I-DN (Ububanzi obuqhelekileyo) ithetha ububanzi obuqhelekileyo bombhobho, obungumyinge wobubanzi obungaphandle kunye nobubanzi obungaphakathi. Ixabiso le-DN = ixabiso le-De -0.5 * ixabiso lobukhulu bodonga lwetyhubhu. Qaphela: Olu alulo ububanzi obungaphandle okanye ububanzi obungaphakathi.

Umbhobho wentsimbi othutha amanzi, igesi (umbhobho wentsimbi othutha nge-galvanized okanye umbhobho wentsimbi ongengo-galvanized), umbhobho wentsimbi ephosiweyo, umbhobho odibeneyo wentsimbi-plastiki kunye nombhobho we-polyvinyl chloride (PVC), njl., kufuneka ubhalwe ngobubanzi obuqhelekileyo "DN" (njenge-DN15, DN50).

I-De (Ububanzi bangaphandle) ithetha ububanzi bangaphandle bombhobho, i-PPR, umbhobho we-PE, umbhobho we-polypropylene ububanzi bangaphandle, ngokubanzi iphawulwe ngo-De, kwaye zonke kufuneka ziphawulwe njengohlobo lobubanzi bangaphandle * ubukhulu bodonga, umzekelo i-De25 × 3.

I-D ngokubanzi ibhekisa kububanzi bangaphakathi bombhobho.

I-d ngokubanzi ibhekisa kububanzi bangaphakathi bombhobho wekhonkrithi. Imibhobho yekhonkrithi eqinisiweyo (okanye ikhonkrithi), imibhobho yodongwe, imibhobho yeseramikhi engamelani ne-asidi, iithayile zesilinda kunye neminye imibhobho, apho ububanzi bombhobho bufanele bumelwe bububanzi bangaphakathi be-d (njenge-d230, i-d380, njl.njl.)

U-Φ umele ububanzi besangqa esiqhelekileyo; ungamela nobubanzi bangaphandle bombhobho, kodwa ngeli xesha kufuneka buphindaphindwe ngobukhulu bodonga.