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Water and other stuff in my Vacuum Pump

Water and other contaminates can cause corrosion and hurt your pump!!!!

Problem List

Poor mans solutions Oil Filtering Systems
Rich mans solutions Before or After
What is the gas ballast valve? Water in the pump
Modifications Acids in the pump
Oil Change Intervals Solvents in the pump
How to change oil. Particulates
Other Information Other Stuff
Oils for Pump Vapor Pressures of Common Contaminants
Test Kits for Pump Oil How do I stop this?
Traps Return pump for repair. (RGA)
Separation Equipment  

The basic principle of any oil sealed rotary vane pump is what allows it to be such a good and efficient producer of excellent vacuum pressures. Oil here was the key. Because the oil in the pump and the oils quality level is integral to the pumps operation, it is very important to keep contaminants out of the oil and to a minimum. Contaminants usually become apparent by a discoloration or degradation of the oil in the vacuum pump. For the most part this process is called oxidation and is very similar to what happens to your cars engine oil. Over time the oil gets stuff in it to cause its decomposition or degradation. When this happens the total acid number of the oil (TAN or neut number) will start to go acidic.

This process is extremely important due to the materials of construction of the most, if not all the rotary vane vacuum pumps in the marketplace. The fact of the matter is we have a rotating mechanical device generally made of cast gray or ductile iron. As the oil gets acidic, these constituents attack the iron and causes rust or scale to form eventually seizing the pump. Addition of external contaminants such as water, acid or other materials serve only to hasten this process and can accelerate the process to unacceptable levels.

We have made an effort to address most of these areas and will be adding to them as time and user input allows. Hope we are of some help in your understanding of these concepts. They are applicable to most vacuum pumps of this design.

Before or After ? - Identifying and dealing with a problem.

We are now making the assumption there is contamination in the pump and that this is a very bad thing.

There are two basic methods of dealing with a contaminant. Before it gets in the pump or after it gets in the pump and there are numerous solutions for each.

First and foremost identify the contaminant. All "things" in the universe have boiling points or sometimes technically referred to as vaporization points. This is generically the temperature at which the "thing" turns into a gas. It can be below freezing or well above 1000 degrees but all things have some specific temperature at which they boil and turn into a gas. If you are working with a compound lets say an asphalt mix immersed in water there may be numerous boiling points involved. The water being one, any solvent in the asphaltic mix, and some tar like heavy oils. They all have different boiling points.

In using a vacuum, we can lower a "things" boiling point. As an example water will boil at room temperature, 70 degrees F (Not 212 Degrees F) under a full vacuum. This is basic physical chemistry and are scientific laws and can be calculated should you so desire. The benefit to the user is reactions or extractions can be done under varying temperatures and pressures and these reaction points manipulated using vacuum pressure.

Another basic example is that under full vacuum levels of various contamination can be manipulated or eliminated. "Water is in the process and we want it out throw it in the vacuum oven and get it out." Cool no water...... hummmm..... Where did it go? In the pump.

Once you know what is in the pump then you can deal with it.

To stop a product from getting in the pump we use what is called a "trap". These traps come in all shapes and sizes and we can trap or stop lots of potentially bad actors before they get in and start attacking your pump. Some basic examples:

Water - The main problem out there. There is only one way to stop water effectively from getting into the
               pump and that is to freeze it out of the air stream before the pump sees it. These traps are
               generically called cold traps.
Solvents - Same as water but the traps can go to colder
temperatures depending on the offending product.
Particulates - Particulate traps of correct mesh size or micron size to stop the thing.
Mercury - Traps mercury
Acids - Neutralizing Traps convert acids to water and salt with a chemical reaction. Turn a pretty blue color
             too. Neato.
Oil - Molecular sieve traps

Other traps and their information can be reviewed on another page hot link from here for more information.


I added this because a lot of people have no clue as to the gas ballast valve present on most of our pumps. We have a special page which you can hot link to but suffice to say that for vacuum pressures in use; greater than 250 micron and problems with contaminants, then running the pump with the gas ballast valve open or cracked may help significantly the amount of contaminants that actually end up in the pump. Hot link here for more detailed information.

After it's in the pump.

I want it out of the pump now!!!! Change the oil. Try running the pump for a couple hours with the gas ballast valve open.

I want to deal with it regularly and efficiently.

You will need an external oil filtration system. These systems can be hooked up to your pump to continually filter and remove unwanted contaminants. They are a filter based system employing an external pump and can use differing filters or even a series of filters depending on the problem to be solved.

