | 304L, 316L (wrought low carbon) | Lower ratings, since low-carbon grades are weaker |
| 2.4 to 2.8 | 321, 347, 309, 310, special austenitic grades | Individual tables for each group |
| 3.x | Duplex, super duplex and high-alloy steels | Separate tables, see standard |
Pressure values above are for about 38 °C and are approximate. Group 2.3 materials, such as F304L and F316L, have lower ratings than groups 2.1 and 2.2, around 16 bar for Class 150, so it is important to know which exact grade is used. The correct table for each material group is in the standard, and we supply the relevant table with each data sheet.
What the standard defines
- Pressure-temperature ratings: allowable pressure at each temperature, for each class and material group.
- Minimum wall thickness: body and end connection wall at each size and class.
- End connection dimensions: flanges per ASME B16.5, butt weld ends per ASME B16.25, socket weld ends per ASME B16.11.
- Stem design: stems must be retained so they cannot be blown out of the valve by pressure.
- Marking and testing: body marking, shell test and closure test requirements.
Valve Types and Sizes Available to ASME B16.34
B16.34 is the general standard, so it can be applied to many valve types. We list below the products we typically supply to B16.34 ratings, along with the design standards used alongside it. If you need a product not shown, please ask, since our range is wider than this table.
| Valve Type | Design Standard Used with B16.34 | Size and Class Range |
|---|---|---|
| Flanged ball valves | API 608, ISO 17292, API 6D (selected) | 1/2 inch to 12 inch; Class 150, 300, 600 |
| Gate valves, bolted bonnet | API 600 | 1/2 inch to 24 inch; Class 150, 300, 600 |
| Forged gate, globe and check valves | API 602 | 1/2 inch to 2 inch; Class 800, 1500 |
| Globe valves | BS 1873, API 623 (steel globe valves) | 1/2 inch to 12 inch; Class 150, 300, 600 |
| Check valves | API 594, BS 1868 | 1/2 inch to 24 inch; Class 150, 300, 600 |
| Butterfly valves, double offset | API 609 | 2 inch to 24 inch; Class 150, 300 |
| Butt weld and socket weld valves | Standards above, with ASME B16.25 and B16.11 ends | 1/2 inch to 12 inch |
| Strainers | Manufacturer standard aligned with B16.34 pressure classes | 1/2 inch to 12 inch |
Choosing class and material
- Start with the line design data: design pressure and design temperature, including upset conditions.
- Choose the material: grade determines the material group, and therefore the rating at temperature.
- Choose the class: select the lowest class whose rating at your temperature is above design pressure, with margin.
- Check the seat: soft seats such as PTFE often limit the valve to a lower temperature than the body can handle.
Send us your line list with design pressure and temperature, and we will propose class, material and valve type for each line.
How ASME B16.34 Works with Other Standards
ASME B16.34 does not stand alone. It sets general rules for pressure containment, and other standards add detailed rules for each valve type. Understanding the structure helps you write clearer purchase specifications.
| Role | Standard Reference |
|---|---|
| Pressure-temperature ratings, wall thickness, marking, testing | ASME B16.34 |
| Flanges | ASME B16.5 (to NPS 24), ASME B16.47 (large sizes) |
| Butt weld ends | ASME B16.25 |
| Socket weld and threaded ends | ASME B16.11, ASME B1.20.1 |
| Face-to-face dimensions | ASME B16.10 |
| Gate valves | API 600, API 602 |
| Ball valves | API 608, API 6D |
| Butterfly valves | API 609 |
| Check valves | API 594 |
| Testing | API 598, ISO 5208 |
| Material specifications | ASTM A351 (castings), A182 (forgings), A479 and A276 (bar), A193 / A194 (bolting) |
| Piping codes using these valves | ASME B31.3, B31.1, B31.4, B31.8 |
Standard, Special and Limited classes
B16.34 defines Standard Class valves, which are the normal choice, Special Class valves, which require additional examination of castings, such as radiography of critical areas and other NDE, and Limited Class valves, which are restricted to certain types, sizes and end connections. Most projects specify Standard Class. If your project requires Special Class, tell us in the inquiry, since it adds testing and documents.
The edition of B16.34 is also important, since rating tables are updated. We state the edition used in each data sheet.
Reference note: B16.34 is updated every few years, and rating tables, material groups and special requirements may change. Project specifications normally fix an edition, and we follow it. If the edition is not named, tell us whether you prefer the current one, so that data sheets and tests match your expectations from the start.
