Te WP421HeKo te tuku pēhanga pāmahana waenga me te pāmahana teitei he mea hanga ki ngā wāhanga tairongo ātete pāmahana teitei kawemai, ā, ka taea e te tirotiro pūoko te mahi pumau mō te wā roa i te pāmahana teitei o te 350℃. Ka whakamahia te tukanga whakarewa matao taiaho i waenganui i te matua me te anga maitai kore waikura hei whakarewa katoa i roto i te tinana kotahi, kia mau ai te haumaru o te tuku i raro i ngā āhuatanga pāmahana teitei. Kua whakamahanatia te matua pēhanga o te pūoko me te ara iahiko whakakaha ki ngā gaskets PTFE, ā, ka tāpirihia he totohu wera. Kua whakakīia ngā kōhao arataki o roto ki te rauemi whakamahana wera tino pai konumohe silicate, e ārai pai ana i te kawe wera me te whakarite kia mahi te wāhanga ara iahiko whakakaha me te huri i te pāmahana e whakaaetia ana.
Ka tīpakohia e te tuku pēhanga WP402B kounga teitei ngā wāhanga kawemai, tino tika, me te kiriata ārai-waikura. Ka whakakotahihia e te wāhanga te hangarau whakauru totoka me te hangarau diaphragm wehe, ā, mā te hoahoa hua ka taea e ia te mahi i raro i ngā āhuatanga taiao uaua me te pupuri tonu i te mahi pai rawa atu. Ko te ātete o tēnei hua mō te whakatikatika pāmahana ka mahia ki runga i te papa uku whakaranu, ā, ka whakaratohia e ngā wāhanga tairongo he hapa pāmahana iti o te 0.25% FS (mōrahi) i roto i te awhe pāmahana whakatikatika (-20~85℃). He kaha te ārai-aukati o tēnei tuku pēhanga, ā, he pai mō te tono tuku tawhiti.