The reference tables behind every valve datasheet — body grades, seal limits, flange facings, gaskets and bolting.
A valve material specification has three layers, and quoting only the first is the most common cause of a mis-purchase. The body sets the pressure boundary and the broad temperature envelope. The trim — stem, disc or ball, seat ring — takes the wear and usually fails first. The soft parts — seat inserts, seals, packing — set the real temperature ceiling, which is almost always lower than the body could tolerate.
A "316 stainless ball valve" with a PTFE seat is a 200 °C valve, not a 400 °C valve. The body grade is not the answer to "how hot can this go".
| ASTM | EN | GB | JIS | Service note |
|---|---|---|---|---|
| A216 WCB | 1.0619 (GP240GH) | WCB / ZG230-450 | SCPH2 | General service cast carbon steel. Typical −29 to 425 °C. |
| A217 WC6 | 1.7357 (G17CrMo5-5) | ZG15Cr1Mo | SCPH21 | 1.25Cr-0.5Mo low alloy. Elevated-temperature steam and hydrocarbon. |
| A217 WC9 | 1.7379 (G17CrMo9-10) | ZG15Cr2Mo1 | SCPH32 | 2.25Cr-1Mo. Higher creep resistance than WC6. |
| A351 CF8 | 1.4308 | ZG07Cr19Ni9 | SCS13A | Cast 304 stainless. Corrosion resistance, cryogenic capable. |
| A351 CF8M | 1.4408 | ZG07Cr19Ni11Mo2 | SCS14A | Cast 316 stainless. Molybdenum improves chloride pitting resistance. |
| A890 Gr 4A | 1.4470 | ZG022Cr22Ni5Mo3N | — | Duplex 2205. Strength plus chloride stress-corrosion resistance. |
| A395 | EN-GJS-400-18 | QT450-10 | FCD450 | Ductile iron. Water and utility service; not for hydrocarbon or high temp. |
| A105 | 1.0460 (P250GH) | 20 / 16Mn | SFVC2A | Forged carbon steel for small-bore and forged-body valves. |
| A182 F316 | 1.4401 | 06Cr17Ni12Mo2 | SUS316 | Forged 316 stainless, small-bore and compact valves. |
| B62 C83600 | CC491K | ZCuSn5Pb5Zn5 | CAC406 | Leaded red brass / bronze. Water, marine, low-pressure. |
These are orientation equivalents, not drop-in substitutions. Composition tolerances, impact test requirements and certification differ between systems — the full treatment is in Chinese valve material grades cross-reference.
| Material | Working range | Strong against | Fails against |
|---|---|---|---|
| PTFE | −200 to +200 °C | Almost universal chemical resistance; lowest friction | Cold flow / creep under sustained load |
| RPTFE (glass or carbon filled) | −100 to +230 °C | Much better creep resistance than virgin PTFE | Filler can be attacked by some media (glass in HF) |
| PEEK | −50 to +250 °C | High pressure, high temperature, wear resistant | Higher torque, higher cost |
| NBR (Buna-N) | −30 to +100 °C | Oils, fuels, general hydraulic | Ketones, esters, ozone, steam |
| EPDM | −40 to +120 °C | Water, steam, glycol, brake fluid | Swells destructively in hydrocarbons |
| FKM (Viton) | −20 to +200 °C | Hydrocarbons, aggressive chemicals, high temperature | Steam and hot water; poor at low temperature |
| Flexible graphite | to ~450 °C in air | High-temperature packing and gaskets, fire-safe | Oxidises above its air limit; galvanic issues with some alloys |
| Stellite 6 hard-facing | to ~800 °C | Erosion and galling resistance on metal trim | Cost; weld procedure control required |
Field note: the EPDM-versus-FKM mistake happens on almost every mixed-service site. EPDM is the right answer for steam and water and the wrong answer for oil; FKM is the reverse. Plants that try to standardise on a single seal material across both services end up replacing seals in one of them continuously.
