Ngakhalemavavu apulasitikiNthawi zina amaonedwa ngati chinthu chapadera - chisankho choyamba cha anthu omwe amapanga kapena kupanga mapaipi apulasitiki a mafakitale kapena omwe ayenera kukhala ndi zida zoyera kwambiri - mwachidule tikuganiza kuti ma valve awa alibe magwiritsidwe ntchito ambiri. Ndipotu, ma valve apulasitiki amakono ali ndi ntchito zosiyanasiyana, chifukwa mitundu ya zipangizo ikupitilira kukula, ndipo opanga abwino omwe amafunikira zipangizozi amatanthauza kuti pali njira zambiri zogwiritsira ntchito zida zambirizi.

Katundu wa Pulasitiki

Ubwino wa ma valve a thermoplastic ndi osiyanasiyana—kukana dzimbiri, mankhwala ndi kukana kukwawa; makoma osalala mkati; kulemera kopepuka; kusavuta kuyika; kukhala ndi moyo wautali; komanso mtengo wotsika wa moyo. Ubwino uwu wapangitsa kuti ma valve apulasitiki azigwiritsidwa ntchito kwambiri m'mafakitale ndi mafakitale monga kugawa madzi, kukonza madzi otayira, kukonza zitsulo ndi mankhwala, chakudya ndi mankhwala, malo opangira magetsi, malo oyeretsera mafuta ndi ma valve apulasitiki amatha kupangidwa kuchokera ku zipangizo zosiyanasiyana zomwe zimagwiritsidwa ntchito m'njira zosiyanasiyana. Ma valve odziwika kwambiri a thermoplastic amapangidwa ndi polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polypropylene (PP), ndi polyvinylidene fluoride (PVDF). Ma valve a PVC ndi CPVC nthawi zambiri amalumikizidwa ku mapaipi pogwiritsa ntchito ma socket socket osungunula, kapena ma threaded ndi flange; pomwe, PP ndi PVDF zimafuna kulumikizidwa kwa zigawo za mapaipi, kaya pogwiritsa ntchito ukadaulo wotentha, wa butt- kapena electro-fusion.

Ma valve a thermoplastic ndi abwino kwambiri m'malo owononga, koma ndi othandiza kwambiri pa ntchito ya madzi chifukwa alibe lead1, sagwira ntchito yochotsa zinc ndipo sachita dzimbiri. Makina ndi ma valve a mapaipi a PVC ndi CPVC ayenera kuyesedwa ndikuvomerezedwa ndi muyezo wa NSF [National Sanitation Foundation] 61 kuti apeze zotsatira zabwino pa thanzi, kuphatikizapo lead yochepa yofunikira pa Annex G. Kusankha zinthu zoyenera zamadzimadzi owononga kungathe kuchitidwa poyang'ana buku lothandizira mankhwala la wopanga ndikumvetsetsa momwe kutentha kudzakhudzira mphamvu ya zipangizo za pulasitiki.

Ngakhale kuti polypropylene ili ndi theka la mphamvu ya PVC ndi CPVC, ili ndi mphamvu zambiri zotsutsana ndi mankhwala chifukwa palibe zosungunulira zodziwika. PP imagwira ntchito bwino mu acetic acid ndi hydroxides, ndipo imagwiranso ntchito ngati njira zochepetsera ma acid ambiri, alkalis, mchere ndi mankhwala ambiri achilengedwe.

PP imapezeka ngati chinthu chokhala ndi utoto kapena chopanda utoto (chachilengedwe). PP yachilengedwe imawonongeka kwambiri ndi kuwala kwa ultraviolet (UV), koma mankhwala omwe ali ndi utoto wakuda wa kaboni woposa 2.5% amakhala ndi UV yokhazikika mokwanira.

