Valve specifications and categories shall conform to the requirements of pipeline design documents
1, the check valve model should be indicated according to the NATIONAL standard number requirements. If the enterprise standard, should indicate the relevant description of the model.
2, the check valve working pressure, requirements ≥ pipeline working pressure, without affecting the price of the premise, the valve can withstand the pressure should be greater than the actual pipeline pressure; Either side of the valve should be able to withstand 1.1 times the valve pressure without leakage; Valve open condition, valve body should be able to withstand twice the valve pressure requirements.
3, check valve manufacturing standards, should explain the basis of the NATIONAL standard number, if the enterprise standard, the procurement contract should be attached to the enterprise document
Select check valve material
1. Valve material, as gray cast iron pipe is gradually not recommended to be used, the valve body material should be mainly ductile cast iron, and indicate the brand number and the actual physical and chemical testing data of the casting.
2, stem material, strive to stainless steel stem (20Cr13), large diameter valve should also be stainless steel embedded stem.
3, nut material, using cast aluminum brass or cast aluminum bronze, and hardness and strength are greater than the stem
4, stem bushing material, its hardness and strength should not be greater than the stem, and in water immersion condition and stem, valve body does not form electrochemical corrosion.
5. Material of sealing surface:
Valve types are different, sealing methods and material requirements are different;
(2) Common wedge gate valve, copper ring material, fixing mode, grinding mode should be explained;
(3) Physical, chemical and health testing data of soft seal gate valve and valve plate lining material;
(4) Butterfly valve should indicate the sealing surface material on the valve body and the sealing surface material on the butterfly plate; Their physical and chemical testing data, especially rubber health requirements, anti-aging performance, wear resistance; Rubber and epDM rubber are usually used, and recycled rubber is strictly prohibited.
6, valve shaft packing
(1) Because the valves in the pipe network are usually opened and closed infrequently, the packing is required to be inactive in a few years, the packing is not aging, and the sealing effect is maintained for a long time;
(2) Valve shaft packing should also bear frequent opening and closing, good sealing effect;
(3) In view of the above requirements, the valve shaft filler does not change for life or more than ten years;
(4) If the packing needs to be replaced, the valve design should consider the replacement measures under the condition of water pressure.
Check valve performance test
1. When a certain specification of the valve is manufactured in batches, the following performance shall be tested by the authority:
The opening and closing torque of the valve under working pressure;
(2) under working pressure, the continuous opening and closing times of the valve can be ensured;
(3) The valve in the pipeline water transmission condition of flow resistance coefficient detection.
2. The following tests should be carried out before the valve leaves the factory:
(1) When the valve is opened, the valve body should bear two times the internal pressure detection of the valve working pressure value;
(2) Under the closed condition, both sides of the valve respectively under 11 times the valve pressure value, no leakage; But the metal seal butterfly valve, leakage value is not greater than the relevant requirements
Internal and external anticorrosion of check valve
1, valve body (including gearbox) inside and outside, first should be shot blasting sand cleaning rust, strive to electrostatic spraying powder non-toxic epoxy resin, thickness up to 0? More than 3 mm. Large valve electrostatic spraying non-toxic epoxy resin is difficult, should also be brushed, sprayed with similar non-toxic epoxy paint.
2. All parts of the valve body and valve plate require comprehensive anticorrosion. On the one hand, it will not rust if soaked in water, and there will be no electrochemical corrosion between the two metals. Two aspects of smooth surface to reduce water resistance.
3. The health requirements of anticorrosive epoxy resin or paint in the valve body should be tested by the corresponding authoritative authorities. Chemical and physical properties should also meet relevant requirements.
Valve packaging and transportation
1. Both sides of the valve should be fixed with light blocking plate.
2. Medium and small caliber valves should be tied with straw rope and transported in containers.
3, large diameter valve also has a simple wooden frame fixed packaging, so as to avoid damage during transportation
Post time: Oct-22-2021