a decompression valve assembly is normally open thereby allowing thermal pressure build - up in an auxiliary circuit to be dissipated via a bleed path . during operation , the bleed path is sealed by a check valve , whereby high pressure flow can be fully directed to the work tool powered by the auxiliary circuit , for high system efficiency . in addition , a velocity fuse feature limits the rate of flow to the bleed path , thereby to allow for controlled release of pressure from the auxiliary circuit , as is desirable to protect against a rapidly falling load .