Mapaipi a PVDF amagwiritsidwa ntchito m'mafakitale osiyanasiyana kuyambira ku mankhwala mpaka ku migodi chifukwa cha mphamvu ya PVDF, kutentha kwa ntchito komanso kukana mankhwala ku mchere, ma asidi amphamvu, maziko osungunuka ndi zinthu zambiri zachilengedwe. Mosiyana ndi PP, PVDF siiwonongeka ndi kuwala kwa dzuwa; komabe, pulasitikiyo imaonekera bwino ku kuwala kwa dzuwa ndipo imatha kuwonetsa madziwo ku kuwala kwa UV. Ngakhale kuti kapangidwe ka PVDF kachilengedwe, kopanda utoto ndi kabwino kwambiri pakugwiritsa ntchito mkati, kuwonjezera utoto monga wofiira wa chakudya kungathandize kuwonetsa kuwala kwa dzuwa popanda kuwononga madzi.

Makina apulasitiki ali ndi zovuta pakupanga, monga kukhudzidwa ndi kutentha ndi kufalikira ndi kufupika kwa kutentha, koma mainjiniya amatha kupanga mapaipi okhala ndi nthawi yayitali komanso otsika mtengo kuti agwiritsidwe ntchito m'malo wamba komanso owononga. Chofunika kwambiri pakupanga ndikuti kuchuluka kwa kutentha kwa mapulasitiki ndi kwakukulu kuposa chitsulo - thermoplastic ndi yowirikiza kasanu mpaka kasanu ndi kamodzi kuposa chitsulo, mwachitsanzo.

Popanga mapaipi ndi kuganizira momwe ma valve amagwirira ntchito komanso momwe ma valve amathandizira, chinthu chofunikira kwambiri chomwe chimaganiziridwa mu thermoplastics ndi kutalika kwa kutentha. Kupsinjika ndi mphamvu zomwe zimachitika chifukwa cha kufalikira ndi kupindika kwa kutentha zimatha kuchepetsedwa kapena kuthetsedwa mwa kupereka kusinthasintha kwa mapaipi kudzera mu kusintha pafupipafupi kwa njira kapena kuyambitsa ma expansion loops. Mwa kupereka kusinthasintha kumeneku kudzera mu mapaipi, valavu ya pulasitiki sidzafunika kuyamwa kupsinjika kwakukulu (Chithunzi 1).

Popeza ma thermoplastics amakhudzidwa ndi kutentha, mphamvu ya valavu imachepa pamene kutentha kukukwera. Zipangizo zosiyanasiyana zapulasitiki zimakhala ndi kusokonekera kofanana ndi kutentha kokwera. Kutentha kwamadzimadzi sikungakhale kokha gwero la kutentha lomwe lingakhudze mphamvu ya mavalavu apulasitiki—kutentha kwakukulu kwakunja kuyenera kukhala gawo la kuganizira kapangidwe kake. Nthawi zina, kusapanga mapaipi kutentha kwakunja kungayambitse kutsika kwambiri chifukwa cha kusowa kwa zothandizira mapaipi. PVC ili ndi kutentha kwakukulu kwa ntchito ya 140°F; CPVC ili ndi mphamvu yayikulu ya 220°F; PP ili ndi mphamvu yayikulu ya 180°F; ndipo mavalavu a PVDF amatha kusunga mphamvu mpaka 280°F (Chithunzi 2).

Kumbali ina ya kutentha, mapaipi ambiri apulasitiki amagwira ntchito bwino kutentha komwe kuli pansi pa kuzizira. Ndipotu, mphamvu yokoka imawonjezeka mu mapaipi a thermoplastic kutentha kukachepa. Komabe, kukana kwa mphamvu ya pulasitiki yambiri kumachepa kutentha kukatsika, ndipo kusweka kumawonekera m'mapaipi omwe akhudzidwa. Bola ngati ma valve ndi mapaipi oyandikana nawo sakusokonezedwa, osakhudzidwa ndi kugundana kapena kugwedezeka kwa zinthu, ndipo mapaipiwo sakugwa panthawi yogwira ntchito, zotsatirapo zoyipa pa mapaipi apulasitiki zimachepa.

