In general, specifications, types and working pressure are always indicated when purchasing the valves. However, the information is inadequate for you to buy the suitable valves for your applications, especially in such competitive markets. In order to stand out among the competitors, each valve factory innovates the design and manufacture of the valves, though the basic standards remain the same. It leads to product variations from manufacturer to manufacturer. Therefore, it is suggested to bring up technical requirements as detailed as you can and come to consensus with the manufacturers.

1. Basic Standards 1.1 Valve specifications and types should conform to the documents.
1.2 Product numbers to should follow the international standards. If valve is numbered by manufacturers themselves, documents about the number systems are needed.
1.3 The actual pressure the valves can take should be bigger than that of real applications. 1.4 The valves should be manufactured according to international standards. If produced to manufacturers' standards, related documents are needed.

2. Valve Materials
2.1 Valve body should be made of ductile iron. Material code and testing data should also be included.
2.2 Valve stem should be made of stainless steel.
2.3 Screw should be made of brass or bronze, and its hardness and strength are bigger than stems.
2.4 The hardness and strength of sleeve has to be smaller than that of stem.
2.5 Packing materials differ based what kind of valve it is.
2.6 Stem filler should choose materials which won't deteriorate for decades.

3. Transmission Gearbox
3.1 The body of box is made of anti-corrosive materials, same with valve body
3.2 Sealing unit is necessary, and the box should bear soaking in water of 3 square meters.
3.3 On-off operation only makes valve shaft to rotate, and other parts remain the same.
3.4 There are no unrelated stuff in the box. The connection between gear tooth are applied by lubricant.
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