API Trim Numbers 1 to 12 Explained for Gate and Globe Valves

Technical guide · Supreme Valves India · Updated 2026-10-28

Direct answer: An API trim number is a shorthand for the seat, disc or wedge, backseat and stem materials on a gate or globe valve. On RFQs, Trim #8 (13Cr family) is the most common general-service callout for WCB and A105 valves; hardfaced / Stellite trims are specified when steam or erosion will destroy soft seats. Always match the number to the manufacturer’s published trim table and name the surfaces that are hardfaced.

Across our quotation archive, line items like “API TRIM #8” or “TRIM SS410 + STELLITE” appear constantly on Class 150–600 cast gates and Class 800 forged valves. Misreading the trim is one of the fastest ways to quote the wrong valve.

What a trim number actually covers

Trim is not the body material. Body might be ASTM A216 WCB or A105 while trim is stainless or hardfaced. A complete trim definition usually includes:

• Seat ring (or integral seat) facing
• Disc, plug or wedge facing
• Backseat (where fitted)
• Stem

API 600 (cast steel gate) and API 602 (compact forged steel) practices use numbered trim tables. Manufacturers publish Trim 1, 5, 8, 12 and others with exact UNS / ASTM grades. Use the number as a buyer shorthand, then lock alloys on the approved datasheet.

Common trim numbers buyers see on BOQs

For the complete material matrix (seat, disc, backseat, stem for Trim 1–18), use our standard valve trim chart. Confirm against the edition of the standard and the manufacturer table referenced in the purchase order.

How trim language appears on real BOQs

• API TRIM #8 — cast WCB gate Class 150/300/600
• TRIM SS410 + STELLITE — forged A105 Class 800 with hardfaced seats
• FULL STELLITE SEAT AND WEDGE — explicit hardfacing scope
• TRIM SS316 STELLITED — often on butterfly discs / seats, not gate trim tables

Butterfly and ball valves rarely use gate trim numbers. For those, write body, disc/ball, seat and stem materials in plain language.

Trim #8 vs hardfaced / Stellite

Choose Trim #8 (or the project’s default 13Cr trim) for clean hydrocarbon, utility water and general process isolation on carbon-steel bodies. Move to hardfaced seats when:

• Continuous or intermittent blowdown and flashing steam
• High differential pressure throttling on globes
• Erosive condensate or slurry
• The piping class already mandates hardfaced seating

Hardfacing adds cost and lead time. If the BOQ only says “STELLITED”, ask which surfaces — seat rings only, or seat and wedge/disc.

Cast (API 600) vs forged (API 602)

The same trim number idea applies to both, but face-to-face, bore and pressure class differ. Forged Class 800 SW/NPT gates on Saudi and India RFQs almost always carry Trim #8 or Stellite seat language. Cast Class 150 RF flanged gates usually say Trim #8 unless the steam class upgrades them.

RFQ checklist — trim

• Trim number from the piping spec, or explicit alloys for seat / wedge / stem
• Hardfacing scope (seat only / seat + wedge) and alloy (e.g. Stellite 6 equivalent)
• Body material and class (WCB CL150, A105 CL800, etc.)
• Test standard (API 598) and whether hardfacing NDE is required

Send the line list with trim callouts and we will map each tag to a published trim table on the quotation datasheet. For steam and blowdown packages, see the Stellite trim RFQ page and A105 Class 800 gate RFQ.