How to Read Valve Nameplate Markings: Body, Trim, Class & Material Codes
Every industrial valve carries markings on its body and/or nameplate that identify the manufacturer, material, pressure class, size, and test credentials. Understanding these markings is essential for valve procurement, inspection, and maintenance. This guide explains the standard marking requirements per MSS SP-25, API 600, and ASME B16.34.
Required Body Markings per MSS SP-25
MSS SP-25 (Standard Practice for Marking) defines the minimum information that must be cast, forged, stamped, or stenciled on every valve body. The following markings are mandatory for most industrial valves:
1. Manufacturer's Name/Logo
Cast or stamped on the body. Identifies the original manufacturer for traceability.
2. Body Material
ASTM material designation. Example: WCB, CF8M, LCB, A995 4A. Identifies the casting or forging grade.
3. Pressure Class
ANSI Class (150, 300, 600, etc.) or PN rating. Defines pressure-temperature capability.
4. Size (NPS/DN)
Nominal Pipe Size in inches or DN in mm. Example: 4" or DN100.
5. Trim Number
Identifies internal parts material (stem, seat, disc). Example: Trim 8 = SS316 body + SS316 trim.
6. Heat Number
Traceability code linking the valve body to the original casting/forging heat and its MTR.
Understanding Trim Numbers
The trim number is a shorthand code defined by API 600 (gate valves) and API 602 (forged valves) that identifies the materials of the internal wetted components: stem, seat ring, disc/wedge face, backseat, and other trim parts.
| Trim No. | Stem | Seat Surface | Disc/Wedge | Typical Application |
|---|---|---|---|---|
| 1 | 13Cr (410) | 13Cr (410) | 13Cr (410) | Non-corrosive oil/gas/water |
| 2 | 13Cr (410) | 13Cr (410) | 13Cr (410) | Same as 1, different hardness |
| 5 | 13Cr (410) | Stellite #6 HF | Stellite #6 HF | High-pressure steam, erosive service |
| 8 | SS316 | SS316 | SS316 | Corrosive chemical service |
| 10 | SS316 | Stellite #6 HF | Stellite #6 HF | Corrosive + high-temp/erosive |
| 12 | Monel 400 | Monel 400 | Monel 400 | Seawater, chloride environments |
Common Body Material Markings
- WCB — ASTM A216 Grade WCB, carbon steel (the most common material)
- WCC — ASTM A216 Grade WCC, higher-strength carbon steel
- LCB / LCC — ASTM A352, low-temperature carbon steel (-46°C / -59°C)
- CF8 — ASTM A351 Grade CF8, equivalent to SS304
- CF8M — ASTM A351 Grade CF8M, equivalent to SS316
- CF3M — ASTM A351 Grade CF3M, equivalent to SS316L
- WC6 — ASTM A217, 1.25Cr-0.5Mo alloy for high temperature
- WC9 — ASTM A217, 2.25Cr-1Mo alloy for high temperature
- 4A — ASTM A995 Grade 4A, Duplex stainless steel
- 5A / 6A — ASTM A995 Grade 5A/6A, Super Duplex stainless steel
- C95800 — ASTM B148/B271, Nickel Aluminium Bronze (NAB)
Additional Nameplate Information
Beyond body markings, a valve nameplate (metal tag) may include:
- Serial number — unique to each valve for traceability
- Manufacturing date or year code
- Test pressure — shell and seat test pressures per API 598
- Cv/Kv value — flow coefficient (for control valves and globe valves)
- CE mark — indicates PED 2014/68/EU compliance for European market
- IBR stamp — Indian Boiler Regulation certification mark
- API monogram — indicates API licensee manufacturing
- SABER mark — Saudi Arabian conformity certification
Frequently Asked Questions
What does Trim 5 mean on a gate valve?
How do I verify valve body material in the field?
What is the difference between a heat number and a serial number?
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