Pump sealing issue

The first stage of the mechanical seal is leaking, and the low-temperature medium is leaking into the methanol tank. The fundamental solution is, of course, to stop the pump and replace the mechanical seal. If operation must continue in the short term, the valve at the top of the methanol tank can be closed (the design pressure of such tanks is generally higher than the operating pressure of the pump). The freezing point of methanol is -97.8°C; frost may form on the lines connected to the mechanical seal, but this does not affect the flow of methanol within those lines. The temperature of the medium handled by this pump should also be taken into consideration. It is important to prevent the low-temperature medium from vaporizing and affecting the surrounding environment. Additionally, mechanical seals on low-temperature pumps usually have a nitrogen protection system (PLAN62); opening this protection system’s valve slightly will ensure that, in the event that the second stage of the seal also leaks, the low-temperature medium will not be released into the environment and cause injury to personnel.

Agree with what was said above. Additionally, be sure to pay close attention: if the mechanical seal uses a gas-liquid film arrangement (which is the case for dry gas pumps in general), then the pressure on the solid medium side must always be higher than the pressure in the sealing chamber. For example, at startup, the pump must be filled first, followed by the introduction of sealing gas ； When parking, turn off the sealing gas first, then drain the medium (I don’t know what the term for draining the medium is).

Otherwise, first, nitrogen enters the medium and causes contamination； Second, it will flip the O-ring of the inner moving ring seat, causing misalignment and preventing the moving ring from returning to its original position.

Thank you all. I have another question: the main pump is working fine, but it’s the backup pump that’s having this issue