The stem nut of gate valves directly bears the axial force of the stem during the opening and closing of the gate valve, so it must have certain strength. At the same time, it is a thread drive with the valve stem, which requires a small friction coefficient, rust resistance and avoidance of biting.

   The stem nut mainly comes available in material of copper alloy and Steel.

I. Copper alloy

The coefficient of friction of the copper alloy is small, and it does not rust. For low-pressure valves with Pg <1.6Mpa, ZHMn58-2-2 cast brass can be used. For the medium-pressure valve of PN1.6-6.4Mpa, ZQAL9-4 bronze can be used. For high pressure valves, ZHAL66-6-3-2 cast brass can be used.

II. Steel

When the working conditions do not allow the use of copper alloys, 35, 40 and other high-quality carbon steel as well as 2Cr13, 1Cr18Ni9, Cr17Ni2 and other stainless acid-resistant steel can be selected.

Working conditions, under which copper alloys are not permitted, refer to the following situations.

1. In case of electric valves, stem nuts with melon-shaped clutch need heat treatment to obtain high hardness or surface hardness.

2. When the working medium or surrounding environment is not suitable for the selection of copper alloys. For example. ammonia will corrodes copper.

When selecting steel for stem nut, pay special attention to the thread seizure phenomenon.

If you want to know more details, freely contact us via sales@jhflow.com