This is done via a cold trap (aka inlet condenser) located at the pump inlet. There are four stages of operation in a typical rotary vane pump (Fig. 
Herring, Daniel H., Vacuum Heat Treatment, Volume I, BNP Media, 2012. As the rotor
With the combination of mode selection and gas-ballast (see below) the pump performance can be optimized. pump. One of the critical components in a rotary vane pump is the exhaust valve (Fig. 
In two-stage rotary vane pumps, the isolation valve is located on the high-vacuum stage. Although vacuum feed oil distribution is still used, more modern pumps use a separate oil pump, to circulate the oil via passages machined into the stator to the rotor bearings and seals (Fig. In his latest column, Amin Almasi discusses BEP's relationship to the sizing, selection, control and operation of pumps. In addition to the foreline trap, other accessories are used on the pump inlet side to capture moisture, vapors and solid contaminants. An insiders guide to maintaining electrical enclosure temperatures and protecting heat-sensitive equipment. When the pump is turned back on, the valve does not open immediately but is delayed until the pressure in the pump has reached the approximate pressure in the vacuum chamber, thereby also preventing suckback while the pump is reaching pressure. This can take several hours with badly contaminated pumps. 10). Vacuum processes, Fundamentals of total pressure measurement, Mass spectrometers and residual gas analysis, From surface molecular contamination (SMC) to The metal backing plate limits the movement of the elastomer part of the valve. When running at higher vacuum, this issue does not occur. 2) is machined and assembled with tight tolerances so that the gap between the top of the rotor and the stator wall (often referred to as the Dou seal) is approximately .025 mm (1.0 mils). After leaving the pump, the pumped gas is passed through the mist filter, which contains a filter element that reduces the oil mist into droplets and collects it. Over time, this will slow pump-down as the alumina becomes clogged with water. The vanes can be spring loaded, but otherwise, rely on centrifugal force to push outward against the stator wall. This is a dynamic style seal, which also requires lubrication. The large sight glass gives visible indication of water in the oil. Air is trapped inside these chambers, and as they rotate, their volume is constantly reduced. outlet valve opens against atmospheric pressure. 
The two-stage rotary vane pump can achieve an inlet pressure of 3 x 10-3 Torr (4 x 10-3 mbar). See #3 in the diagram below. Whether or not an oil pump is used, the excess oil is exhausted from the pumping mechanism via the exhaust valve. The negative effect of ballast on ultimate vacuum and oil loss is less in the low flow mode than during high flow. Air then passes through several stages of internal oil-and-mist eliminators to remove 99.9% of the lubricating oil from the exhaust. Community needs, infrastructure life span and viability of existing systems must be considered. An internal oil circuit allows for high operational reliability, high vacuum levels (0.1 mbar = 99.99%), high water vapor tolerance and a self-cleaning effect (Image 1). side. Figure 4.2: Operating principle of a rotary vane
All rights reserved. Two-stage designs are available, which utilize two rotors in series internal to the pump. Create service tickets and find all product-related documents. This creates backstreaming, that is, the movement of pumping oil back into the vacuum furnace chamber. Operating a vacuum pump with an incorrect lubricant, even with an equivalent oil, may void the warranty in the event of damage. Exhaust. In the case of gas ballast operation, a hole to the outside is
In any vacuum system with a pressure lower than 0.75 Torr (10-1 mbar) there is a potential for backstreaming, which is the migration of oil vapors against the flow of pumped gas, and back into the vacuum furnace chamber (Fig. Mr. David Sobiegray, Edwards Vacuum, technical contributions, and private correspondence. 14), which is a molecular sieve installed on the inlet of the pump.
Some pump designs, especially older ones using circulation of the lubricating oil relied on a vacuum feed system whereby the vacuum generated by the pump itself was also employed to draw the lubricating oil through the rotor bearings. Rotary vane pumps are often equipped with an inlet isolation valve (aka anti-suckback or vacuum safety valve). The oil drain valve kit will help with this step. With a pump rotational speed of 1750 RPM, for example, the valve will open and close 2.5 million times every 24 hours at a frequency of 29 Hz. The pumping system consists of a housing (1), an eccentrically
moving parts, fills both the dead volume under the outlet valve as
Know how they operate and how to use them properly. into two separate compartments with variable volumes. The working chamber (5) is located inside the
This pressure lifts a spring-loaded elastomer disc which allows oil to flow into a trough feeding the pump interior and rotor bearings as well as the vanes of the vacuum pump. The selection of trap(s) is based on the specific application and the constituents of the pumped gas. 
As the name implies, this device closes when pumping stops, preventing gas (or air) from being sucked back into the vacuum chamber through the pump.
ballast. the high pressure stage. 
Two factors are thus of vital importance: the temperature of the intake vapor and the temperature of the pump. One key component is the vacuum pumps exhaust filter. Rotary vane pumps (Fig. For this reason, when moisture is present in the pumped gas it is, Vacuum Heat Treating: Education & Training, Vacuum Technology with The Heat Treat Doctor, Vacuum Pump Technology: Education & Training, Specific Heat Treating & Brazing Approvals. Above this, the duo seal will start to leak oil from the high-pressure side to the low-pressure side (Fig. Only after roughing is complete and higher vacuum is achieved is backstreaming a concern. This draws the gas into the pump and generates the required vacuum. Check and adjust the oil level once again. For this reason, when moisture is present in the pumped gas it isrecommended that an inlet condenser be used with the foreline trap. 
