Txhua Yam Arc Flash: Qhov Tseeb, Cov Qauv, thiab Cov hnab looj tes tiv thaiv

Txhua Yam Arc Flash: Qhov Tseeb, Cov Qauv, thiab Cov hnab looj tes tiv thaiv

Arc flash - nws suab hnyav, thiab nrog ntau dua 30,000 qhov xwm txheej thiab 400 tus neeg tuag hauv ib xyoos *, nws's tuag loj. Ib qho arc flash tshwm sim thaum muaj qhov tso tawm tam sim ntawm hluav taws xob los ntawm huab cua los ntawm kev ua txhaum hauv hluav taws xob hluav taws xob. Qhov no ua rau muaj qhov kub thiab txias ceev ntawm cov hluav taws xob conductors, feem ntau ua rau tawg hu ua arc blast.

Ib qho xwm txheej arc flash tshwm sim tuaj yeem ua tsis tiav, tab sis cov uas tsim cov arc blasts hnyav tuaj yeem ua rau muaj kev phom sij heev thiab ua rau muaj kev puas tsuaj rau lub neej thiab khoom nyob ib puag ncig. Qhov kev tawg no feem ntau tshwm sim yam tsis muaj kev ceeb toom - ua rau cov khoom siv hluav taws xob raug puas tsuaj tag nrho, nrog rau kev raug mob hnyav (lossis tuag) rau leej twg hauv ob peb ko taw ntawm qhov tawg.

Hnav PPE kom raug thiab paub koj li cas'rov tawm tsam yog qhov yuav tsum muaj thaum ua haujlwm, tshwj xeeb tshaj yog thaum koj'rov ua haujlwm nyob ib puag ncig uas muaj peev xwm rau arc flash thiab blasts. Pab koj tawm, peb'tau muab tso ua ke ib qho kev piav qhia ntawm txhua yam koj xav paub txog arc flash.

Tsuas yog Lub Hwj Chim Ntau npaum li cas hauv Arc Flash?

Ntawm no'yog ceev saib. Lub zog loj tso tawm nyob rau hauv arc flash txhaum ua rau lub teeb ci, khaus thiab thermal tawg nrog qhov kub thiab txias uas tuaj yeem ncav cuag lossis tshaj 35,000° Fahrenheit (F) lossis 19,400° Celsius (C) ntawm lub arc terminals. Txhawm rau kom nkag siab zoo li lub hwj chim, saib cov kev sib piv hauv qab no:

Lub caij ntuj sov hnub: 100° F (38° C)

Lub Hnub Nyoog: 10,000° F (5,540° C)

Arc ntawm arc terminals: 35,540° F (19,700° C)

High-voltage arcs tuaj yeem ua rau lub arc blast uas tam sim ntawd heats hlau conductors thiab cov khoom nyob ib puag ncig kom vaporizing kub, blasting super-rhuab shrapnel, siab tsis, thiab nthuav plasma sab nraud nrog lub zog txawv tshaj plaw.

Suab nrov? Nws yog.

Cov teebmeem radiant ntawm qhov no tuaj yeem pom ntawm feem ntau ablated thiab eroded nyob ib sab phab ntsa thiab cov khoom siv - nrog rau cov neeg ua haujlwm hauv nws txoj kev. Kev tawg tuaj yeem cuam tshuam cov neeg ua haujlwm tawm ntawm lawv txhais taw, ua rau cov pob txha tawg lossis ua rau hluav taws xob, nrog rau ua rau kub hnyiab, pob txha pob ntseg tawg, lub ntsws tawg, thiab tuag taus.

Txawm hais tias ob qho tib si tshwm sim los ntawm tib lub arc txhaum, nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias arc flash txawv ntawm qhov arc blast.

