Dry vacuum pump
What is dry vacuum pump:
Oil-free dry mechanical vacuum pump (also referred to as dry vacuum pump) is a kind of mechanical vacuum pump that can start pumping under atmospheric pressure, and can be pumped directly into the atmosphere. There is no oil or other working medium in the pump chamber, and the pump’s limit pressure is equal to or close to that of oil-sealed vacuum pump.
Oil-free dry mechanical vacuum pump (also referred to as dry mechanical pump) is a kind of mechanical vacuum pump that can start pumping under atmospheric pressure, and can be pumped directly into the atmosphere. There is no oil or other working medium in the pump chamber, and the pump’s limit pressure is equal to or close to that of oil-sealed vacuum pump.
Up to now, most mechanical vacuum pumps used in vacuum industry use oil, water or other polymer fluids as the working medium of the pump, cooling, sealing, lubrication and other functions in the pump. With the development of science and technology and the expansion of vacuum application field, there are two urgent problems to be solved in the original mechanical vacuum pump and its pumping system. One is that the working medium of the pump is polluted by the backflow of the pumping vessel, which in many cases affects the quality and quantity of the product and increases the maintenance cost of the equipment. Secondly, the reaction substance in some process seriously deteriorates the medium in the vacuum pump, so that the pump can not work properly.
For ordinary oil-free vacuum system, although oil-sealed vacuum pump with cold trap or adsorption trap accessories to prevent reflux, but not completely solve the problem, and make the system appears complex. The proper use of dry mechanical vacuum pump can achieve the desired results.
Dry vacuum pump application:
The application of dry mechanical vacuum pump is extensive, mainly in the following aspects:
1. polysilicon preparation process in low pressure chemical vapor deposition;
2. semiconductor etching process. Corrosive gases and abrasive particles are often used or produced in these production processes.
3. In addition to the semiconductor process, some of the particulate production process, do not want to mix particulate into the pump oil, and hope that particulate discharge pump, then a certain type of dry mechanical vacuum pump can meet the requirements;
4. In chemical industry, pharmaceutical industry, food industry, such as distillation, drying, defoaming, packaging, to prevent organic solvent pollution, suitable for the use of dry vacuum pump;
5. used as a general oil free clean vacuum system of the front pump to prevent oil contamination.
Dry vacuum pump classification:
Double circular lobes:
The design of double circular lobes is very similar to the most popular and widely used Roots pumps nowadays. In fact, some of the earliest design ideas for dry pumps are to add Roots pumps together. This multi-stage design makes the gas path quite complex, and each stage requires a larger flow of nitrogen to dilute and isolate. At the same time, in order to achieve a good degree of vacuum, there are very strict requirements for clearance at all levels. Of course, the power consumption of this design is relatively low due to the increased internal compression ratio.
Clover lobes:
The three-leaf circular-lobe design and the double-lobe design have exactly the same principle, except that the gas is divided into three parts in a circle of rotation rather than two parts like the double-lobe design. The two designs have the same advantages and disadvantages. In order to further reduce power consumption, some manufacturers choose two DC motors in the transmission part, but this will also lead to torque reduction, restart ability – decline. Like the double-lobe design, each stage of the clover design requires a larger flow of nitrogen to dilute and isolate.
Combined (roots + claw):
The combined (Roots + Claw) design uses Roots to improve the pumping efficiency at lower pressure and claws to improve the pumping efficiency at higher pressure. Its basic principle and gas path are exactly the same as the circular lobes design introduced previously. Some manufacturers have also changed their last stage to a star-shaped design, which divides the gas into five parts in a circle of rotation, just as a three-slice design divides it into three parts. Similarly, in many processes, each stage of the combined design requires a larger flow of nitrogen to dilute and isolate.
External compression screw type:
In the external compression screw design, a pair of equidistant screws is used. This minimized the internal compression and made the gas path shortest and simplest. In this way, the gas stays in the pump body for the shortest time. Although this design is relatively high in power consumption due to reduced internal compression ratios, it exhibits extremely high stability in many complex semiconductor processes. This single-stage design makes the requirement of nitrogen consumption very small and simple, so that it has good interchangeability in different processes. Even in many clean processes, nitrogen is not used.
Internal compression screw type:
In addition to the use of a pair of non-equidistant screw, the basic principles of the internal compression screw design and the external compression screw design are very similar. The reduction of the volume between the screws causes compression inside the screw. This design reduces the power consumption to the same level as the multistage pump due to the internal compression. However, in many processes, this internal compression, like multi-stage pumps, is very easy to cause physical and chemical changes in the pump body, resulting in solidification or liquefaction.
