墊圈是動環和靜環的總稱，是構成瀘定機械密封主要的元件，很大程度上決定了瀘定機械密封的使用性能和壽(shou)命。使用閥門時(shi)，往(wang)往(wang)根據具體(ti)情況更換原帶墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)。常用墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)有：橡(xiang)(xiang)膠平(ping)墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、橡(xiang)(xiang)膠O形圈(quan)(quan)(quan)(quan)(quan)、塑料平(ping)墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、聚四氟乙烯(xi)包墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、石棉橡(xiang)(xiang)膠墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、金屬(shu)平(ping)墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、金屬(shu)異形墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、金屬(shu)皮墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、波形墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)、纏繞墊(dian)(dian)(dian)(dian)(dian)(dian)圈(quan)(quan)(quan)(quan)(quan)等。

　　(1)橡(xiang)膠(jiao)(jiao)平墊圈：變形容易，壓緊(jin)時不費力(li)，但(dan)耐壓、耐溫(wen)(wen)能(neng)力(li)都(dou)較差，只(zhi)用(yong)(yong)于(yu)壓力(li)低、溫(wen)(wen)度(du)不高的地(di)方。天然橡(xiang)膠(jiao)(jiao)有一定(ding)耐酸堿(jian)(jian)性(xing)能(neng)，使用(yong)(yong)溫(wen)(wen)度(du)不宜(yi)超過(guo)60℃；氯丁橡(xiang)膠(jiao)(jiao)也能(neng)耐某些酸堿(jian)(jian)，使用(yong)(yong)溫(wen)(wen)度(du)80℃；橡(xiang)膠(jiao)(jiao)耐油，可用(yong)(yong)至80℃；氟(fu)橡(xiang)膠(jiao)(jiao)耐腐蝕性(xing)能(neng)很好，耐溫(wen)(wen)性(xing)能(neng)也比一般(ban)橡(xiang)膠(jiao)(jiao)強，可在150℃介質中使用(yong)(yong)。

　　(2)橡膠O形墊(dian)圈：斷面形狀(zhuang)是(shi)正(zheng)圓，有一定的自(zi)緊作用(yong)，密(mi)封效果比(bi)平(ping)墊(dian)圈好，壓緊力更小。

　　(3)塑料(liao)(liao)平(ping)墊圈：塑料(liao)(liao)的特點是耐(nai)腐蝕性好,大部分塑料(liao)(liao)耐(nai)溫性能不(bu)好。聚四氟乙烯為塑料(liao)(liao)，不(bu)但耐(nai)腐蝕性能優異，而且耐(nai)溫范圍比較寬闊，可在-180℃～+200℃之內長期使用(yong)。

　　(4)聚四(si)氟乙烯包墊(dian)圈(quan)：為了充分發揮(hui)聚四(si)氟乙烯的(de)優點，同時彌補它彈性較差的(de)缺點，做(zuo)成(cheng)聚四(si)氟乙烯包裹(guo)橡(xiang)膠或石棉橡(xiang)膠的(de)墊(dian)圈(quan)。這樣(yang)，既(ji)同聚四(si)氟乙烯平墊(dian)圈(quan)一(yi)樣(yang)耐腐蝕，又有良好的(de)彈性，增強密封(feng)效果，減小壓緊力。

　　(5)石棉橡(xiang)膠墊圈(quan)：由石棉橡(xiang)膠板剪成。它的(de)組分是60～80%的(de)石棉和10～20%的(de)橡(xiang)膠，以及填充劑(ji)、硫化劑(ji)等。它有很好的(de)耐熱性(xing)、耐冷性(xing)、化學穩定性(xing)，而且貨(huo)源(yuan)豐富，價格便宜。使用時(shi)，壓(ya)緊力不必(bi)很大。由于它能粘附(fu)金屬，所以表面涂一層(ceng)石墨粉，以免拆卸時(shi)費(fei)勁。

　　瀘定機械密封對墊圈有哪些要求(qiu)呢？

　　(1)需(xu)要有足(zu)夠的(de)強度(du)和剛(gang)度(du)，在工(gong)作條(tiao)件(jian)(jian)下(如壓力、溫(wen)度(du)和滑動速度(du)等(deng))不損(sun)壞，變(bian)形應盡量的(de)小，工(gong)作條(tiao)件(jian)(jian)波動時仍能保持密封性(xing)。

　　(2)密封端面應有足夠(gou)的硬(ying)度和(he)耐(nai)腐蝕性(xing)，以保證工作條件下有滿(man)意的使用壽命。

　　(3)應有良好的耐(nai)熱沖(chong)擊能力，為此要求材料有較(jiao)(jiao)高(gao)的導熱系數和較(jiao)(jiao)小(xiao)的線膨脹系數，承(cheng)受熱沖(chong)擊時不(bu)至于開裂。

　　(5)應(ying)有(you)(you)較(jiao)(jiao)小的(de)摩(mo)擦系數(shu)和良好的(de)自潤(run)滑性(xing)，墊圈匹配應(ying)有(you)(you)較(jiao)(jiao)小的(de)摩(mo)擦系數(shu)和良好的(de)自潤(run)滑性(xing)，墊圈材(cai)料與(yu)密封(feng)(feng)流體還要(yao)有(you)(you)很好的(de)浸潤(run)性(xing)。工作中如發(fa)生短時間的(de)干摩(mo)擦，不損傷密封(feng)(feng)端面(mian)。

　　(5)應力求(qiu)簡單對稱并優先(xian)考慮用整體型(xing)結構，也可采(cai)用組合式(shi)(如鑲裝式(shi))墊圈，盡量(liang)避免用密封端(duan)面噴涂式(shi)結構。

　　(6)墊圈要(yao)容易加工(gong)制造，安裝和維修要(yao)方便。