Mechanical seal fitted to cooling water pump - has auxiliary static seal for protection during high pressure testing using piston pushed against flange

摘要

The seal is intended for radioactive cooling water pumps in atomic power stations. Between the mechanical seal (8) and the pump chamber (6) the shaft (4) carries a flange (12) with an axial face (14). A sealing piston (18) surrounds the flange and presses on the axial face of the flange with a corresponding lapped face and can slide in the housing (22) of the mechanical seal. When the pump is put under a high test pressure the piston (18) is pushed against the flange by the test pressure and any liquid escaping across the seal face is drawn off through passages (30) in the seal housing. When the pump pressure returns to normal an axial spring (26) in the housing pushes the piston (18) away from the flange (12).