A crusher includes first and second crusher bodies defining a crushing gap. A hydraulic cylinder is coupled to one of the crusher bodies to adjust a width of the crushing gap. A pressure relief valve includes a pressure chamber communicated with the hydraulic cylinder. A pressure relief piston is movable between a closed position and an open position. The pressure relief piston includes at least one piston pressure surface delimiting the pressure chamber in the closed position transversely to the actuation direction of the piston, the pressure relief piston including a surface area at an end facing away from the pressure chamber, which surface area delimits the chamber area transverse to the actuating direction of the piston to transfer a closing force to the pressure relief piston in a closing direction of the closed position when pressure is applied in a chamber area.

A hammer mountable at a rotor of a horizontal shaft impact crusher (HSi-crusher), the hammer including a front face, a rear face and at least one recess projecting inwardly into a main body of the hammer from the front face. The at least one recess being arranged to receive an attachment element to mount the hammer at a hammer lifting device.

A crusher hammer lifting device facilitates raising and lowering of a hammer mountable at a rotor of a horizontal shaft impact crusher (HSi-crusher). The device includes a main body, a mount engager for attachment to an auxiliary lifting tool and a hammer attachment for releasably mounting the hammer in a rotatable manner at the device.

The invention relates to a system for changing the hammers of a shredder including a shredder with one or more covers and a rotating drum equipped with a plurality of hammers; a lifting system suitable to move said hammers and a control unit which controls both the opening of the shredder and the movements of the lifting system and preferably also the unlocking/locking of the hammers from/on the drum to allow their replacement. The system can be managed hydraulically with a single hydraulic supply. It is included to be able to control the system remotely or to include its automation according to a maintenance plan. A relative method for changing the hammers of a shredder is also disclosed.