8 OPERATION No D. 453-0: Checking and adjusting the brake control. IV. CHECKING THE SECURITY VALVE PRESSURE SWITCH. IMPORTANT NOTE : Use exclusively test bench 3654 -T for mineral fluid LHM. (this bench is painted green ) and its ties 3655-T (pipes and pressure gauges bear a green marking ) 15. Connect the security valve feed opening (a) to bench pump opening (c). Seal the three other valve openings (b, d, e) by means of plugs.