Spring loaded safety valve

A spring-loaded safety valve, particularly of small and medium dimensions, comprising a valve housing having an inlet port, an outlet port and an upper region functioning as an additional loading cylinder;

• a valve seat in said valve housing interposed between said ports;
• a valve member movable in said housing to and from a position in which it engages said valve seat;
• spring means permanently biasing said valve member towards said valve seat;
• single means arranged to superimpose upon the biasing force of said spring means an additional force acting upon said valve member in direction of said valve seat while said valve member is in engagement therewith, and to relieve said additional force first before the pressure in said valve reaches a predetermined valve-opening level, said single means comprising piston means engaging said spring means and movable within said additional loading cylinder so as to apply said additional force to said spring means;
• limiting means for limiting the travel of said piston means, said limiting means comprising an inner adjustable sleeve having an abutment limiting the additional loading of said spring means by said piston means by directly contacting said piston means, and an outer adjustable sleeve arranged concentrically about said inner sleeve and having an abutment limiting the travel of said piston means by directly contacting said piston means thereby limiting the lessening of the additional force and setting the predetermined valve-opening level;
• and relieving means to relieve said additional force just before the pressure in said valve reaches a predetermined valve-opening level.