法蘭接頭是由法蘭、密封墊(dian)片及連接螺栓三種元件組成的一個承壓管道連接件。在法蘭密封接頭中，墊片是最主要的密封元件。對于非金屬墊片來說，法蘭接頭的密封是通過擰緊螺栓，使法蘭與墊片接觸表面及其墊片內部造成較大的壓緊應力，從而一方面使墊片表面與法蘭表面緊密貼合以填滿法蘭表面的微間隙，另一方面減小墊片材料的孔隙率，即減小被密封流體的泄漏通道，從而實現法蘭接頭的密封。由于任何制造或加工方法都不可能形成絕對光滑的理想表面，也不可能實現密封面間的完全嵌合以及密封件本身孔隙的完全阻塞，所以在相互接觸的密封面間和密封墊片內部總是存在著微小的間隙或通道。因而，對墊片密封來說，泄漏總是不可避免的。當介質以一定的壓力通過螺栓法蘭連接時，總會在密封點處出現泄漏。

  法蘭接(jie)頭的(de)(de)密(mi)封(feng)失效形式主要表(biao)現為(wei)泄漏。泄漏輕則造成能源、原(yuan)材(cai)料的(de)(de)大(da)量浪費(fei)，重(zhong)則導致設備報(bao)廢(fei)、停(ting)工(gong)停(ting)產、人員傷亡和嚴重(zhong)的(de)(de)環境(jing)污染。隨著現代(dai)石油、化工(gong)、原(yuan)子能、航天及深海技術的(de)(de)迅速發展，對(dui)管道及其裝置的(de)(de)密(mi)封(feng)提出了更嚴格的(de)(de)要求，因而密(mi)封(feng)墊(dian)片的(de)(de)地位(wei)更加重(zhong)要。

  在墊(dian)片(pian)密(mi)封(feng)(feng)的(de)法(fa)蘭(lan)接頭(tou)中，雖然泄(xie)漏(lou)無法(fa)避免，但可以控制在一(yi)定的(de)范圍內。墊(dian)片(pian)密(mi)封(feng)(feng)的(de)可靠(kao)性與連接結(jie)構的(de)形(xing)式、介質特性、工(gong)況條件(jian)等諸(zhu)多(duo)因素有關(guan)，而且最主要(yao)的(de)是(shi)與所(suo)采(cai)用(yong)的(de)密(mi)封(feng)(feng)墊(dian)片(pian)材料和其結(jie)構有關(guan)。影響(xiang)墊(dian)片(pian)密(mi)封(feng)(feng)的(de)因素很多(duo)，至(zhi)(zhi)今(jin)還是(shi)一(yi)個未能定量的(de)問題(ti)，因此(ci)研究(jiu)墊(dian)片(pian)密(mi)封(feng)(feng)的(de)工(gong)作(zuo)，至(zhi)(zhi)今(jin)仍然是(shi)工(gong)業界普遍關(guan)注的(de)問題(ti)。

  本(ben)篇(pian)就墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)基礎知識、墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)結(jie)構及(ji)其標準進行描述，共4章組成，內(nei)容包括墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)的一般結(jie)構型(xing)式、種類、參數和設(she)計(ji)選(xuan)用(yong)；非金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)平墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)（含非金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)軟(ruan)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)及(ji)聚四氟乙烯包覆(fu)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)）；金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)復合(he)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)（含纏繞式墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)包覆(fu)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)沖齒(chi)板柔性(xing)石墨(mo)復合(he)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、柔性(xing)石墨(mo)金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)波齒(chi)復合(he)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)）及(ji)金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)（含金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)環(huan)形墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)、金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)齒(chi)形墊(dian)(dian)(dian)(dian)片(pian)(pian)(pian)及(ji)R型(xing)、RX型(xing)及(ji)BX型(xing)專用(yong)自緊(jin)密封金(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)環(huan)墊(dian)(dian)(dian)(dian)）等(deng)。