Reading an API 6A nameplate: pressure, material class, temperature class, PSL and PR

Two gate valves can share a size and a pressure and still be built for entirely different wells. The difference is on the nameplate, in a row of short codes that most purchase requisitions copy without reading. Each code answers a separate question — what pressure, what fluid, what temperature, how thoroughly tested — and a replacement has to match all of them.

/01The codes on a nameplate.

/02Material class: what the valve can touch.

The sour classes must meet NACE MR0175 / ISO 15156, and their marking carries the maximum partial pressure of H₂S the equipment is rated for, in psia: EE-0.5, EE-1.5, DD-0.5, or NL for no limit. Our gate valve listings show how varied stock can be — units on the 4-1/16" 10,000 psi listing carry DD, DD-0.5 and DD-NL markings, and the 2-1/16" 10,000 psi listing DD and EE-1.5 — with other classes from AA to HH to order. Our 3-1/16" 15,000 psi slab gate valve is class HH: a 4130 body with Inconel 625 internal cladding, an Inconel 625 clad gate and overlaid seats.

/03Temperature class: the operating window.

Each temperature class is a letter for a window of operating temperature. The letters on our listings are P (−29 °C to 82 °C, or −20 °F to 180 °F), U (−18 °C to 121 °C, or 0 °F to 250 °F), X (−18 °C to 180 °C) and L (−46 °C to 82 °C). Combined markings take the lower limit of one and the upper limit of the other: P+U is −29 °C to 121 °C (−20 °F to 250 °F), which is how most of our gate valves are marked, and P+X runs from −20 °F to about 350 °F. Sour-service flow iron on our listings is rated to 82 °C, which is the top of class P.

/04PSL and PR: how thoroughly it was built and proven.

The product specification level, PSL 1 to PSL 4, sets the quality control applied in manufacture — material testing, non-destructive examination, traceability and pressure testing all step up with the level. A G after PSL 3 (PSL 3G) adds gas testing. The performance requirement level, PR1 or PR2, describes how the design was validated; PR2 is the more demanding. Operators specify both for their wells, and a replacement should match or exceed the PSL and PR of the equipment it replaces.

/05The flange tells you the ring.

End connections follow the pressure. Our 3-1/8" and 4-1/16" 5,000 psi gate valves are API 6B flanged for R-35 / RX-35 and R-39 / RX-39 rings; the 2-1/16" to 5-1/8" valves at 10,000 and 15,000 psi are 6BX, for BX-152 to BX-155 and BX-169. For operating the valves, our accessory listings include an 8:1 worm-gear operator for 3" API 6A valves, a double-acting hydraulic actuator with limit switches, ISO 5211 mounting kits and a position indicator. A flanged valve is ordered with its rings and studs, and the rings are explained in R, RX and BX ring joint gaskets. The same markings appear on wellhead equipment, covered in wellhead components explained.