Monday, October 24, 2011

Mechanical Booster Pumps

EVEREST has introduced  Mechanical Booster Pumps to meet the growing demand of the Vacuum Process Industry where fast pump down times are required and energy usage concerns rule out any alternative pump selection.

Everest Boosters pumps  (ROOTS TWIN LOBE TYPE) combine high pumping speed with relatively low power consumption. When such Booster pumps are used in combination with Oil sealed rotary  or Water ring pumps , the speed  and ultimate vacuum of the combination can be increased by TWO to TEN times.. They reduce the effect of oil contamination (back streaming). Rotary Pumps have a limitation to Size, Pumping Speeds, and Temperature rise and consume relatively large amount of power since there is  a continuous friction between the vanes and the casing. A combination of small rotary pump and Everest Booster overcomes the above limitations and gives:- 

  1. High pumping speeds
  2. Higher ultimate vacuums
  3. Low power consumption per unit pumping speed
  4. Prevents oil back streaming
  5. Improvement in overall pumping efficiency
Everest Vacuum Boosters are import substitutes, developed specially to boost the performance of the vacuum pumps, in low-pressure range, where Rotary vacuum pumps have poor volumetric efficiency.  Everest Boosters operate into a fore vacuum created by single or double stage Rotary Pumps (oil sealed or Water ring) . Everest Boosters are capable of moving large quantity of gas at low pressures, with far smaller power consumption than for any other equipment now available. 

The internals of a Booster are totally free of any sealant fluid, and therefore the pumping is dry. Also because of the vapor Compression action by the booster, the pressure at the inlet of the fore pump is relatively high, resulting in higher volumetric pumping efficiency & low back streaming of sealing oil. Everest Twin Lobe Boosters are used in series with fluid sealed Rotary pumps/any other suitable fore pump to achieve higher speeds and lower ultimate pressures. Since the rotors in a Booster rotate within the casing with finite clearances, no lubrication of the internals is required and the pumping is totally oil free.

Everest Twin Lobe Boosters are used mainly in two modes: -
  • Compression mode
  • Transport mode
In compression pumping, the general application, a booster is placed in series with a rotary pump whose rated speed is much lower than the booster speed. The ratio of Booster speed to pump speed is termed as STAGING RATIO and the ratio of Booster outlet pressure to inlet pressure is COMPRESSION RATIO.

In compression mode the staging ratio ranges between 2 - 15 while the compression ratios achieved range between 10-40, depending upon combination selection. Initially, pumping is initiated at atmospheric pressures by Rotary pump/Fore pump and after achieving the recommended cut in pressure the booster is switched on. A bypass line around the booster may be provided for the initial pump down period. Boosters with hydrokinematic drive/Variable Frequency control are also available which allow simultaneous start-up of the booster & the fore pump. This initial pumping by fore pump is necessary since considerable heat is generated by pumping gas at high pressures with the booster and the power input is also considerably higher. For this reason the booster is generally switched on at cut-in pressures of 20-60 Torr. A suitable vacuum switch can be installed between the booster & the fore pump, set for cutin pressure, so that the booster is switched on only on achieving the designed cut-in pressures. However, for short duration the booster can with-stand excessive differential pressure across it. The Booster-Rotary Pump combination are generally recommended when speed of 3000 LPM or  higher are required since the combination is most economical and power saving than any rotary pump of similar capacity. 


As evident from the Typical Performance Curve, booster is most effective in the pressure range of 1 -0.001 Torr having high pumping speeds and relatively low power consumption for this range.  A Typical performance curve is drawn for a Booster combination indicating the individual and combination performance with single stage & double stage rotary pump.

In transport mode pumping, the Booster is used in series with the rotary pump with staging ratio 1. Both the pumps are started simultaneously at atmospheric pressures since the critical pressure drop can never exceed. This combination effects higher ultimate pressure without much increase in pumping speed.  However, throughput at lower pressures increases resulting in higher ultimate pressure. 
INDUSTRIAL APPLICATIONS OF EVEREST VACUUM BOOSTER

Boosting the performance of diffusion pump systems
Improving the quality of lamps
Use in vacuum heat treatment and degassing
Use in drying application
Use in distillation
Use in gas re-circulation and gas pressure boosting
Use in semi – conductor processing

The use and application of Everest Boosters in Industry:  Vacuum Roots Blowers are widely used in the industry. Until recently their use in India was restricted because the item was imported and therefore very expensive. However, for the past few years Everest Blowers have been making the item and its usage has increased by leaps and bounds.  Today there are hundreds of installations using this product.  So this is a good time to look at various applications and see how Everest Boosters can improve performance and reduce energy costs.