Dab tsi OSHA Hais txog Arc Flash

Hauv Tebchaws Meskas, Lub Chaw Haujlwm Saib Xyuas Kev Nyab Xeeb thiab Kev Noj Qab Haus Huv (OSHA) xav kom cov tswv ntiav ua haujlwm los tiv thaiv cov neeg ua haujlwm los ntawm hluav taws xob phom sij, suav nrog arc flash, los ntawm kev xav kom cov neeg ua haujlwm muaj kev tiv thaiv taub hau mus rau ntiv taw, suav nrog cov kaus mom kev nyab xeeb, lub ntsej muag tiv thaiv, tiv thaiv nplaim taws. , thiab tiv thaiv tes thiab pob ntseg. 

Txhawm rau pab ua kom tau raws li qhov yuav tsum tau ua ntawm OSHA cov qauv rau kev nyab xeeb hluav taws xob, cov tswv lag luam kuj saib rau NFPA 70E, uas yog cov txheej txheem dav dav uas muaj cov ncauj lus kom ntxaws txog kev tiv thaiv cov neeg ua haujlwm los ntawm arc flashes. Txawm hais tias tsis yog OSHA xav tau, NFPA 70E qhia txog yuav ua li cas ua raws li OSHA's hluav taws xob kev nyab xeeb yuav tsum. Qhov kev sib raug zoo ntawm NFPA 70E thiab OSHA cov qauv kev nyab xeeb hluav taws xob no pab txhawb kev nyab xeeb hauv chaw ua haujlwm.

Hom Arc Flash-Rated Hnab looj tes

Cov hnab looj tes yog ib qho tseem ceeb ntawm PPE rau cov neeg ua haujlwm hluav taws xob thiab yuav tsum muaj cov dielectric siab thiab lub cev muaj zog nrog kev yoog raws thiab ua haujlwm kom txo tau qhov cuam tshuam ntawm arc flash. Muaj ob pawg tseem ceeb ntawm cov hnab looj tes uas tiv thaiv arc flash:

Roj Hmab insulating: Ua los ntawm roj hmab, cov hnab looj tes no yog txoj hauv kev ua haujlwm ib puag ncig arc flash txaus ntshai thiab tuaj yeem ua rau loj. Raws li NFPA 70E thiab CSA Z472 tus qauv, txhua hom kev ua haujlwm nrog kev poob siab ntawm ntau dua 50 volts (V) yuav tsum tau siv cov hnab looj tes roj hmab insulating.

Cov hnab looj tes tsis yog roj hmab: Ua los ntawm cov tawv tawv lossis cov khoom siv coated, cov hnab looj tes no yog cov nplaim hluav taws kub (FR) (xws li aramid, tawv, ntaub plaub, iav, thiab coated nylon) lossis kho (xws li Pyrovatix, Proban, lossis Indura). Cov hnab looj tes no muab cov khoom siv hluav taws xob uas xav tau ntawm cov hnab looj tes tiv thaiv hluav taws xob nrog kev yooj yim, lub zog, thiab ua haujlwm ntev.

Txhawm rau xaiv cov hnab looj tes zoo tshaj plaws rau txoj haujlwm, koj yuav tsum nkag siab txog qhov sib txawv ntawm qhov sib txawv arc flash. Cov kev ntsuas no yog ua raws li Hazard Risk Category (HRC) cov qauv thiab Arc Thermal Protective Value (ATPV). HRC yog tus qauv kev nyab xeeb uas qhia txog qhov tsawg kawg nkaus ntawm PPE tiv thaiv tus neeg ua haujlwm xav tau raws li qhov muaj feem cuam tshuam rau kev phom sij, xws li 0 txog 4, nrog rau 4 yog qhov txaus ntshai tshaj plaws. ATPV yog qhov xwm txheej lub zog xav tau los ua kom kub hnyiab thib ob; tus nqi no yog muab nyob rau hauv calories ib centimeter squared (cal/cm²). 

ASTM F1506 yog tus qauv txiav txim siab HRC ntawm hnab looj tes, thiab ASTM F2675 yog tus qauv txiav txim siab ATPV. NFPA 70E hais txog ASTM F2675 rau arc flash kuaj cov hnab looj tes thiab OSHA 1910.269 yuav tsum muaj cov hnab looj tes arc rau kev nthuav tawm ntau dua 14 cal / cm².