leakage through the seal
leakage through the seal
(OP)
Hello,
Here in my company we design and manufacture small pumps, among other equipments.
But we're having troubles with the pump sealing. After one year of running, the fluid (usually water - 86°F) starts to leak through the rubber seal. After disassembling the pump to fix the problem, we find out that the rubber seal reamins perfect and the shaft got damaged in the region where its worn by the rubber lip.
I suspect there might be an high eccentricity between the shaft and the rubber seal, or the pump shaft material (AISI 304) is too soft for this application. I'm thinking about changig it from AISI 304 to a martensitic stainless steel ( AISI 410, 420), which is harder.
What would you suggest?
Thank you
Here in my company we design and manufacture small pumps, among other equipments.
But we're having troubles with the pump sealing. After one year of running, the fluid (usually water - 86°F) starts to leak through the rubber seal. After disassembling the pump to fix the problem, we find out that the rubber seal reamins perfect and the shaft got damaged in the region where its worn by the rubber lip.
I suspect there might be an high eccentricity between the shaft and the rubber seal, or the pump shaft material (AISI 304) is too soft for this application. I'm thinking about changig it from AISI 304 to a martensitic stainless steel ( AISI 410, 420), which is harder.
What would you suggest?
Thank you





RE: leakage through the seal
Have you any suspended solids in the system?
May be worth installing a particle filter if this is practical.
Additionally a different material seal? Maybe
Otherwise I would second trying a harder material
RE: leakage through the seal
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: leakage through the seal
RE: leakage through the seal
304 is too soft for reliable shafts unless it has been cold drawn to increase its strength and hardness.
It is common to use 304 for a shaft with a small replaceable sleeve of 420 installed. Then when there is damage you can replace the seal and the sealing surface easily.
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P.E. Metallurgy, Plymouth Tube
RE: leakage through the seal
Perhaps a hard sleeve o-ringed might solve the problem, and it´s a pretty simple solution.
Another solution I've been thinking about is nitriding the shaft surface. So the hardness increases and the excessive wearing stops.
RE: leakage through the seal
Localized hardening of the SS will raise the cost, and when the seal is replace you may have to replace the entire shaft.
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P.E. Metallurgy, Plymouth Tube
RE: leakage through the seal
Thank you
RE: leakage through the seal
The same as EdStainless, use replaceable shaft-sleeve with harder incresed rather than change the shaft or maybe coating the shaft. Easy way, also economist.
RE: leakage through the seal
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)