| MECHANICAL VACUUM BOOSTERS:- | | | | system such as sensitivity to motive fluid |
| Mechanical Vacuum Boosters are dry pumps that | | | | pressures and discharge pressure are overcome |
| meet most of the ideal vacuum pump | | | | easily by the Mechanical Boosters, since the |
| requirements. They work on positive displacement | | | | volumetric displacements/pumping speeds are |
| principle and are used to boost the performance | | | | insensitive to the inlet & outlet working |
| of water ring /oil ring /rotating vane /piston | | | | pressures. |
| pumps and steam or water ejectors. They are | | | | Typical Booster Installation |
| used in combination with any one of the above | | | | (1) Evaporator (2) Gauge (3) Condenser (4) |
| mentioned pumps, to overcome their limitations. | | | | Mechanical Booster |
| Vacuum booster pumps offer very desirable | | | | (5) backup Pump |
| characteristics which make them the most cost | | | | Everest ................. Leaders in Vacuum Booster |
| effective and power efficient option. | | | | Technology Boosters for Vacuum Process © |
| The major advantages are:- | | | | Everest Transmission January, 2005. |
| (a) Can be integrated with any installed vacuum | | | | Calculating the Pump Capacity: - |
| system such as Steam Ejectors, Water Ring | | | | Based on the fundamental gas laws PV= RT, an |
| Pumps, Oil Sealed Pumps, Water Ejectors, etc. | | | | expression can be derived for Volumetric Flow |
| (b) The vacuum booster is a Dry Pump as it does | | | | Rates required for pumping different vapors |
| not use any pumping fluid. It pumps vapor or | | | | gases. Based on the Mass flow rates one can |
| gases with equal ease. Small amounts of | | | | estimate the pump capacity required. |
| condensed fluid can also be pumped. | | | | V = R . Tgas / P Q1/M1 + Q2/M2 ............. Qn/Mn |
| (c) Vacuum boosters are power efficient. Very | | | | Where V = Inlet Volume flow rate m3/hr. |
| often a combination of Vacuum Booster and | | | | R = Universal gas Constant, 83.14 mbar m3/ |
| suitable backup pump results in reduced power | | | | Kgmol x ºK |
| consumption per unit of pumping speed. They | | | | Tgas = Gas/Vapor abs. Temp, in ºK |
| provide high pumping speeds even at low | | | | P = Process Absolute Pressure in mbar |
| pressures. | | | | Q1, Q2, Q3 = Gas / Vapor flow rate, in Kg/hr. |
| (d) Boosters increase the working vacuum of the | | | | M1 , M2 ,M3 = Molar mass, in Kg/mol. of gas |
| process, in most cases very essential for | | | | vapor. |
| processperformance and efficiency. Vacuum | | | | Booster Operation: |
| Booster can be used over a wide working | | | | Power Constraints restrict the total differential |
| pressure range,from 100 Torr down to 0.001 Torr | | | | pressures across the booster. This demands to |
| (mm of mercury), with suitable arrangement of | | | | ensure the total differential pressure across the |
| backup pumps. | | | | Booster must not exceed the rated limits. This |
| Everest ...................... Leaders in Vacuum Booster | | | | can be ensured by any of the following means:- |
| Technology Boosters for Vacuum Process © | | | | 1.) Manual method:- Initially the fore pump is |
| Everest Transmission January, 2005. | | | | switched on until the required cut in pressure is |
| (e) It has very low pump friction losses, hence | | | | achieved and there-after the booster is switched |
| requires relatively low power for high | | | | on. |
| volumetricspeeds. Typically, their speeds, at low | | | | 2.) Auto method:- Installation of mechanical |
| vacuums are 20-30 times higher than | | | | By-pass arrangement across the booster or |
| corresponding vanepumps / ring pumps of | | | | hydro kinematic drive or Variable Frequency Drive |
| equivalent power. | | | | (VFD). In this arrangement, the booster and fore |
| (f) Use of electronic control devices such as | | | | pump can be started simultaneously from |
| Variable Frequency Control Drive allow to | | | | atmosphere. |
| modifyvacuum boosters operating characteristics | | | | Advantages of using Electronic Variable Speed |
| to conform to the operational requirements of | | | | Control Device |
| the primevacuum pumps. Hence they can be | | | | Electronic A.C Variable Frequency Control Drives |
| easily integrated into all existing pumping set up to | | | | are most preferred devices used to regulate the |
| boost theirperformance. | | | | Booster speed to match the varying load |
| (g) Vacuum boosters don't have any valves, rings, | | | | conditions of the process. These drives enhance |
| stuffing box etc., therefore, do not demand | | | | the overall performance of the Boosters and |
| regular maintenance. | | | | offer various advantages for the trouble free |
| (h) Due to vapor compression action by the | | | | operation. |
| booster, the pressure at the discharge of booster | | | | The major advantages are: - |
| (or inlet of backup pump) is maintained high, | | | | 1. Booster can be started directly from |
| resulting in advantages such as low back | | | | atmosphere. |
| streaming of prime pump fluid, effective | | | | Everest ................... Leaders in Vacuum Booster |
| condensation even at higher condenser | | | | Technology |
