What should be done if the mechanical seal of a centrifugal pump keeps leaking?
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For a long time, the horizontal centrifugal pumps used in our unit (made of stainless steel and equipped with water cooling for temperature reduction) have frequently experienced leaks, mainly on the cooling side. They start leaking after being in use for a short period of time, and material leakage occurs after operating for some more time. I’ve tried several different types of mechanical seals, but the results have not been satisfactory – they start leaking within less than a month at most. I would like to ask the experts: what are some solutions to this problem?
1. Assembly issue; not detailed enough. 2. Or it could be a medium issue, causing corrosion of the sealing material. 3. Use dry grinding for the problem.
Please indicate from which position of the mechanical seal water and materials are leaking, as well as what the material being pumped is! Otherwise, it’s impossible to tell! It is recommended that you learn more about the structure of mechanical seals, their working principles, and maintenance techniques! There are countless such materials online! Download some and see if it helps you!
It is recommended that the original poster clarify the medium, operating parameters, pressure in the sealed chamber, machine seal flushing scheme, and cooling scheme, so that others can make an accurate judgment
This post was last edited by Waiter on 2011-7-9 at 14:27. It deals with IH-type chemical centrifugal pumps, used for handling ester-based organic solvents at a temperature of around 140 degrees; there are generally no particles present. The inlet pressure of the pump is approximately 0.05 MPa, while the outlet pressure is around 0.15 MPa. Cooling water is available during pump operation, and it is supplied directly from the circulating water main.
Reply to 2# Equipment Operator: There are no issues with the assembly； If there is corrosion, it won’t be the water side that leaks first ； Dry grinding is a possibility, but it doesn’t seem likely; the aspect most affected by dry grinding is probably the material side.
Reply to 3# Grave Digger: Thank you. We have also looked into some information and suspect it might be a problem with the circulating water. It’s being prepared for renovation.
I encountered the same problem as you; it’s just that the materials and operating temperatures vary from place to place. Our machine seals have leaked four times in a row, which is really giving me a headache. The main reason at present is dry rubbing occurring during operation. I believe that if there are no issues with the installation or the material of the seal O-rings, it is recommended that you disassemble the seal to check whether dry rubbing is taking place in the sealing ring. If so, then check whether there is cavitation inside the pump; if there is, it indicates that gas is present in the pump, which causes dry rubbing of the seal. Additionally, check whether air is being drawn in at the pump inlet, as this can also lead to dry rubbing of the seal due to the presence of air. Also, check whether your cooling water is clogged; if the seal temperature is too high, a liquid film cannot be formed, which can also lead to dry grinding and leakage of the seal.
Given the situation of the poster, there should be several reasons: 1. Operational issues, as centrifugal pumps are not allowed to operate without load; in such cases, it is necessary to check whether the employees are causing the pump to operate without load； 2. Medium-related reasons, which cause corrosion of the sealing material ； 3. Selection issue: It is crucial to choose the appropriate pump based on your medium. For example, for materials with high permeability, magnetic pumps or shielded pumps should be selected.
Organic solvents are corrosive to rubber seals; as you said, there is no problem with the assembly； If there is corrosion, it won’t be the water side that leaks first ； Dry grinding is a possibility, but it doesn’t seem likely; the aspect most affected by dry grinding is probably the material side. The pump can’t leak then.
Can’t the stationary and rotating rings form a membrane? In other words, is there friction? I suggest: 1. Whether the medium is corroding the O-ring, resulting in friction. 2. Could it be that impurities in the medium or cooling water have entered the seal, causing friction between the rotating and stationary rings? 3,. The pump draws in air, resulting in cavitation; this prevents a membrane from forming between the rotating and stationary rings, leading to friction! 4. Check if there is a problem with the pressure of the cooling water – it can’t get in, which leads to friction!