Gas Ballast Is Only Step One: How to Protect Your Vacuum Pump From Water, Solvents & Oil Contamination
Open the sight glass on an oil-sealed vacuum pump and the oil should tell you a lot.
If it has become cloudy, milky, unusually dark, or contaminated with process material, the problem may not be the pump itself.
The problem may be what the pump is being asked to swallow.
Water vapor, solvents and other condensable process vapors can enter an oil-sealed rotary vane pump, condense internally and contaminate the lubricating oil. Once that happens, vacuum performance can suffer and internal pump components may be exposed to accelerated wear or corrosion. Edwards identifies condensable-vapor contamination as a reason to use gas ballast and recommends allowing the pump to clear residual vapor after processing. (Edwards)
Earlier this week we explained what a gas ballast valve does and when to use it.
Gas ballast is an important part of the solution.
But for many applications, it should not be the entire solution.
A better approach is to control contamination at several points in the vacuum system: before it reaches the pump, while the pump is operating, inside the oil system, and at the exhaust.
Here is how.
Stop the Contamination Before It Reaches the Pump
The best place for water, solvent vapor and process contamination is outside the vacuum pump.
That is where an inlet trap or cold trap can make a major difference.
A vacuum trap is installed between the process and the pump. Depending on the design, it can capture condensable vapors, liquids, particulates or other contamination before those materials enter the pumping mechanism.
Vacuum Pump Supply carries vacuum inlet traps, foreline traps and cold traps designed for this type of pump protection. VPS describes these products as a way to capture vapors, condensables, particulates and process contamination upstream of the pump. (vacuumpumpsupply.com)
For applications involving significant condensable vapor, this can be far more effective than repeatedly allowing the contamination into the pump and then trying to clean it out afterward.
When Does a Cold Trap Make Sense?
Consider a cold trap when the process produces a meaningful vapor load from materials such as water or suitable solvents and the process conditions allow a trap to be used safely.
A cold trap lowers the temperature of the vapor stream so a portion of that material condenses in the trap rather than inside the vacuum pump.
Leybold specifically discusses using condensers together with gas-ballast pumps for water-vapor applications. (Leybold)
Vacuum Pump Supply’s 1420H-14 Cold Trap, for example, is designed to provide pre-pump vapor protection using a removable dry-ice/isopropanol cooling well. (vacuumpumpsupply.com)
The exact trap should always be selected around the process chemistry, vapor load, pressure range, connection size and safety requirements.
The important concept is simple:
If you can capture the contaminant before it reaches the pump, the pump does not have to deal with it later.
Use the Gas Ballast Correctly
If condensable vapor does reach an oil-sealed rotary vane pump, the gas ballast can help prevent that vapor from condensing during the pump’s compression cycle.
Edwards describes gas ballast as a means of reducing vapor contamination in pump oil, while Leybold explains that introducing ballast gas allows condensable vapor to be discharged before it condenses internally. (Edwards)
That makes gas ballast extremely valuable for wet processes.
But there is an important limitation:
Every pump has a finite vapor-handling capability.
Gas ballast does not turn a rotary vane pump into an unlimited solvent or water separator.
If the process continually feeds more condensable vapor into the pump than the pump can safely handle, oil contamination may still occur.
That is why applications with substantial vapor loads often benefit from a combination of:
proper gas-ballast operation + upstream vapor trapping.
For the detailed operating explanation, see our complete gas ballast guide.
Watch the Oil — It Is an Early Warning System
Vacuum pump oil performs several jobs inside an oil-sealed rotary vane pump.
It lubricates moving components, helps seal internal clearances and carries heat away from the pumping mechanism.
When process contamination changes the condition of the oil, pump performance can change with it.
Cloudy or milky oil is a particularly important warning sign when water or another condensable material may be entering the pump.
Do not simply keep running the pump and hope the oil clears.
First determine why the contamination is entering the pump.
Then correct the process or operating condition that caused it.
Depending on the severity of contamination, the next step may be gas-ballast decontamination, an oil change, or a complete flushing procedure.
Vacuum Pump Supply carries a broad selection of vacuum pump oils and specialty fluids for Edwards, Leybold, Busch, Welch, Alcatel/Adixen, Becker and many other pump families. VPS also maintains a Vacuum Pump Oil Cross Reference to help match OEM fluids with compatible service options. (vacuumpumpsupply.com)
One example is Plus UG19 Oil – 4 Liter, which VPS lists for numerous Edwards RV and E2M models as well as several Leybold, Welch and Alcatel/Adixen pumps. Always verify the exact oil specification for the pump and process before changing fluid types. (vacuumpumpsupply.com)
When an Oil Change Is Not Enough
There is a major difference between draining contaminated oil and cleaning contamination out of a pump.
Deposits, degraded lubricant and process material can remain on internal surfaces after the drain plug has been opened.
