在使用過程中，大多數龍安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，龍安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。龍安機械密封端面(mian)摩(mo)(mo)擦(ca)(ca)的(de)工況一(yi)般分(fen)為：流體(ti)摩(mo)(mo)擦(ca)(ca)、混(hun)合摩(mo)(mo)擦(ca)(ca)和邊(bian)界摩(mo)(mo)擦(ca)(ca)三(san)類，但不能長時(shi)間(jian)干(gan)(gan)摩(mo)(mo)擦(ca)(ca)。干(gan)(gan)摩(mo)(mo)擦(ca)(ca)狀態時(shi)，兩端面(mian)間(jian)的(de)固體(ti)表面(mian)微凸體(ti)將直接接觸而引起(qi)劇烈的(de)磨(mo)損。磨(mo)損時(shi)一(yi)方(fang)面(mian)會使摩(mo)(mo)擦(ca)(ca)表面(mian)物質喪失或遷(qian)移，導致表面(mian)損壞；另一(yi)方(fang)面(mian)會產生大量的(de)摩(mo)(mo)擦(ca)(ca)熱直至燒毀密(mi)(mi)封(feng)。在無流體(ti)介質的(de)工況下，如何(he)減少磨(mo)損降低(di)摩(mo)(mo)擦(ca)(ca)熱，那就要(yao)依靠干(gan)(gan)磨(mo)密(mi)(mi)封(feng)了(le)。

　　干(gan)磨(mo)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)屬于浮動密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)的(de)(de)一(yi)種(zhong)，常用(yong)材質(zhi)為耐磨(mo)碳精，結構包括環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)行(xing)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)腔體和環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)行(xing)軸(zhou)套，密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)腔體內有(you)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)行(xing)槽，槽內至少裝(zhuang)有(you)二(er)個截面(mian)為矩形的(de)(de)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)行(xing)石墨密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)，石墨密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)的(de)(de)內徑與(yu)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)行(xing)軸(zhou)套之(zhi)間有(you)0.01-0.04的(de)(de)間隙，軸(zhou)套外(wai)表面(mian)涂有(you)耐磨(mo)涂層，涂層材料(liao)一(yi)般(ban)為三(san)氧化(hua)二(er)鋁或三(san)氧化(hua)二(er)鉻。干(gan)磨(mo)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)有(you)時(shi)需(xu)要增加隔離氣，通(tong)(tong)常使用(yong)氮氣，氮氣耗量能控制在(zai)25-40。主(zhu)要應用(yong)于密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)易燃(ran)有(you)毒介(jie)質(zhi)，由于操(cao)作維修簡(jian)單，密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)性好(hao)，不(bu)需(xu)要復雜(za)的(de)(de)潤(run)滑冷卻系統，可以干(gan)運(yun)行(xing)，得到廣泛的(de)(de)應用(yong)。干(gan)磨(mo)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)包括有(you)外(wai)罩及架設于外(wai)罩上且可呈(cheng)相對(dui)旋轉及貼合(he)的(de)(de)動密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)及靜(jing)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)，靜(jing)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)與(yu)外(wai)罩固定(ding)連接，靜(jing)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)及動密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)上分(fen)開設有(you)供旋轉軸(zhou)安裝(zhuang)的(de)(de)通(tong)(tong)孔，且動密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)與(yu)靜(jing)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)貼合(he)的(de)(de)端(duan)面(mian)分(fen)別為動密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)面(mian)及靜(jing)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)面(mian)，外(wai)罩上設有(you)促使動密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)與(yu)靜(jing)密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)(huan)(huan)緊(jin)密(mi)(mi)(mi)貼合(he)的(de)(de)彈(dan)性抵壓件。除了要保持密(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)(feng)面(mian)平(ping)行(xing)之(zhi)外(wai)，主(zhu)要是(shi)摩擦副的(de)(de)材料(liao)問(wen)題。

　　摩(mo)擦材(cai)料應具備下列(lie)條件：

　　(1)機械(xie)強度(du)高(gao)，能耐壓和耐壓力變(bian)形；

　　(2)具有耐干磨性，耐高載荷性，自潤滑性好；

　　(3)配對(dui)材料的(de)磨(mo)合性(xing)好，無(wu)過大的(de)磨(mo)損和(he)對(dui)偶腐(fu)蝕；

　　(4)耐(nai)磨(mo)(mo)性好，摩擦材(cai)料雖然是易損件，起(qi)到保護制動(dong)(dong)或傳動(dong)(dong)裝置的作(zuo)用，但要求具有一定(ding)(ding)的耐(nai)磨(mo)(mo)性，使(shi)用壽命(ming)盡量要長(chang)，刮(gua)傷、腐蝕和(he)粘(zhan)附(fu)對偶，都(dou)會造成(cheng)制動(dong)(dong)或傳動(dong)(dong)的震動(dong)(dong)和(he)不穩定(ding)(ding)；

　　(5)導熱(re)性(xing)(xing)和(he)散熱(re)性(xing)(xing)好，導熱(re)性(xing)(xing)是傳導熱(re)量的能力大小(xiao)，即包括吸熱(re)，也(ye)包括散熱(re)，所以，導熱(re)性(xing)(xing)好的必(bi)然散熱(re)性(xing)(xing)也(ye)好；

　　(6)抗熱裂(lie)性(xing)好，根(gen)本解決(jue)抗熱裂(lie)性(xing)問題可能需要(yao)改變封孔方法；

　　(7)耐(nai)腐蝕性(xing)強，一些有色金(jin)屬合金(jin)能(neng)將良好的摩擦學特性(xing)與有些流(liu)體的耐(nai)腐蝕性(xing)結合；

　　(8)線膨脹(zhang)系數小，熱膨脹(zhang)會造成(cheng)摩擦(ca)材料與摩擦(ca)對偶(ou)之間的(de)間隙過(guo)小，發(fa)生拖摩，損毀(hui)制動、傳動裝置。