Introduction to Volm vacuum pumps

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The DMB series of Roots vacuum pumps – Roots vacuum pumps (also simply referred to as Roots pumps) work by using two octagonal-shaped rotors that rotate within the pump casing to create suction and exhaust action. Its principle is similar to that of a Roots blower. Since rotary vane pumps are pumps without internal compression, single-stage pumps typically have a very low compression ratio; therefore, they need to be used in series when applied to medium and high vacuum conditions. Generally speaking, rotary vane pumps have the following characteristics: they exhibit a high pumping speed over a wide range of pressures ； Fast to start up, ready to work immediately ； Compact in structure, occupying little floor space; it has a horizontal design with vertical gas flow within the pump chamber, which facilitates the removal of the dust or condensate to be pumped out ； There are gaps between the rotors, as well as between the rotor pump and the chamber walls. The moving parts inside the pump experience no friction, so no lubrication is required; there is no oil in the pump chamber ； The rotor has a symmetrical shape, excellent dynamic balance, and smooth operation; high-precision gear drives are used, resulting in low noise during operation ； Low mechanical friction loss, high efficiency ； Operating and maintenance costs are low. DMY series rotary vane vacuum pumps: The DMY series of rotary vane pumps is an upgraded version of the DMB series, equipped with a bypass relief valve that provides overpressure protection for the pump. At the same time, this series of Roots pumps is designed to handle severe corrosion in chemical processing environments, as well as situations where the medium to be pumped tends to coking and requires online cleaning. The overcurrent components are made of duplex steel to withstand severe corrosion conditions ； By using a 5-point mechanical seal, zero leakage can be achieved ； The overcurrent components of the vacuum pump can be cleaned and soaked with solvents online. The DML series air-cooled Roots pumps transfer the heat generated during the compression process of the Roots pump to the rotor and the pump body. It is difficult for the rotor to transfer heat outside the pump, while the heat from the pump body can be easily dissipated into the surrounding atmosphere. As a result, a temperature difference arises between the rotor and the pump body, exacerbating the thermal expansion of the rotor. As the pump load increases, the rotor expansion eliminates the gap, causing it to get stuck. As a result, air-cooled Roots pumps were developed, which use cooled gas or atmospheric air to directly cool the hot rotor, thereby reducing the temperature difference between the rotor and the pump casing and enhancing the heat resistance of the Roots pump. It can be connected in series with a preceding pump to form a Roots unit, achieving significant energy-saving effects. Compared to ordinary Roots pumps, the DML air-cooled Roots vacuum pump can operate at high pressure differences, allowing the use of a pump with lower performance as a pre-pump and thus achieving energy savings. Wide range of applications. It can be used to operate under conditions of high pressure differences and high compression ratios. Since the exhaust side can withstand high pressures, this design effectively solves the problems of overload and overheating that occur in conventional Roots vacuum pumps due to excessive pressure differences and poor vacuum levels in the pre-pump. The pump has a simple structure, with the cooler connected to the pump’s outlet, which facilitates maintenance and replacement ； Thanks to uniform heat dissipation, the gap between the rotor and the pump body can remain very small, which helps improve the volumetric efficiency of the pump. When venting to the atmosphere, the maximum pressure of the small pump can reach 200 hPa, while that of the large pump can reach 100 hPa; if the two are connected in series, a maximum pressure of 20–30 hPa can be achieved. Sealing methods: expansion ring sealing and mechanical sealing. Mechanical seal, silicon carbide against graphite, non-enclosed type. The entire series comes with mechanically sealed shaft sleeves. The machine seal rubber ring is made of perfluoroether or fluororubber. Working principle of double-diaphragm coupling with intermediate section. The working principles of air-cooled Roots vacuum pumps with two-lobe wide-head and three-lobe rotors are shown in Figures 1-1 and 1-2. The rotor and the pump body create three phases. When the rotor is in communication with the intake port, the rotor head isolates the intake port from the exhaust port and the cooling air port, allowing gas to be drawn in. When the left rotor rotates counterclockwise by a certain angle, the working chamber is sealed (isolated from the air inlet, the refrigerant return port, and the exhaust port). The rotor continues to rotate, and the working chamber becomes connected to the cooling air inlet; cold air flows into the working chamber, causing the pressure inside it to reach that of the cooling air