Determine the purpose of needle valves by looking at the diagram
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QV1 and QV2 are two high-pressure ball valves, while NV1 and NV2 are two small needle valves. Does anyone know what the purpose of these NV1 and NV2 needle valves is? It is said to be for exhaust through the piping, but I don’t understand how the exhaust takes place. Also, are these two valves connected to the ball valve body?
Is it mainly used for ball valve flushing?
It shouldn’t be; as far as I know, it’s supposed to be for pressure relief and exhaust (there is high-pressure gas inside the pipeline). But I don’t understand how to arrange it
If it’s just exhaust gas, then it can be directly discharged into the downstream pipeline – why go through the ball valve body?
Downstream of QV1 is waste discharge; if anything is discharged, it goes downstream. How can it be discharged upward through NV1?
Personally, I think it serves to reset the valve or to relieve pressure. Ball valves have good sealing properties, which is why they are used for sealing purposes; they must be placed downstream. However, there may be situations where the medium solidifies or sticks, and this is due to the large sealing surface of ball valves as well as high pressures that result in a tight seal. It is best to use a needle valve for rinsing again, or for purposes such as decompression.