通過減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)雖有很大的(de)(de)水頭損失，但由于減(jian)(jian)少了(le)(le)水的(de)(de)浪費并使(shi)系統(tong)流量(liang)(liang)分布合(he)理、改(gai)善了(le)(le)系統(tong)布局與工況(kuang)，因(yin)此總體上講(jiang)仍是節能的(de)(de)。先(xian)(xian)(xian)(xian)導(dao)(dao)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)當減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)的(de)(de)輸出(chu)壓(ya)(ya)(ya)力(li)較高或通徑較大時(shi)，用調(diao)壓(ya)(ya)(ya)彈簧直(zhi)(zhi)(zhi)接調(diao)壓(ya)(ya)(ya)，則(ze)(ze)彈簧剛度必然過大，流量(liang)(liang)變化時(shi)，壓(ya)(ya)(ya)縮空氣(qi)、氣(qi)體減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)輸出(chu)壓(ya)(ya)(ya)力(li)波(bo)動(dong)(dong)較大，閥(fa)(fa)(fa)(fa)的(de)(de)結(jie)構(gou)尺寸也將增大。祝(zhu)茂(mao)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)門為(wei)了(le)(le)克(ke)服這些(xie)缺點，可采用先(xian)(xian)(xian)(xian)導(dao)(dao)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)。先(xian)(xian)(xian)(xian)導(dao)(dao)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)的(de)(de)工作原理與直(zhi)(zhi)(zhi)動(dong)(dong)式(shi)(shi)的(de)(de)基本相同。先(xian)(xian)(xian)(xian)導(dao)(dao)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)所(suo)用的(de)(de)調(diao)壓(ya)(ya)(ya)氣(qi)體，是由小(xiao)(xiao)型(xing)的(de)(de)直(zhi)(zhi)(zhi)動(dong)(dong)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)供給的(de)(de)。若把小(xiao)(xiao)型(xing)直(zhi)(zhi)(zhi)動(dong)(dong)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)裝在(zai)(zai)閥(fa)(fa)(fa)(fa)體內部(bu)，則(ze)(ze)稱為(wei)內部(bu)先(xian)(xian)(xian)(xian)導(dao)(dao)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)；若將小(xiao)(xiao)型(xing)直(zhi)(zhi)(zhi)動(dong)(dong)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)裝在(zai)(zai)主閥(fa)(fa)(fa)(fa)體外部(bu)，則(ze)(ze)稱為(wei)外部(bu)先(xian)(xian)(xian)(xian)導(dao)(dao)式(shi)(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)(fa)。