Patent ID: 7878256

Claim:
A burst plug for positioning in a downhole fluid passage, the burst plug comprising: a shear disc installable in a sealing position in the fluid passage, blocking fluid flow through the passage and being releasable from the sealing position to a fluid flow-restricting position by applying fluid at a burst pressure against the shear disc, the flow-restricting position restricting fluid flow through the passage; a first part having a shear disc retaining position to retain the shear disc in the fluid flow restricting position after the shear disc is removed from the sealing position and the first part is in communication with the burst pressure; and the first part thereafter assuming a shear disc removal position when fluid in communication with the first part is reduced to a selected pressure lower than the burst pressure, the shear disc being expellable from the passage while the first part is in the shear disc removal position and the fluid in communication with the first part is at the selected pressure.