Esi sixhobo silungele ukususwa kokungcola okunokuthi kushiywe phezu kweendonga zangaphakathi ze-casing, ezifana nesamente eqinileyo, i-wax eqinile, iikristale ezahlukeneyo zetyuwa okanye iidiphozithi, i-perforation burrs, i-iron oxideresidues ebangelwa ukurusa, ukwenzela ukuba wenze zonke izixhobo zomngxuma. dlula ungavalwanga. Ngokukodwa xa kukho ucoceko olusetyhula oluncinane phakathi kwezixhobo zomngxuma osezantsi kunye nedayamitha engaphakathi, ukukrazula okupheleleyo kuba yimfuneko ngakumbi phambi kokuba kusetyenzwe ngakumbi. Okwangoku kwi-petroleum enkulu ukukrazula kudonga lwangaphakathi lwe-casing ngokusebenzisa i-casing scraper linyathelo eliyimfuneko.