Technical Requirements for the Procurement of Valve Products
The specifications and categories of valves shall meet the requirements of pipeline design documents.
1. The model of the valve shall indicate the national standard according to numbering rules. If it is an industry-standard, the relevant description of the model shall be marked.
2. The working pressure of the valve should be greater than or equal to the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can bear should be greater than the actual working pressure of the pipeline. Either side of the valve in the closed condition should be able to bear 1.1 times the valve working pressure without leakage. When the valve is open, the valve body should be able to bear twice the working pressure of the valve.
3. The national standard number on which the valve manufacturing standard is based shall be stated. If it is an enterprise standard, enterprise documents should be attached to the procurement contract.
Selecting the material of the valve
1. Valve material: As gray cast iron pipes are not recommended gradually, the valve body material should be mainly ductile iron. The grade and actual physical and chemical test data of castings should be indicated.
2. It would be best to choose stainless steel as the material of valve stems, and for large-diameter valves, stainless steel embedded valve stems are also a good choice.
3. The nut can be made from cast aluminum brass or cast aluminum bronze, whose hardness and strength should be greater than those of the valve stem.
4. The hardness and strength of the valve stem bushing should not be greater than that of the valve stem, and it will not form electrochemical corrosion with the valve stem and the valve body under the condition of water immersion.
5. Material of sealing surface:
(1) Different valve categories have different sealing methods and material requirements.
(2) Materials, fixing methods and grinding methods of common wedge gate valves and copper rings should be explained.
(3) Physical, chemical and sanitary test data of rubber lining materials of soft seal gate valves and valve plates should be marked.
(4) The butterfly valve shall be marked with the sealing surface material on the valve body and the butterfly plate. Their physical and chemical test data, especially the hygienic requirements, aging resistance and wear resistance of rubber. Butadiene rubber and ethylene propylene diene monomer rubber are usually used, and recycled rubber is strictly prohibited.
6. Packing of the valve shaft
(1) Because the valves in the pipe network are usually opened and closed infrequently, it is required that the packing will not be moved for several years so that the packing will not age to maintain the sealing effect for a long time.
(2) The valve shaft-packing should also possess a good sealing effect when it is frequently opened and closed.
(3) In view of the above requirements, the valve shaft-packing shall not be replaced for life or for 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.
Variable speed transmission cases
1. The material and internal and external anticorrosion requirements of the box body are consistent with the valve body principle.
2. The box body should be sealed and can withstand the immersion of a 3-meter water column after assembly.
3. For the opening and closing limit device on the box body, its adjusting nut should be in the box body.
4. The design of the transmission structure is reasonable. When opening and closing, the valve shaft can only be driven to rotate, without moving up and down. The transmission parts are moderately engaged, and there is no separation slip when opening and closing with the load.
5. The seal between the variable speed transmission box and the valve shaft cannot be connected into a leak-free whole.
6. There are no sundries in the box body, and the gear meshing parts should be protected by grease.
The operating mechanism of valves
1. The opening and closing direction of the valve should be clockwise.
2. Because the valves in the pipe network are often manually opened and closed, the opening and closing revolutions should not be too much, that is, even the large-diameter valves should also be controlled within 200 to 600 revolutions.
3. In order to facilitate one's opening and closing operation, the maximum opening and closing torque should be 240m under the condition of pipeline pressure.
4. The opening and closing operation end of the valve should be square tenon, with standardized dimensions and facing the ground so that people can operate directly from the ground. Valves with wheel discs are not suitable for underground pipe networks.
5. Display panels that show the valve opening and closing degrees
(1) The scale line of the valve opening and closing degree should be cast on the cover of the gearbox or the shell of the display panel after changing the direction, all of which should face the ground, and the scale line should be painted with fluorescent powder to be clearly visible.
(2) The material of the indicating dial needle can be stainless steel plate if it can be well managed; otherwise, it should be painted steel plate and should not be made of aluminum.
(3) The indicating dial needle is clear and firmly fixed. Once the opening and closing adjustments are accurate, they should be locked with rivets.
6. If the valve is buried deep and the distance between the operating mechanism with the display panel and the ground is over 15 meters, the extension rod facilities shall be provided and fixed firmly, so that people can observe and operate from the ground. That is to say, the opening and closing operation of valves in the pipe network is not suitable for downhole operation.