If the oil was severely contaminated, simply pouring fresh oil into a dirty pump can immediately contaminate the new oil.
That is where flushing fluid becomes useful during maintenance.
Vacuum Pump Supply’s VP FF Vacuum Pump Flushing Fluid is intended to help loosen and carry away old lubricant, deposits, dirt and contamination before the pump is refilled with the correct operating oil. (vacuumpumpsupply.com)
Flushing is particularly worth considering after severe contamination events, degraded oil, or before refilling a pump after maintenance when the internal oil circuit needs to be cleaned.
It is not a substitute for fixing the contamination source.
If a process continues feeding water or solvent into the pump, the new oil will eventually suffer the same fate.
The goal should be:
Clean the pump. Correct the source. Refill with the proper oil.
Do Not Forget the Exhaust Side
Contamination control does not stop at the pump inlet.
Oil-sealed rotary vane pumps can discharge oil aerosol through the exhaust, particularly during higher gas throughput.
Edwards notes that even a pump operating normally may produce some oil mist and that significant oil mist over time can contribute to loss of the pump’s oil charge. (Edwards)
An exhaust mist filter helps capture that oil aerosol before it enters the surrounding workspace or exhaust system.
Vacuum Pump Supply carries oil mist filters, replacement elements and exhaust filtration for a wide variety of vacuum pumps.
For Edwards RV-series pumps, for example, the Edwards EMF20 Oil Mist Filter is available as a genuine OEM exhaust-filter assembly. (vacuumpumpsupply.com)
Edwards also offers oil-return arrangements for some pump and mist-filter combinations, and Vacuum Pump Supply lists these alongside its Edwards filtration products. (vacuumpumpsupply.com)
This becomes especially relevant when a pump spends significant time operating with gas ballast, because higher gas throughput can increase the amount of oil aerosol reaching the exhaust.
Think of Contamination Control as a System
The most reliable setup is rarely a single replacement part.
Instead, look at the complete path the process gas follows.
| Where the problem occurs | What to consider |
|---|---|
| Before contamination enters the pump | Inlet trap, cold trap or foreline trap |
| During pumping of condensable vapor | Correct gas-ballast operation |
| Oil already contaminated | Fresh vacuum pump oil |
| Heavy contamination or degraded oil | Vacuum pump flushing fluid |
| Oil aerosol leaving the exhaust | Oil mist filter or replacement element |
| Pump performance still poor after cleaning | Seals, filters, vanes or repair kit |
This is why troubleshooting strictly by pump model can sometimes miss the real problem.
Two identical vacuum pumps can have completely different maintenance requirements if one pumps clean dry air and the other processes water vapor or solvents.
The application matters just as much as the pump.
Has Contamination Already Damaged the Pump?
Sometimes correcting the oil and vapor problem restores performance.
Sometimes it exposes wear that has already occurred.
If the pump still has poor ultimate vacuum, long pump-down times, oil leakage or abnormal operation after the contamination source has been corrected and the oil system has been serviced, internal wear may need to be addressed.
Vacuum Pump Supply stocks rotary vane vacuum pump repair kits and parts for Edwards, Leybold, Busch, Becker, Welch, Alcatel/Adixen, Rietschle and other pump manufacturers.
For example, the current VPS OEM Edwards E2M28/E2M30 major repair kit contains vanes, shaft seals, O-rings, gaskets, filters, bearings and other wear components used during a comprehensive rebuild. (vacuumpumpsupply.com)
Replacing parts, however, should come after identifying why the contamination occurred.
A freshly rebuilt pump placed back into the same uncontrolled wet process can simply start the cycle again.
Spend Money Preventing the Failure, Not Recovering From It
The cost of vacuum pump contamination is rarely limited to a few liters of oil.
There can also be labor spent troubleshooting, repeated oil changes, filters, expedited parts, production downtime and eventually a premature pump rebuild.
That is why contamination control can be one of the better places to spend a maintenance budget.
A cold trap may prevent gallons of contaminated oil.
A correctly used gas ballast may prevent vapor from condensing inside the pump.
An exhaust mist filter may reduce oil loss and improve the working environment.
The correct oil protects the pump after the contamination source has been addressed.
And flushing fluid can help start the pump with a cleaner oil system after a serious contamination event.
The objective is not to sell more parts.
It is to stop buying the same maintenance parts because the original process problem was never corrected.
Not Sure What Your Pump Needs? Start With the Application.
If you are dealing with cloudy vacuum pump oil, water contamination, solvent vapor, excessive oil mist or repeated oil changes, send Vacuum Pump Supply:
the pump manufacturer, complete model number, process being pumped, current oil, and a photo of the pump nameplate.
That information often tells us far more than the pump model alone.
Vacuum Pump Supply can help identify the correct vacuum pump oil, trap or mist filter, repair kit or maintenance component for the application.
Protect the oil. Protect the pump. Reduce the rebuilds.