NAFCO | Technical Requirements Should Attention When Purchasing Brass Valves

NAFCO | Technical Requirements Should Attention When Purchasing Brass Valves
Time:2018-09-29 From: NAFCO | Brass Valves China Manufacturer
Today we talk about the technical requirements should attention when purchasing brass valves, it's extremely imoirtant to ensure every details before purchasing, to avoid any further problems after installation and uses.
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1. The specifications and categories of brass valves should meet the requirements of the pipeline design documents
1.1 The model of the brass valve should indicate the national standard numbering requirements. If it is an enterprise standard, the relevant description of the model number should be indicated.
1.2 The working pressure of the brass valve requires ≥ the working pressure of the pipeline. Under the premise of not affecting the price, the working pressure of the brass valve should be greater than the actual working pressure of the pipeline; any side of the brass valve should be closed. Can withstand 1.1 times the brass valve pressure value, without leakage; when the brass valve is open, the valve body should be able to withstand the requirements of twice the brass valve pressure.
1.3 Brass valve manufacturing standards, should be based on the national standard number, if it is an enterprise standard, the procurement contract should be accompanied by corporate documents
2. Choose the material of the brass valve
2.1 Brass valve material, because gray cast iron pipe is gradually not recommended, the valve body material should be mainly ductile iron, and the physical and chemical test data of the grade and casting are indicated.
2.2 Valve stem material, and strive for stainless steel valve stem (2CR13), large diameter brass valve should also be stainless steel embedded valve stem.
2.3 Nut material, cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem
2.4 The material of the valve stem bushing should be no more than the valve stem, and it will not form electrochemical corrosion with the valve stem and valve body under water immersion conditions.
2.5 Sealing surface material 1 brass valve type is different, sealing method and material requirements are different; 2 ordinary wedge gate valve, copper ring material, fixing method, grinding method should be explained; 3 soft sealing gate valve, valve plate lining Physical and chemical testing data of rubber materials; 4 butterfly valves 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 the sanitary requirements, anti-aging properties and wear resistance of rubber; Usually, the use of butyl rubber and EPDM rubber is prohibited.
2.6 Valve shaft packing: 
2.6.1 Due to the brass valve in the pipe network, usually open and close infrequently, the filler is required to be inactive for several years, the filler is not aging, long-term sealing effect;
2.6.2 Valve shaft packing should also be subject to frequent When opening and closing, the sealing effect is good; 
2.6.3 In view of the above requirements, the valve shaft packing should not be replaced for life or not replaced for more than ten years; 
2.6.4 If the packing needs to be replaced, the brass valve design should be considered to be replaced under water pressure measures.
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3. Variable speed gearbox
3.1 The material of the box and the internal and external anti-corrosion requirements are consistent with the valve body principle.
3.2 The box should have sealing measures. After the box is assembled, it can withstand the immersion of 3 meters of water column.
3.3 The opening and closing limit device on the box should have the adjusting nut in the box.
3.4 The transmission structure design is reasonable, can only drive the valve shaft to rotate when opening and closing, do not make it up and down, the transmission parts bite the appropriate degree, does not produce separation and slip when the load is opened and closed.
3.5 The variable speed transmission case and the valve shaft seal cannot be connected to a leak-free whole.
3.6 There is no debris in the box, and the gear bite should be protected by grease.
4. The operating mechanism of the brass valves
4.1 The opening and closing direction of the brass valve should be closed clockwise.
4.2 Due to the brass valve in the pipe network, often manual opening and closing, the opening and closing rotation number should not be too much, that is, the large diameter brass valve should also be within 200-600 rpm.
4.3 In order to facilitate the opening and closing operation of a person, the maximum opening and closing torque should be 240m-m under the condition of pipeline pressure.
4.4 Brass valve opening and closing operation end should be square, and the size is standardized, and facing the ground, so that people can directly operate from the ground. Brass valves with discs are not suitable for underground pipe networks.
4.5 The display panel of the brass valve opening and closing degree
4.5.1 The scale line of the opening and closing degree of the brass valve shall be cast on the outer cover of the display panel after the gearbox cover or the direction of the change, and the surface shall be facing the ground, and the scale line shall be coated with phosphor to show eye-catching;
4.5.2 Indicates that the material of the disc needle can be made of stainless steel when the management is good, otherwise it is painted steel, do not use aluminum skin;
4.5.3 Indicates that the disc needle is conspicuous and securely fixed. Once the opening and closing adjustment is accurate, it should be locked with rivets.
4.5.4 If the brass valve is buried deep, and the distance between the operating mechanism and the display panel from the ground is ≥15m, the extension rod installation should be provided and fixed firmly so that people can observe and operate from the ground. That is to say, the brass valve opening and closing operation in the pipe network is not suitable for down hole operation.
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5. The performance test of brass valves
5.1 When a certain specification of a brass valve is manufactured in batches, an authoritative organization shall be entrusted to perform the following performance tests:
5.1.1 The opening and closing torque of the brass valve under the working pressure condition;
5.1.2 Under the condition of working pressure, it can ensure the tight continuous opening and closing times of the brass valve;
5.1.3 The detection of the flow resistance coefficient of the brass valve under the condition of pipeline water delivery.
5.2 Brass valves should be tested as follows before leaving the factory:
5.2.1 When the brass valve is opened, the valve body should withstand the internal pressure detection of the brass valve pressure twice;
5.2.2 Brass valve under the closed condition, the two sides respectively withstand 11 times the brass valve pressure value, no leakage; but the metal sealed butterfly valve, the leakage value is not greater than the relevant requirements
6. Internal and external anticorrosion of brass valves
6.1 Inside and outside the valve body (including the variable speed transmission case), firstly, the shot blasting should be used to remove rust, and the electrostatic spraying powdery non-toxic epoxy resin should be used, and the thickness is more than 0~3mm. Extra large brass valves should be brushed and sprayed with similar non-toxic epoxy paint when it is difficult to electro statically spray non-toxic epoxy resin.
6.2 The interior of the valve body and the various parts of the valve plate require comprehensive anti-corrosion. On the one hand, it will not rust when immersed in water, and no electrochemical corrosion will occur between the two metals. On the other hand, the smooth surface will reduce the water resistance.
6.3 The hygienic requirements for epoxy resin or paint for anti-corrosion in the valve body shall be tested by the corresponding authority. Chemical and physical properties should also meet the relevant requirements.
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7. Brass valve packaging and transportation
7.1 The brass valve should be fixed with light blocking plates on both sides.
7.2 Medium and small caliber brass valves should be bundled with straw ropes and transported by container.
7.3 Large-diameter brass valves also have a simple wood frame retaining package to avoid damage during transportation
8. Check the factory manual of the brass valve
8.1 Brass valves are equipment. The following relevant data should be indicated in the factory manual: brass valve specifications; model; working pressure; manufacturing standard; valve body material; valve stem material; sealing material; valve shaft packing material; Bushing material; internal and external anti-corrosion materials; operation starting direction; number of revolutions; opening and closing torque under working pressure conditions;
8.2 The name of the manufacturer; ex-factory date; factory number: weight; the aperture of the connecting flange, the number of holes, the center hole distance to indicate the overall length, width, height control size; effective opening and closing times; brass Valve flow resistance coefficient; relevant data of factory inspection of brass valves and precautions for installation and maintenance.
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