Lub hauv paus ntsiab lus ntawm tshuaj lom thiab teeb meem roj ntes
Combustible gases yog cov pa phem tshaj plaws uas tau ntsib nyob rau hauv kev lag luam chaw xws li petrochemicals. Lawv feem ntau yog cov pa roj carbon monoxide xws li alkanes thiab qee cov roj inorganic xws li carbon monoxide. Kev tawg ntawm combustible gases yuav tsum tau tej yam kev mob, uas yog: ib tug tej yam concentration ntawm combustible gases, ib tug npaum li cas ntawm cov pa oxygen, thiab ib qhov chaw ntawm hluav taws kub txaus rau ignite lawv. Cov no yog peb lub ntsiab lus tseem ceeb ntawm kev tawg, thiab tsis muaj ib qho tseem ceeb. Hauv lwm lo lus, qhov tsis muaj ib qho ntawm cov xwm txheej no yuav tsis ua rau hluav taws kub lossis tawg. Thaum cov roj hluav taws xob (steam, plua plav) thiab cov pa oxygen sib xyaw thiab ncav cuag ib qho concentration, lawv yuav tawg thaum raug hluav taws kub nrog qee qhov kub. Peb xa mus rau qhov concentration ntawm cov roj combustible tawg thaum raug hluav taws kub raws li qhov kev txwv ntawm qhov tawg, luv luv li qhov txwv tsis pub tawg, uas feem ntau qhia hauv%. Qhov tseeb, qhov sib xyaw no tsis tas yuav tawg ntawm qhov sib tov sib xyaw thiab yuav tsum muaj qhov sib txawv. Thaum lub concentration ntawm cov roj combustible qis dua LEL (* tsawg explosive limit) (tsis txaus combustible gas concentration) thiab saum toj no UEL (* siab explosive limit) (tsis txaus oxygen), tsis muaj tawg yuav tshwm sim. LEL thiab UEL ntawm cov roj hluav taws xob sib txawv sib txawv (saib cov lus qhia hauv qhov teeb meem thib yim),
Qhov no yuav tsum tau ua tiag tiag thaum calibrating cov cuab yeej. Rau cov laj thawj kev nyab xeeb, feem ntau peb yuav tsum tau tshaj tawm lub tswb thaum lub siab ntawm cov roj hluav taws xob yog 10% thiab 20% ntawm LEL, qhov twg 10% LEL raug xa mus. Ua kev ceeb toom ceeb toom, thaum 20% LEL hu ua kev ceeb toom txaus ntshai. Yog vim li cas peb hu lub combustible gas detector LEL detector.
Nws yuav tsum tau muab sau tseg tias 100% tso tawm nyob rau hauv lub LEL detector tsis qhia hais tias cov concentration ntawm combustible gas ncav cuag 100% ntawm cov roj ntim, tab sis mus txog 100% ntawm LEL, uas yog sib npaug rau qhov tsawg explosive txwv ntawm combustible gas. Yog tias nws yog methane, 100% LEL=4% ntim concentration (VOL). Hauv kev ua haujlwm, tus ntes uas ntsuas cov pa roj hauv LEL hom yog cov khoom siv catalytic combustion detector. Nws lub hauv paus ntsiab lus yog tus choj dual (feem ntau hu ua Wheatstone choj) nrhiav kom pom. Cov tshuaj catalytic combustion yog coated ntawm ib qho ntawm cov platinum hlau txuas hniav. Txawm hais tias cov roj hluav taws xob tsis zoo, tsuav nws tuaj yeem raug hluav taws xob los ntawm electrode, qhov kev tiv thaiv ntawm platinum hlau choj yuav hloov vim qhov kub thiab txias. Qhov kev hloov pauv no yog proportional rau qhov concentration ntawm cov roj hluav taws xob, thiab qhov concentration ntawm cov roj hluav taws xob tuaj yeem raug xam los ntawm qhov ntsuas qhov ntsuas hluav taws xob thiab microprocessor. Thermal conductivity VOL detectors uas ncaj qha ntsuas lub ntim concentration ntawm combustible gases kuj muaj nyob rau hauv kev ua lag luam, thiab twb muaj detectors uas ua ke LEL / VOL. VOL combustible detector yog tshwj xeeb tshaj yog haum rau ntsuas combustibles nyob rau hauv ib puag ncig tsis muaj oxygen.