Documentation for B16.34 Compliant Valves
Engineers who specify B16.34 want to see that the standard was really applied, not just mentioned in a catalogue. We therefore prepare a documentation set that shows the link between the standard and the valve, including the design data, the materials and the tests.
- Valve data sheet: class, material group, rating table for the supplied grade, temperature limits of seat and packing, and edition of B16.34.
- Material test certificates: EN 10204 3.1 for pressure-containing parts, with chemistry and mechanical properties.
- Wall thickness record: measured thickness of body at critical locations compared to the minimum required.
- Pressure test report: shell and closure tests per the standard and API 598.
- Marking and nameplate sample: showing manufacturer name, class, material, size and heat number.
- NDE reports: for Special Class or where specified, radiography and dye penetrant results.
- Heat treatment records: solution annealing records for castings and forgings.
- Quality management: ISO 9001 style system and batch records.
- Third-party inspection: SGS, BV, TUV, DNV or the buyer's inspector can witness inspection and testing.
"Designed to" or "certified to"? Many manufacturers state that valves are "designed to" B16.34. There is no official certification scheme for B16.34 itself, but conformity can be supported by design calculations, wall thickness checks, marking and testing records. We provide that evidence on request.
Sample data sheets and documentation lists can be sent before order confirmation.
Audit tip: ask for the valve data sheet with the rating table at the start of the project, before the valves are made. Reviewing it early lets your engineers confirm that class, material group and temperature limit fit the line, and avoids discovering a mismatch when the valves are delivered and installation is already planned.
Marking and Traceability Required by the Standard
B16.34 requires valves to carry permanent markings that identify the manufacturer, the pressure rating, the material and, for some valves, the flow direction. This marking forms the basis of the traceability system, since it lets an inspector read key data directly from the valve.
- Body marking: manufacturer name or mark, material grade, class designation, nominal size and heat number.
- Flow direction: arrow for valves with a preferred flow direction, such as globe valves and check valves.
- Nameplate: data on rating, temperature limits and the standard, as required by the project.
- Material records: mill certificates and PMI results linked to heat numbers.
- Test records: pressure test results linked to the valve serial number.
- Document package: certificates and reports refer to the valve serial number.
| Marking | Meaning |
|---|---|
| CL 150, CL 300, CL 600 | Pressure class |
| Material grade, such as CF8M or F316L | Body material |
| Nominal size in inches | NPS size of the valve |
| Heat number | Link to mill certificate |
| Manufacturer mark | Identification of producer |
| Arrow | Direction of flow where required |
| Temperature limit | Where seat or packing limits the rating |
Marking is made by low-stress stamping or by casting, so it does not reduce the strength of the valve body, and it remains legible after painting, insulation and years of service.
Why marking is part of safety: in a plant with thousands of valves, a clear and permanent marking is the fastest way to confirm that a valve has the correct class and material. We apply markings in positions that stay visible after insulation is fitted, and keep a record of what was marked on each valve.
Verification of Compliance: Testing and Inspection
Compliance with B16.34 is confirmed by checking the body dimensions, the materials and the pressure tests. We combine these checks so that each valve has evidence behind its class marking.
| Check | Method | Frequency |
|---|---|---|
| Body wall thickness | Ultrasonic thickness gauge and calipers on critical sections | First article and sampling |
| Material grade | PMI by XRF analyser | Incoming and sampling |
| Chemistry and mechanical properties | Mill certificates and laboratory tests | Each heat |
| Shell test | 1.5 x 38 °C rating, per B16.34 and API 598 | 100% of valves |
| Closure test | 1.1 x 38 °C rating, per API 598 | 100% of valves |
| Stem retention check | Design review and sample inspection | First article |
| Flange dimension inspection | Per ASME B16.5, with drilling templates | First article and sampling |
| NDE for Special Class | Radiography and dye penetrant per standard | On request |
| Marking inspection | Visual check for completeness and legibility | 100% of valves |
Why wall thickness matters. The rating of a valve depends on its wall. A casting with a thin section, caused by core shift in the foundry, can be below the minimum thickness even though the valve looks normal. We therefore measure thickness at critical points on sample valves, and on every valve when the specification asks for it.
You are welcome to witness these inspections, and we can arrange visits or provide photographs of the measurements.
Reading the wall thickness record: measured values are compared with the minimum thickness of the standard for each size and class. A valve passes if every measured point is at or above the minimum. We keep the measurement points and values on file, and can send them on request for valves that need extra confidence.