Performance test of valves
1. When valves are manufactured in batch, an authoritative organization shall be entrusted to test the following performance:
(1) The opening and closing torque of the valve under working pressure
(2) Under the condition of industrial pressure, the continuous opening and closing times of valves when closed tightly
(3) Detection of the flow resistance coefficient of the valve under the condition of pipeline water conveyance
2. The valves should be tested as follows before leaving the factory:
(1) When the valve is open, the valve body shall bear the internal pressure test twice the working pressure value of the valve.
(2) When the valve is closed, both sides bear 11 times of valve working pressure respectively without leakage. The leakage value of metal sealed butterfly valves should also be not greater than the relevant requirements.
Internal and external anticorrosion of valves
1. Inside and outside the valve body (including the variable speed transmission case), firstly, adopt shot blasting and sand cleaning to clean the rust. Powder nontoxic epoxy resin should be electrostatically sprayed with a thickness of over 3mm. When it is difficult to electrostatically spray nontoxic epoxy resin on oversize valves, similar non-toxic epoxy paint should also be brushed and sprayed instead.
2. The interior of the valve body and all parts of the valve plate require comprehensive corrosion protection. On the one hand, it will not rust when immersed in water, and it will not produce electrochemical corrosion between the two metals. On the other hand, a smooth surface reduces water resistance.
3. For the sanitary requirements of epoxy resin or paint for anticorrosion in the valve body, the inspection report of the corresponding authority should be provided. Chemical and physical properties shall also meet relevant requirements.
Packaging and transportation of valves
1. Light blocking plates should be set on both sides of the valve for solid sealing.
2. Medium and small diameter valves should be bundled with straw ropes and transported in containers.
3. Large-diameter valves also have retention packaging with a simple wooden frame to avoid damage during transportation.
Check the factory instruction of the valve
1. The valve is a kind of equipment, so the following relevant data should be indicated in the factory manual: valve specifications, model number, working pressure, manufacturing standards, the material of the valve body, the material of the valve stem, sealing material, the material of the valve packing, material of the valve stem sleeve, internal and external anticorrosion materials, the operation direction, number of revolutions, opening and closing torque under working pressure.
2. Other information that should be indicated: name of the manufacturer, date of production, ex-factory number, weight, effective opening and closing times, Flow resistance coefficient of the valve, relevant data of ex-factory inspection, precautions for installation and maintenance, etc. The aperture, hole number and center hole distance of the connecting flange should be marked with the overall control dimensions of length, width and height in a graphic way.
1. The model of the valve shall indicate the national standard according to numbering rules. If it is an industry-standard, the relevant description of the model shall be marked.
2. The working pressure of the valve should be greater than or equal to the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can bear should be greater than the actual working pressure of the pipeline. Either side of the valve in the closed condition should be able to bear 1.1 times the valve working pressure without leakage. When the valve is open, the valve body should be able to bear twice the working pressure of the valve.
3. The national standard number on which the valve manufacturing standard is based shall be stated. If it is an enterprise standard, enterprise documents should be attached to the procurement contract.
Selecting the material of the valve
1. Valve material: As gray cast iron pipes are not recommended gradually, the valve body material should be mainly ductile iron. The grade and actual physical and chemical test data of castings should be indicated.
2. It would be best to choose stainless steel as the material of valve stems, and for large-diameter valves, stainless steel embedded valve stems are also a good choice.
3. The nut can be made from cast aluminum brass or cast aluminum bronze, whose hardness and strength should be greater than those of the valve stem.
4. The hardness and strength of the valve stem bushing should not be greater than that of the valve stem, and it will not form electrochemical corrosion with the valve stem and the valve body under the condition of water immersion.
5. Material of sealing surface:
(1) Different valve categories have different sealing methods and material requirements.
(2) Materials, fixing methods and grinding methods of common wedge gate valves and copper rings should be explained.
(3) Physical, chemical and sanitary test data of rubber lining materials of soft seal gate valves and valve plates should be marked.
(4) The butterfly valve shall be marked with the sealing surface material on the valve body and the butterfly plate. Their physical and chemical test data, especially the hygienic requirements, aging resistance and wear resistance of rubber. Butadiene rubber and ethylene propylene diene monomer rubber are usually used, and recycled rubber is strictly prohibited.
6. Packing of the valve shaft
(1) Because the valves in the pipe network are usually opened and closed infrequently, it is required that the packing will not be moved for several years so that the packing will not age to maintain the sealing effect for a long time.
(2) The valve shaft-packing should also possess a good sealing effect when it is frequently opened and closed.
(3) In view of the above requirements, the valve shaft-packing shall not be replaced for life or for 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.
