Ukuhlolwa kobufakazi kuyingxenye ebalulekile yokugcinwa kobuqotho bokuphepha kwezinhlelo zethu zokuphepha (i-SIS) kanye nezinhlelo ezihlobene nokuphepha (isb. ama-alamu abalulekile, izinhlelo zomlilo negesi, izinhlelo zokuvala ezisebenzisa izinsimbi, njll.). Ukuhlolwa kobufakazi kuwukuhlolwa okwenziwa njalo ukuthola ukwehluleka okuyingozi, ukuhlola ukusebenza okuhlobene nokuphepha (isb. ukusetha kabusha, ukudlula, ama-alamu, ukuxilongwa, ukuvala ngesandla, njll.), nokuqinisekisa ukuthi uhlelo luhlangabezana nezindinganiso zenkampani nezangaphandle. Imiphumela yokuhlolwa kobufakazi nayo iyisilinganiso sokusebenza kahle kohlelo lobuqotho bemishini ye-SIS kanye nokuthembeka kwensimu kohlelo.
Izinqubo zokuhlola ubufakazi zihlanganisa izinyathelo zokuhlola kusukela ekutholeni izimvume, ukwenza izaziso nokususa uhlelo ekusebenzeni ukuze luhlolwe kuya ekuqinisekiseni ukuhlolwa okuphelele, ukubhala phansi ukuhlolwa kobufakazi nemiphumela yako, ukubuyisela uhlelo ekusebenzeni, kanye nokuhlola imiphumela yokuhlolwa yamanje kanye nemiphumela yokuhlolwa kobufakazi bangaphambilini.
I-ANSI/ISA/IEC 61511-1, Isigaba 16, sihlanganisa ukuhlolwa kobufakazi be-SIS. Umbiko wobuchwepheshe we-ISA TR84.00.03 – “Ubuqotho Bokusebenza Kwezinhlelo Zokuphepha Ezisetshenziswayo (SIS),” uhlanganisa ukuhlolwa kobufakazi futhi okwamanje ungaphansi kokubuyekezwa kanti inguqulo entsha kulindeleke ukuthi iphume maduze. Umbiko wobuchwepheshe we-ISA TR96.05.02 – “Ukuhlolwa Kobufakazi Bendawo Yamavalvu Azenzakalelayo” okwamanje kuyathuthukiswa.
Umbiko we-HSE wase-UK CRR 428/2002 – “Izimiso zokuhlola ubufakazi bezinhlelo zokuphepha embonini yamakhemikhali” zinikeza ulwazi mayelana nokuhlolwa kobufakazi kanye nalokho okwenziwa yizinkampani e-UK.
Inqubo yokuhlola ubufakazi isekelwe ekuhlaziyweni kwezindlela zokwehluleka eziyingozi ezaziwayo zengxenye ngayinye endleleni yokuhamba ye-safety instrumented function (SIF), ukusebenza kwe-SIF njengohlelo, nokuthi (futhi uma) kufanele kuhlolwe kanjani imodi yokwehluleka okuyingozi. Ukuthuthukiswa kwenqubo kufanele kuqale esigabeni sokuklama se-SIF ngokuklama uhlelo, ukukhethwa kwezingxenye, kanye nokunqunywa kokuthi ukuhlolwa kobufakazi kuzohlolwa nini futhi kanjani. Izinsimbi ze-SIS zinezinga elihlukahlukene lobunzima bokuhlola ubufakazi okumele bucatshangelwe ekwakhiweni, ekusebenzeni nasekugcinweni kwe-SIF. Isibonelo, amamitha e-orifice kanye nama-pressure transmitters kulula ukuwahlola kune-Coriolis mass flowmeters, mag meter noma izinzwa zezinga le-radar emoyeni. Ukusetshenziswa kanye nokwakheka kwe-valve nakho kungathinta ukuphelela kokuhlolwa kobufakazi be-valve ukuqinisekisa ukuthi ukwehluleka okuyingozi nokuqala ngenxa yokuwohloka, ukuxhuma noma ukwehluleka okuncike esikhathini akuholeli ekwehlulekeni okubalulekile ngaphakathi kwesikhawu sokuhlola esikhethiwe.
Nakuba izinqubo zokuhlola ubufakazi zivame ukwakhiwa ngesikhathi sesigaba sobunjiniyela be-SIF, kufanele futhi zibuyekezwe yi-SIS Technical Authority, i-Operations kanye nochwepheshe bezinsimbi abazokwenza ukuhlolwa. Ukuhlaziywa kokuphepha komsebenzi (i-JSA) kufanele kwenziwe futhi. Kubalulekile ukuthola imvume yesitshalo mayelana nokuthi yiziphi izivivinyo ezizokwenziwa nokuthi nini, kanye nokwenzeka kwazo ngokomzimba nangokwezokuphepha. Isibonelo, akusizi ngalutho ukucacisa ukuhlolwa kwe-partial-stroke lapho iqembu le-Operations lingavumi ukukwenza. Kunconywa futhi ukuthi izinqubo zokuhlola ubufakazi zibuyekezwe uchwepheshe ozimele wendaba (i-SME). Ukuhlolwa okuvamile okudingekayo ukuze kuhlolwe ubufakazi bokusebenza okugcwele kuboniswe kuMfanekiso 1.
