法蘭接頭是由法蘭、密封墊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(lan)接頭的(de)密封(feng)失效形式主要表現為泄漏。泄漏輕則造成能源、原(yuan)材料的(de)大(da)量浪費，重則導(dao)致設備(bei)報廢、停工(gong)停產、人(ren)員傷(shang)亡(wang)和嚴重的(de)環境污染。隨(sui)著現代石油(you)、化(hua)工(gong)、原(yuan)子能、航天及深(shen)海(hai)技術的(de)迅(xun)速(su)發展，對(dui)管道及其(qi)裝(zhuang)置的(de)密封(feng)提出了更嚴格的(de)要求，因而密封(feng)墊片的(de)地位更加重要。

  在(zai)墊片密(mi)(mi)封(feng)(feng)的(de)法(fa)(fa)蘭接(jie)頭中(zhong)，雖然泄漏無法(fa)(fa)避免(mian)，但可(ke)以(yi)控制在(zai)一(yi)定(ding)的(de)范圍(wei)內。墊片密(mi)(mi)封(feng)(feng)的(de)可(ke)靠性與(yu)連接(jie)結構(gou)的(de)形式、介質特(te)性、工(gong)況條件等諸多(duo)因素有關，而且(qie)最主要的(de)是(shi)(shi)與(yu)所采用(yong)的(de)密(mi)(mi)封(feng)(feng)墊片材料和其結構(gou)有關。影響(xiang)墊片密(mi)(mi)封(feng)(feng)的(de)因素很多(duo)，至(zhi)今(jin)還是(shi)(shi)一(yi)個(ge)未能定(ding)量的(de)問(wen)題，因此研究墊片密(mi)(mi)封(feng)(feng)的(de)工(gong)作，至(zhi)今(jin)仍然是(shi)(shi)工(gong)業(ye)界普遍關注的(de)問(wen)題。

  本(ben)篇就墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)基礎知識(shi)、墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)結構及(ji)(ji)其標準進行描述，共4章組成(cheng)，內容包括墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)的一般(ban)結構型(xing)式、種類(lei)、參(can)數和設計選用(yong)；非金(jin)(jin)屬(shu)(shu)(shu)(shu)平(ping)墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)（含(han)非金(jin)(jin)屬(shu)(shu)(shu)(shu)軟墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)及(ji)(ji)聚四氟(fu)乙烯包覆墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)）；金(jin)(jin)屬(shu)(shu)(shu)(shu)復(fu)合墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)（含(han)纏繞式墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)、金(jin)(jin)屬(shu)(shu)(shu)(shu)包覆墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)、金(jin)(jin)屬(shu)(shu)(shu)(shu)沖齒板(ban)柔性石墨(mo)復(fu)合墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)、柔性石墨(mo)金(jin)(jin)屬(shu)(shu)(shu)(shu)波齒復(fu)合墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)）及(ji)(ji)金(jin)(jin)屬(shu)(shu)(shu)(shu)墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)（含(han)金(jin)(jin)屬(shu)(shu)(shu)(shu)環(huan)形墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)、金(jin)(jin)屬(shu)(shu)(shu)(shu)齒形墊(dian)(dian)(dian)(dian)(dian)(dian)片(pian)(pian)及(ji)(ji)R型(xing)、RX型(xing)及(ji)(ji)BX型(xing)專用(yong)自緊密封(feng)金(jin)(jin)屬(shu)(shu)(shu)(shu)環(huan)墊(dian)(dian)(dian)(dian)(dian)(dian)）等。