Why Ball valve stem is so important?

The valve stem is an important part of the valve, used for transmission, connected to the actuator or the handle, and directly drives the spool to move or rotate to realize the valve switching or regulating function.

How to choose ball valve stem?

Characteristics 

The valve stem is not only a moving part, a force receiving part but also a sealing part during the opening and closing process of the valve. At the same time, it is subject to the impact and corrosion of the media and also creates friction with the filler. Therefore, when selecting the valve stem material, it must be ensured that it has sufficient strength, good impact toughness, scratch resistance and corrosion resistance at the specified temperature. The valve stem is a wearing part, and the mechanical processing property and heat treatment performance of the material should also be paid attention to when selecting.

Common materials

Generally used 410 (1Cr13), 420 (2Cr13), F304, F304L, F316, F316L, F321, Inconel 718, Inconel 625, Incoloy825, A105, LF2, Monel 400, Monel 500, F51, F53, F55, 17-4PH ( 630), titanium alloy, XM-19 and other materials.

Stem process

The round bar head is thickened to manufacture the valve stem blank, and the valve stem is heated, insulated, quenched, tempered, normalized, secondary tempered, solid solution treated, and aged. After turning, the threaded part is cold-formed by a thread rolling machine, the milling machine processes the T-slot (flat) at the end of the stem and the head, the grinding machine handles the roughness of the product, and the joint between the stem and the ball and the valve stem and valve There should be an anti-static mechanism at the body contact to prevent static electricity from collecting on the sphere.

Product accuracy

Tolerances:

1. Stem rod diameter tolerance is less than 0.03mm

2. Stem length tolerance is less than 0.25mm

3. Stem head tolerance is less than 0.05mm

4. Stem end tolerance is less than 0.05mm

Stem geometric tolerance Tolerances of geometrical

1. Stereo head parallelism is less than 0.035mm Head Parallelism

2. Stem head symmetry is less than 0.2mm Head Symmetry

3. The verticality of the stem head and the flat end is less than 0.12mm. Head and End Perpendicularity

4. Stem end symmetry is less than 0.12mm End Symmetry

5. The coaxiality between the stem end and the stem is less than 0.07mm End and Rod Coaxiality

6. The stem stem is fully beaten less than 0.1mm. Rod total run-out

Indicates roughness roughness:

The arithmetic mean deviation of the contour Ra: 0.4~3.2

1. Stem rod section roughness Rod: 0.402

2. Stem head roughness Head: 0.774

3. Stem end roughness End: 0.410

Wenzhou Yuzheng Valve adopts high quality valve stem, and the packaging valve does not leak during use.