A lever safety valve consists of a valve body that has flange fixed to the steam boiler. The valve seat made of bronze is screwed to the body. The valve seat contains the valve which is also made up of bronze. Since the valve seat and valve is made up of same material, the rusting is prevented. The strut transmits the thrust on the valve. One end of the lever is fixed as fulcrum. Other end is attached to the load. A guide is also provided to move the lever vertically.
- In lever safety valve, during the normal pressure inside the boiler, the valve remains in the seat. The thrust applied by the strut made the valve to stay in the seat until the steam pressure exceeds the safe working pressure.
- As the steam pressure inside the boiler exceeds the safe working pressure, the valve rises above the seat and steam blows off outside the boiler. The valve returns back to its normal position when the pressure inside the boiler falls back to its normal pressure.
- The valve rises in the condition when the steam pressure force becomes greater than the thrust applied by the strut on the valve. The thrust on the valve can be varied by varying the load attached at one end of the lever.