Ncej yog ib hom kev sib txhuam los yog lub thawv ntim khoom, uas yog siv los tiv thaiv cov kua xau ntawm cov ncej thiab cov kabmob ntawm cov twj tso kua mis lossis lwm yam khoom siv sib txuas, thiab nws tseem yog cov khoom siv sib khi los tiv thaiv cov dej ntws ntawm lub twj tso kua mis thiab lub plhaub. Feem ntau siv cov ntsaws ruaj ruaj muaj xws li ntim cov foob, mechanical seal thiab fais fab foob
