Hydraulic circuit for longwall support

A hydraulic circuit for longwall support for use in underground mining for supporting a longwall by means of a plurality of support shields where each support shield is equipped with hydraulic cylinder/piston units to perform the support functions for removing the timbering, progressing, setting and where each cylinder/piston unit is by means of an unblockable check valve (load maintaining valve) and a pressure line connected with a shield control valve and, upon demand by the shield control device that is assigned to each support shield, is either connected by the shield control valve with the pump line or, when the check valve is simultaneously unblocked, is connected with the return line, or is blocked against the pressure line by the check valve,

• wherein the annular piston line of each cylinder/pinto unit is monitored by means of a pressure sensor, which in turn activates a pressure deviation signal when a predetermined maximum pressure is reached, which causes the entire longwall to be depressurized by means of a longwall shut-off valve, and wherein the pressure deviation signal is locked against the triggering signal of the hydraulic valves in such a manner that the pressure deviation signal does not cause the longwall shut-off valve to become depressurized if a triggering signal is present.