Ubuninzi bombhobho wentsimbi uthotho luvela kwiyunithi ye-metrology yaseBritani, kwaye amanqaku asetyenziselwa ukuvakalisa ubungakanani.Iubukhulu bodonga lweumbhobho ongenamthungo wenziwa ngoluhlu lweShedyuli (40, 60, 80, 120) kwaye ixhunywe kuluhlu lobunzima (STD, XS, XXS).Ezi xabiso ziguqulelwa kwiimilimitha njengenxalenye yoluhlu lobuninzi bodonga lwetyhubhu.(Qaphela: Ubungakanani - ixabiso leShedyuli40 alikho rhoqo, kodwa ukujonga ububanzi obungaphandle bombhobho.)

Indlela yokubonakalisa ububanzi bombhobho kunye nobukhulu, i-diameter yangaphandle yegama kunye nobukhulu obuncinci bombhobho kwindawo yokufudumeza, i-NPS yombhobho wepayipi kunye nenani leshedyuli yodonga lombhobho.Uluhlu lobunzima bodonga luqulathe uluhlu olu-8 ukusuka kwi-10 ukuya ku-20, 30, 40, 80, 120, 140, 160. Uluhlu lwama-40 luluhlu oluqhelekileyo, i-80 luluhlu olungqingqwa, kwaye i-120 yinto eyongezelelweyo.uthotho.

Ubukhulu bodonga lomgangatho waseMelika kunye nomgangatho wasekhaya wahluke kakhulu.Ngokuqhelekileyo, amabakala amabini oxinzelelo lwe-CL.150 kunye ne-CL.300 ayiphezulu.Ngokubanzi, i-SCH10S kunye ne-SCH40 zisetyenziswa.Ngaphantsi kwama-50 khetha i-SCH80 kunye ne-SCH40S.

I-SCH40, inombolo yombhobho, nokuba isekhaya okanye yangaphandle, i-Sch.XX isetyenziselwa ukubonisa ubuninzi bodonga lombhobho.I-GB/T81631 HG20553 ikwabandakanyiwe kumgangatho wesizwe we-GB/T81631 HG20553, njl., ngokwe-diameter yangaphandle yombhobho okanye ubungakanani bombhobho, ubukhulu bodonga lobukhulu obuhlukeneyo obuboniswe ngenombolo yombhobho efanayo buhluke.

Indlela yokubonakalisa ubukhulu bodonga lombhobho wentsimbi engenamthungo ineendlela ezintathu: ubungakanani begeyiji yombhobho, ubukhulu bodonga lombhobho wentsimbi kunye nobunzima bombhobho:

1) Ubunzima bodonga buboniswa inombolo yombhobho "Sch".
Inombolo yokulinganisa umbhobho ngumlinganiselo woxinzelelo loyilo lombhobho kuxinzelelo oluvumelekileyo lwezinto eziphathekayo kwiqondo lokushisa lokuyila liphindwe nge-1000 kwaye lijikelezwe.Oko kukuthi: I-Sch=P/[σ]t×1000
ANSI B36.10 ukukala ubukhulu bodonga: Sch10, Sch20, Sch30, Sch40, Sch60, Sch80, Sch100, Sch120, Sch140, Sch160 amabanga alishumi;
I-ANSI B36.19 ibakala lokutyeba kodonga: Sch5s, Sch10s, Sch40s, Sch80s amabanga amane;

I-2) Ngokutsho kodonga lombhobho wensimbi, i-China, i-ISO, iJapan, imigangatho ethile yombhobho yensimbi yamkelwa.

3) Ubukhulu bodonga lombhobho bubonakaliswa ubunzima bombhobho, owahlula udonga lombhobho kwiindidi ezintathu:
a.ityhubhu yobunzima obuqhelekileyo, echazwe kwi-STD
b ityhubhu ejiyileyo, echazwe kwi-XS
c.Ityhubhu etyebileyo eyongezelelekileyo, ichazwa ngu-XXS.
Kwimibhobho ene-DN ≤ 250mm, i-Sch40 ilingana ne-STD, i-DN <ipayipi ye-200mm, i-Sch80 ilingana ne-XS.