Vacuum pumps can leak from 3 basic locations and their causes can be various. The first area and main culprit to examine is the shaft seal of the pump. This is a mechanically rotating shaft in an area that can wear and then leak over time. We improved the HyVac 28s and 45s style vacuum pump in 1997 replacing the mechanical seal with a new generation lip seal. If your pump employes the old style internally mounted mechanical shaft seal then you can not use the new style lip seal with out purchaing a "conversion kit" to accommodate this update. If you look inside the belt guard and down the side of the pump south of where the shaft comes through the pump, you may find evidence of a shaft seal leak. Usually the side of the pump is shiny from the oil. Also running the pump for a period of time on top of a sheet of newspaper can pinpoint a leak.

The second most common location is from the pumps exhaust port. If the pump is operated at high pressures less than 28" of mercury vacuum, then high gas flows create high levels of lubricant agitation inside the pump which can exit the pump, come down the sides of the pump and create what can be construed as a leak. If this is observed to be your problem we can enclose the top of the pump and trap the exhaust of the pump using an exhaust filter or by enabling the user to port the exhaust to a nearby "hood". Sometimes adding an exhaust port extension using a section of standard plumbing pipe of appropriate size and length 6-10" can help. This will help keep the oil and associated oil mist inside your vacuum pump.

The second solution is to make sure your system is really, vacuum tight because the cause of this problem is basically a leaky system.

Water or acids have been present in pump for an extended period of time. See also water in the pump.

I think all high vacuum pumps are made from cast iron predominately, aluminum and steel secondarily. We tried making one from stainless steel and will revisit sometime in future but in a nut shell, it failed. Cast iron and water don't get along. This is the same for acids like hydrochloric or sulphuric. The tend to attack the cast iron of the pump and cause oxidation or rust to form. On the outside this is ok but left standing, formation starts internal to the pump and will cause the pump to seize up after some period of time days to years depending on contaminant source and level.

I have seen ads for corrosion resistant pumps. Right…., great marketing ploy. They fail in 4 months instead of 3. Spend your money elsewhere on solutions that work. There is no cheap solution only correct ones. Teflon coating… phooey. The vacuum pumps lock up because the rust forms on the cast iron rotating parts "period". No teflon coating is going to last long with the metal to metal contact that we have in rotary vane pumps. Coating the oil sump with teflon protects the aluminum housing. I have never seen a pump yet with an uncoated aluminum housing eaten through, although I have seen thousands of pumps with corroded cast iron parts.

The basic fact of the matter is contaminants must be eliminated from the pump. You can either deal with it before the pump or after it gets in the pump. For systems with high contamination potential then probably both types of systems are required. For the front end or suction side of the pump, employ a vacuum inlet trap. For dealing with contamination once it is in the pump consider an oil filtration system that can be hooked up to the pump to recirculate and deacidify the oil.

The poor users solution to oil contamination problems "Change the oil frequently". Create a larger oil sump that lasts longer in getting contaminated.

Assuming the pump is OK (see below). You have air leaks in you system, collapsing vacuum hoses or contaminants which cause "outgassing". Check system for leaks (Link to procedures). Fix leaks and time again. Remove contaminants.