inlet. It then connects to the working chamber and exhausts air. When the rotor closes the intake port, the pump chamber is first connected to the refrigerant return port; once the cold air returning fills the pump chamber automatically due to the pressure difference between the intake and exhaust ports (with the pressure inside the pump chamber rising from P to P Exhaust), the exhaust port is then connected. The cold air is provided by the heat exchanger installed below the exhaust port. This design allows the heat generated by compression to be balanced by cold air, preventing the pump from overheating and overloading; as a result, the Roots vacuum pump can operate at high pressure differences (8.7×104 Pa) and discharge directly into the atmosphere. Water ring vacuum pump TCM two-stage cone water ring pump. The two-stage cone pump is a vacuum pump designed for the high-vacuum industry and meets HEI standards. It is a further improvement based on the original two-stage flat disc pump. The inlet and outlet of the flat-type vacuum pump are designed on the end face, adopting a structure with intake at the top and exhaust also at the top. The inlet and outlet of the cone-type vacuum pump are designed on the cone, featuring an upper inlet and a lower outlet configuration. The special design of the structure results in a much larger area ratio between the inlet and outlet ports in a conical shape compared to those in a flat design. Planar vacuum pumps have a small intake area, resulting in a low volume of air intake. During intake, gas enters the impeller chamber from the end face; poor airflow directly affects the pumping volume. Pumps are sensitive to water vapor in the inlet gas, which has a significant impact on their efficiency; therefore, it is not possible to spray cooling water at the pump inlet to condense the condensable gases in the inlet gas. The conical opening of the cone-type vacuum pump serves as the air intake, which increases the air intake area and thus the amount of air drawn in ； The conical opening extends deep into the impeller chamber, allowing air flow to enter the pump body smoothly and thus increasing the pumping capacity. The pump is not sensitive to water vapor present in the intake air, so its efficiency decreases only slightly. Therefore, cooling water can be sprayed at the pump inlet to condense the condensable gases; the water formed as a result enters the pump body, with only minimal reduction in the pump’s efficiency. Meanwhile, the volume of gas drawn into the pump decreases due to this condensation, further enhancing the pump’s pumping capacity. This unique combination of a conical-shaped opening and a condensation nozzle provides additional pumping capacity, and this design is key to selecting an appropriate pump capacity and reducing the power consumption of the vacuum pump. The vacuum pump features a large cone opening and smooth flow channels, resulting in low resistance to air and water flow. Water and air can mix directly; by condensing saturated air, the pumping capacity of the vacuum pump is increased, the suction temperature is reduced, and cavitation is minimized. Circular pump body. 2BE1 elliptical pump body. 2BV/2BE3 and TCM circular pump housings. The eccentric design of the impeller helps to balance the forces acting on the bearings (which is the difference between the operating pressure and the weight of the impeller, whereas in flat-disc pumps it is the sum of the operating pressure and the weight of the impeller), thereby reducing power consumption and lowering the starting current. In a horizontal vacuum pump, the impeller is located near the upper end of the casing, with the exhaust port situated at the upper part of the pump. During operation, the compressive force generated by the horizontal vacuum pump acts from top to bottom; thus, the force acting on the shaft is the sum of the compressive force and the weight of the impeller. In a conical vacuum pump, the impeller with its opening is positioned near the lower part of the casing, with the exhaust port at the lower side of the pump. When gas is compressed, the compressive force acts from bottom to top, which helps to counteract part of the weight of the impeller. As a result, the force on the shaft is smaller, and the lifespan of the shaft is longer compared to that of a horizontal vacuum pump. Two-stage cone vacuum pump: its patented two-stage cone design prevents bubbles from accumulating on the metal surface, allows it to withstand low pressures, and enables timely expulsion of these bubbles without rupture. This approach fundamentally avoids the impact of the working fluid on the root of the impeller caused by bubble rupture, thereby preventing erosion damage. The patented special GSV vacuum bucket design for the cone section allows the gas flowing back from the exhaust port to return to that port via drainage channels, enabling the vacuum pump to achieve an ultimate vacuum level of 2700 PaA. Radial exhaust, cone-shaped structure design, high efficiency and energy saving ； One impeller achieves two-stage compression; it has a simple structure, reduces radial forces, and generates no axial forces ； Reliable