Abstract: For the parallel vacuum system composed of more than two pumps, the total pumpage always shows a certain decline compared with the sum of the rated pumpage of every single pump. This causes difficulty for precise design of vacuum systems. A testing assessment method of the pumping performance for large parallel vacuum systems was presented in this paper. The mathematic model was built to describe the pumping performance of parallel vacuum systems, and two important indexes, the total pumpage and the decline of average individual pumpage, were defined and analyzed. For the engineering feasibilities, the means by which the total pumpage could be predicted with the data from a small parallel system was explored, and the corresponding small test model, procedure and measurement were determined. Based on the small parallel system test data, the total pumpage of the large parallel system was predicted by two different means. The results show that the testing assessment method can realize accurate prediction of the pumping performance for the large parallel vacuum system with a relative low testing cost.

Key words: parallel vacuum pump, total pumpage, decline of average individual pumpage