You can also employ "water white" type vacuum pump oils that start off with ultra low sulfur content in your pump. A little better on contaminant load.

Acids in the Pump

Acid contamination is very, very, tough on most vacuum pumps. It is best to deal with an acidic stream in front of the pump. Try not to let the acids get in the pump. When vacuum pump oils degrade or go acidic they do so logarithmically or exponentially. Introducing acidic boosters always hastens the oils degradation. We have seen pumps with oil that just slumps out of the pump when the pump was opened it is so oxidized. We have also seen pumps that are so rusted up they are basically scrap at that point. Sometimes a series of cold traps on the front end is even warranted.  It is possible to use chemically inert vacuum oils of the per fluorinated type.  Depending on pressures required there are some additives that can be introduced to the oil to help this situation somewhat.


Employ the gas ballast when evacuating the system.

You need to change the oil regularly, flush it out also.

You can invest in a cold trap or traps to -70F. Buy it them from us please.

Use acid neutralizing traps before the cold traps.

Consider an external oil filtration system.

Solvents in the Pump

Solvents are not as bad as acids at least for the generic ones that is. There is the potential for attack of the shaft seals and elastomers employed in the pump. Direct drive pumps are more susceptible in this area due to use of more elastomers than belt drive pumps. Ultimate vacuum pressures may suffer.


Employ the gas ballast when evacuating the system.

Specify fluorocarbon based solvent resistant elastomers, perfluoro or silicone based seals in construction or rebuild.

You need to change the oil regularly, flush it out also with HyVac Flushing Oil.

You can invest in a cold trap or traps to -70F or sometimes -120F needed. Buy them from us please.

Use activated carbon traps before the cold traps.

Use molecular sieve traps for the big molecules.

Consider an external oil filtration system.


Goods things to keep out of pumps or for that matter any rotating mechanical device with running tolerances of .0005" -.001". HyVac has these traps and they are relatively inexpensive. All vacuum pumps should have them in front of the pump.  We can filter down to 1 micron on particulates.

Poor Mans Solution to many of these problems

Establish a working oil change interval and stick to it. Use HyVac pump oils for quality assurance. Flush the pump with HyVac Flushing Oil, If possible, separate the contaminated oil from the problem and reuse the oil.

Rich Mans Solution

Buy enough traps to stop everything but basic air from getting in your pump. Establish a oil change interval and stick to it. We have over 50 years in vacuum pumps and we have some really clean users out there with pumps that old. Protect your pump and save your money. A little planning, adequate care and preventative maintenance go a long way.

Always change the oil before storing a pump!

What the heck is this gas ballast thing?
Hot link here for the answer.


Can I modify my pump to be more forgiving of contaminants?  Yes and no. Elastomers can be changed to be more resistant to differing contaminant streams. I like to debate this question because it comes up a lot under the heading "corrosion resistant vacuum pumps". I often have to sell against this "gray" term with black and white solutions and I could argue this till I am blue in the face. As an alternative, you can also call most of the independent vacuum pump repair houses and ask them about corrosion resistant pumps. Just say something like "Right, corrosion resistant pumps" and see what they say. Unfortunately a lot of uneducated users get a false sense of security from this "debatable" marketing phrase.

Oil Problems

First off inspect the pump for correct oil level. 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 change intervals

Wow I get asked this a lot. The oil change interval of any vacuum pump is totally dependant on what the user is doing. Clean, air only, systems can get by with a lot of time between changes, like once every 6 months or so. Untrapped acidic systems I have heard as high as every other day. All points in between. It is really a trial and error type of thing. When the oil gets contaminated, change it. If the oil starts getting real dark, change it. Oil is much less expensive than a new pump.

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. On our newer pumps there is a fitting on top to accommodate this procedure.  The intake port (suction) should only be used as a last resort, is slow but ultimately acceptable. Manual pump rotation probably will be necessary to accomplish.   In either case fill pump to correct level based on oil sight glass.  For most HyVac pumps this is a little past the halfway mark on the sight glass with pump running.   For our newer HyperVac pumps there are markings on the large sight window.

How do I stop water getting in  the oil?

We have heard all kinds of stories from people using a myriad of problem solving methods.  The ones we have a history with are the use of traps.  The only way we know to reduce this issue is to use a "cold" trap to sublimate the water molecule from gas to ice.  There are also other styles of traps and there are varying success with differing applications.  Hey we are for what ever is successful.  We probably repair more pumps for this problem than any other reason.

Other problem areas not covered.

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

11/27/2005 ęCopyright HyVac Products, Inc. All Right Reserved
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