How to determine whether the valve is internal leakage or external leakage?

Daily valve use process, often encounter a variety of faults, valve leakage is the most common one of many faults, and valve leakage is generally internal leakage and leakage of two situations!  So, what's the difference between the two?

Valve leakage, generally refers to when the valve is completely closed, there are still media from the valve outlet outlet flow, leakage or drip, and so on. Popular point of view, is not tightly closed, poor sealing! The cause of the failure is usually due to erosion and wear of the medium or impurities. Even if the valve lead screw (stem) is tightened in place, the medium can flow through because there is still a gap between the valve core and the valve body.

How to judge whether the valve is leaking or leaking?

Valve leakage, generally refers to when the valve is fully closed or opened, the valve packing external sealing components, media leakage. That is, between the valve and the connecting flange or connecting thread, improper sealing results in the medium flowing out of the connecting sealing surface, or the medium leakage caused by the improper sealing between the stem and Gran (i.e. the cover of the pressure plate root on the stem), or the external leakage caused by trachoma on the blank of the valve body, as well as the external leakage caused by the wear of the valve body caused by the erosion of the medium.

The main parts of cryogenic valves are treated at low temperature and low temperature impact test is carried out on each batch of samples to ensure that the valves do not crack at low temperature and can withstand the impact of cryogenic medium.

Test each valve as follows:

1. Strength test of shell at room temperature;

2. Sealing test at room temperature and low pressure;

3. Sealing test at room temperature and low pressure;

4. Gas 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 of main components and low temperature impact test of each batch of samples are carried out to ensure that the valve does not crack at low temperature and can withstand the impact of low temperature medium.

7. Low temperature (cryogenic) valves are processed and impacted according to the corresponding material specifications.

8. The electrostatic function is more powerful. The on-resistance between the valve body and the stem or between the internals and the valve body is less than 1 ohm.