mechanical seal, available in single-face, double-face, and modular types ； The conical-shaped air intake and exhaust ports reduce the risk of scaling, making them suitable for use in environments with poor water quality ； The working fluid is distributed evenly within, preventing noise, vibration, and overload caused by overcompression ； The anti-startup pre-pumping over-compression design can improve efficiency and reduce pre-pumping time ； Reliable axial positioning design simplifies the complicated gap adjustment, making maintenance easier ； Various transmission methods are available, with couplings, belts, and reducers as options. SME small water ring pumps/compressors are suitable for explosion-proof applications with an exhaust volume of 200 m3/h or less. It features a low water flow rate and low power consumption design, thereby **reducing** operating costs. It also avoids the motor’s rated operating point, thereby extending the pump’s service life. High quality and small size are the main features of this series of pumps. The ultimate vacuum can reach 3100 PaA. The SM features a co-axial design for the pump and motor, resulting in a compact structure and small size. The SME features a direct connection structure for pumps, and can be equipped with explosion-proof motors, offering high adaptability ； Equipped with a reliable mechanical seal, suitable for harsh operating conditions ； Standard motors are used, facilitating maintenance and replacement ； The unique structural design ensures that the shaft does not come into contact with the medium, preventing corrosion ； The entire series is made of stainless steel, suitable for corrosive environments ； Variable exhaust port design, suitable for gas compression ； Castings are precision cast and then heat-treated. The leaves are densely packed and have a curved design. Its strength is higher than that of 2BV straight blades. Therefore, it can be used as a compressor. HPM high-pressure liquid ring compressors are designed specifically for compressing toxic, corrosive, and explosive gases. It is particularly suitable for the compression and recovery of flare gas in petrochemical refineries and chemical plants ； Compression of dry and wet chlorine gas ； Hydrogen compression ； Conditions such as oil and gas recovery. An oval-shaped double-acting casing, allowing the impeller to complete two suction and two discharge cycles per rotation. Single-stage, double-suction, double-row design with radial force balance mechanism ； Conical distributor with larger inlet and outlet areas, allowing solid particles and liquids to be entrained in the gas ； Nearly isothermal compression ； Modular mechanical seal, with balanced single-face/double-face options available ； Multiple seal fluid supplies to prevent gas backflow ； Designed to withstand pressures of 2.0~5.0 Mpa, with high reliability. 2BE1 series water ring vacuum pumps: The 2BE1 type water ring pump is an energy-saving product developed by utilizing technology from German company Siemens. It adopts a single-stage, single-acting design, offering the advantages of simple structure, reliable operation, and high efficiency along with energy savings. Suitable for processes such as vacuum concentration, vacuum dehydration, vacuum decolorization, vacuum drying, vacuum preservation, vacuum storage, vacuum transportation, vacuum molding, vacuum filtration, vacuum water pumping, and vacuum degassing, the water ring pump has the following advantages over other mechanical vacuum pumps: it has a simple structure, does not require high manufacturing precision, and is easy to process ； It has a compact structure, with a high rotation speed; it can generally be connected directly to the motor without the need for a reduction gear. Thus, a small physical size enables a large pumping capacity, resulting in minimal floor space required ； Compressed gas is essentially isothermal, meaning that the temperature changes very little during the compression process ； There are no metal friction surfaces inside the pump chamber, so no lubrication is required within the pump, and wear is minimal. The sealing between the rotating part and the fixed part can be achieved directly by a water seal ； It features even air intake, stable and reliable operation, simple handling, and easy maintenance. Disadvantages of water ring pumps: Low efficiency, generally around 30%, with better models reaching up to 50% ； The low vacuum level is due not only to structural constraints but, more importantly, to the saturated vapor pressure of the working fluid. Using water as the working fluid, the ultimate pressure can only reach 2000~4000 Pa. Using oil as the working fluid, a pressure of 130 Pa can be achieved. The 2BE1S series water ring vacuum pumps – these single-stage water ring pumps are suitable for inlet pressures ranging from 130 to 1013 KpaA, with a compression ratio of approximately 1:7. When the inlet pressure is below 130 KpaA, it is recommended to use the 2BE1S series two-stage water ring vacuum pump. Its main feature is that it maintains a high pumping speed even at high vacuum levels, with stable operating conditions. In a two-stage pump, the two pump chambers