dˈʊɹɹɪŋ ðɪ ˌaɪpˌiːˈɛs pˈiəɹɪəd, pˈaɪps wɜː kˈæst ɪn hˈævz ænd wˈɛldᵻd təɡˈɛðɚ, ænd pˈaɪp sˈaɪzᵻz ɹᵻfˈɜːd tə ðɪ ɪnsˈaɪd daɪˈæmɪɾɚz.
During the IPS period, pipes were cast in halves and welded together, and pipe sizes referred to the inside diameters.