在使用過程中，大多數金臺機械密封都屬于接觸式密封，其機理是靠動密封環與靜密封環的接觸端面在密封流體壓力和彈性元件壓緊力的作用下緊密貼合，并相對滑動而達到密封。工作時，金臺機械密封端面上同時發生摩擦、滑動與磨損等現象，摩擦是它的基本特征。金臺機械密封端(duan)面(mian)(mian)摩(mo)(mo)擦(ca)(ca)的(de)(de)工況一般(ban)分為(wei)：流體摩(mo)(mo)擦(ca)(ca)、混(hun)合摩(mo)(mo)擦(ca)(ca)和(he)邊界摩(mo)(mo)擦(ca)(ca)三類，但不能長時間(jian)(jian)干摩(mo)(mo)擦(ca)(ca)。干摩(mo)(mo)擦(ca)(ca)狀態時，兩端(duan)面(mian)(mian)間(jian)(jian)的(de)(de)固(gu)體表面(mian)(mian)微凸(tu)體將(jiang)直接(jie)接(jie)觸而引起劇烈的(de)(de)磨損。磨損時一方(fang)(fang)面(mian)(mian)會使摩(mo)(mo)擦(ca)(ca)表面(mian)(mian)物(wu)質喪失或(huo)遷(qian)移，導致表面(mian)(mian)損壞(huai)；另(ling)一方(fang)(fang)面(mian)(mian)會產(chan)生大量的(de)(de)摩(mo)(mo)擦(ca)(ca)熱直至燒毀密封(feng)。在(zai)無流體介質的(de)(de)工況下，如何減少磨損降(jiang)低摩(mo)(mo)擦(ca)(ca)熱，那就要依靠干磨密封(feng)了。

　　干磨(mo)(mo)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)屬于(yu)浮(fu)動(dong)(dong)(dong)(dong)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)的(de)(de)一種(zhong)，常用(yong)(yong)材(cai)質為耐磨(mo)(mo)碳精(jing)，結構包括(kuo)環(huan)(huan)(huan)(huan)(huan)行(xing)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)腔體和環(huan)(huan)(huan)(huan)(huan)行(xing)軸(zhou)套，密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)腔體內(nei)(nei)有(you)環(huan)(huan)(huan)(huan)(huan)行(xing)槽，槽內(nei)(nei)至少裝有(you)二(er)個截面(mian)為矩(ju)形的(de)(de)環(huan)(huan)(huan)(huan)(huan)行(xing)石(shi)墨密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)，石(shi)墨密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)的(de)(de)內(nei)(nei)徑與環(huan)(huan)(huan)(huan)(huan)行(xing)軸(zhou)套之間有(you)0.01-0.04的(de)(de)間隙(xi)，軸(zhou)套外表面(mian)涂有(you)耐磨(mo)(mo)涂層，涂層材(cai)料一般為三氧化二(er)鋁或(huo)三氧化二(er)鉻。干磨(mo)(mo)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)有(you)時(shi)需(xu)要(yao)(yao)增加(jia)隔(ge)離氣，通常使用(yong)(yong)氮氣，氮氣耗量能控(kong)制在25-40。主要(yao)(yao)應(ying)用(yong)(yong)于(yu)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)易(yi)燃(ran)有(you)毒介質，由于(yu)操(cao)作維(wei)修簡單，密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)性好，不需(xu)要(yao)(yao)復雜的(de)(de)潤滑冷卻系(xi)統，可(ke)以干運行(xing)，得到廣泛的(de)(de)應(ying)用(yong)(yong)。干磨(mo)(mo)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)包括(kuo)有(you)外罩及架設(she)于(yu)外罩上(shang)(shang)且可(ke)呈相(xiang)對(dui)旋轉及貼合(he)的(de)(de)動(dong)(dong)(dong)(dong)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)及靜(jing)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)，靜(jing)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)與外罩固定連(lian)接，靜(jing)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)及動(dong)(dong)(dong)(dong)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)上(shang)(shang)分開設(she)有(you)供旋轉軸(zhou)安裝的(de)(de)通孔，且動(dong)(dong)(dong)(dong)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)與靜(jing)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)貼合(he)的(de)(de)端面(mian)分別為動(dong)(dong)(dong)(dong)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)面(mian)及靜(jing)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)面(mian)，外罩上(shang)(shang)設(she)有(you)促使動(dong)(dong)(dong)(dong)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)與靜(jing)密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)緊密(mi)(mi)(mi)(mi)(mi)(mi)貼合(he)的(de)(de)彈性抵壓件。除(chu)了要(yao)(yao)保(bao)持密(mi)(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)面(mian)平行(xing)之外，主要(yao)(yao)是(shi)摩擦副的(de)(de)材(cai)料問(wen)題。

　　摩擦材(cai)料應(ying)具備下列條件(jian)：

　　(1)機械強度(du)高，能耐壓和(he)耐壓力變(bian)形；

　　(2)具有耐干磨性，耐高載(zai)荷性，自潤滑(hua)性好(hao)；

　　(3)配對(dui)材料的磨合(he)性好(hao)，無過(guo)大(da)的磨損和對(dui)偶腐蝕；

　　(4)耐(nai)磨(mo)性(xing)好，摩擦材料雖(sui)然是易損件，起到保(bao)護制(zhi)動(dong)(dong)或(huo)(huo)傳動(dong)(dong)裝(zhuang)置的(de)(de)作用，但要(yao)求具(ju)有一定的(de)(de)耐(nai)磨(mo)性(xing)，使(shi)用壽(shou)命盡(jin)量要(yao)長，刮傷、腐蝕和(he)粘附對偶，都會造成制(zhi)動(dong)(dong)或(huo)(huo)傳動(dong)(dong)的(de)(de)震動(dong)(dong)和(he)不穩定；

　　(5)導(dao)熱(re)性(xing)和散(san)(san)熱(re)性(xing)好(hao)(hao)，導(dao)熱(re)性(xing)是傳導(dao)熱(re)量的能力大小，即包(bao)括吸熱(re)，也包(bao)括散(san)(san)熱(re)，所以，導(dao)熱(re)性(xing)好(hao)(hao)的必(bi)然散(san)(san)熱(re)性(xing)也好(hao)(hao)；

　　(6)抗(kang)熱裂性好，根本解決抗(kang)熱裂性問題可能需(xu)要改變(bian)封(feng)孔方(fang)法；

　　(7)耐(nai)腐蝕(shi)性強，一(yi)些(xie)有色金屬合金能將良好(hao)的摩擦學(xue)特性與有些(xie)流體的耐(nai)腐蝕(shi)性結合；

　　(8)線膨脹(zhang)系數(shu)小(xiao)，熱(re)膨脹(zhang)會造成摩擦材(cai)料與摩擦對偶之間(jian)的間(jian)隙(xi)過(guo)小(xiao)，發生拖摩，損毀制動(dong)、傳動(dong)裝置。