The company Vakuum-Härterei Petter GmbH (VHP) in Quickborn, Germany conducted an evaluation in which an oil lubricated rotary vane vacuum pump was replaced by a Busch COBRA NX screw vacuum pump.

The vacuum pump was installed as the forepump of a 3-stage system to supply a heat treatment oven, and the objective of the evaluation was to find an efficient alternative to the vacuum generators previously used.

During the one year testing period no servicing work was carried out. The power consumption remained the same as the old vacuum pump, but the substantially increased pumping speed allowed heat treatment processes to be carried out more rapidly. The low noise levels generated by the COBRA NX test unit were also a pleasant surprise. In future VHP says that it will invest only in ovens equipped with COBRA NX screw vacuum pumps.

The dry-compressing vacuum pump is a new development by Busch, and has been designed specifically for heat treatment applications. No operating fluids are present in the compression chamber, making contact between the pumped medium and oil or other operating fluids impossible. This is achieved by two screw profiles which contra-rotate in the compression chamber without making contact with each other or the housing. This simple construction makes the COBRA NX a robust and economical forepump for the vacuum supply system.