Vacuum pressure control system

A vacuum pressure control system comprising:

• a vacuum open-close valve placed between a vacuum chamber and a vacuum pump for exhausting gas from the vacuum chamber, and provided with a valve element and a valve seat which the valve element contacts with or separates from, the vacuum open-close valve being configured to control a pressure value in the vacuum chamber by adjusting an opening degree of the valve element;
• and
• a controller configured to output an opening-degree command value to the vacuum open-close valve to command the opening degree required to adjust the pressure value to a target value,
• wherein the vacuum open-close valve includes a drive unit that provides driving force to the valve element based on the opening-degree command value,
• the drive unit includes:
• a drive shaft connected to the valve element;
• a piston connected to the drive shaft on an opposite side from the valve element;
• a cylinder provided with a piston chamber in which the piston is housed;
• and
• a bellofram that is retained by the piston to partition the piston chamber, the controller is provided with an abnormality detection program configured to:
• calculate an opening degree difference, which is a difference between the opening-degree command value outputted to the vacuum open-close valve and an actual opening degree of the valve element driven by the opening-degree command value;
• and
• determine that the bellofram is damaged when the opening-degree difference is a first predetermined threshold value or more.