Cartridge-type direct loaded safety and pressure-relief valve having flow path for preventing supersonic flow and minimizing valve hysteresis

A safety and pressure relief valve, comprising:

• a seat means, a poppet means, and a skirt means which are all movable relative to each other;
• said poppet means normally being seated on said seat means and being liftable therefrom to provide an escape orifice when a pressure differential across said poppet means reaches a predetermined level;
• said skirt means being movable between an operative position which it occupies during lifting of said poppet means and a retracted position which it occupies during reseating of said poppet means, said skirt means when in its operative position being operable to reduce the flow of fluid downstream of said escape orifice to prevent the velocity of fluid in the valve from becoming supersonic.

A safety and pressure relief valve, comprising:

• first pressure sensitive means, mounted to move relative to a valve seat, for permitting fluid flow through the valve;
• and
• second pressure sensitive means, mounted to move relative to said first pressure sensitive means as said first pressure sensitive means moves relative to said valve seat, for substantially controlling supersonic flow proximate said first pressure sensitive means.