1.General requirements

① Valve specifications and categories should be consistent with the requirements of piping design documents.

② Valve should be specified in accordance with the model number of the GB requirements. If the enterprise standards, identifying types of instructions.

③ Valve working pressure ≥ pipeline operating pressure, without affecting the price of the premise, the valve can withstand working pressure should be greater than the actual working pressure pipelines; valve closing conditions on either side should be able to withstand 1.1 times the working pressure valve value without leakage; valve open position, the valve should be able to withstand twice the working pressure valve requirements.

④ Valve manufacturing standards, should explain the basis of the GB code, if the enterprise standards, procurement contracts should be attached business documents.

2.Valve of material

① Valve of material, gray cast iron pipe gradually due not recommended for use, shall be ductile iron main body material, and indicate grades and casting the actual physical and chemical test data.

② Stem material, and strive stainless steel stem (2CR13), large diameter valves should also be embedded in the package of stainless steel stem.

③ Nut material, the use of aluminum bronze, brass or aluminum, and the hardness and strength are greater than the stem.

④ Stem bushing material, its hardness and strength shall be not greater than the stem, and is immersed in water conditions and valve body is not the formation of electrochemical corrosion.

⑤ The sealing surface of the material.

a. Valves category different sealing methods and materials requirements;

b. Ordinary wedge gate valve, brass ring material, fixed way, polishing should note;

c. Soft seal gate valve, the valve plate rubber lining materials, physical chemistry and health testing data;

d. Valve should be marked on the valve body sealing surface material and butterfly board sealing surface material; their physical and chemical test data, especially rubber, sanitary requirements, anti-aging properties, wear resistance; usually NBR and EPDM rubber etc., prohibited mixed with recycled plastic.

3.Fill valve shaft

① As the pipe network in the valve, which is usually not open and close frequently, requiring the filling in a few years of inactivity, not aging filler, long-term effects remain sealed;

② Fill valve shaft should bear the frequent opening and closing, sealing effect of good character;

③ In view of the above requirements, fill valve shaft life does not seek to replace or ten years without replacement;

④ Packing For replacement, valve should be designed to have water pressure conditions change measures.

Keywords:butterfly valve ,knife gate valve,ball valve,globe valve,slurry gate valve