Variable speed transmission cases
1. The material and internal and external anticorrosion requirements of the box body are consistent with the valve body principle.
2. The box body should be sealed and can withstand the immersion of a 3-meter water column after assembly.
3. For the opening and closing limit device on the box body, its adjusting nut should be in the box body.
4. The design of the transmission structure is reasonable. When opening and closing, the valve shaft can only be driven to rotate, without moving up and down. The transmission parts are moderately engaged, and there is no separation slip when opening and closing with the load.
5. The seal between the variable speed transmission box and the valve shaft cannot be connected into a leak-free whole.
6. There are no sundries in the box body, and the gear meshing parts should be protected by grease.
The operating mechanism of valves
1. The opening and closing direction of the valve should be clockwise.
2. Because the valves in the pipe network are often manually opened and closed, the opening and closing revolutions should not be too much, that is, even the large-diameter valves should also be controlled within 200 to 600 revolutions.
3. In order to facilitate one's opening and closing operation, the maximum opening and closing torque should be 240m under the condition of pipeline pressure.
4. The opening and closing operation end of the valve should be square tenon, with standardized dimensions and facing the ground so that people can operate directly from the ground. Valves with wheel discs are not suitable for underground pipe networks.
5. Display panels that show the valve opening and closing degrees
(1) The scale line of the valve opening and closing degree should be cast on the cover of the gearbox or the shell of the display panel after changing the direction, all of which should face the ground, and the scale line should be painted with fluorescent powder to be clearly visible.
(2) The material of the indicating dial needle can be stainless steel plate if it can be well managed; otherwise, it should be painted steel plate and should not be made of aluminum.
(3) The indicating dial needle is clear and firmly fixed. Once the opening and closing adjustments are accurate, they should be locked with rivets.
6. If the valve is buried deep and the distance between the operating mechanism with the display panel and the ground is over 15 meters, the extension rod facilities shall be provided and fixed firmly, so that people can observe and operate from the ground. That is to say, the opening and closing operation of valves in the pipe network is not suitable for downhole operation.
Performance test of valves
1. When valves are manufactured in batch, an authoritative organization shall be entrusted to test the following performance:
(1) The opening and closing torque of the valve under working pressure
(2) Under the condition of industrial pressure, the continuous opening and closing times of valves when closed tightly
(3) Detection of the flow resistance coefficient of the valve under the condition of pipeline water conveyance
2. The valves should be tested as follows before leaving the factory:
(1) When the valve is open, the valve body shall bear the internal pressure test twice the working pressure value of the valve.
(2) When the valve is closed, both sides bear 11 times of valve working pressure respectively without leakage. The leakage value of metal sealed butterfly valves should also be not greater than the relevant requirements.
Internal and external anticorrosion of valves
1. Inside and outside the valve body (including the variable speed transmission case), firstly, adopt shot blasting and sand cleaning to clean the rust. Powder nontoxic epoxy resin should be electrostatically sprayed with a thickness of over 3mm. When it is difficult to electrostatically spray nontoxic epoxy resin on oversize valves, similar non-toxic epoxy paint should also be brushed and sprayed instead.
2. The interior of the valve body and all parts of the valve plate require comprehensive corrosion protection. On the one hand, it will not rust when immersed in water, and it will not produce electrochemical corrosion between the two metals. On the other hand, a smooth surface reduces water resistance.
3. For the sanitary requirements of epoxy resin or paint for anticorrosion in the valve body, the inspection report of the corresponding authority should be provided. Chemical and physical properties shall also meet relevant requirements.
Packaging and transportation of valves
1. Light blocking plates should be set on both sides of the valve for solid sealing.
2. Medium and small diameter valves should be bundled with straw ropes and transported in containers.
3. Large-diameter valves also have retention packaging with a simple wooden frame to avoid damage during transportation.
Check the factory instruction of the valve
1. The valve is a kind of equipment, so the following relevant data should be indicated in the factory manual: valve specifications, model number, working pressure, manufacturing standards, the material of the valve body, the material of the valve stem, sealing material, the material of the valve packing, material of the valve stem sleeve, internal and external anticorrosion materials, the operation direction, number of revolutions, opening and closing torque under working pressure.
2. Other information that should be indicated: name of the manufacturer, date of production, ex-factory number, weight, effective opening and closing times, Flow resistance coefficient of the valve, relevant data of ex-factory inspection, precautions for installation and maintenance, etc. The aperture, hole number and center hole distance of the connecting flange should be marked with the overall control dimensions of length, width and height in a graphic way.
