起重(zhong)(zhong)設(she)備(bei)(bei)所(suo)吊運的(de)(de)(de)重(zhong)(zhong)物多種(zhong)多樣(yang)，載荷是變化的(de)(de)(de)。有(you)的(de)(de)(de)重(zhong)(zhong)物重(zhong)(zhong)達(da)幾百噸(dun)乃至上千噸(dun)，有(you)的(de)(de)(de)物體長達(da)幾十米(mi)，起重(zhong)(zhong)設(she)備(bei)(bei)生產廠家，形狀也很(hen)不規則，輕(qing)小型起重(zhong)(zhong)設(she)備(bei)(bei)，有(you)散粒、熱融狀態、危(wei)險(xian)物品等，吊運過程(cheng)復雜而危(wei)險(xian)。門座(zuo)起重(zhong)(zhong)機能(neng)完成起升、變幅、回轉和(he)大車運行4個(ge)運動。在(zai)作(zuo)業過程(cheng)中(zhong)，常(chang)(chang)常(chang)(chang)是幾個(ge)不同(tong)方向的(de)(de)(de)運動同(tong)時(shi)操作(zuo)，蘇州起重(zhong)(zhong)設(she)備(bei)(bei)，技(ji)術難度較大。大多數起重(zhong)(zhong)設(she)備(bei)(bei)，起重(zhong)(zhong)設(she)備(bei)(bei)廠家，需(xu)要在(zai)較大的(de)(de)(de)空間范圍內運行，有(you)的(de)(de)(de)要裝設(she)軌(gui)道和(he)車輪（如(ru)塔吊、橋吊等）；有(you)的(de)(de)(de)要裝上輪胎或履(lv)帶(dai)在(zai)地面(mian)上行走(zou)（如(ru)汽車吊、履(lv)帶(dai)吊等）。

起(qi)(qi)(qi)(qi)重(zhong)(zhong)機。起(qi)(qi)(qi)(qi)重(zhong)(zhong)機是在(zai)(zai)一定范圍內垂直(zhi)提升并水平搬運重(zhong)(zhong)物的(de)多動(dong)作起(qi)(qi)(qi)(qi)重(zhong)(zhong)設(she)備。橋(qiao)式類型起(qi)(qi)(qi)(qi)重(zhong)(zhong)機包括橋(qiao)式起(qi)(qi)(qi)(qi)重(zhong)(zhong)機、特種起(qi)(qi)(qi)(qi)重(zhong)(zhong)機、門式起(qi)(qi)(qi)(qi)重(zhong)(zhong)機、裝卸(xie)橋(qiao)等(deng)。起(qi)(qi)(qi)(qi)重(zhong)(zhong)機械亦(yi)可稱(cheng)為(wei)起(qi)(qi)(qi)(qi)重(zhong)(zhong)設(she)備，是工(gong)業、交通、建(jian)筑企業中(zhong)實現生(sheng)產過(guo)程機械化(hua)、自動(dong)化(hua)，減輕繁重(zhong)(zhong)體力勞(lao)動(dong)，提高(gao)勞(lao)動(dong)生(sheng)產率(lv)的(de)重(zhong)(zhong)要工(gong)具和設(she)備，在(zai)(zai)我(wo)國已(yi)擁有大量的(de)各式各樣的(de)起(qi)(qi)(qi)(qi)重(zhong)(zhong)設(she)備。液(ye)缸(gang)(gang)(gang)的(de)活(huo)塞向下(xia)(xia)運動(dong)，液(ye)壓油經防(fang)爆型電磁(ci)換(huan)向閥(fa)(fa)進入液(ye)缸(gang)(gang)(gang)上端，液(ye)缸(gang)(gang)(gang)下(xia)(xia)端回油經平衡閥(fa)(fa)、液(ye)控單向閥(fa)(fa)、節流閥(fa)(fa)、隔爆型電磁(ci)換(huan)向閥(fa)(fa)回到油箱(xiang)。

有(you)的起(qi)重(zhong)機(ji)械需要直(zhi)接載運(yun)(yun)人(ren)員在導軌、平臺或鋼(gang)絲繩上(shang)(shang)做升(sheng)降運(yun)(yun)動(dong)(dong)（如電(dian)(dian)梯、升(sheng)降平臺等），其可靠性(xing)直(zhi)接影響人(ren)身安(an)全(quan)。作業環境復雜。從(cong)大型鋼(gang)鐵聯合(he)企業，到(dao)現代化港口、建筑工地、鐵路樞(shu)紐(niu)、旅游勝(sheng)地，都(dou)有(you)起(qi)重(zhong)機(ji)械在運(yun)(yun)行；作業場所常(chang)常(chang)會遇有(you)高溫、高壓(ya)、、輸電(dian)(dian)線路、強磁等危(wei)險因(yin)素。各種起(qi)重(zhong)設備(bei)的用途不(bu)同，構造上(shang)(shang)有(you)很大差異，但都(dou)具有(you)實現升(sheng)降這(zhe)一基本動(dong)(dong)作的起(qi)升(sheng)機(ji)構。