Frequently Asked Questions about ASME B16.34 Valves
Q: What does ASME B16.34 specify?
It specifies pressure-temperature ratings, dimensions, tolerances, marking, testing and materials for flanged, threaded and welding-end valves in classes from 150 to 4500.
Q: Is B16.34 a certificate I can get?
There is no official B16.34 certificate. Compliance is shown by design, materials, inspection and testing records. We can provide the data to support that.
Q: What is the difference between Standard, Special and Limited Class?
Standard Class is the normal choice. Special Class requires additional examination of castings and other NDE. Limited Class applies to specific valve types and sizes with restrictions.
Q: Why does the rating of 316L differ from 316?
Low-carbon grades such as 316L are weaker at high temperature, so B16.34 gives them lower pressure ratings than 316 or 316H. It is important to specify the exact grade.
Q: Can I use a Class 300 valve on a Class 150 line?
Pressure-wise, yes, but the flanges are different, so a Class 300 valve will not bolt directly to Class 150 flanges.
Q: Does B16.34 cover butterfly valves?
Yes, double offset and triple offset butterfly valves can be rated to B16.34. Resilient-seated wafer valves are usually rated by manufacturer or by API 609 Category A.
Q: Which edition do you follow?
We follow the edition named in your order. If none is named, we use the current edition and state it in the data sheet.
Still have questions? Send us your line data, with design pressure, design temperature, medium and material preference. We will reply with a class and material recommendation, the matching rating from the standard and the valve type that suits each line, so your team can make a decision with clear numbers in front of them.
MOQ and Pricing for B16.34 Valves
B16.34 valves are typically bought for projects, so quantities range from a single large valve to several hundred small ones. We keep terms flexible and price according to size, class and material.
| Item | Typical Terms |
|---|---|
| Sample order | 1 to 3 pieces per model |
| Standard MOQ | 20 to 50 pieces per size; large valves from 1 piece |
| Special Class requirements | Quoted separately, with NDE and documents |
| Pricing basis | EXW, FOB Ningbo, CFR or CIF in USD |
| Quote validity | 30 days, adjusted for stainless steel and nickel prices |
| Payment | 30% T/T deposit, 70% before shipment; L/C at sight for approved accounts |
What drives the price
- Class: higher classes need thicker walls and flanges, so the price rises with each step.
- Size: weight increases quickly with size.
- Material group: duplex and high-alloy grades cost more than 304 and 316.
- Special Class: additional NDE and documentation increase cost and time.
- Trim and seat: hard facing and metal seats are priced above soft seats.
Avoid over-specification. Choosing a class that is higher than needed raises the price without adding useful safety. Sending the design pressure and temperature lets us recommend the lowest suitable class, and we mention where a higher class could be a wise choice because of surge or future expansion.
Ordering advice: send the whole valve list at once, with class, size, material and end connection for each item. We group similar lines, suggest where a lower class is enough, and prepare one clear quotation, which usually saves time on both sides and gives a better overall price than many separate small inquiries.
Lead Time, Customisation, Packaging and Trade Terms
Lead time
Standard Class 150 and 300 valves in popular sizes ship in 20 to 35 days. Higher classes, large sizes, Special Class valves and orders with extended NDE normally need 45 to 90 days. We provide a schedule with milestones at order confirmation.
Customisation
We can customise class, material, end connections, face-to-face length, trim, seat, packing, stem extension, operator, nameplate and documents. For retrofit projects, we can match existing valve dimensions to new B16.34 rated designs.
Packaging
- Flange faces and weld ends protected with covers
- Valves drained, dried and wrapped after testing
- Cartons with dividers for small valves, wooden cases or pallets for heavy ones
- Documents in a waterproof envelope with each shipment
- Marking and labels showing class, material, size and tag number
Shipping and trade terms
| Term | Details |
|---|---|
| Incoterms | EXW, FOB Ningbo, CFR, CIF, DAP |
| Port | Ningbo-Zhoushan; Shanghai as an alternative |
| Transport | Sea freight, air freight for urgent items, express courier for samples |
| Documents | Invoice, packing list, bill of lading, origin certificate, material and test certificates |
We can ship valves together with flanges, gaskets and bolting built to matching classes, which helps your site team assemble joints without waiting for missing parts.
Handling advice: keep protective covers on flange faces and weld ends, lift heavy valves with slings around the body, and store them off the ground in a dry area. Careful handling protects sealing surfaces and markings, which are the features most often damaged before installation and most expensive to repair afterwards.
