在使用過程中，大多數丹江口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，丹江口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。丹江口機械密封端(duan)面(mian)(mian)摩(mo)擦(ca)的(de)工(gong)況一般分(fen)為：流體摩(mo)擦(ca)、混(hun)合摩(mo)擦(ca)和邊界摩(mo)擦(ca)三類，但不能(neng)長時間干摩(mo)擦(ca)。干摩(mo)擦(ca)狀態(tai)時，兩端(duan)面(mian)(mian)間的(de)固體表面(mian)(mian)微凸體將直(zhi)(zhi)接(jie)接(jie)觸而引起劇烈(lie)的(de)磨損(sun)。磨損(sun)時一方(fang)面(mian)(mian)會使摩(mo)擦(ca)表面(mian)(mian)物質喪失或(huo)遷移，導(dao)致表面(mian)(mian)損(sun)壞(huai)；另一方(fang)面(mian)(mian)會產生大量的(de)摩(mo)擦(ca)熱(re)直(zhi)(zhi)至燒毀密封。在無流體介質的(de)工(gong)況下，如何減(jian)少磨損(sun)降低摩(mo)擦(ca)熱(re)，那就(jiu)要依靠干磨密封了。

　　干(gan)磨(mo)(mo)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)屬于(yu)(yu)浮動(dong)(dong)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)的(de)一種，常(chang)用材(cai)質(zhi)(zhi)為(wei)耐(nai)磨(mo)(mo)碳精，結構包括(kuo)環(huan)(huan)(huan)(huan)(huan)行(xing)(xing)(xing)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)腔體和環(huan)(huan)(huan)(huan)(huan)行(xing)(xing)(xing)軸(zhou)套，密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)腔體內有(you)環(huan)(huan)(huan)(huan)(huan)行(xing)(xing)(xing)槽(cao)，槽(cao)內至少裝(zhuang)有(you)二個截(jie)面(mian)為(wei)矩形的(de)環(huan)(huan)(huan)(huan)(huan)行(xing)(xing)(xing)石墨(mo)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)，石墨(mo)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)的(de)內徑與(yu)(yu)環(huan)(huan)(huan)(huan)(huan)行(xing)(xing)(xing)軸(zhou)套之間有(you)0.01-0.04的(de)間隙，軸(zhou)套外(wai)(wai)表面(mian)涂(tu)有(you)耐(nai)磨(mo)(mo)涂(tu)層，涂(tu)層材(cai)料(liao)一般為(wei)三氧化二鋁或三氧化二鉻。干(gan)磨(mo)(mo)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)有(you)時(shi)需要增加隔離氣，通常(chang)使用氮氣，氮氣耗(hao)量(liang)能控制在25-40。主(zhu)要應(ying)用于(yu)(yu)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)易燃有(you)毒介質(zhi)(zhi)，由于(yu)(yu)操(cao)作維修簡單，密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)性好，不需要復雜的(de)潤滑冷卻系統，可以(yi)干(gan)運行(xing)(xing)(xing)，得到廣泛(fan)的(de)應(ying)用。干(gan)磨(mo)(mo)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)包括(kuo)有(you)外(wai)(wai)罩(zhao)(zhao)及(ji)架設(she)于(yu)(yu)外(wai)(wai)罩(zhao)(zhao)上且(qie)可呈相對旋轉(zhuan)及(ji)貼(tie)(tie)合的(de)動(dong)(dong)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)及(ji)靜(jing)(jing)(jing)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)，靜(jing)(jing)(jing)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)與(yu)(yu)外(wai)(wai)罩(zhao)(zhao)固定(ding)連(lian)接，靜(jing)(jing)(jing)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)及(ji)動(dong)(dong)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)上分開設(she)有(you)供旋轉(zhuan)軸(zhou)安裝(zhuang)的(de)通孔，且(qie)動(dong)(dong)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)與(yu)(yu)靜(jing)(jing)(jing)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)貼(tie)(tie)合的(de)端(duan)面(mian)分別為(wei)動(dong)(dong)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)面(mian)及(ji)靜(jing)(jing)(jing)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)面(mian)，外(wai)(wai)罩(zhao)(zhao)上設(she)有(you)促(cu)使動(dong)(dong)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)與(yu)(yu)靜(jing)(jing)(jing)密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)環(huan)(huan)(huan)(huan)(huan)緊密(mi)(mi)(mi)(mi)貼(tie)(tie)合的(de)彈性抵壓(ya)件(jian)。除了(le)要保(bao)持密(mi)(mi)(mi)(mi)封(feng)(feng)(feng)(feng)(feng)(feng)面(mian)平(ping)行(xing)(xing)(xing)之外(wai)(wai)，主(zhu)要是摩擦副的(de)材(cai)料(liao)問(wen)題。

　　摩擦材料應具(ju)備下列條(tiao)件：

　　(1)機械強度高，能耐壓(ya)和耐壓(ya)力(li)變形；

　　(2)具(ju)有(you)耐(nai)干磨性，耐(nai)高(gao)載荷性，自潤滑性好；

　　(3)配對材料的磨合性好，無過(guo)大的磨損和對偶腐(fu)蝕；

　　(4)耐(nai)磨性好，摩擦(ca)材料雖然是易損件(jian)，起到(dao)保(bao)護制(zhi)動或(huo)(huo)傳(chuan)動裝置(zhi)的(de)作用(yong)，但要求具有一定(ding)的(de)耐(nai)磨性，使用(yong)壽命(ming)盡量(liang)要長，刮傷、腐(fu)蝕和(he)(he)粘(zhan)附對偶，都會(hui)造成制(zhi)動或(huo)(huo)傳(chuan)動的(de)震(zhen)動和(he)(he)不穩定(ding)；

　　(5)導(dao)(dao)熱性(xing)和散熱性(xing)好，導(dao)(dao)熱性(xing)是傳導(dao)(dao)熱量(liang)的能力大(da)小，即包(bao)括吸(xi)熱，也(ye)包(bao)括散熱，所以，導(dao)(dao)熱性(xing)好的必然(ran)散熱性(xing)也(ye)好；

　　(6)抗熱裂性好，根(gen)本解決(jue)抗熱裂性問題可(ke)能需要改變(bian)封孔方法；

　　(7)耐(nai)腐(fu)蝕(shi)性強，一些(xie)有色(se)金(jin)屬合金(jin)能將良好的(de)(de)摩擦學特性與有些(xie)流體的(de)(de)耐(nai)腐(fu)蝕(shi)性結合；

　　(8)線膨脹(zhang)系數小，熱膨脹(zhang)會造(zao)成摩擦(ca)材料與摩擦(ca)對偶之間(jian)的間(jian)隙過(guo)小，發生拖摩，損毀制動、傳動裝(zhuang)置。