Mitundu ya ma valve otenthetsera kutentha

Ma valve a mpira,ma valve owunikira,mavavu a gulugufeNdipo ma valavu a diaphragm amapezeka mu zipangizo zosiyanasiyana za thermoplastic za schedule 80 pressure piping systems zomwe zilinso ndi mitundu yosiyanasiyana ya trim ndi zowonjezera. Vavu ya mpira yodziwika bwino imapezeka kuti ndi yogwirizana bwino kuti ithandize kuchotsa thupi la valavu kuti likonzedwe popanda kusokoneza mapaipi olumikizira. Ma valavu owunikira a thermoplastic amapezeka ngati ma check ball, swing checks, y-checks ndi cone checks. Ma valavu a gulugufe amalumikizana mosavuta ndi ma flange achitsulo chifukwa amafanana ndi mabowo a bolt, ma bolt circles ndi miyeso yonse ya ANSI Class 150. M'mimba mwake wosalala wamkati mwa zigawo za thermoplastic zimangowonjezera kuwongolera kolondola kwa ma valavu a diaphragm.

Ma valve a mpira mu PVC ndi CPVC amapangidwa ndi makampani angapo aku US ndi akunja okhala ndi kukula kwa mainchesi 1/2 mpaka mainchesi 6 okhala ndi zolumikizira za socket, ulusi kapena flange. Kapangidwe kameneka ka ma valve a mpira amakono kamakhala ndi mtedza awiri womwe umakulungika pathupi, kukanikiza zisindikizo za elastomeric pakati pa thupi ndi zolumikizira kumapeto. Opanga ena akhala akusunga kutalika komweko kwa valavu ya mpira ndi ulusi wa mtedza kwa zaka zambiri kuti alole kusintha mosavuta ma valve akale popanda kusintha mapaipi oyandikana nawo.

Ma valve a mpira okhala ndi zisindikizo za ethylene propylene diene monomer (EPDM) elastomeric ayenera kuvomerezedwa ndi NSF-61G kuti agwiritsidwe ntchito m'madzi akumwa. Zisindikizo za Fluorocarbon (FKM) elastomeric zingagwiritsidwe ntchito ngati njira ina m'malo mwa machitidwe omwe akugwirizana ndi mankhwala. FKM ingagwiritsidwenso ntchito pazinthu zambiri zokhudzana ndi ma acid amchere, kupatula hydrogen chloride, njira zamchere, ma hydrocarbons a chlorinated ndi mafuta a petroleum.

Chithunzi 3. Valavu ya mpira yolumikizidwa ku thanki Chithunzi 4. Valavu yowunikira mpira yoyikidwa molunjika. Mavavu a mpira a PVC ndi CPVC, 1/2-inch mpaka 2 mainchesi, ndi njira yabwino yogwiritsira ntchito madzi otentha ndi ozizira pomwe ntchito yayikulu yosagwedezeka madzi ingakhale yabwino ngati 250 psi pa 73°F. Mavavu akuluakulu a mpira, 2-1/2 mainchesi mpaka 6 mainchesi, adzakhala ndi mphamvu yotsika ya 150 psi pa 73°F. Amagwiritsidwa ntchito kwambiri poyendetsa mankhwala, mavavu a mpira a PP ndi PVDF (Zithunzi 3 ndi 4), omwe amapezeka mu kukula kwa 1/2-inch mpaka 4 mainchesi okhala ndi socket, threaded kapena flanged-end nthawi zambiri amawerengedwa kuti ndi ntchito yayikulu yosagwedezeka madzi ya 150 psi pa kutentha kwa mlengalenga.

Ma valve oyezera mpira a thermoplastic amadalira mpira wokhala ndi mphamvu yokoka yochepa kuposa ya madzi, kotero kuti ngati mphamvu yatayika kumbali yakumtunda, mpirawo udzamiranso motsutsana ndi pamwamba potseka. Ma valve awa angagwiritsidwe ntchito mofanana ndi ma valve ofanana a mpira wa pulasitiki chifukwa sabweretsa zinthu zatsopano mu dongosololi. Mitundu ina ya ma valve oyezera ikhoza kukhala ndi ma spring achitsulo omwe sangapitirire m'malo owononga.

