Bawul ɗin dubawa  ne ga kananan size high matsa lamba rajistan bawuloli, wanda aka yi da ƙirƙira karfe.mu kullum sanya su a lilo rajistan shiga bawul, fistan rajistan bawul (daga duba bawul).Akwai a cikin ƙirar bonnet guda uku.Zane na farko shine Bolted Bonnet, tare da haɗin gwiwar mace-mace, gask ɗin rauni mai karkace, wanda aka yi a cikin F316L/graphite.Ring hadin gwiwa gasket kuma akwai a kan bukatar.Zane na biyu shi ne welded bonnet, tare da zare da hatimi welded hadin gwiwa.A kan buƙatar cikakken ƙarfin shigar da ƙarfi welded haɗin gwiwa yana samuwa, ƙira ta ƙarshe shine mashin hatimin matsi, wanda shine ƙira don manyan bawuloli.

Duba bawuloli, bawuloli marasa dawowa, an ƙera su don hana juyawar kwarara a cikin tsarin bututun.Ana kunna waɗannan bawuloli ta hanyar kayan da ke gudana a cikin bututun.Matsalolin ruwan da ke wucewa ta cikin tsarin yana buɗe bawul ɗin, yayin da duk wani juzu'i na gudana zai rufe bawul.