Valavu yothandizira, yomwe imadziwikanso kuti valavu yochepetsera kupanikizika (PRV), ndi mtundu wa valavu yotetezera yomwe imagwiritsidwa ntchito kulamulira kapena kuchepetsa kupanikizika mu dongosolo. Ngati kupanikizika sikunalamuliridwe, kungadziunjikane ndikupangitsa kusokonezeka kwa njira, kulephera kwa chida kapena zida, kapena moto. Mwa kulola madzi opanikizika kutuluka mu dongosolo kudzera munjira yothandizira, kupanikizika kumachepetsedwa. Pofuna kupewa zombo zopanikizika ndi zida zina kuti zisakumane ndi kupsinjika komwe kumapitirira malire awo opangira,valavu yothandiziraimapangidwa kapena kukonzedwa kuti itsegule pa mphamvu inayake.

Thevalavu yothandiziraimakhala "njira yosavuta kukana" pamene kuthamanga kwayikidwa kwapitirira chifukwa valavu imatsegulidwa mwamphamvu ndipo madzi ena amatumizidwa ku njira yothandizira. Madzi, gasi, kapena mpweya wamadzimadzi womwe umasinthidwa m'makina okhala ndi madzi oyaka umabwezeretsedwanso kapena kutulutsidwa mpweya.

[1] imatumizidwa kudzera mu njira yolumikizira mapaipi yotchedwa flare header kapena relief header kupita ku flare yapakati, yokwezeka ya mpweya komwe imatenthedwa, kutulutsa mpweya woyaka mumlengalenga, kapena ndi njira yochepetsera mpweya wotuluka ndi mphamvu yochepa.

[2] Mu machitidwe omwe si oopsa, madzi nthawi zambiri amatulutsidwa mumlengalenga kudzera mu mapaipi oyenera otulutsira madzi omwe amaikidwa bwino kwa anthu ndipo amamangidwa kuti apewe kulowerera kwa mvula, zomwe zingakhudze kuthamanga kwa mpweya komwe kumayikidwa. Kupanikizika kumasiya kumangidwa mkati mwa chotengera pamene madziwo akusinthidwa. Valavu imatseka kuthamanga kukafika pa kuthamanga kwa mpweya komwe kumayikidwanso. Kuchuluka kwa kuthamanga komwe kuyenera kuchepetsedwa valavu isanayikenso kumadziwika kuti blowdown, komwe nthawi zambiri kumawonetsedwa ngati peresenti ya kuthamanga komwe kumayikidwa. Mavavu ena ali ndi ma blowdown osinthika, ndipo blowdown imatha kusinthasintha pakati pa 2% ndi 20%.

Alangizidwa kuti malo otulutsira mpweya wa valavu yothandiza m'makina a mpweya wopanikizika kwambiri akhale pamalo otseguka. Kutseguka kwa valavu yothandiza kudzapangitsa kuti kuthamanga kwa mpweya kuchuluke mumakina a mapaipi omwe ali pansi pa valavu yothandiza m'makina omwe malo otulutsira mpweya amalumikizidwa ndi mapaipi. Izi nthawi zambiri zikutanthauza kuti kuthamanga komwe mukufuna kukapezeka, valavu yothandizayo sidzakhazikikanso. Ma valve otchedwa "differential" relief amagwiritsidwa ntchito nthawi zambiri m'makina awa. Izi zikusonyeza kuti kuthamanga kwa mpweya kumangogwira ntchito pamalo ochepa kwambiri kuposa malo otseguka a valavu.

Kuthamanga kwa valavu kumatha kupangitsa kuti valavuyo ikhale yotseguka mosavuta ngati valavuyo yatsegulidwa chifukwa kuthamangako kuyenera kutsika kwambiri valavuyo isanatseke. Pamene kuthamanga kwa payipi yotulutsa mpweya kukukwera, mavalavu ena othandizira omwe amalumikizidwa ku payipi yotulutsa mpweya angatseguke. Ichi ndi chinthu choyenera kukumbukira. Izi zitha kubweretsa khalidwe losayenera.