Relief valve isolating means

Claim 1

In a fluid pressure system having a relief valve for protecting it from over-pressure, said fluid pressure system having an exit passage for communication with the valve with a flange at the end thereof, said valve having an inlet end and an inlet passage for communication with said exit passage and a discharge outlet for connection thereto of discharge piping, an isolation system for the relief valve comprising rupture disc means isolating the relief valve from said fluid pressure system, said rupture disc means comprising a relatively thin rupturable disc having a central dome and a generally flat annular flange surrounding said dome and integral therewith at a circular transition between the outer periphery of the dome and the inner periphery of said annular flange of the disc, said dome being of smaller diameter than one of the said passages, and said rupture disc being secured in position via securement of the inlet end of the relief valve to said flange at the end of said exit passage with its dome accommodated in said one passage, and its said annular flange sealed with respect to both said passages and with said inlet end of the relief valve and said flange at the end of said exit passage closely adjacent one another without any substantial change in the position of the outlet of the relief valve from what its position would be with the relief valve installed on said flange at the end of said exit passage without the said rupture disc means, whereby said rupture disc means may be installed wiThout substantial alteration of said discharge piping, said dome being adapted to rupture at a predetermined over-pressure in said fluid pressure system to communicate said over-pressure to said relief valve, and said relief valve having a port therein for communication between the outside of the relief valve and the inside of the relief valve downstream from the disc, said rupture disc being a reverse acting disc with its dome of smaller diameter than the said exit passage of said fluid pressure system, said disc being secured in position with the dome accommodated in said exit passage with its convex side directed upstream in said exit passage, said dome being adapted to snap over in downstream direction at said predetermined overpressure, said rupture disc means further comprising knife means for cutting the dome when it snaps over, said knife means comprising at least one knife blade and an annular support for the blade, said annular support overlying the downstream face of said annular flange of the disc and being in sealed relation thereto, said annular support having an annular flange overlying the downstream face of the said annular flange of the disc, both these flanges being clamped between the inlet end of the relief valve and the said flange at the end of said exit passage, said relief valve having a counterbore at its inlet end around its inlet passage, and said annular support and knife blade being at least partially accommodated in said counterbore.