Dry Vacuum Systems for Centralization of Vacuum Supply

Maulburg, Germany The concept, design and realization of central vacuum supplies is one of Busch Vacuum Pumps and Systems' core competencies. Thousands of such vacuum systems are in operation worldwide. A wide range of operating principles for generating vacuum in the individual pump modules are applied. In addition to oil-lubricated R 5 rotary vane vacuum pumps, dry-compressing vacuum modules can be used, for example in vacuum systems with COBRA NX screw vacuum pumps. The operators of these central vacuum supply systems value the absolutely clean exhaust air, which is entirely free of contaminants, the extremely low maintenance effort involved, and the energy-efficient operation in conjunction with pumping speeds and vacuum levels adjusted precisely to process requirements.
Fig. 1: Central vacuum system with COBRA NX screw vacuum pumps and Panda vacuum boosters. Source: Busch Dienste GmbH
Fig. 1: Central vacuum system with COBRA NX screw vacuum pumps and Panda vacuum boosters. Source: Busch Dienste GmbH

The centralization of vacuum supply in a plant should be seriously considered if multiple processes or machines require vacuum. With the COBRA NX screw vacuum pump, Busch is able to configure complex vacuum systems for many applications. These vacuum systems are used whenever absolutely clean exhaust air is required or when contamination between the pumped medium and an operating fluid must be avoided at all costs. This is the case when a house vacuum is generated in research and development departments, laboratories, production areas in the semiconductor industry, or in areas where hygiene is critical such as in the pharmaceutical industry. 

Busch tailors the design of such a central vacuum system (Fig. 1) to the specific application. The main modules are COBRA NX screw vacuum pumps whose working principle does not require operating fluids. Vacuum systems such as these can be adapted to the required pumping speed by selecting the appropriate size and number of COBRA NX screw vacuum pumps. By also using vacuum boosters, it is possible to cost-efficiently and effectively increase pumping speed and vacuum level (Fig. 2). 

Fig. 2: Pumping speed of a vacuum pump combination of backing pump and vacuum booster. Source: Busch Dienste GmbH

COBRA NX screw vacuum pumps (Fig. 3) can be operated without operating fluids since the moving parts do not come in contact with each other. In the cylinder of the vacuum pump, the screw rotors rotate in opposite directions. The pumped medium is trapped between the cylinder and screw chambers, compressed, and transported to the gas outlet. There is a very small clearance between the screws and the housing so that the individual components do not touch. This means that there is no friction, which would otherwise require a lubricant be used in the compression chamber. The newly developed screw profile and the unimpeded gas discharge ensure even temperature distribution throughout the pump body, which leads to a lower thermal load and a longer life cycle.  

Fig. 3: Cutaway drawing of a COBRA NX screw vacuum pump. Source: Busch Dienste GmbH

COBRA NX screw vacuum pumps require a lower motor power per se than oil-lubricated vacuum pumps or liquid ring vacuum pumps. A further advantage is that COBRA NX screw vacuum pumps can be equipped with a frequency-controlled motor, which enables demand-driven operation. This can lead to further considerable energy savings as compared with a decentralized vacuum supply. In decentralized vacuum supply, every individual vacuum pump must be designed to meet the maximum demand at the respective consumer. However, in practice, it is often the case that the maximum power is seldom required simultaneously by all vacuum consumers. The central vacuum system control allows only the number of vacuum pumps to be in operation as is required for the actual demand. Through frequency control these can be powered down even further. By using this dry vacuum technology and demand-driven control, central vacuum systems can achieve energy savings of up to 60 percent.

In addition to energy savings, there is also a reduction in operating costs: maintenance is reduced to a minimum thanks to contact-free operation. Only the gear oil has to be changed every 8,500 operating hours or once a year. COBRA NX screw vacuum pumps are water-cooled. This enables the easy use of pump waste heat. All vacuum pumps can, for example, be connected to a common cooling water circuit and cooled via a heat exchanger, thereby generating warm water for other applications in the plant.

Central vacuum systems must always be individually adjusted to the application and the specific circumstances on site. Busch vacuum experts have many years of experience in the design and realization of such facilities in a wide variety of industries.

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