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Pump Oil Levels / Changing Oil


Most HyVac rotary vane vacuum pumps employ oil for the creation of vacuum.

Level - The oil level of most vacuum pumps is stated on the sight glass. If not stated a level (meniscus) should be observed just past the halfway mark of the oil sight glass with the pump in operation. Oil levels typically are maintained by filling through the exhaust port of the pump. No damage will occur by filling the intake port. The preferred oil fill entry port is the exhaust port and is easier for the user to accomplish quick filling and adjustment of the oil level in this manner. Correct oil level can affect high vacuum pressures if the oil level falls below the actuation level of the exhaust flutter valve typically found on the top of the exhaust stator on the vacuum pump. (Typically inside the pump casing)

To change the oil loosen the oil stopcock or bottom bolt and tilt the pump over a container of appropriate size.  It is beneficial to do this after the pump is warmed up so the oil is less viscous.  In the case of trap plate pumps like the MegaVac, PressoVac or HyVac 1 Vacuum Pump it is beneficially to manually actuate the pump pulley and drain a couple times in a row.  It is a good time to consider flushing the pump with HyVac Flushing oil if the oil comes out highly discolored or with apparent contamination. When refilling, use the correct oil for the pump and fill to correct level, plug pump in and start and top off with pump running.  We suggest strongly the pump be at a hard vacuum to minimize a mess.

The oil serves a number of purposes in this type of vacuum pump and reviewing these enables the user to understand the importance of a quality vacuum pump oil.

First off, the oil lubricates the pump. The tight tolerances that all HyVac vacuum pumps are manufactured to, do not allow for much metal to metal contact void of correct lubrication. With inadequate or no oil, the pump can be expected to seize with potentially pump killing consequences. Usually when this occurs, the rubber V-belt fries and melts off the pulley and creates a terrible stink, or the motor burns out. It is possible that the user can simply fill the pump to the correct level with oil and manually actuate the pump a number of times (if possible) and it will work again. If manual actuation is not possible, the pump needs to come back to HyVac for an overhaul.

Second the pump oil creates a boundary layer of lubrication between the rotor and the vane/stator contact points in the pump. This boundary or film layer is what enables the pump to work and create a high vacuum. Using the correct vacuum pump oil from HyVac Products allows for vacuum pressures to 10-6 Torr. Use of other vacuum pump oils may lead to inadequate vacuum pressure. If the user installs an oil with a vapor pressure specification of 10-2 Torr then the best vacuum pressure the pump will be capable of is 10-2 Torr irregardless of the fact the pump is rated to 10-4 Torr. Use of HyVac vacuum pump oils assures the user the maximum vacuum pressure of the pump.

Third, the oil serves as a coolant or heat transfer mechanism for the pump. Because many of the manufacturing tolerances are so close in the pump, it is necessary to have an oil in place that is extremely efficient at heat transfer. HyVac vacuum pump oils serve this task well, having extremely good heat transfer specifications.

Other benefits to good quality HyVac Oil.

Demulsibility is also required of the oil because often contaminants are introduced to the pump. HyVac oils have excellent demulsibility and are able to separate from contaminants such as water with very good yields. It is possible to play junior chemist with use of reparatory funnels to often reclaim a water contaminated pump oil by simply letting the oil sit overnight in a reparatory funnel and decanting off the water and "cuff" (oil water interface) in the morning. Adding heat like 100-150 Degree F improves yields. Usually this method is ok for users trying to get to 29" of mercury vacuum and is not acceptable for users actually hitting a specific high vacuum pressure number like 20 micron .02mm Hg vacuum.

HyVac pump oils have a very high natural viscosity index or "VI". This allows them to maintain good viscosity (vacuum boundary film strength) over the varying temperature ranges that most pumps will typically go through and exhibit in normal operation. This property also improves the oils lubrication ability.

Quick get me some of this great oil so my pump will be happy!!!


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