Every industrial valve quotation is written in shorthand: “2” 800# A105 gate, welded bonnet, F8 trim” or “6” 150# WCB/13Cr API 600”. If you can read these codes, you can compare offers line by line — and catch a wrong material before it ships. Here is the decoder.
1. Size and Pressure Class
NPS (nominal pipe size, inches) or DN (mm) gives the bore; Class (150 / 300 / 600 / 800 / 1500 / 2500, often written 150#) gives the ASME B16.34 pressure-temperature rating. Class 800 is an intermediate class used almost exclusively for forged small-bore valves per API 602.
2. Body Material Codes
| Code | Material | Where you see it |
|---|---|---|
| WCB | Cast carbon steel | General process, −29 to +425 °C |
| LCB / LCC | Low-temp cast carbon steel | Down to −46 °C |
| WC6 / WC9 | Cr-Mo alloy castings | High-temperature steam |
| CF8 / CF8M / CF3M | Cast 304 / 316 / 316L stainless | Corrosive, hygienic, cryogenic |
| A105 | Forged carbon steel | Small-bore forged valves |
| LF2 | Forged low-temp carbon steel | Cold climates, −46 °C |
| F316/F316L, F51/F55 | Forged stainless / duplex | Chlorides, offshore — see stainless range |
3. Trim Numbers (API 600 Table)
“Trim” = the wetted internals: seat, wedge/disc facing, stem, backseat. API trim numbers standardize combinations: Trim 1 (13Cr / F6a), Trim 5 (Stellite hardfaced), Trim 8 (13Cr with hardfaced seats), Trim 12 (316 stainless), Trim 10 (Monel), Trim 16 (F316 + Stellite). If the fluid is erosive or the valve throttles, hardfacing (Trim 5/8/16) earns its cost back quickly.
4. Ends, Bonnet, Operator
- Ends: RF (raised face flange), RTJ (ring joint, high pressure), BW (butt weld), SW (socket weld), NPT (threaded).
- Bonnet: bolted, welded (zero-leak small bore), pressure-seal (Class 600+ large bore).
- Operator: handwheel, gear, or actuated — electric/pneumatic packages on our actuation page.
5. The Overlay Codes That Change Everything
NACE MR0175 (sour service), API 607 (fire-safe), ISO 15848-1 (fugitive emissions), BS 6364 (cryogenic). These words at the end of a line item change materials, testing and price — never drop them when comparing quotes.
Frequently Asked Questions
WCB vs CF8M — can I substitute?
No. WCB is carbon steel, CF8M is 316 stainless. Corrosion resistance, temperature range and price are entirely different; substitution requires engineering approval.
What does “800#” really mean?
An intermediate rating class defined for compact forged valves (API 602). It is not an ASME B16.34 standard class like 600 or 1500, and it exists only in small bore.
Why do two “identical” quotes differ 40% in price?
Usually trim (13Cr vs Stellite), bonnet type, origin/documentation level, or a missing overlay like NACE. Line up the codes side by side and the gap explains itself.
Want a second pair of eyes on a valve quotation? Send it to ValveAtlas — we will normalize the specs so you compare like for like.
