Views: 0 Author: J-VALVES Publish Time: 2026-10-30 Origin: Site
Every steel valve carries two sets of information, and buyers treat them as one. Permanent marking on the body, bonnet or cover gives manufacturer, size, pressure designation and body material, cast or forged where the section allows. The identification plate is a separate stainless tag carrying what a casting cannot hold: trim symbols, serial number, test data. MSS SP-25 defines both, and its scope is marking, not fitness for service. A plate that reads correctly proves the valve was marked correctly, not that it was built to the standard you named.
Size is the mark least often wrong. Pressure designation is the one that hurts, because Class 150 and PN 16 look like the same claim and are not: different flange standards, different drilling at several sizes, and no valve built to both. A body carrying both on one line was designed to neither. Body material has to be a grade rather than a family, since WCB, LCB, CF8M and 4A come from named ASTM specifications, while a body marked only stainless steel has been marked to none. Flow direction completes the set, and API 603 and API 600 bodies diverge the same way.
Trim identification goes on the plate wherever the trim differs from the body, and for gate, globe, angle and cross valves it takes three symbols in order: stem, disc or wedge face, seat face. Check valves carry two, disc and seat, because there is no stem. The symbol table is deliberately coarse: CR 13, SS, 18-8SMo, HF. So SS SS SS names a family while 18-8SMo names the grade with molybdenum, and only one tells a planner what he is replacing.
Purchase orders say Trim 5 or Trim 8 and everyone nods, but no marking standard defines those numbers. They are rows in the trim chart of the product standard governing the valve, and the charts disagree with each other as often as with the catalogue the number was copied from. An order quoting a trim number without the design standard is unenforceable, and an inspector holding a plate marked only with a number has nothing to check. Ask for the number, the three symbols, and the chart page.
The marking standard says melt identification; mill certificates say heat number. They mean the melt a casting or forging came from, and the mark is required on bodies, bonnets and covers where the section allows and the material specification calls for it. What turns the mark into evidence is the document behind it: EN 10204 3.1 is issued by the manufacturer's inspection function independent of production, 3.2 by an independent third party nominated by the purchaser. A 3.1 certificate whose heat numbers cannot be matched to the marks in the crate describes somebody else's valves.
Packing, gasket and seat material, design standard, test standard and duration, and the pressure-temperature basis behind the class are all absent. A plate reading 150 does not say whether the rating came from ASME B16.34 or a manufacturer's own table, and that decides whether the valve may run at 400 degrees C. Those answers live in the datasheet, drawing and test report.
The API monogram may only be applied by a manufacturer licensed for that product specification, covering the size and class supplied; the CE mark under PED 2014/68/EU only after a conformity assessment for the category; classification society marks after type approval and survey. Each is a claim about a process rather than a valve, so the check is the licence scope: a monogram outside the licensed range survives goods-in and surfaces at the audit.
The plate matches the order but the body symbol does not. Trim is marked with one symbol, so the stem is recorded and the seating faces are not. The heat number on the plate never appears on the certificate. The plate says Class 150 while the flange drilling measures to the metric standard, which no photograph reveals and a caliper settles. None is caught by looking at the valve; a receiving inspection that puts plate, body, certificate and drawing on one bench catches all four.
| Mark | Where | Commits the maker to | Check |
|---|---|---|---|
| Manufacturer, size, class | Body, cast or stamped | Rating system and size | One system, drilling measured |
| Body material symbol | Body | The ASTM grade cast or forged | A grade, not a family |
| Trim symbols | Identification plate | Stem, disc and seat materials | Three symbols, in order |
| Trim number | Plate or tag | One row of the design chart | The chart page behind it |
| Melt identification | Body, bonnet, cover | The melt the part came from | One line of the 3.1 certificate |
| Serial and tag | Identification plate | Traceability to the test record | Same serial on the report |
Five lines settle it: marking to MSS SP-25 with trim symbols in stem, disc and seat order; the trim chart page for every trim number quoted; melt identification reconciled with an EN 10204 3.1 certificate; serial and tag number on the plate; legal marks only where the licence covers the size and class. J-VALVES marks gate, globe, check, butterfly, plug and strainer valves to MSS SP-25, with gate and check valves from 1/2 to 56 inch, globe 1/2 to 48 inch, butterfly 2 to 112 inch, Class 150 to 2500 for rising stem families and to 900 for butterfly, shell tests at 1.5 times and seat tests at 1.1 times rated pressure, and EN 10204 3.1 certificates for body, bonnet, stem and disc with heat numbers carried to the API 600 gate valve plate. Goods-in is half that loop; the other half runs at start-up, where a start-up strainer protects what the plate promised.
Is a valve nameplate the same as body marking? No. MSS SP-25 covers both, but they carry different data. Permanent body marking gives the manufacturer, size, pressure designation and body material, cast or stamped into the metal. The identification plate is a separate tag that carries trim symbols, serial number, test data and the project tag number, because those items cannot be cast into a body.
What does Trim 5 actually mean? Not from MSS SP-25. The marking standard defines material symbols such as CR 13, SS, 18-8SMo and HF, not numbered trims. Numbers are rows in the trim chart of the product standard that governs the valve, so Trim 5 only means something once that standard is named in the order. Without it the number cannot be checked against a plate or a certificate.
Does an EN 10204 3.1 certificate prove the material? It proves the manufacturer inspected and declared the material through an inspection function independent of production. It is not third-party verification, which is what 3.2 provides. Whether the part in hand meets the grade is answered by positive material identification on it, read against the heat number.
