Vacuum Pump FAQs(Frequently Asked Questions)
A Rotary vacuum pump works by mechanically compressing and pushing out the air from inlet to outlet. The outlet pressure therefore has to be higher than atmospheric pressure for exhaust to take place. In two stages rotary pump the outlet of one chamber is connected to inlet of next chamber. This increases the compression and makes the air exhaust possible.
On average, a common AC technician does not need to change oil with two years. Pay attention to oil level, if you used it for long time and oil level is low than minimum, you need to add more oil. Usually you don’t need to add oil.
Usually one of these three reasons trigger oil change:
- Rotary pump starts taking longer to create vacuum or is unable to reach the desired vacuum level.
- Color of oil changes from transparent or golden yellow to dark brown indicating oxidation.
- Some engineers prefer to change oil after a fixed number of working hour which are either recommended by manufacturer or are based on experience.
No, rotary vacuum pump oil cannot be recycled. This is because vacuum pump oils work under very demanding conditions. Used vacuum oil, even if recycled, will still be carrying various contaminants. For the safety of expensive vacuum pump, used oil is best discarded.
Normally rotary pumps work noiselessly.
Noise in rotary vacuum pump could be because of following reasons:
- Excessive gas load because of some leak in system. This may also be accompanied be release of oil mist from pump.
- Some foreign object lodged in rotary pump. This will cause intermittent, loud noise.
- Worn out ball bearings. This causes continuous noise.
Normal working temperature of rotary pump is about 80o C.
Yes, this is serious as pump can get seriously damaged if temperature of pump exceeds 100oC. Rotary pumps need to be run in well-ventilated areas and in case of extremely hot climates, as is common in India, use a fan to cool the pump externally. Overheated pumps will not give the required vacuum and thus unduly affect either the working of diffusion pump or the entire process. Also, the oil in an overheated pump will turn less viscous (too thin) and will not lubricate the pump interiors well; thereby leading to pump failure.
A dry pump does not depend on Rotary Vacuum Pump Oil for its operation. In this pump a set of spirals draw air in to the center of spiral, continuously compressing it. Air thus compressed finally exits from the center of spiral. These spirals are normally made of Ceramic materials.
Because of very high cost this pump is not very popular in vacuum industry and is used only where oil free vacuum is essential.
A conventional rotary vacuum pump using rotary vacuum pump oil works out cheaper. Dry pump have a very high cost because of ceramic components used in them. Dry pumps are mainly used in industries like semi conductor industry where cost is not of much importance.
Never ever use motor/engine oil for your Rotary vacuum pump. People tend to make this mistake so very often only to end up regretting eventually. Motor oils are lubricants designed for automobile engines which work under different principles whereas rotary vacuum pump oils are specialty fluids manufactured keeping in mind the requirements of a vacuum pump. Motor oils have a different viscosity from vacuum pump oils and have no vacuum properties at all. Motor oils carry various additives like rust inhibitors and anti-corrosion compounds. When put in the rotary pump, under low pressure and high temperature, these additives separate from the base fluid and cling to the insides of the pump as sticky/gummy solids. This affects the vacuum pressure and harms the pump. Under high temperature of the vacuum pump, motor oils/hydraulic oils start releasing vapors, thus bringing down the vacuum, where as good quality rotary vacuum pump oils do not release any vapors.
No, you should never do that as this can seriously damage your rotary pump. Rotary vacuum pump oil is not an ordinary lubricant. It is a special fluid manufactured with thermal and oxidative stability. Unlike hydraulic oil, rotary vacuum pump oil has a low vapor pressure. It is therefore absolutely different from normal hydraulic oil or motor oil.
Synthetic rotary vacuum pump oils give higher vacuum, create vacuum faster and have longer working life. In addition, synthetic rotary vacuum pump oil preserves and protects the pump interiors. So these next generation synthetic oils are superior to commonly used organic rotary vacuum pump oils. The latter is used only where cost is an issue.
Kozyvacu products comes with one bottle of synthetic oil. Once you use up the oil, it is highly recommended to purchase synthetic rotary vacuum oil to change your used oil.
Rotary vacuum pump oil must have following properties:
- Low vapor pressure of less than 1×10-3 Torr.
- Should have viscosity between 65 to 80 cst at 40oC.
- Should not contain corrosive elements like sulphur.
- Should be resistant to oxidation.
- Viscosity of the oil should not change much with change of temperature.
A Roughing Pump is nothing but an ordinary Rotary vacuum pump which is used to evacuate the vacuum system. It is also known as Mechanical vacuum pump as well as Vane pump. Depending upon the vacuum level desired, it is used either independently (for low vacuum level) or behind a Booster pump or a Diffusion pump (for high or ultra high vacuum level) as a Backing pump.