How to choose a high-quality electric ball valve

When purchasing electric ball valves, only specifying the specifications, categories and working pressure to meet the purchasing requirements is not perfect in the current market economic environment. For the competition of products, the electric ball valve manufacturers carry out different innovations under the concept of unified design of electric ball valves, forming their own enterprise standards and product personality. Therefore, it is very necessary to put forward technical requirements in detail when purchasing electric ball valves, and coordinate with manufacturers to reach a consensus as an accessory of electric ball valve purchase contract.

1. General requirements

1.1 The specifications and categories of electric ball valves should meet the requirements of pipeline design documents.

1.2 The model of the electric ball valve should indicate the requirements of the national standard number. If it is an enterprise standard, the relevant description of the model should be indicated.

1.3 The working pressure of the electric ball valve is required to 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 electric ball valve can withstand should be greater than the actual working pressure of the pipeline; any side of the electric ball valve should be able to withstand 1.1 times when the electric ball valve is closed. Electric ball valve working pressure value without leakage; when the electric ball valve is open, the valve body should be able to withstand twice the working pressure of the electric ball valve.

1.4 The manufacturing standard of electric ball valve should state the national standard number based on it. If it is the enterprise standard, the enterprise document should be attached to the purchase contract.

2. Variable speed gearbox

2.1 The box material and internal and external anti-corrosion requirements are consistent with the valve body principle.

2.2 The box should have sealing measures, and the box can withstand immersion in a water column of 3 meters after assembly.

2.3 For the opening and closing limit device on the box, its adjusting nut should be inside or outside the box, but special tools are required for operation.

2.4 The design of the transmission structure is reasonable. When opening and closing, it can only drive the valve shaft to rotate, not to make it move up and down.

2.5 The variable speed transmission case and the valve shaft seal should not be connected to form a leak-free whole, otherwise there should be reliable anti-leakage measures.

2.6 There is no sundries in the box, and the gear engagement part should be protected by grease.

3. Standard quality of electric ball valve

3.1 The material of the valve body should be mainly ductile iron, and the grade and actual physical and chemical testing data of the cast iron should be indicated.

3.2 The material of the valve stem should be made of stainless steel (2CR13), and the large-diameter electric ball valve should also be a valve stem embedded in stainless steel.

3.3 The nut is made of cast aluminum brass or cast aluminum bronze, and its hardness and strength are greater than those of the valve stem.

3.4 The hardness and strength of the valve stem bushing shall not be greater than that of the valve stem, and there shall be no electrochemical corrosion with the valve stem and valve body under water immersion.

3.5 The material of the sealing surface: ①The types of electric ball valves are different, and the sealing methods and material requirements are different; ②Ordinary wedge gate valve, the material, fixing method and grinding method of the copper ring should be explained; ③Soft sealing gate valve, the valve plate is lined with rubber The physical chemical and hygienic testing data of the material; ④The butterfly valve should be marked with the material of the sealing surface on the valve body and the material of the sealing surface on the butterfly plate; their physical and chemical testing data, especially the hygienic requirements, chemical properties and wear resistance of rubber; usually used Nitrile rubber and EPDM rubber are strictly prohibited to be mixed with reclaimed rubber.

3.6 Valve shaft packing: ①Because the electric ball valve in the pipe network is usually opened and closed infrequently, the packing is required to be inactive for several years, the packing will not age, and the sealing effect will be maintained for a long time; ②The valve shaft packing should also withstand frequent opening and closing. When closed, the sealing effect is good; ③ In view of the above requirements, the valve shaft packing is not replaced or not replaced for more than ten years; ④ If the packing needs to be replaced, the design of the electric ball valve should consider measures to replace it under the condition of water pressure.

