Valve Markings - Continued.

Other manufacturers, such as Crane use some of the following systems.

i. Sometimes only a number, such as “150”, is given. This indicates the steam pressure rating.

ii. If a number is followed by one or more letters, then the letters indicate the fluid the valve is suitable for. Here is a listing of common letters:

W: Water

L: Liquid

O: Oil

G: Gas

S: Steam

iii. Sometimes multiple pressure ratings are given. For example, one for hot pressure (steam), and another for cold pressure (L, W, O or G).

Example:

150 S
300 WOG

This set of markings on a valve will indicate that the valve is rated for 150 psig if used in steam service; otherwise, it is rated for 300 psig if cold water, oil or gas is the medium being handled.