Compatibility against specific chemicals is covered in the body and trim compatibility guide and the corrosive media guide.
| System | Designations | Governing standards |
|---|---|---|
| ASME Class | 150, 300, 600, 900, 1500, 2500 | ASME B16.5 (to NPS 24), B16.47 Series A / B; HG/T 20615 in China |
| PN | PN 6, 10, 16, 25, 40, 63, 100, 160 | EN 1092-1; GB/T 9124; HG/T 20592 |
| JIS K | 5K, 10K, 16K, 20K, 30K, 40K | JIS B2220 |
The three systems have different bolt circles, bolt counts and hole diameters. They do not mate, and no arithmetic conversion makes them mate — see PN vs ASME Class and the Chinese Class-series standard HG/T 20615.
| Facing | Where used | Notes |
|---|---|---|
| Raised face (RF) | The default for steel flanges, Class 150–2500 | Concentrates gasket load on a smaller annulus; serrated finish around Ra 3.2–6.3 µm. |
| Flat face (FF) | Cast iron and other brittle-bodied equipment | Full-face gasket supports the whole flange; mandatory when mating steel to cast iron. |
| Ring type joint (RTJ) | Class 600 and above, high temperature and pressure | Metal ring (oval or octagonal) seated in a machined groove; ring material must be softer than the flange. |
| Tongue and groove | Critical service where gasket blowout is unacceptable | Gasket fully confined; requires matched pairs. |
| Male and female | Legacy and some lined systems | Similar confinement benefit; matched pairs required. |
Field note: raised-face steel bolted to flat-face cast iron cracks the casting. The raised face only touches the inner annulus, so tightening bends the unsupported outer rim of a material with essentially no ductility. Use a flat-face steel flange with a full-face gasket whenever steel meets cast iron.
| Stud / nut | Service |
|---|---|
| A193 B7 / A194 2H | General purpose carbon and low-alloy flanges |
| A193 B7M / A194 2HM | Sour service, hardness controlled per NACE MR0175 |
| A193 B8 / B8M | Cryogenic and corrosive service (304 / 316), lower allowable stress |
| A193 B16 | Sustained high temperature |
Bolting and gasket must be selected together, because the gasket seating stress determines the required bolt load. End connection options beyond flanges — butt weld, socket weld, threaded, wafer — are compared in end connection types.
WCB body, 13Cr or 316 trim, graphite packing, spiral-wound gasket, B7/2H bolting. Detail in petrochemical material selection.
Duplex or super duplex body; avoid standard 316 where chloride stress-corrosion cracking is credible.
WC6 or WC9 body, Stellite-faced trim, graphite packing, RTJ facing at higher class. See high-temperature selection.
Ductile iron or bronze body, EPDM seat, epoxy coating, flat-face flanges with full-face gaskets.
They are closely related but not identical. CF8M is the ASTM A351 cast designation, 316 is the wrought AISI/UNS designation, and 06Cr17Ni12Mo2 is the Chinese GB/T 20878 wrought designation broadly corresponding to 316. Cast and wrought grades differ in permitted composition ranges and in the ferrite content typical of castings, and the national systems differ again in test and certification requirements. Treat them as equivalents for orientation and verify at clause level before substituting on a purchase order.
FKM (Viton) or PTFE-family materials for elastomeric and soft seats, and metal seats where temperature or abrasion rules out polymers. Do not use EPDM: it is excellent in water, steam and glycol, and swells badly in hydrocarbons. The mirror-image mistake is equally common — FKM specified on a steam line, where it degrades. If a plant runs both services, resist the temptation to standardise on one seal material.
Because the raised face contacts only the inner annulus of the cast iron flange, leaving the outer rim unsupported. Tightening the bolts then bends the brittle cast rim, and cast iron has almost no ductility to absorb it, so the flange cracks — sometimes immediately, sometimes months later. The correct practice is to use a flat-face steel flange with a full-face gasket so the load is distributed across the whole face, or to machine the raised face off.
Generally from ASME Class 600 upward, and specifically where high temperature, high pressure or hydrogen service makes a compressed sheet or spiral-wound gasket unreliable. An RTJ uses a solid metal ring compressed into machined grooves, giving a very high seating stress on a small area. The ring material must be softer than the flange material so the ring, not the groove, deforms — soft iron or 316 rings against carbon or alloy steel flanges.
ASTM A193 B7 studs with A194 2H nuts is the general-purpose combination for carbon and low-alloy steel flanges. B7M with 2HM is the hardness-controlled version for sour service under NACE MR0175. A193 B8 and B8M (304 and 316 stainless) are used for cryogenic and corrosive duty where B7 would embrittle or corrode, at the cost of lower allowable stress. A193 B16 is specified for sustained high temperature. The bolting must be reviewed alongside the gasket, because gasket seating stress determines the required bolt load.
They do not convert. PN (EN 1092-1, GB/T 9124, HG/T 20592) is a European-lineage designation, ASME Class (B16.5, B16.47, HG/T 20615 in China) is a US-lineage tabulated rating, and JIS K (B2220) is a third independent Japanese system. Each has its own bolt circle diameters, bolt counts and hole sizes, so flanges from different systems will not mate even when the nominal pressures look similar. Match the flange standard, not the number.