Some two-stage rotary vane pumps are provided with the ability to operate in either high-throughput mode or high-vacuum mode. 
Although foreline traps are common, the first defense against backstreaming is to use a pump oil with a low vapor pressure, which is less prone to vaporization and therefore less likely to backstream. This process, referred to as hydrotreating, provides a strong, stable formulation with low vapor pressure. With normal one-shift operation, filters should be changed at least annually. In addition to providing lubrication of the rotor bearings, it must: In addition, the vapor pressure of the oil is critical because the oil is exposed to the gas being pumped from the chamber. In a container of water (at room temperature), the pump will begin to lower the pressure to the water evaporation point (if the water is at 25C at sea level, the evaporation pressure will be 31.67 mbar absolute). 4), which is fed by multiple ports. Air is compressed and discharged into the exhaust box as rotation continues. Energy costs and operating costs can also vary greatly. A rotary vane vacuum pump is an oil-sealed rotary displacement
housing and is restricted by the stator, rotor and the vanes. This creates increasing cell volume on the inlet port side, creating vacuum. The high-throughput mode is used to provide faster drawdown at inlet pressures greater than approximately 38 Torr (50 mbar). 6). The oil seals the gaps, lubricates the vanes and removes the heat of compression. The ultimate pressure achievable by the pump is limited by back-leakage through the Duo seal and by the outgassing of the lubricating oil. Moisture and vaporized contaminants (typically from dirty work introduced into the vacuum chamber) will find their way into the pump oil and interfere with efficient pump operation. The main purpose for selecting a multistage pump is to efficiently operate in systems that require a high total head. Jon Mavrick is the business development manager for after sales and service at Busch Vacuum Solutions. In the high-throughput mode, the oil pressure (and therefore flow) is increased, and in high-vacuum mode, the oil flow is decreased. 
The filters can only be efficient and effective when proper maintenance is completed. This may cause the oil to lose viscosity over time along with some of its beneficial characteristics. Oils designed specifically for rotary pumps are distilled mineral oils to which hydrogen atoms have been attached to any loose molecules in the chain. Oil and water droplets collect on the filter fibers. Manufacturers of heat treating and brazing vacuum furnaces and controls, complete hot zone and vacuum furnace retrofits, thermal spray coatings, plasma, HVOF and paint coating services. Inlet condensers can be water cooled using a shell and tube heat exchanger or cooled with refrigerant or cryogens such as liquid nitrogen. Another set of critical internal components are the vacuum pumps rotary vanes. Upgraded technology improves White Rock, British Columbia, water quality and worker safety. Particularly harsh applications or heavy-duty operations, such as high dust loads in the environment or in the process gas, other contamination or ingress of process material, can make it necessary to shorten the maintenance intervals. 
Other pumps use spring loaded lip type shaft seals around the rotor shaft. This feature overcomes the problem at higher pressures of an insufficient pressure differential across the low-vacuum stage thus ensuring an adequate supply of oil into the high-vacuum stage (which is later in the lubrication circuit). First, measure the filter pressure. It is important to consider maintenance work and the resulting downtime, costs for spare parts and the procurement and disposal of operating fluids. In some critical applications or where dirty work is being run and significant outgassing is anticipated, it is good practice to ballast the pump after each cycle for 20 to 30 minutes between runs. It lubricates all
The oil vapor pressure is generally one of the factors limiting the ultimate achievable.
It is filled with activated alumina (also referred to as sorbent), which traps and collects the oilvapors. The mode selector switch can be actuated while the pump is on or off, and some larger pumps switch between modes automatically. once the pressure in the pump has reached the approximate pressure in
The outlet of the high-vacuum stage is piped to the inlet of the low-vacuum stage. Even with an inlet condenser, a rotary pump can still accumulate condensed contaminants in the oil. 9). Oil Sealed Rotary Vane Pumps Part 1) is a result of vaporization of the oil under low pressure. In order to generate a higher vacuum using a rotary vane pump, a two-stage pump design is used. When an oil-lubricated rotary vane vacuum pump is operational, air is being pulled through the inlet into a cylindrical housing. A wide range of pumping characteristics (i.e., pressure versus flow performance) is achievable through the selection of these two modes in combination with (high, low, or no) gas ballasting (Table 1). It is important to use an exhaust filter with an ultra-fine medium and a tight mesh for better filtration performance. Filters can only be efficient and effective when proper maintenance is completed. He has been in the vacuum technology industry for over 15 years, helping design, construct and maintain several wastewater projects. The recently retired Osephius still plans on sharing industry knowledge. Also, if smoke is coming out of the exhaust, it is time for a filter change. 
After refilling the oil, run the pump for one or two minutes, then turn the pump off. Copyright Cahaba Media Group, Inc. All Rights Reserved. In addition to gas ballast, another approach to pumping gases containing condensed vapors or moisture is to remove them prior to entering the pump. well as the narrow gap between the inlet and outlet. multiple tasks to perform in a rotary vane pump. This provides additional protection against suck back into the vacuum chamber. Features of the DEKKER Vacuum rotary vane pumps include: At a given temperature, vapor may be compressed only as far as the saturation vapor pressure; beyond that point, the vapor condenses. They are often called wet pumps because the gas being pumped is exposed to oil used as a lubricant to help provide the seal.
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