We rely on valves to stop and seal the flow of media in its various forms: solids, liquids, and gases. Leakage of solids or liquids is relatively easy to spot, but some gas leakage isn't something that can be detected by the naked eye.
Nrog kev pab los ntawm kev sim, peb tau paub txog qhov tsis ua haujlwm ntawm lub valve kom txaus kom tsis txhob muaj cov pa roj tawm ntawm kev khiav tawm. Nrog rau qhov kev paub no, peb tuaj yeem txhim kho peb cov txheej txheem los ntawm kev txhim kho cov teeb meem li qub.
Qhov tseem ceeb ntawm Cov Txheej Txheem Kev Xeem
Cov qauv zoo rau kev ntsuas valve thiab ntim khoom yog tsim los ntawm cov koom haum kev lag luam xws li ANSI, API, ISO, MESC, thiab TA-LUFT.
Today, we'll focus on API pressure testing standards. The American Petroleum Institute (API) was founded in 1919 after World War I. The war raised awareness of the vital role the petroleum industry holds in the United States, so the API was formed to bolster and secure domestic oil and gas production. Over 700 API standards have been put in place to promote efficiency, sustainability, and safety for both operations and the environment.
3 Hom API Valve Test
· API 622 – Tests process valve packing for levels of fugitive emissions.
· API 624 – Tests rising stem valves equipped with graphite packing for any fugitive emissions.
· API 641 Cov – Tests quarter-turn valves for levels of fugitive emissions.
Because API 622 is the first in the series of embedded low E valve and packing standards, it's what we'll cover today. For valves tested at API 641, packing must first qualify for the API 622 test. Also, for the packing used in an API 624 test, the valve must have been tested with API 622 first.
Vim li cas thiaj yuav tsum xeem Fugitive Emission Test?
Depending on what is leaked, fugitive emissions can be costly. There is concern surrounding methane gas emissions because this gas is flammable, considered to be harmful to the environment, and is a commodity. Not only is fugitive methane emission an environmental concern, but it's also a financial loss when seeping valuable methane or incurring costly governmental fines.
With valves being to blame for over 50 percent of fugitive emissions, they are the main focus for testing. The Natural Resources Defense Council estimates that leak monitoring and repair could potentially account for 18 percent of methane emission reduction. When plant operations call for fugitive emissions monitoring, LDAR (leak detection and repair) is typically part of a monthly testing protocol.
Qhov xwm zoo yog tias cov khoom siv roj ntsha tau nce ntxiv, emissions los ntawm qhov kev tsim tawm no tseem txo qis. Cov kev txhim kho no yog vim kev yeem ua raws li cov cai, lossis ob qho tib si. Kev nce qib hauv kev siv thev naus laus zis nrog rau kev txhim kho kev sim yog li cas peb txuas ntxiv txo cov pa phem tawm mus.
API 622 Kev Ntsuas Kev Ua Haujlwm
API 622 has three iterations. The first was established in 2006, the second in 2011, and the latest in 2018.
Qhov tsab xov xwm tsis ntev los no ntxiv txwv tsis pub tso pa tawm los ntawm kev txo tus lej mus rau 100 qhov chaw ib lab volumetric (ppmv) thiab nws tseem tsis tau txais kev tso cai ntawm lub caj pas bolt hloov. Ntxiv rau qhov 1/4-nti packing (raws li ib feem ntawm qhov kev xeem dhau los), qhov thib peb tsab muaj 1/8-nti packing qauv kuaj. Qhov no kho qhov teeb meem nrog cov kev xeem dhau los iterations.
API 622 yog qhov kev sim ua tau zoo. Cov hauv qab no piav qhia txog qhov tsis muaj zog ntawm qhov kev ntsuam xyuas li qub tau kuaj xyuas.
Fugitive Emissions
For the purpose of leak detection, the fugitive emission test for API 622 is not a pass/fail test. It's a 6-day stress test to see how many thermal cycles the valve can take before emissions exceed a certain threshold (previously 500 ppm and now 100 ppm).
Kev ntsuam xyuas yog txheej txheem 6-hnub uas suav nrog 1500 cycles. Vim tias cov roj methane siv rau qhov kev sim no, nws yog qhov zoo tshaj plaws uas cov txheej txheem no tshwm sim sab nraum zoov. Txhua hnub, lub valve raug kuaj ntawm 150 cycles nyob rau hauv ambient kub, ces rau lwm 150 cycles ntawm 500 degree F. Cheebtsam txias ib hmos rau lwm hnub ntawm kev sim. Yog tias los ntawm hnub tsib lub valve tuav, nws muaj nws qhov kev sim zaum kawg rau hnub rau nrog qhov kub thiab txias mus txog 10.
Rau qhov kev sim no ua pov thawj ua tiav, qhov xau tsis tuaj yeem tshaj 100 ppm thiab tsis zoo li cov qauv ua ntej ntawm qhov kev sim no, lub caj pas tsis tuaj yeem hloov kho kom raug rau cov dej xau.
Kev kuaj Corrosion
Ib yam li qhov kev sim ntsuas kev khiav tawm, qhov no kuj tsis yog qhov kev ntsuas dhau / poob. Nws saib xyuas rau pitting hauv cov hlau kom pom tias cov khoom ntim tau zoo npaum li cas rau lub qia. Nws kuj ntsuas qhov zoo ntawm tag nrho cov ntim.
Qhov kev ntsuas hlau no suav nrog kev ntub dej thiab compressing cov ntim 30, 000 megapascals. Cov ntim no ces qhwv ib ncig ntawm cov hlau. Cov kab sib txawv tuaj yeem kuaj tau raws li cov hlau sib txawv.
Khoom noj khoom haus
Sib txawv los ntawm kev khiav tawm thiab kev kuaj corrosive, cov khoom siv kev noj qab haus huv yog dhau / tsis ua haujlwm. Nws tshuaj xyuas cov khoom ntawm cov khoom ntim nrog rau cov ntsiab lus lubrication, cov ntsiab lus polytetrafluoroethylene, tshuaj leaching, ntxiv rau qhov hnyav thiab ntom.
Rau qhov kev ntsuas no, cov qauv valve tsis ua raws li yog:
· The graphite foil loses an excess of 15 percent of its weight at a temperature of 1000 degree F
· Graded packing loses more than 50 percent of its weight.
Tau txais API daim ntawv pov thawj foob yog cov txheej txheem nyuaj thiab meej, tab sis nws muab rau peb hauv kev lag luam kev thaj yeeb ntawm lub siab tias cov li qub uas peb siv tau zoo rau kev txo qis kev tawm tsam.