4. Performance testing of electric ball valve

4.1 When a certain specification of electric ball valve is mass-produced, an authoritative agency should be entrusted to carry out the following performance tests: ①The opening and closing torque of the electric ball valve under the working pressure condition; ②Under the working pressure condition, the electric ball valve can be guaranteed to close tightly and continuously open and close. ③ Detection of flow resistance coefficient of electric ball valve under the condition of pipeline water delivery.

4.2 The electric ball valve should be tested as follows before leaving the factory: ① When the electric ball valve is open, the valve body should be subjected to an internal pressure test that is twice the working pressure of the electric ball valve; ② When the electric ball valve is closed, both sides are subjected to 1.1 times. The working pressure value of the electric ball valve has no leakage; but the leakage value of the metal-sealed butterfly valve is not greater than the relevant requirements.

5. Operating mechanism of electric ball valve

5.1 The opening and closing direction of the electric ball valve should always be closed clockwise.

5.2 Since the electric ball valve in the pipe network is often opened and closed manually, the opening and closing revolutions should not be too many, and the large-diameter electric ball valve should also be within 200-600 revolutions.

5.3 In order to facilitate the opening and closing operation of one person, the opening and closing torque should be 240N-m under the condition of pipeline construction pressure.

5.4 The opening and closing operation end of the electric ball valve should be a square tenon with standardized dimensions and face the ground, so that people can directly operate it from the ground. Electric ball valves with discs are not suitable for underground pipe networks.

5.5 The display plate for the opening and closing degree of the electric ball valve: ① The scale line for the opening and closing degree of the electric ball valve should be cast on the gearbox cover or on the casing of the display plate after the direction is changed, all facing the ground, and the scale line is brushed with fluorescent powder. ②The material of the indicator dial needle can be made of stainless steel if the management is good, otherwise it is painted steel plate, do not use aluminum skin; ③The indicator dial needle is eye-catching and fixed firmly, once the opening and closing adjustment is accurate, Should be locked with rivets.

5.6 If the electric ball valve is buried deep, and the distance between the operating mechanism and the display panel is ≥1.5m from the ground, there should be an extension rod facility, and it should be fixed firmly so that people can observe and operate from the ground. That is to say, the electric ball valve in the pipeline network is not suitable for downhole operation.

6. Electric ball valve packaging and transportation

6.1 Lightweight blocking plates should be installed on both sides of the electric ball valve to seal.

6.2 Medium and small diameter electric ball valves should be bundled with straw ropes and transported in containers.

6.3 The large-diameter electric ball valve also has a simple wooden frame solid packaging to avoid damage during transportation.

7. Internal and external anticorrosion of electric ball valve

7.1 The inside and outside of the valve body (including the variable speed transmission box) should first be shot blasted to remove rust and sand, and strive to electrostatically spray powder epoxy resin with a thickness of more than 0.3mm. When it is difficult to electrostatically spray epoxy resin for extra-large electric ball valve, it should also be brushed and sprayed with similar epoxy paint.

7.2 The interior of the valve body and all parts of the valve plate require comprehensive anti-corrosion. On the one hand, it will not corrode when immersed in water, and there will be no electrochemical corrosion between the two metals; on the other hand, the surface is smooth to reduce the water resistance.

7.3 The hygienic requirements of the anti-corrosion epoxy resin or paint in the valve body should have a corresponding test report. The chemical and physical properties should also meet the relevant requirements.

8. Factory manual of electric ball valve

Electric ball valve is equipment, the following relevant data should be marked in the factory manual: electric ball valve specification; model; working pressure; manufacturing standard; valve body material; valve stem material; sealing material; valve shaft packing material; valve stem bushing material; Anti-corrosion material; direction of operation and start; number of revolutions; opening and closing torque under industrial pressure; name of manufacturer; date of manufacture; serial number; weight; aperture, number of holes, and center hole distance of connecting flange; Control dimensions of overall length, width and height; flow resistance coefficient of electric ball valve; effective opening and closing times; relevant data of electric ball valve factory inspection and precautions for installation and maintenance, etc.