are connected in series, with a volume ratio of the working chambers of approximately 2.5:1. The 2BV series water ring vacuum pumps feature a direct-drive design, making them easy to install and maintain. It features a flexible exhaust port design that can automatically adjust the appropriate exhaust port opening based on the actual inlet pressure of the pump, thereby preventing over-compression. Unique motor stainless steel shaft design. The pump and the motor are coaxial, so the shaft will not corrode either. The cavitation protection device ensures the safe and reliable operation of the pump at pressures below 8 Kpa (A). Lip seal of screw vacuum pump: The sealing action of the lip seal is achieved through a tight fit between a flexible sealing element (PTFE composite graphite) and the rotating shaft. Its sealing mechanism is such that on the contact surface between the lip seal and the shaft, dry friction, boundary lubrication, and fluid lubrication coexist simultaneously and alternate continuously. Dry friction causes wear, while fluid lubrication leads to leakage. In the case of boundary lubrication, a stable hydrodynamic oil film is formed at the interface between the lip seal and the shaft; the thickness of this oil film is approximately 0.0025 mm. In addition to its lubricating function, this oil film also serves as a seal. If the oil film is too thick, the fluid will leak ； If the oil film is too thin, a fluid lubrication film cannot be formed, and the lip seal will wear out. With the worn lip seal, when the pump stops operating, the seal between the lip and the shaft is not reliable. If the gas being drawn in would condense into a liquid at normal temperature and pressure, and if the liquid is not discharged from the discharge end of the screw pump in a timely manner, it can enter the gearboxes at the front and rear, contaminating the lubricating oil inside them; common issues include the emulsification of the lubricating oil ； Mechanical seal: The mechanical seal is a new type of sealing mechanism for screw pumps that our company has developed to address the harsh operating conditions in chemical production. This type of screw pump has a total of five mechanical seal points: four at both ends of the main and drive shafts as well as at the seal locations in the pump chamber, and one point at the coupling location on the drive shaft – making a total of five points. The mechanical seal features a balanced design, and all the O-ring materials used in it are perfluoroether-based, enabling it to handle most corrosive media. After the mechanical seal is installed, the elastic force of the spring is used to overcome the frictional resistance between the compensating ring and the auxiliary sealing ring and the shaft, so that the end face of the compensating ring presses tightly against the non-compensating end face. Due to the high flatness and low roughness of the end faces, under the force of the spring, a boundary friction or semi-liquid friction condition arises between the relatively sliding end faces, which is sufficient to prevent significant leakage of the pressurized fluid, thereby achieving primary sealing. A mechanical seal achieves axial end-face sealing by means of the pre-tensioning of the friction pair between the stationary and rotating rings through elastic elements, as well as the compressive force exerted by those elastic elements. Pumps of this type use external oil tanks and oil pumps, which allows the leakage amount to be kept very low. Thanks to the continuous flushing by gear oil, heat and impurities between the friction pairs can be removed in a timely manner, ensuring the safe operation of the pump. Operating conditions for lip seals: dry and clean gases, such as in electronics factories ； Operating conditions for mechanical seals: corrosive gases containing moisture, gases containing particles, gases containing large amounts of liquid components that will condense at normal temperature and pressure, and solvent recovery units. Differences between mechanically-sealed screw pumps and ordinary screw pumps: In terms of appearance, the bottom of the pump is equipped with an oil pump, oil tank, heat exchanger, oil flow switch, etc. In terms of performance: A mechanical seal allows liquid to remain within the pump chamber, and the oil on both ends does not get emulsified. There is no need to change the oil frequently. There should be no liquid in the pump chamber with lip seals; especially when flushing, the addition of solvents can cause the oil in the oil chambers at both ends to become emulsified and lose its effectiveness. In terms of service life: Mechanical seals, thanks to the external forced circulation mechanism which provides cooling and filtering functions, significantly extend the service life of the seal; under normal conditions, this service life can reach 25,000 hours. Given that the suction medium contains corrosive and gelling components, a liquid solvent must be introduced into the pump chamber to clean it. If there is a seal leakage, the oil chamber is prone to oil emulsification; therefore, our company’s improved mechanical seal design screw vacuum pump is recommended.