Draft page. The factory document pack for this page is still under review. Values marked “To be confirmed” have not been verified yet.
Metal seated ball valves
Ball valves · API 6D · API 608
A metal seated ball valve uses metal-to-metal contact between the ball and the seat instead of a soft polymer insert, so it can seal at high temperature and in abrasive service where PTFE or PEEK would degrade. The trade-off is a higher operating torque and a leakage rate agreed in the purchase order.
Who makes this valve
We publish one number per API specification, never a factory-by-factory row: a row with its licence set and expiry year would point at a single registry entry. One RFQ is quoted by several panel factories, and each quotation names the manufacturer, its API licence number and where to verify it, so you can check the source before you order. How we check licences
How it compares
| Feature | Soft seated | Metal seated |
|---|---|---|
| Seat sealing | Polymer insert (PTFE, RPTFE or PEEK) pressed against the ball | Lapped metal seat against the ball, often hard-faced |
| Temperature | Limited by the polymer: about 200 °C for PTFE and about 250 °C for PEEK | Limited by the body and trim materials, not by a polymer insert |
| Abrasive and high-temperature service | Not recommended | Suited to abrasive, high-temperature and cycling service |
| Operating torque | Lower, because the polymer conforms to the ball | Higher, because the metal seat has to be forced onto the ball |
| Leakage acceptance | API 598 requires no visible leakage from a soft-seated valve | API 598 allows a measured leakage rate for a metal-seated valve |
| Typical use | Water, gas and general process service | Steam, hot oil, abrasive and high-temperature service |
Specification range
Grades listed are common ASTM designations for this valve type. The size and class range offered by the partner factory is confirmed against its datasheet before this page goes live.
| ASTM grade | Form | Sizes (NPS) | Pressure classes | End connections | Partner factory supplies |
|---|---|---|---|---|---|
| ASTM A216 WCB | Cast carbon steel body | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A105 | Forged carbon steel body | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A351 CF8M | Cast 316 stainless steel | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A182 F316 | Forged 316 stainless steel | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
| ASTM A995 5A | Cast super duplex 2507 | To be confirmed | To be confirmed | To be confirmed | To be confirmed |
Pressure–temperature rating (ASME B16.34)
The pressure class sets the maximum working pressure at each temperature for a given body material group. The table shows ASME B16.34 Standard Class values for material group 1.1 (for example WCB and A105) at −29 °C to 38 °C. The metal seat does not raise the rating: the body material and the temperature decide it.
| Pressure class | Max. working pressure (bar) | (psi) |
|---|---|---|
| Class 150 | 19.6 | 285 |
| Class 300 | 51.1 | 740 |
| Class 600 | 102.1 | 1,480 |
| Class 900 | 153.2 | 2,220 |
| Class 1500 | 255.3 | 3,705 |
| Class 2500 | 425.5 | 6,170 |
Partner factory P-T curve for this valve: To be confirmed
How a metal seat seals
The ball and the seat ring are machined and lapped so that they meet on a narrow contact band. Spring load and line pressure push the seat onto the ball, and the contact band deforms elastically to close the gap. The harder the seat, the higher the force needed for the same seal.
Hard facing with a cobalt-chromium alloy or tungsten carbide reduces erosion and galling on that contact band. Ask for the hard-facing procedure and the hardness check, and for the lapping and roundness records for the ball.
Leakage rates under API 598
API 598 requires no visible leakage from a soft-seated valve, but allows a measured leakage rate for a metal-seated valve, depending on size and test medium. A metal seat is therefore not bubble-tight by the soft-seat definition.
State the acceptance rate and the test pressure in the purchase order. If the specification asks for zero leakage, the seat design, the lapping and the test method all have to be agreed before the valve is made.
Temperature limits and seat material
The seat material sets the practical temperature limit. PTFE seats are commonly limited to about 200 °C and PEEK to about 250 °C; above that a metal seat is used. The body and trim still have to meet the ASME B16.34 rating for the material group, which falls as the temperature rises.
A metal seat does not raise the rating of the valve. It removes the polymer limit, but the body material, the gaskets and the stem packing remain the limiting parts.
Tests and documents to request
The assembled valve is pressure tested, normally with a hydrostatic shell test and a seat test per API 6D or API 598. For a metal-seated valve, ask for the measured leakage rate rather than a pass or fail statement.
Add the operating torque measured on the test stand, the EN 10204 3.1 material certificates and the hard-facing records, so the actuator can be sized from measured data instead of an estimate.
Fire-safe design
A metal seat survives a fire better than a polymer one, but that does not make the valve fire-safe by itself: the stem seal and the body gasket also have to hold. API 607 and ISO 10497 test the assembled valve, so the certificate has to cover the complete design.
No fire-test certificate for a partner factory valve is published on this page.
Datasheet and drawings
Datasheet: To be confirmed
A datasheet, dimension drawing and STEP file will be published here, without factory branding, after the panel factory authorises them. Until then, ask for them in your RFQ.
Prices, lead times and minimum order quantities are quoted per enquiry against the datasheet you send; they are not listed on this page.
Frequently asked questions
- What is a metal seated ball valve?
- A ball valve whose seat seals against the ball metal to metal, without a polymer insert. It is chosen for high temperature, abrasive service or where a polymer seat would swell or degrade.
- What is the difference between a soft seated and a metal seated ball valve?
- A soft-seated valve uses a PTFE, RPTFE or PEEK insert, which conforms to the ball and gives tight shut-off at moderate temperature. A metal-seated valve uses a lapped metal contact, which takes higher temperature and abrasion but needs more torque and allows a small measured leakage.
- Is a metal seated ball valve leak-tight?
- It meets the leakage rate API 598 allows for metal-seated valves, not the zero-leakage requirement for soft-seated valves. If your specification needs tighter shut-off, agree the test pressure and the acceptance rate in the purchase order.
- Why does a metal seated ball valve need more torque?
- The metal seat does not conform to the ball, so the actuator has to deform the contact band elastically to seal. Torque also rises with pressure and temperature, so the actuator should be sized from measured torque data with a margin.
- What is API 608?
- API 608 is the specification for metal ball valves with flanged, threaded and welding ends. It refers to ASME B16.34 for pressure–temperature ratings and to API 598 for pressure testing.
Standards cited
- API Std 608: Metal ball valves with flanged, threaded and welding ends.
- API Std 598: Valve inspection and pressure testing (shell, backseat and seat).
- ASME B16.34: Valves with flanged, threaded and welding ends: pressure–temperature ratings by material group and pressure class. Edition quoted to: ASME B16.34-2025.
- API Spec 6D: Pipeline and piping valves: design, manufacture, testing and documentation of ball, gate, plug and check valves.
- EN 10204: Types of inspection documents, including the 3.1 and 3.2 certificates.
- API Std 607: Fire test for quarter-turn valves with non-metallic seats: a type test of the design.
- ISO 10497: Fire type-testing requirements for valves: test procedure and acceptance criteria.