Sealing coring tools mainly consists of external threaded adapter, balance piston, limit joint, inner and outer barrel, core catcher, locating pin, sealing head and coring bit.

Hydraulic valve block balance weight piston sleeve has thin wall, high precision of geometry dimension and strict roughness, and its quality determines the lifetime of balance weight directly.

Rotary piston pump is a volume type vacuum pump and is applied widely, but there has been no method for exactly calculating dynamic balance of rotary piston up to the present.