Valve Trim Numbers (1, 5, 8, 12)

Quick Answer

Valve trim numbers are standardized codes defined in API 600 that specify the material combination for a valve’s internal components (disc, seat, stem, backseat). Trim 1 uses 13Cr stainless steel for all wetted trim parts. Trim 5 uses Stellite-faced seats. Trim 8 uses Monel. Trim 12 uses Stellite with 13Cr, compliant with NACE MR0175 for sour service.

API 600 Trim Number Chart

The table below shows the most commonly referenced trim numbers per API 600 for cast steel gate, globe, and check valves.

Trim No.	Disc	Seat Surface	Stem	Backseat	Typical Application
1	13Cr (410 SS)	13Cr (410 SS)	13Cr (410 SS)	13Cr (410 SS)	Standard, non-corrosive service (most common)
2	13Cr (410 SS)	Stellite hard-faced	13Cr (410 SS)	13Cr (410 SS)	High-temperature, moderate erosion
4	13Cr (410 SS)	13Cr (410 SS)	Hard-faced	13Cr (410 SS)	Abrasive packing, frequent cycling
5	Stellite hard-faced	Stellite hard-faced	13Cr (410 SS)	13Cr (410 SS)	High-temperature, high-erosion steam service
5A	Stellite hard-faced	Stellite hard-faced	Hard-faced	Stellite	Severe erosion, high-cycle applications
7	316 SS	316 SS	316 SS	316 SS	Moderate corrosion, chemical service
8	Monel 400	Monel 400	Monel 400	Monel 400	Seawater, brine, HF acid
9	Ni-Cu alloy	Ni-Cu alloy	13Cr (410 SS)	13Cr	Mixed service with moderate corrosion
10	316 SS	Stellite hard-faced	316 SS	316 SS	Corrosion + erosion combination
12	13Cr (410 SS)	Stellite hard-faced	13Cr (410 SS)	13Cr (410 SS)	Sour service (NACE MR0175 compliant)

Most Common Trim Selections

Trim 1: the default for carbon steel valves in non-corrosive hydrocarbon and utility service. All trim parts are 13% chromium martensitic stainless steel (AISI 410 / ASTM A182 F6a). Cost-effective and sufficient for most refinery and petrochemical applications at moderate temperatures.

Trim 5: specified when the seating surfaces need extra hardness and erosion resistance. Both disc and seat faces are hard-faced with Stellite (typically Stellite 6, ~38-44 HRC). Standard for high-pressure steam gate valves and globe valves in erosive service.

Trim 8: full Monel (nickel-copper alloy) trim for corrosive services including seawater, brackish water, HF alkylation units, and salt cavern applications. Monel resists chloride corrosion far better than 13Cr.

Trim 12: the standard NACE MR0175/ISO 15156 compliant trim for sour gas service (containing H2S). The 13Cr components must meet NACE hardness limits (22 HRC max), and the Stellite hard-facing provides erosion resistance on seating surfaces.

Trim Selection Guidelines

Service Condition	Recommended Trim	Reason
General hydrocarbon (sweet)	Trim 1	Cost-effective, adequate corrosion resistance
High-temperature steam (>425 degC)	Trim 5	Stellite resists high-temp erosion and galling
Seawater / brine	Trim 8	Monel resists chloride pitting and crevice corrosion
Sour gas (H2S per NACE)	Trim 12	NACE-compliant hardness + Stellite seating
Corrosive chemicals	Trim 7 or Trim 10	316 SS body + Stellite or SS seating
Cryogenic service (-46 degC)	Trim 7 or special	Austenitic SS retains toughness at low temperatures

Pro Tip

Always cross-reference the trim number with the project’s piping material specification and corrosion engineer recommendations. Trim numbers are standardized in API 600, but some manufacturers use proprietary numbering that may not align exactly.

For details on valve body materials, see the valve materials guide. For trim component descriptions, see valve parts and trim.

Read the full guide to valve types