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30L/55L Tech Support 


Problem List

No vacuum
Low vacuum
Pump locked up
Oil problems
Pump leaking oil
Water in pump
Pump corroded
Slow to pull down
How to capture exhaust
Hose nipple too big
Hose nipple too small
Other problems not covered ??
How to change oil.

Other Information

Exploded view

Parts list

Working on this pump.


Return pump for repair. (RGA)

Next pump bigger

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General practices for long life

Oil change intervals



The HyVac 30L and 55L vacuum pumps are basic oil sealed rotary vane pumps known for years. These pumps are direct driven by a motor connected directly to the vacuum pump using a coupling arrangement. The rotor is offset in and rotates off-center in the stator. The rotor has 2 opposing slots cut in it where the vanes sit and ride in and out maintaining constant contact with the stator using a spring to maintain constant pressure as it rotates eccentrically in the stator. These pumps are relatively simple in operation and are easy to repair. Because of the assembly and manufacturing processes each pump is very consistent and the parts are not unique, are interchangeable and often can even be refurbished. Parts are readily available and can be purchased as needed based on the exploded view diagram in the manual.

Because they are direct drive and small in capacity they are light weight, quiet small in size.

The 2 sizes are 30L (1 cubic foot per minute) and (55L 1.9 cubic feet per minute). The 30L is a single stage pump capable of 15 micron .015 Torr or greater than 29.9" Hg Vacuum. The 55L is a two stage pump capable of .1 micron or .0001 Torr or greater than 29.9" Hg vacuum.

These pumps are extensively used in laboratories, and medical equipment, vacuum ovens and a myriad of other applications. They generate vacuum pressures in a very efficient manner and are still a favorite for many applications.

No Vacuum - The 30 and 55L pump

First off inspect the pump for correct oil level.

Second inspect the base of the hose nipple (inlet port) for a good sealant bead. I can't tell you how many pumps we get with the hose nipple replaced with some other fitting that is not properly sealed with a good vacuum sealant. For threaded sealing of HyVac pumps we recommend HyVac PST sealant.

Assuming adequate oil and lubrication has been inspected and is present. Then remove belt guard and turn pump motor on. If the pump pulley is rotating and still no vacuum is present then turn the pump off. Your pump needs to see us or have an overhaul.

Generally assuming no vacuum often means no pump rotation, then your pump may have one of the following problems.

First possibility, the coupling joining the pump and motor is not present or slipping. The coupling rotation can be reviewed by shining a flashlight between the pumped mounting plate and the motor housing with the pump turned on. If this is not rotating then the removal of the four screws in the back of the motor will disconnect pump and motor for closer examination. If the coupling is secure on the pump shaft and the "spider" that joins both couplings is present, the user can manually attempt to rotate the pump. If this can not be accomplished the pump is locked and needs disassembly.

Second the vanes are stuck or locked in the rotor and the pump needs disassembly and repair. Your pump rotates but vanes are not working. Your vane springs and / or vane spring pins could be shot.

Third all valving on the top of the stators is missing.

Low Vacuum -

First off inspect the pump for correct oil level and oil quality.

Second inspect the base of the hose nipple (inlet port) for a good sealant bead. I can't tell you how many pumps we get with the hose nipple replaced with some other fitting that is not properly sealed with a good vacuum sealant. For threaded sealing of HyVac pumps we recommend HyVac PST sealant.

Assuming adequate oil quality and lubrication has been inspected and is present. Then remove belt guard and turn pump motor on. If the pump pulley is rotating and still low vacuum pressures (500 micron or so) are present then turn the pump off. Best guess is the exhaust valves on the exhaust stator are broken. The pump needs repair or overhaul.

The pump is locked up  

Well you gone and done it now. Check the pump for oil. Fill to correct level and manually actuate pump, assuming you can. Sometimes it is possible to manually actuate a pump back into service using the method described above. Other potential problem areas include vanes stuck in up or out position. See "No vacuum" section above. Call us if you are unsuccessful. The pump needs repair or overhaul.

Oil Problems

Oil problems come in various shapes and styles and are highly dependant on the vacuum pressure the user is trying to achieve. Because there are many questions related to oil in our type of pumps we have a separate section just for oil questions and tech support. Hot link to Oil Problems.

Oil in the System

We found oil from the pump inside our system when we came in this morning. Hot Link for explanation and solutions.

Why is the pump leaking oil?

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. Running the pump for a period of time on top of a sheet of newspaper can pinpoint a leaks location.

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. The pump will operate over extended periods with this symptom but it is important to monitor the oil level of the pump on a regular basis.

Third is from a bad gasket or O-ring. Solution is to replace the leaking part with a new one.

Water in the Pump Water in the Pump Water in the Pump -

Hot link for the answers…. This is a big very common problem. One of our most common problems is water in the pump.

Why is it bad? Corrosion. Pump destruction.

How does it happen? Waters vapor pressure less than pumps vacuum pressure.

How do I tell? Oil is milky colored.

What are solutions? Freeze those water molecules.

Pump is corroded. Why?

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.

Why is the pump is slow to pull down?

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

How can I check my pump to see if it is OK?
Hook you pump up to a good vacuum gauge at the pump intake port with out the system attached in any manner. This is the best and only real way to baseline the pump. In problem areas or troubleshooting vacuum systems this is the first step in the process. Determine the "blank off" pressure of the vacuum pump. For a 30 and 55L the blank off pressure is 15 micron or .015mm and .1 micron .0001 mm respectively. For those with inexpensive vacuum gauges roughly 20/7 micron, .020/.007mm with thermocouple or TC gauge. And for you real misers out there, 29.99 with Bourdon Tube 0-30" gauges and between 0 and 1mm with manometers (0-760) in both cases depending on atmospheric pressure variables.

How do I capture the exhaust?
The 30 and 55L vacuum only model pump requires only an exhaust filter of correct pipe size that allows for capture of the exhaust fumes. This can be ordered from HyVac for this use. As am alternative you then hook up an exhaust line and port the exhaust to a hood or adapt it to an exhaust filter then to the hood. The 30 and 55L vacuum pumps all have an exhaust port as part of their design.

My hose nipple is too big / too small?
HyVac Products stocks and manufactures a myriad of solutions for conforming to a users system. If we don't have it, we can get it. HyVac manufactures both conventional hose fittings and also the newer generation quick disconnect vacuum fittings often referred to as NW or ISO or KF fittings, flanges, piping, adapters and clamps which allow a wide variety of connection sizes and terminations.
How do I change the oil?
Generally we recommend changing the oil through the exhaust port of any high vacuum pump. This port generally is a straight dump into the oil sump of most vacuum pumps. The intake port should only be used as a last resort, is slow but ultimately acceptable. Manual pump rotation probably will be necessary to accomplish.
Other problem areas not covered.

You get em to me, I'll post em.

11/26/2005 ęCopyright HyVac Products, Inc. All Right Reserved
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