Chithunzi 5. Valavu ya gulugufe yokhala ndi elastomeric liner. Valavu ya gulugufe ya pulasitiki yokhala ndi mainchesi 2 mpaka mainchesi 24 ndi yotchuka pamakina akuluakulu opachikira mapaipi. Opanga mavavu a gulugufe a pulasitiki amagwiritsa ntchito njira zosiyanasiyana pomanga ndi kutseka malo. Ena amagwiritsa ntchito elastomeric liner (Chithunzi 5) kapena O-ring, pomwe ena amagwiritsa ntchito elastomeric-coated disc. Ena amapanga thupi kuchokera ku chinthu chimodzi, koma zigawo zamkati, zonyowa zimagwiritsidwa ntchito ngati zipangizo za dongosolo, zomwe zikutanthauza kuti thupi la vavu ya gulugufe la polypropylene lingakhale ndi EPDM liner ndi PVC disc kapena ma configurations ena angapo okhala ndi thermoplastics ndi elastomeric seals zomwe zimapezeka nthawi zambiri.

Kukhazikitsa valavu ya gulugufe ya pulasitiki ndikosavuta chifukwa mavalavu amenewa amapangidwa kuti akhale a wafer okhala ndi zisindikizo za elastomeric zomwe zimapangidwa m'thupi. Safunikira kuwonjezera gasket. Pakati pa ma flange awiri ogwirizana, kutsekeka kwa valavu ya gulugufe ya pulasitiki kuyenera kuchitidwa mosamala powonjezera mphamvu ya bolt m'magawo atatu. Izi zimachitika kuti zitsimikizire kuti pali chisindikizo chofanana pamwamba pake komanso kuti palibe kupsinjika kwa makina kosagwirizana komwe kumagwiritsidwa ntchito pa valavu.

Chithunzi 6. Valavu ya diaphragm Akatswiri a valavu yachitsulo adzapeza ntchito zapamwamba za mavalavu a pulasitiki a diaphragm okhala ndi zizindikiro zoyendetsera mawilo ndi malo (Chithunzi 6); komabe, valavu ya diaphragm ya pulasitiki ikhoza kukhala ndi zabwino zina kuphatikiza makoma osalala amkati mwa thupi la thermoplastic. Mofanana ndi valavu ya mpira wa pulasitiki, ogwiritsa ntchito mavalavu awa ali ndi mwayi woyika kapangidwe kake kogwirizana, komwe kungakhale kothandiza kwambiri pantchito yokonza valavu. Kapena, wogwiritsa ntchito akhoza kusankha maulumikizidwe olumikizana. Chifukwa cha zosankha zonse za thupi ndi zida za diaphragm, valavu iyi ingagwiritsidwe ntchito pazinthu zosiyanasiyana zamankhwala.

Monga momwe zilili ndi valavu iliyonse, chinsinsi choyendetsera mavalavu apulasitiki ndikuzindikira zofunikira pakugwira ntchito monga mphamvu ya pneumatic motsutsana ndi magetsi komanso mphamvu ya DC motsutsana ndi AC. Koma ndi pulasitiki, wopanga ndi wogwiritsa ntchito ayeneranso kumvetsetsa mtundu wa malo omwe angazungulire choyendetsera. Monga tanenera kale, mavalavu apulasitiki ndi njira yabwino kwambiri yogwiritsira ntchito zinthu zowononga, zomwe zimaphatikizapo malo owononga akunja. Chifukwa cha izi, zinthu zomwe zimayikidwa mu mavalavu apulasitiki ndizofunikira kwambiri. Opanga mavalavu apulasitiki ali ndi njira zokwaniritsira zosowa za malo owononga awa monga ma actuator ophimbidwa ndi pulasitiki kapena zikwama zachitsulo zophimbidwa ndi epoxy.

Monga momwe nkhaniyi ikusonyezera, ma valve apulasitiki masiku ano amapereka mitundu yonse ya njira zogwiritsira ntchito ndi zochitika zatsopano.