after china's accession to the wto, with the tide of the integration of the world economy, it has become an irresistible trend for the global manufacturing industry to accelerate the transfer to mainland china, and china will gradually develop into a world-class manufacturing base. connoisseur predicts, preponderant guangdong especially pearl river delta area, will develop into world ball valve production center in 10 years. at the same time, because in recent years our country imports the mold with nearly 1 billion dollars every year, among them the precision, the large-scale, the complex, the long life mold occupies the majority, therefore embarks from the reduction import angle, this kind of high grade mold in the market proportion will also increase gradually.
pressure reducing valve, safety valve, pressure stabilizing valve, pressure relief valve belong to the pressure valve, the main difference is the function.
pressure-reducing valve is the medium of high pressure into low pressure of the equipment, the characteristics of the valve is in the case of constant changes in the import pressure, keep the export pressure and temperature value in a certain range.
relief valve a valve used to prevent damage to equipment such as boilers, pressure vessels, or piping due to overpressure. when the pressure is slightly higher than the normal working pressure, the safety valve automatically opens to reduce the pressure. when the pressure is slightly below normal operating pressure, the relief valve automatically closes, stops discharging fluid and maintains the seal.
pressure relief valve is mainly used in the occasions of excessive pressure, when the pressure is greater than the set value of the valve when the inner plate is pushed open timely release pressure, pressure reduced to the original position, and the safety valve is not much different, pressure relief valve refers to the liquid, the safety valve refers to the gas, steam.
stabilizer valve is a region of medium to maintain a certain pressure range of equipment. and the difference between relief valve:
pressure relief valve: reduces the outlet pressure to the rated value to reduce pressure, regardless of the change of inlet pressure.
regulator: maintains a constant upstream pressure regardless of downstream pressure and demand.
safety valve and pressure relief valve is two types of valves, is a special valve. among them, the safety valve belongs to the safety release device, is the special valve, only when the working pressure exceeds the allowable range, plays the protective role to the system. the pressure-reducing valve belongs to the process valve, which can reduce the pressure of the high-pressure logistics to meet the pressure requirements of the post-system, and its working process is continuous.
selection standard of pressure reducing valve:
1. for the pressure relief valve with soft seal, there shall be no leakage within the specified time; for the metal seal pressure relief valve, its leakage should not be greater than 0.5% of the maximum flow;
2. within the range of the given spring pressure level, the outlet pressure can be continuously adjusted between the maximum value and the minimum value of the pressure-reducing valve, without jamming and abnormal vibration;
3. when the outlet flow rate changes, the outlet pressure deviation value of the direct acting formula shall not be more than 20%, and the pilot formula shall not be more than 10%;
4. when the inlet pressure changes, the outlet pressure deviation of the direct acting type shall not be more than 10%, and that of the pilot type shall not be more than 5%;
5, bellows direct action type pressure reducing valve is suitable for low pressure, small diameter steam medium;
6, reducing the scope of application is very wide, in the steam, compressed air, industrial gas, water, oil and many other liquid medium equipment and pipeline can be used, medium flow through the outlet of the reducing valve, generally expressed by mass flow or volume flow;
7, generally, the pressure relief valve after the valve should be less than 0.5 times the pressure before the valve;
8, film direct action type pressure reducing valve is suitable for medium and low pressure, medium and small diameter air, water medium;
9, the pilot piston pressure reducing valve, suitable for all kinds of pressure, all kinds of caliber, all kinds of temperature of steam, air and water medium, if using stainless acid resistant steel manufacturing, can be applied to all kinds of corrosive medium;
10, pilot bellows type pressure reducing valve, suitable for low pressure, small and medium diameter steam, air and other media;
11. the fluctuation of the inlet pressure of the reducing valve should be controlled within 80% ~ 105% of the given value of the inlet pressure.
12, pilot film type pressure reducing valve, suitable for low pressure, medium pressure, small and medium diameter steam or water and other media;
13, usually the pressure relief valve after the valve should be less than 0.5 times the pressure before the valve;
14, each gear of the valve spring only in a certain range of outlet pressure is applicable, beyond the scope of the spring should be replaced;
15, the medium for air or water (liquid) occasions, generally should choose direct action film type pressure reducing valve or pilot film type pressure reducing valve;
16, in the medium working temperature is relatively high occasions, the general selection of pilot piston type pressure relief valve or pilot bellows type pressure relief valve;
17, the medium for the occasion of steam, it is appropriate to choose the pilot piston type or pilot bellows type pressure relief valve;
18. for the convenience of operation, adjustment and maintenance, the pressure reducing valve should be installed in the horizontal pipeline.
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