Butterfly bawul, wanda kuma aka sani da flap valve, shine bawul mai daidaitawa tare da tsari mai sauƙi, wanda za'a iya amfani dashi don sarrafa kan-kashe matsakaici a cikin ƙananan bututun mai.Bawul ɗin malam buɗe ido yana nufin bawul ɗin da ɓangaren rufewa (bawul diski ko farantin malam buɗe ido) diski ne kuma yana jujjuya magudanar bawul don buɗewa da rufewa.
Ana iya amfani da bawul don sarrafa magudanar ruwa iri-iri kamar iska, ruwa, tururi, kafofin watsa labaru iri-iri, laka, samfuran mai, ƙarfe na ruwa da kafofin watsa labarai na rediyoaktif.An fi amfani da shi don yankewa da ƙumburi a kan bututun.Bangaren buɗewa da rufewa na bawul ɗin malam buɗe ido wani farantin malam buɗe ido ne mai siffar diski, wanda ke jujjuya axis ɗinsa a cikin bawul ɗin, don cimma manufar buɗewa, rufewa ko daidaitawa.
A cikin 1930s, Amurka ta ƙirƙiramalam buɗe ido, wanda aka shigar a cikin Japan a cikin 1950s kuma ba a yi amfani da shi sosai a Japan ba har zuwa 1960s.An inganta shi a China bayan shekarun 1970.
Babban fasalulluka na bawul ɗin malam buɗe ido sune: ƙaramin ƙarfin aiki, ƙaramin sarari shigarwa da nauyi mai nauyi.Ɗaukar DN1000 a matsayin misali, bawul ɗin malam buɗe ido yana da kusan tan 2, yayin da bawul ɗin ƙofar yana da kusan tan 3.5, kuma bawul ɗin malam buɗe ido yana da sauƙi a haɗa shi da na'urorin tuƙi daban-daban, tare da inganci mai kyau da aminci.Rashin hasara naroba shãfe haske malam buɗe ido bawulshi ne idan aka yi amfani da shi wajen murƙushewa, cavitation zai faru saboda rashin amfani da shi, wanda zai haifar da bawon da lalata kujerar roba.Saboda haka, yadda za a zabi daidai ya kamata ya dogara da bukatun yanayin aiki.
Dangantakar da ke tsakanin buɗaɗɗen bawul ɗin malam buɗe ido da gudana ta asali tana canzawa cikin madaidaicin madaidaiciya.Idan ana amfani da shi don sarrafa magudanar ruwa, halayensa ma suna da alaƙa da juriya na kwararar bututun.Misali, diamita da nau'in bawuloli da aka sanya a cikin bututun guda biyu iri ɗaya ne, kuma kwararar bawul ɗin zai bambanta sosai idan adadin asarar bututun ya bambanta.Idan bawul ɗin yana cikin yanayin babban kewayon throttling, cavitation yana da sauƙin faruwa a bayan farantin bawul, wanda zai iya lalata bawul ɗin.Gabaɗaya, ana amfani dashi a waje da 15°.Lokacin damalam buɗe idoyana cikin tsakiyar buɗewa, siffar buɗewa da aka kafa ta jikin bawul da ƙarshen gaban farantin malam buɗe ido yana tsakiya akan mashin bawul, kuma an kafa jihohi daban-daban a bangarorin biyu.Ƙarshen gaban farantin malam buɗe ido a gefe ɗaya yana motsawa tare da hanyar gudana kuma ɗayan gefen yana motsawa a kan hanyar gudana.Don haka, jikin bawul da farantin bawul a gefe ɗaya suna yin bututun ƙarfe kamar buɗewa, ɗayan kuma yana kama da rami mai matsewa kamar buɗewa.Matsakaicin magudanar ruwa a gefen bututun ƙarfe yana da sauri fiye da na gefen magudanar, za a haifar da matsa lamba mara kyau a ƙarƙashin bawul ɗin gefen magudanar, kuma hatimin roba sau da yawa zai faɗi.
Ƙarfin aiki na bawul ɗin malam buɗe ido yana da ƙima daban-daban saboda buɗewa daban-daban da buɗaɗɗen bawul da hanyoyin rufewa.Ƙarfin wutar lantarki da aka yi ta hanyar bawul ɗin malam buɗe ido, musamman maɗaukaki mai girma, saboda zurfin ruwa da bambanci tsakanin babba da ƙananan shugabannin bawul shaft ba za a iya watsi da su ba.Bugu da ƙari, lokacin da aka shigar da gwiwar hannu a gefen shiga na bawul, an samar da raɗaɗi mai banƙyama, kuma karfin zai karu.Lokacin da bawul ɗin ya kasance a tsakiyar buɗewa, tsarin aiki yana buƙatar zama mai kulle kansa saboda aikin motsin ruwa mai ƙarfi.
Masana'antar Valve tana taka muhimmiyar rawa a cikin ci gaban tattalin arzikin duniya a matsayin muhimmiyar hanyar haɗin masana'antar kera kayan aiki.Akwai sarƙoƙin masana'antar bawul da yawa a cikin Sin.Gabaɗaya, Sin ta shiga cikin jerin manyan ƙasashe na bawul na duniya.