An oil-sealed rotary vane pump has a rotor with sliding vanes inside a chamber. The vanes rotate and trap gas that enters via the pump's inlet port, reducing the volume between the rotor and stator. The compressed gas goes out through the outlet port into the atmosphere.
To optimize the performance and operation of rotary vane pumps, follow these eight tips for using oil effectively.
1. Oil Loss Prevention
Avoiding/reducing oil losses requires an effective exhaust valve. A popular valve design incorporates an elastomer with a metal backing plate (which restricts the mobility of the valve's rubber portion). All-metal valves are prone to "suck-back" if the pump stops under vacuum, allowing oil to escape past the valve and be "sucked" back through the pump and into the vacuum chamber. As a result, in addition to collecting and recycling oil mist, an adequate 'exit', or exhaust, valve is required to prevent/reduce oil losses.
2. Condensing Vents Prevent Corrosion
In chilly atmospheres, moist air condensates like water vapor will collect in the oil upon starting the vane pump. The pump should be run on 0% load with the gas ballast valve open to expel condensate from the oil until it warms up. To purge condensates from the oil, operate the pump again on 0% load with the gas ballast valve open before turning it off. This method dramatically reduces rusting.
3. Type of Oil
Oil-seal rotary vane pumps typically use molecularly modified, distilled mineral oil since it is a stable fluid with low vapor pressure. In addition, the oil will undergo additional purification procedures if the pump is subjected to reactive or corrosive gasses. Highly inert, synthetic lubricants that cannot be heated over 280 °C are advised for use in environments with a high concentration of oxygen or other chemically reactive gasses. Failure can occur from overheating and lack of lubrication if the wrong oil is used in a chemically hostile environment and then breaks down, leaving a tar-like deposit that blocks the internal passageways.
Gas ballasting cleans oil polluted with water droplets. Upon opening the pump's gas ballast valve, airflow captures water vapor and expels it. Check oil levels since increased airflow through the pump may cause more oil mist at the exhaust. Depending on pollution, gas ballasting can take hours.
5. Pump Maintenance
Set up a proactive servicing program based on pump duty hours and inspect the pump regularly between servicing. Visible/audible leaks, extreme vibration, unusually high oil consumption, discolored oil, raised running temperature, excessive time, and/or failure to reach pressure/vacuum levels indicate trouble. These signs indicate seal and vane tip replacement.
6. Oil Change
Draining and refilling the pump is analogous to car engine maintenance. That is, make sure the pump is warm, drain the oil using an extension port (if available), fill with clean oil (allowing the first part of fresh new oil to flush out the last part of old oil), run the pump for a short time, drain the oil again, refill to the correct level, and close the drain plug.
7. Oil Color
Most oil reservoirs for oil-sealed rotary vane pumps are transparent units which (assuming that the glass or plastic has not been prematurely and permanently discolored) will enable the color of the oil to be viewed and checked against a color chart. Such color charts, which are readily available from reputable pump and oil suppliers, are specific to each different type of oil. Any change of color (particularly a darkening) will indicate an unacceptably high level of degradation, contamination, and/or condensate. Regular checking of the oil color, particularly if the oil mist is being filtered, collected, and recycled should be an active part of the pump’s maintenance schedule.
8. Exhaust Mist Filters
Oil-sealed rotary vane pumps are "oil-wet" by definition and, when working, release some oil as mist (along with the gas being transported). An oil vapor filter will collect the emitted oil. After exiting the pump, the gas travels through the mist filter, which converts the mist into oil droplets and "sumps" it via an elemental filter. This trapped oil can be emptied manually or via other attachments and returned to the pump. The filter element is a consumable item that must be replaced regularly.
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