Dry vacuum pump working principle:
1. dry screw vacuum pump
Dry-type screw vacuum pump is a suction and exhaust device which uses a pair of screw rods to rotate in the pump shell at high speed and reverse synchronously. The two screw rods are supported by bearing and installed in the pump shell after fine dynamic balance correction. There is a certain gap between the screw and the pump shell. Therefore, when the pump works, there is no wear between the screw and the screw. Wipe, smooth operation, low noise, working chamber without lubricating oil, therefore, dry screw pump can be pumped containing a large amount of steam and a small amount of dust in the gas occasion, higher limit vacuum, lower power consumption, energy saving, maintenance-free and so on. It is an upgrading product of oil seal / water ring / jet vacuum pump.
LG Series Screw Vacuum Pump
Technical Parameter:
| Model | Unit | LG50 | LG70 | LG100 | LG150 | LG200 | LG300 | LG350 | ||
| Suction Capacity | 50 Hz | m³/hr | 180 | 250 | 430 | 540 | 720 | 1080 | 1260 | |
| 60 Hz | 216 | 300 | 360 | 650 | 850 | 1296 | 1512 | |||
| Ultimate Pressure | 50 Hz | mbar | 0.02 | |||||||
| 60 Hz | 0.01 | |||||||||
| Motor power | 50 Hz | Kw | 5.5 | 7.5 | 11 | 15 | 18.5 | 22 | 22 | |
| 60 Hz | 7.5 | 11 | 15 | 15 | 22 | 26 | 26 | |||
| Rotary Speed | 50 Hz | RPM | 2900 | |||||||
| 60 Hz | 3550 | |||||||||
| Inlet diam | mm | 50 | 65 | 70 | 90 | 100 | 100 | 100 | ||
| Outlet diam | mm | 40 | 40 | 55 | 65 | 65 | 65 | 65 | ||
| Lubricating oil consumption | L | 0.85 | 0.85 | 1.4 | 2 | 2 | 2 | 2 | ||
| Cooling water consumption | L/min | 2.5 | 2.6 | 2.8 | 3 | 4 | 4 | 4 | ||
| gal/min | 0.67 | 0.7 | 0.75 | 0.8 | 1.07 | 1.07 | 1.07 | |||
| Weight | Kg | 295 | 350 | 480 | 520 | 680 | 850 | 850 | ||
| Noise | dB(A) | 68 | 70 | 70 | 72 | 74 | 84 | 84 | ||
| Working temperature | ℃ | 5～40 | ||||||||
| Max. Permissible humidity | / | 90% | ||||||||
2. oil free reciprocating vacuum pump
Vacuum pump, also called piston vacuum pump, relies on the reciprocating motion of the piston to periodically change the working volume of the pump cavity (cylinder). The structure of reciprocating vacuum pump is similar to reciprocating piston compressor. When working, the suction pipe is vacuumed and the exhaust pipe passes through the atmosphere. Reciprocating vacuum pump can be used in vacuum distillation, vacuum concentration, vacuum crystallization, vacuum filtration, vacuum drying and concrete vacuum operation.
3. jaw vacuum pump
Claw vacuum pump is composed of multi-stage rotor, each stage has two rotors, two rotors rotate in the opposite direction, suction port and pump cavity connected, pump cavity volume becomes larger and suction, when the rotor closed suction port suction end, after the pump cavity becomes smaller and compressed gas, when the exhaust opening after the pump cavity exhaust, exhaust port closed, then Exhaust is finished, so circulate.
4. oil free scroll vacuum pump
The scroll disc of a scroll oil-free vacuum pump is a scroll disc structure formed by one or more involute spirals connecting one end with a plane. A pair of scroll disks composed of a static scroll disk and a moving scroll disk constitute the basic pumping mechanism of a scroll oil-free vacuum. For example, in a two-stage scroll oil-free vacuum pump, there are two directions corresponding to the fixed scroll disk, a rotating scroll disk located between the two scroll disks. The relative motion of the dynamic and static vortex disks forms a crescent-shaped vacuum chamber with constant volume change, which makes the air be sucked in and discharged from the exhaust port, and completes the exhaust cycle.
