Na farko shine ciyar da ruwa, wato, shigar da ruwa a cikin tukunyar jirgi. Gabaɗaya, an sanye shi da famfo na musamman don sanya tsarin karkatar da ruwa ya fi dacewa da sauri. Lokacin da aka shigar da ruwa a cikin tukunyar jirgi, saboda yana ɗaukar zafi da aka saki ta hanyar konewa na man fetur, tururi tare da wani matsa lamba, zazzabi da tsabta ya bayyana. Yawancin lokaci, ƙara ruwa a cikin tukunyar jirgi dole ne ya bi ta matakai uku na dumama, wato: ruwan da ake amfani da shi yana zafi don zama cikakken ruwa; cikakken ruwan yana zafi kuma yana ƙafe don ya zama tururi mai cike da ruwa; mahada.
Gabaɗaya, dole ne a fara zazzage ruwan da ke cikin tukunyar ganga a cikin injin tattalin arziƙi zuwa wani yanayi mai zafi, sannan a aika zuwa ganga don haɗawa da ruwan tukunyar, sannan a shigar da kewayawa ta hanyar mai saukarwa, ruwan yana dumama. a cikin riser Ana samar da cakuda ruwan tururi a lokacin da ya kai yawan zafin jiki kuma wani ɓangare na shi ya ƙafe; sa'an nan, dangane da yawa bambanci tsakanin matsakaici a cikin riser da downcomer ko tilasta wurare dabam dabam famfo, da tururi-ruwa cakuda ya tashi a cikin drum.
Drum wani jirgin ruwa ne na siliki wanda ke karɓar ruwa daga mai ƙona gawayi, yana ba da ruwa zuwa madauki na wurare dabam dabam kuma yana ba da cikakken tururi zuwa babban zafi, don haka yana da alaƙa tsakanin matakai uku na dumama ruwa, evaporation da superheating. Bayan an raba cakuda ruwan tururi a cikin drum, ruwan yana shiga madauki na zagayawa ta hanyar mai saukarwa, yayin da cikakken tururi ya shiga cikin tsarin zafi mai zafi kuma yana mai zafi cikin tururi tare da wani digiri na superheat.