Boosting the performance of Diffusion Pump Systems:  Vacuum metallizing plants are widely used to produce a vast range of metallized plastic/glass/metallic  objects, such as reflectors, mirrors, clock and radio cabinets.  A typical plant is shown in Figure before.  For fast production, a typical cycle time is 6 to 10 minutes, though times in excess of 30 minutes are not unknown.  A series combination of a rotary oil-=sealed mechanical pump and a Diffusion pump are generally used.  The problem is that in the pressure range 10 –3  Torr to 1 Torr, the speed of both the pumps is very low, hence pump-down times are generally slow.  A look at the speed characteristics of typical Oil-Sealed Rotary Pump will show that the pump speed rapidly starts falling at pressures below one Torr.  The speed of the diffusion pump starts to fall rapidly at pressures above 0.001 Torr.  Hence, in the transition pressure range of 0.0001 to 1 Torr both rotary and diffusion pumps perform well below their optimum levels.  The consequence of this is that the overall process cycle is lengthened.  This results in high energy and overhead costs.  Everest Booster has its peak pumping speeds in the pressure range of 0.001 Torr and 1 Torr.  Further because there is little friction in the rotating parts, high pumping speeds are possible at low power consumption.  In the transition pressure range Everest Booster can provide five to ten times more pumping speed than the Rotary Pump of the same HP.  Thus, to boost the performance of a Diffusion Pumped system, the modern trend is to use a Mechanical Booster between the rotary pump and diffusion pump.  Everest Vacuum Booster inserted between the Diffusion and Rotary pump provides a high or boosted pumping speed and thereby enables a fast pump-down process cycle.  The productivity improvement can be as high as 100% to 200%.  Advantages of using Everest Booster.

  1. Higher pumping speed by a factor of 5 to 10 times that of the rotary pump.
  2. Power Saving: The Everest Booster, by virtue of speed enhancement and shorter process cycles, saves power.
  3. Long service life and very low maintenance because there are no rubbing/mechanical friction between internals.
  4. Less frequent oil changing.
Improving the Quality of Lamps:  Process lines for the production of tube lights, miniature and auto lamps
typically require vacuums of the order of 0.01 to 0.001 Torr.  The requirement of high-speed machine operation where frequent leakages occur due to breakage and wear and tear places heavy demands on pumping systems. The consequence of this is that rotary pumps are frequently replaced due to deterioration in performance. Everest Booster improves matters by:

  1. Increasing the speed of the Rotary pumps by a factor of 3-5 times.
  2. Enables less frequent maintenance of the rotary pump, since it can deliver less than peak performance and still provide adequate/superior vacuum to the machine.
  3. In the production of vacuum lamps using Everest Booster substantially improves the product quality and life.
Use in Vacuum Heat Treatment and Degassing:  Vacuum annealing is necessary for those special steels, which would get embrittled due to incorporation of oxygen if heated in air.  Heating under vacuum and subsequent quenching in inert gas is sometimes the only method that is possible for treatment of such steels.  Since heating imposes considerable gas loads on the rotary pump, Everest Booster provides the benefit of being able to handle these heavy gas loads at low pressures in an economical way.  A major advantage with Everest Booster is easy and instantaneous startup, unlike diffusion pump or oil booster, which requires substantial heat up time (and consequent waste of energy) to come up to a state of operational readiness.

Use in Drying Applications:  Drying or removal of moisture is an important industrial process.  The  applications range from dehydration of foods products to removal of moisture from cable and transformer oils.  The problem of moisture removal is especially acute  at low pressures where even a small amount of water results in a large release of water vapor.

Everest Boosters are capable of providing pumping speeds of the order of 5,000 liters per minute to 1,50,000 liters per minute and more at low pressures in the range of 0.001 to 50m Torr, at very modest power requirements as compared to oil booster pumps and steam ejectors, providing efficient solutions.

Use in Distillation:  In distillation applications Everest Booster Pump and water – ring / oil-sealed rotary
vacuum pump combination can provide low pressure and high pumping speeds more economically than steam ejectors.  The outstanding advantage of using Everest Booster is:
Negligible environmental pollution compared to steam ejectors
  • Dry operation- This means that no working fluids are used in the operation of the pump and therefore there are no problems of contaminations of or by the condensate
  • Instantaneous startup and shut down
  • High energy efficiency per unit of pumping capacity
Use in Gas-recirculation and Gas Pressure Boosting:  In systems that re-circulate gases, such as lasers, heat exchangers and chemical process plants, the use of Everest Booster is essential to overcome the pressure losses of pipeline and sealed chambers.  Everest Boosters have the outstanding advantage that they offer dry operation, which can be totally sealed off from the surrounding atmosphere.

In long pipelines, Everest Boosters can be used to boost the gas pressure. This reduces the requirement of high driving pressures to pump gases through pipes and because Everest Booster is totally sealed and oil free, even inflammable gases such as biogas, L.P.G, C.N.G, etc., can be easily pumped.  

Use in Semi-Conductor Processing:  Mechanical Boosters are used in Semi-conductor processing industry as a part of dry pumping / oil-free pumping systems.  Such systems are necessary to handle the high corrosive and often poisonous gases used in semi-conductor production.  The main advantage of the Everest Booster is its sealed – off operation and long life between maintenance procedures.  

Typical Installations:-

Typical arrangement of Booster installations are shown. The booster can be directly mounted on the suction of the fore pump or mounted on a base frame with connection  to fore pump.  For applications involving pumping of CONDENSABLE VAPOR  like in distillation, a suitable condenser can be installed in between the Booster & Fore pump. In such cases the Fore pump size can be reduced drastically, to match  the NON-CONDENSABLE load.


Initially the fore pump is switched on until the required cut in pressure is achieved and there-after the booster is switched on. In case mechanical b-pass arrangement across the booster or hydrokinematic drive or Variable frequency drive is used , the booster and fore pump can be started simultaneously from atmosphere.

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