By Jim Grann, Ipsen Technical Director
Why is my vacuum pump oil milky?
Oil that appears to be milky when inspected within a vacuum pump is normally caused by water infiltration. When water and oil are mixed in a pump, small bubbles of water suspended in the oil can create a froth from the agitation. When it does, the oil’s appearance could be compared to coffee when milk or creamer has been added.
Water can reduce the viscosity of the oil, causing increased wear and introducing the possibility of rust. Signs of water suspended in your pump oil indicate the need for prompt maintenance attention.
Why is there water in my vacuum pump oil?
There are many reasons why water may have infiltrated into the oil in your vacuum pump. Here are some common issues you can check for to resolve the problem or to find evidence of where water infiltration may have occurred.
- In a relatively new, or a recently relocated furnace, if a hot zone was exposed to water or excessive humidity during transit, that can cause a temporary elevation in water infiltration within the oil of the pump. An oil change followed by a burnout cycle can often resolve this issue.
- If you haven’t performed an oil change in more than six months, it’s probably time to replace your oil. The owner’s manual for each furnace has recommendations for regular maintenance, and periodic oil changes for your pumps are included in those recommendations. Review your manual and make sure to follow the instructions for regular oil changes as part of your maintenance schedule. Once you’ve replaced your oil, make sure to monitor the oil quality daily over the next week, then twice weekly for the first month to see if there are any further signs of water infiltration.
While these first two steps will typically resolve the most common issues, if you’re still seeing signs of water in the oil after an oil change, these next steps can help identify where problems are occurring.
- Is the pump or the furnace in a temperature-controlled environment? A pump that is allowed to freeze at some point in time can experience thermal contraction or expansion that can crack the pump casting. Running a pressure test on the water circuits can help you discover this kind of leak.
- Occasionally on very old pumps, there may have been less effective sand-casting processes that were used at that time. In those instances, casting issues like cracks can surface years later. If you’re operating a furnace with aging pumps, even if it is in an environmentally controlled area, check for a cracked inner casting on the pump by pressure testing the water circuits.
- Many pumps are vented outside the building. Those vent lines need to be protected with a rain cap. If the rain cap is missing or broken, water can find its way into the vent lines and may run back to the pump whenever rain happens. Be sure to inspect any places where vent lines interact with the environment to make sure the caps are intact.
- Purge lines on certain pumps are necessary for processes that utilize combustible gas. On occasion, someone may have mistakenly connected water to the incorrect port. Inspect the purge lines and water connections to confirm everything is in its place.
- If you have a carbon hot zone that interacts periodically with a high-humidity environment, or if there are signs of a water-cooling leak inside the furnace, the felt insulation can absorb water like a sponge. Inspect the felt for moisture and, if there is a significant amount along the bottom of the furnace, look for low water levels in the cooling system.
- There may be an issue with the water temperature regulating valve. In a case where the valve is not set correctly (between 140 °F and 160 °F), or when the valve is defective, the pump may be collecting water vapor, rather than discharging it. Check the settings and, if necessary, inspect and test the valve.
- If you still suspect that there may be a water leak in the furnace somewhere, here’s a quick system test you can run: drain the pump, fill it with fresh oil, then run the pump, but DO NOT pump down the furnace.
Once you’ve run this test you can answer this question: Are there any indications that the new oil has water content?
If Yes, there’s a water leak in the pump.
If No, there’s an issue with the furnace.
These are some of the most common methods that operators use to discover the source of water in their pump oil. If you’ve inspected your furnace for each of these potential issues and still can’t figure out what’s causing water to infiltrate your pump, schedule an Ipsen Field Service Engineer to come to your site and diagnose the issue. To schedule your appointment, call 1-844-GO-IPSEN (1-844-464-7736).
Is your diffusion pump backstreaming oil into the furnace during a pump-down? Use this troubleshooting checklist to find out what might be causing the issue: Troubleshooting Checklist – Diffusion Pump Backstreaming