Iyo valve ndeye undidirectional control element.Kana Uchipfuura vharafu, svikiro rekushanda rinogona kungoyerera richitevedza gwara rakapihwa.Mukushanda, kana iyo medium pressure direction yachinja.Ivhavha inoshanda kumisa kudzoka kwe meduim muhurongwa.Naizvozvo, chigadzirwa chinonziwo chisiri-kudzoka vharafu.