Stator for a vacuum pump

A stator for a vertically oriented vacuum pump, comprising:

• a plurality of walls defining therebetween at least a part of a pumping chamber;
• a channel formed within one or more of the walls of the plurality of walls, the channel comprising a first opening at a first end of the channel and a second opening at a second end of the channel, the first opening being an opening in an internal surface of the one or more of the walls, the first opening being in fluid communication with the pumping chamber;
• and
• a pressure relief valve disposed within the channel;
• wherein the plurality of walls comprises:
• a top end wall;
• and
• one or more sidewalls extending from the top end wall, wherein the top end wall and the one or more sidewalls define an internal cavity;
• and
• an inlet channel formed through a sidewall of the one or more sidewalls for allowing a fluid to flow from an outside of the stator into the internal cavity;
• wherein:
• the channel is formed in the top end wall;
• the top end wall and the one or more sidewalls are a single, unitary item;
• the first opening is formed in an internal surface of the top end wall and the second opening is formed in the internal surface of the top end wall;
• the first opening is located at an exhaust side of the pumping chamber;
• the second opening is located at a suction side of the pumping chamber;
• and
• the top end wall comprises one or more through bores, each of the one or more through bores being for receiving a respective rotor shaft.