| temperatures and improvement of the backup | | | | Boosters for Vacuum Process © Everest |
| pump efficiency. | | | | Transmission January, 2005. |
| The Table below gives a rough estimate of how | | | | 2. No need for separate pressure switch, by pass |
| the boosters enhance the working vacuums of | | | | line or offloading valves. |
| the processes when installed in combination with | | | | 3. Considerable savings in power. |
| various types of industrial vacuum pumps | | | | 4. Prevents over-heating of Boosters. |
| currently used in the industry. They can | | | | 5. Protects the Booster against overload and |
| effectively replace multistage steam ejectors, | | | | excessive pressures. |
| resulting in considerable steam savings and | | | | 6. Offers complete protection to motor against |
| reduced loads on cooling towers. Mechanical | | | | over voltage, under voltage, over current, |
| Vacuum Boosters are versatile machines and their | | | | Over-heating, ground fault. |
| characteristics depend largely on backing pump. | | | | 7. Eliminates the needs of separate starter and |
| Various types of backing pump can be used, | | | | overload relays for the Motor. |
| depending upon the system requirement and | | | | 8. Automatically adjusts the speed of Booster |
| ultimate vacuum needs. | | | | between low and high range set giving |
| However, the final vacuum is governed by the | | | | highpumping speeds with relatively low input |
| suitable selection of the backing pump and | | | | power. |
| boosterarrangement. The table below gives a | | | | The Electronic Variable Frequency Control Drive is |
| broad range of vacuum achieved with various | | | | a microprocessor based electronic drive which is |
| backing pumps combinations. | | | | specially programmed to meet the demands of |
| Vacuum Pump Expected vacuum Vacuum on | | | | the Booster allowing it to operate directly from |
| installation Range of Booster (single stage) | | | | atmosphere along with suitable fore pump. |
| Single Stage Ejector 150 Torr 15 - 30 Torr | | | | Conventionally, Boosters can be started only after |
| Water Ejector 100 Torr 10 - 20 Torr | | | | achieving fore vacuum in the range of 30 - 100 |
| Water Ring Pump 40 - 60 Torr 5 - 10 Torr | | | | Torr, as they are not recommended for direct |
| Liquid Ring Pump 20 - 30 Torr 2 - 5 Torr | | | | discharge into the atmosphere. Use of Pressure |
| Piston Pumps 20 - 30 Torr 2 - 5 Torr | | | | Switch, Hydro kinematic drive and by pass valves |
| Rotary Piston Pumps 0.1 Torr 0.01 Torr | | | | is necessary to prevent the overloading of the |
| Rotary Vane Oil Pump 0.01 - 0.001 Torr 0.001 - | | | | Booster. However with the installation of Electronic |
| 0.0001 Torr. | | | | Variable Frequency Control Drive all the |
| Everest ................ Leaders in Vacuum Booster | | | | conventional methods can be bypassed since the |
| Technology Boosters for Vacuum Process © | | | | drive is programmed to regulate the Booster |
| Everest Transmission January, 2005. | | | | speed automatically, keeping the load on motor |
| For example, if a process is using water ring | | | | within permissible limits. This allows the Booster to |
| Pump, the estimated working vacuums would be | | | | start simultaneously with backup pump. When the |
| of the order of about 670-710 mmHg gauge | | | | backup-pump and Booster are started the drive |
| (90-50 mmHg abs.), largely depending on the | | | | reduces the Booster speed to the pre-set levels |
| water temperature and pump design. When a | | | | and as the vacuum is created the Booster speed |
| Booster is installed prior to the water ring pump, | | | | picks up, reaching the final pre-set speed, giving |
| in series, the vacuum levels of the order of 5-10 | | | | most optimum performance over the entire |
| Torr can be easily achieved. In a Multi-Stage | | | | range. Since all the parameters are easily |
| booster installation, vacuum levels of the order of | | | | programmable, one can adjust the booster |
| 0.5 Torr & better can easily be expected. | | | | pumping speeds to match the system |
| Mechanical Boosters offer a completely dry | | | | requirements easily and quickly. The drive limits |
| pumping solution and do not add to any vapor | | | | the current to the motor and safeguards the |
| load, unlike steam ejectors, and therefore, do not | | | | motor against over voltage, under voltage, |
| require large inter stage condenses. At low | | | | electronic thermal, overheat ground faults. i.e. |
| vacuums, higher pumping speeds are required to | | | | protects the motor against all possible faults. |
| maintain the through-put, since the specific volume | | | | External computer control over all aspects of |
| increases with the increase in vacuum. Vacuum | | | | booster performance is possible via RS485 serial |
| boosters enhance the pumping speeds by about | | | | interface built into the drive electronics. This |
| 3-10 times depending upon the selection by virtue | | | | enables the Booster to be integrated into any |
| of which one can expect higher process rates and | | | | computer-controlled operating system. |
| through-puts. The drawbacks of steam ejector | | | | |