在使用過程中，大多數河曲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，河曲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。河曲機械密封端(duan)面(mian)(mian)摩(mo)(mo)擦(ca)(ca)的(de)(de)工(gong)況一般分(fen)為：流(liu)體摩(mo)(mo)擦(ca)(ca)、混合摩(mo)(mo)擦(ca)(ca)和邊界(jie)摩(mo)(mo)擦(ca)(ca)三(san)類，但不能長時間干摩(mo)(mo)擦(ca)(ca)。干摩(mo)(mo)擦(ca)(ca)狀態(tai)時，兩端(duan)面(mian)(mian)間的(de)(de)固體表(biao)面(mian)(mian)微凸體將直接接觸而引起劇烈的(de)(de)磨損(sun)(sun)(sun)。磨損(sun)(sun)(sun)時一方(fang)面(mian)(mian)會使摩(mo)(mo)擦(ca)(ca)表(biao)面(mian)(mian)物質喪失或遷(qian)移，導(dao)致(zhi)表(biao)面(mian)(mian)損(sun)(sun)(sun)壞；另一方(fang)面(mian)(mian)會產生大量(liang)的(de)(de)摩(mo)(mo)擦(ca)(ca)熱直至燒(shao)毀(hui)密(mi)封(feng)。在無流(liu)體介(jie)質的(de)(de)工(gong)況下(xia)，如何(he)減少磨損(sun)(sun)(sun)降(jiang)低摩(mo)(mo)擦(ca)(ca)熱，那(nei)就要(yao)依靠干磨密(mi)封(feng)了。

　　干(gan)磨(mo)(mo)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)屬于(yu)(yu)(yu)浮動(dong)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)的(de)(de)一種(zhong)，常用(yong)(yong)(yong)材(cai)(cai)質為(wei)耐磨(mo)(mo)碳精，結構包(bao)括環(huan)(huan)(huan)(huan)(huan)(huan)行(xing)(xing)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)腔體(ti)(ti)和(he)環(huan)(huan)(huan)(huan)(huan)(huan)行(xing)(xing)軸套(tao)，密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)腔體(ti)(ti)內有(you)環(huan)(huan)(huan)(huan)(huan)(huan)行(xing)(xing)槽，槽內至少(shao)裝有(you)二(er)個截面(mian)(mian)(mian)(mian)(mian)為(wei)矩(ju)形的(de)(de)環(huan)(huan)(huan)(huan)(huan)(huan)行(xing)(xing)石墨(mo)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)，石墨(mo)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)的(de)(de)內徑與(yu)環(huan)(huan)(huan)(huan)(huan)(huan)行(xing)(xing)軸套(tao)之(zhi)間(jian)有(you)0.01-0.04的(de)(de)間(jian)隙，軸套(tao)外表(biao)面(mian)(mian)(mian)(mian)(mian)涂有(you)耐磨(mo)(mo)涂層，涂層材(cai)(cai)料(liao)(liao)一般為(wei)三氧化二(er)鋁或三氧化二(er)鉻。干(gan)磨(mo)(mo)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)有(you)時(shi)需要(yao)(yao)(yao)增(zeng)加隔離氣(qi)(qi)，通常使(shi)用(yong)(yong)(yong)氮氣(qi)(qi)，氮氣(qi)(qi)耗量能控制在(zai)25-40。主要(yao)(yao)(yao)應(ying)用(yong)(yong)(yong)于(yu)(yu)(yu)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)易(yi)燃有(you)毒(du)介(jie)質，由于(yu)(yu)(yu)操作維(wei)修(xiu)簡單(dan)，密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)性(xing)好，不需要(yao)(yao)(yao)復雜的(de)(de)潤滑冷卻系(xi)統(tong)，可(ke)(ke)以干(gan)運(yun)行(xing)(xing)，得到(dao)廣泛的(de)(de)應(ying)用(yong)(yong)(yong)。干(gan)磨(mo)(mo)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)包(bao)括有(you)外罩(zhao)(zhao)及(ji)架設于(yu)(yu)(yu)外罩(zhao)(zhao)上且(qie)可(ke)(ke)呈相對(dui)旋轉(zhuan)及(ji)貼(tie)合(he)的(de)(de)動(dong)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)及(ji)靜密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)，靜密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)與(yu)外罩(zhao)(zhao)固定連接，靜密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)及(ji)動(dong)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)上分開設有(you)供旋轉(zhuan)軸安(an)裝的(de)(de)通孔，且(qie)動(dong)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)與(yu)靜密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)貼(tie)合(he)的(de)(de)端(duan)面(mian)(mian)(mian)(mian)(mian)分別(bie)為(wei)動(dong)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)面(mian)(mian)(mian)(mian)(mian)及(ji)靜密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)面(mian)(mian)(mian)(mian)(mian)，外罩(zhao)(zhao)上設有(you)促使(shi)動(dong)密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)與(yu)靜密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)(huan)緊密(mi)(mi)(mi)(mi)(mi)貼(tie)合(he)的(de)(de)彈性(xing)抵壓件。除了要(yao)(yao)(yao)保持密(mi)(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)面(mian)(mian)(mian)(mian)(mian)平(ping)行(xing)(xing)之(zhi)外，主要(yao)(yao)(yao)是摩擦副(fu)的(de)(de)材(cai)(cai)料(liao)(liao)問題(ti)。

　　摩擦材料應(ying)具備下(xia)列條(tiao)件：

　　(1)機械強(qiang)度高，能耐(nai)壓(ya)和(he)耐(nai)壓(ya)力變形；

　　(2)具有耐干磨性，耐高載荷(he)性，自潤滑性好；

　　(3)配對材料的磨合性好，無過大的磨損和(he)對偶腐(fu)蝕；

　　(4)耐磨(mo)性好，摩擦(ca)材料雖(sui)然是易損(sun)件，起到保護制動(dong)或傳動(dong)裝置的作用(yong)，但要(yao)求具有一定的耐磨(mo)性，使用(yong)壽(shou)命盡量要(yao)長，刮傷、腐蝕和(he)粘(zhan)附對偶(ou)，都會造成制動(dong)或傳動(dong)的震動(dong)和(he)不(bu)穩定；

　　(5)導(dao)(dao)熱(re)性(xing)(xing)和散(san)熱(re)性(xing)(xing)好(hao)，導(dao)(dao)熱(re)性(xing)(xing)是傳(chuan)導(dao)(dao)熱(re)量的(de)能力(li)大小，即包括吸熱(re)，也(ye)包括散(san)熱(re)，所以，導(dao)(dao)熱(re)性(xing)(xing)好(hao)的(de)必然散(san)熱(re)性(xing)(xing)也(ye)好(hao)；

　　(6)抗熱(re)裂(lie)(lie)性好，根本(ben)解決(jue)抗熱(re)裂(lie)(lie)性問題可能需要(yao)改變(bian)封孔方法；

　　(7)耐腐蝕性強，一些有色金屬合金能將良好的(de)摩擦學特性與(yu)有些流(liu)體的(de)耐腐蝕性結合；

　　(8)線(xian)膨(peng)脹(zhang)系數小(xiao)，熱膨(peng)脹(zhang)會造成(cheng)摩(mo)擦(ca)材(cai)料與(yu)摩(mo)擦(ca)對偶之間(jian)的間(jian)隙過小(xiao)，發(fa)生拖(tuo)摩(mo)，損毀制動(dong)、傳動(dong)裝置。