At present, there is no material content in the performance spot check of valve castings, but there is a jerry-building behavior in the production of products in which low-cost materials are used instead of high-cost materials.
1) the stem. The standard requires that the stem should be replaced with carbon steel instead of stainless steel. Hazards: The plasticity of carbon steel is greater than that of stainless steel. When the stem is lower than the standard value, it may deform or even break during the opening process, especially for large diameter valves with large opening torque.
2) body. Standard requirements for body castings are made of alloy steel instead of carbon steel. Specifically manifested in anti-sulfur, anti-corrosion valves and other special requirements of the valve requires the use of alloy steel, forged steel, the actual use of the cheapest carbon steel (WCB) instead.
3) stem nut. The standard requirement is that the stem nut is made of copper alloy material, but the iron surface paint or copper plating. The stem nut hardness is greater than that of the stem, which accelerates the wear of the stem.
4) gate. For the gate that needs to be surfacing, the strength of the gate should be ensured, and there is still a certain plasticity. However, the actual surfacing thickness often does not meet the standard requirements, and there is no wear allowance, which greatly shortens the service life of the gate.
