How to judge whether the valve is leaking inside or outside?

In the daily use of valves, we often encounter a variety of failures, valve leakage is the most common one among many failures, and valve leakage generally has internal leakage and external leakage two cases! So, what is the difference between the two?

Valve internal leakage, generally refers to when the valve is completely closed, there is still a medium from the flow path outlet of the valve, leakage or drip leakage, in popular terms, is not tightly closed, sealing is not good! The cause of the fault is usually due to erosion and wear of the medium or impurities. Even if the valve lead screw (stem) is screwed in place, the medium can still flow through because there is still a gap between the valve core and the valve body.

How to judge whether the valve is leaking inside or outside?

Valve leakage, generally refers to when the valve is completely closed or opened, the valve packing external sealing parts, the leakage of media. That is, between the valve and the connecting flange or connecting thread, the medium flows out of the connection sealing surface, or the medium leakage between the valve stem and the gland (i.e. the gland of the pressure plate root on the valve stem), or the leakage caused by the sand hole on the blank of the valve body, and the leakage caused by the wear of the valve body caused by the medium erosion.

The main parts and components of low temperature valve shall be treated at low temperature, and each batch shall be sampled for low temperature impact test, so as to ensure that the valve is not brittle under low temperature condition and can withstand the impact of low temperature medium.

The following tests were performed on each valve:

1. Strength test of shell at normal temperature;

2. Sealing test at room temperature and low pressure;

3. Normal temperature and low pressure sealing test;

4. Air tightness test of upper seal at low temperature (with upper seal);

5. Low temperature gas seal test, etc. to ensure that the whole cryogenic valve meets the requirements of the standard;

6. Low temperature treatment shall be conducted for main parts and components, and low-temperature impact test shall be conducted for each batch of samples to ensure that the valve is not brittle under low-temperature working condition and can withstand the impact of low-temperature medium;

7. Low temperature (cryogenic) valves shall be subject to low temperature treatment and impact test according to corresponding material specifications;

8. Electrostatic function is more powerful, and the on resistance between valve body and valve stem or between internal parts and valve body is less than 1 ohm.