Patent ID: 9695814
Date: 2017-07-04
CPC Classifications: F04B,F04D,Y02B,Y10T

Claim:
1. A method of reducing noise generated by a vacuum pumping system operating to evacuate a chamber, the method comprising the steps of: operating a booster pump of the vacuum pumping system at a rated speed while a valve between an inlet to the vacuum pumping system and the chamber is open to reduce chamber pressure to a first pressure; determining that a pressure in the chamber increased to a second pressure that is higher than the first pressure while the pressure at the inlet of the vacuum pumping system remained at the first pressure due in part to the valve being closed; determining that the closed valve is going to open such that the pressure at the inlet of the vacuum pumping system is going to change to the second pressure; in response to determining that the pressure at the inlet of the vacuum pumping system is going to change to the second pressure, reducing the speed of the booster pump to a second speed that is below the rated speed; and then increasing the speed of the booster pump to the rated speed when the pressure at the inlet of the vacuum pumping system increases from the first pressure when the valve is opened.