Bolt cover, structure of flip-chip balanceable pressure and light on/off operation. There is an oil groove setting on the body and plug seal surface. lt can realize the highPerformance of sealing by injecting the sealant through the check valve on theaxis.Bolted body and bonnet connection is used, And there is an adjusted gasketbetween the body and bonnet which should not only ensure the sealing effectsbetween the body and bonnet but also between the plug and body.