耐火電纜的選用注意事(shi)項

一，耐(nai)火(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)是(shi)指(zhi)在(zai)火(huo)焰(yan)燃(ran)燒(shao)情況下能夠保持一定(ding)時(shi)(shi)間安(an)全運行的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)。耐(nai)火(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)廣泛應(ying)用(yong)于高(gao)層建筑、地下鐵道(dao)、地下街、大型電(dian)(dian)(dian)(dian)(dian)(dian)(dian)站及重要的(de)(de)工礦企業等與防(fang)火(huo)安(an)全和(he)(he)消(xiao)防(fang)救生有關(guan)的(de)(de)地方，例如，消(xiao)防(fang)設(she)(she)備(bei)及緊急(ji)向導燈等應(ying)急(ji)設(she)(she)施的(de)(de)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)線路和(he)(he)控制線路。 耐(nai)火(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)與阻(zu)(zu)燃(ran)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)的(de)(de)主要區(qu)別(bie)是(shi)：耐(nai)火(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)在(zai)火(huo)災發生時(shi)(shi)能維持一段時(shi)(shi)間的(de)(de)正常供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，而阻(zu)(zu)燃(ran)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)不(bu)具(ju)備(bei)這個特(te)性(xing)。

二，耐火電纜選用時應注意以下幾個問題：
  （1）當耐火電纜用于電纜密集的電纜隧道、電纜夾層中，或位于油管、油庫附近等易燃場所時，應首先選用A類耐火電纜。除上述情況外且電纜配置數量少時，可采用B類耐火電纜。
  （2）耐火電纜大多用作應急電源的供電回路，要求火災時正常工作。由于火災時環境溫度急劇上升，為保證線路的輸送容量，降低壓降，對于供電線路較長且嚴格限定允許電壓降的回路，應將耐火電纜截面至少放大一檔。
  （3）耐火電纜不能當作耐高溫電纜使用。
  （4）為降低電纜接頭在火災事故中的故障機率，在安裝中應盡量減少接頭數量，以保證線路在火災中能正常工作。如果需要做分支接線，應對接頭做好防火處理。