EVP Series Dry Scroll Vacuum Pump
Technical Parameter:
| Model | EVP1000 | EVP600 | EVP300 | EVP150 | EVP75 | ||||||
| Displacement | 50Hz | l/s | 16.6 | 8.7 | 4.3 | 2.0 | 1.0 | ||||
| l/min | 996 | 522 | 258 | 120 | 60 | ||||||
| m3/h | 59.8 | 31.3 | 15.5 | 7.2 | 3.6 | ||||||
| cfm | 35.8 | 18.7 | 9.3 | 4.3 | 2.2 | ||||||
| 60Hz | l/s | 19.9 | 10.4 | 5.1 | 2.4 | 1.2 | |||||
| l/min | 1194 | 624 | 306 | 144 | 72 | ||||||
| m3/h | 71.6 | 37.4 | 18.3 | 8.6 | 4.32 | ||||||
| cfm | 42.8 | 22.3 | 10.9 | 5.1 | 2.5 | ||||||
| Ultimate pressure | Pa | ≦1.0 | ≦1.0 | ≦2.6 | ≦8.0 | ≦8.0 | |||||
| torr | ≦7.5×10-3 | ≦7.5×10-3 | ≦1.9×10-2 | ≦6.0×10-2 | ≦6.0×10-2 | ||||||
| mbar | ≦1.0×10-2 | ≦1.0×10-2 | ≦2.6×10-2 | ≦8.0×10-2 | ≦8.0×10-2 | ||||||
| psi | ≦1.4×10-4 | ≦1.4×10-4 | ≦3.8×10-4 | ≦1.2×10-3 | ≦1.2×10-3 | ||||||
| Leakage with outlet & air flush port off |
1×10-2Pa·l/s（1×10-4mbar· l/s） | ||||||||||
| Max. inlet /outlet pressure | mpa | 0.1 /0.13 | |||||||||
| Ambient Temperature | ℃/℉ | 5～40 / 41～104 | |||||||||
| Max. moisture disposal capacity | G/h | 60 | 60 | 60 | 50 | 50 | |||||
| Motor | Power | kw/hp | 1.50/2.00 | 0.75/1.00 | 0.55/0.74 | 0.25/0.30 | 0.25/0.3 | ||||
| Voltage | VAC | 380/220 | 380/220 | 220 | 380/220 | 220 | 380/220 | 220 | 380/220 | 220 | |
| Speed | rpm | 1410 | 1425 | ||||||||
| Noise level | dB(A) | ≦63 | ≦63 | ≦63 | ≦57 | ≦54 | |||||
| Inlet/outlet diameter | mm | KF40/16×2 | KF40/16 | KF25/16 | KF25/16 | KF25/16 | |||||
| External dimension | mm | 548×359×397 | 487×316×360 | 457×290×336 | 416×245×277 | 405×225×260 | |||||
| Weight | kg | 52 | 36 | 32 | 18 | 15 | |||||
| Cooling type | / | Air cooled | |||||||||
| Others | / | With timer & air ballast | |||||||||
Performance comparison of dry vacuum pumps:
1. Vacuum degree: Dry screw vacuum pump, claw vacuum pump, oil-free scroll vacuum pump limit vacuum degree is very high, the maximum limit vacuum can reach 1-2 Pa; oil-free reciprocating vacuum pump for coarse vacuum equipment, limit vacuum degree is low, need to be matched with Roots vacuum pump to improve the limit vacuum.
2. Pumping capacity: Oil-free scroll vacuum pump due to internal structure problems, the pumping capacity is small, only suitable for small pumping capacity technology; Dry screw vacuum pump model is complete, can be applied to large pumping capacity technology, with Roots vacuum pump can meet the needs of different customers.
3. Stability: Dry screw vacuum pump performance is stable, low noise, low failure rate; Oil-free reciprocating vacuum pump structure is simple, high noise, the need for frequent replacement of slides. Because of the complex assembly of the claw vacuum pump, the rotor and shaft are not integrated, and all the faults need to be disassembled and assembled again and again, which reduces the performance and stability of the product.
4. Special treatment: Because the chemical, pharmaceutical and other related process gas will contain flammable, explosive and corrosive gases to varying degrees, so the dry vacuum pump needs special treatment. Dry screw vacuum pump internal structure is simple, two rotor, pump cavity can do anticorrosion treatment, can choose two kinds of coating nickel phosphorus and Teflon. It is difficult to do anticorrosion treatment for claw vacuum pump. It is almost impossible to do surface treatment between all levels of baffles. The anticorrosion coating on rotor surface is also easy to be damaged during assembly. Oil-free scroll vacuum pump is only suitable for the extraction of clean gas, can not extract inflammable, explosive and corrosive gas.
(The article comes from the Internet. If reprinting is not allowed, please contact our company to delete it.)