Original text - Engels - Use Description

When the blower runs loaded , the main valve disk is closed . The bellows and outlet pipeline are connected by the control valve. If the pressure exceeds the limits , the control valve open and releases air into atmosphere. The pressure in the bellows is reduced and the main valve disk starts to open . When the pressure enters the limits , the control valve closes and no more air is released into the atmosphere and the pressure in the bellows rises causing the disk valve to close fully.