Izidingo zokuhlolwa kobufakazi bokusebenza okugcwele Umfanekiso 1: Incazelo yokuhlolwa kobufakazi bokusebenza okugcwele yomsebenzi wezinto zokuphepha (SIF) kanye nohlelo lwawo lwezinto zokuphepha (SIS) kufanele ichaze noma ibhekisele ezinyathelweni ngokulandelana kusukela ekulungiseleleni ukuhlolwa kanye nezinqubo zokuhlola kuya kuzaziso kanye nemibhalo.
Umfanekiso 1: Ukucaciswa kokuhlolwa okugcwele kobufakazi bomsebenzi womsebenzi wezinto zokuphepha (i-SIF) kanye nohlelo lwawo lwezinto zokuphepha (i-SIS) kufanele kuchaze noma kubhekisele ezinyathelweni ngokulandelana kusukela ekulungiseleleni ukuhlolwa kanye nezinqubo zokuhlola kuya kuzaziso kanye nemibhalo.
Ukuhlolwa kobufakazi kuyisenzo sokulungisa esihleliwe okufanele senziwe ngabasebenzi abanekhono abaqeqeshwe ekuhlolweni kwe-SIS, inqubo yobufakazi, kanye nama-loop e-SIS abazowahlola. Kufanele kube nokuqondiswa kwenqubo ngaphambi kokwenza ukuhlolwa kokuqala kobufakazi, kanye nempendulo ku-SIS Technical Authority yesayithi ngemuva kwalokho ukuze kuthuthukiswe noma kulungiswe.
Kunezindlela ezimbili eziyinhloko zokuhluleka (eziphephile noma eziyingozi), ezihlukaniswe ngezindlela ezine—eziyingozi ezingatholakali, eziyingozi ezitholwe (ngokuxilongwa), eziphephile ezingatholakali kanye neziphephile ezitholwe. Amagama okuhluleka okungatholakali ayingozi nayingozi asetshenziswa ngokushintshana kulesi sihloko.
Ekuhlolweni kobufakazi be-SIF, sinesithakazelo esikhulu ezindleleni zokwehluleka ezingabonakali eziyingozi, kodwa uma kukhona ukuxilongwa komsebenzisi okuthola ukwehluleka okuyingozi, lokhu kuhlonza kufanele kuhlolwe ubufakazi. Qaphela ukuthi ngokungafani nokuxilongwa komsebenzisi, ukuxilongwa kwangaphakathi kwedivayisi ngokuvamile akunakuqinisekiswa njengokusebenza ngumsebenzisi, futhi lokhu kungathinta ifilosofi yokuhlola ubufakazi. Uma kuthathwa ikhredithi yokuhlonza ekubalweni kwe-SIL, ama-alamu okuhlonza (isb. ama-alamu angaphandle kwebanga) kufanele ahlolwe njengengxenye yokuhlolwa kobufakazi.
Izindlela zokwehluleka zingahlukaniswa kabanzi zibe yilezo ezihlolwe ngesikhathi sokuhlolwa kobufakazi, lezo ezingahlolwanga, kanye nokwehluleka kokuqala noma ukwehluleka okuncike esikhathini. Ezinye izindlela zokwehluleka eziyingozi zingase zingahlolwa ngokuqondile ngezizathu ezahlukene (isb. ubunzima, isinqumo sobunjiniyela noma sokusebenza, ukungazi, ukungakwazi, ukushiywa noma amaphutha esistimu, amathuba aphansi okwenzeka, njll.). Uma kunezindlela zokwehluleka ezaziwayo ezingeke zihlolwe, isinxephezelo kufanele senziwe ekwakhiweni kwedivayisi, inqubo yokuhlola, ukushintshwa kwedivayisi ngezikhathi ezithile noma ukwakhiwa kabusha, kanye/noma ukuhlolwa kokucabanga kufanele kwenziwe ukuze kuncishiswe umthelela ekuthembekeni kwe-SIF kokungahloli.
Ukwehluleka kokuqala kuyisimo noma isimo esihlazisayo kangangokuthi ukwehluleka okubucayi nokuyingozi kungalindelwa ngokunengqondo ukuthi kwenzeke uma izinyathelo zokulungisa zingathathwa ngesikhathi. Ngokuvamile kutholwa ngokuqhathanisa ukusebenza nokuhlolwa kobufakazi bokuqala noma kwamuva (isb. ukusayina kwe-valve noma izikhathi zokuphendula kwe-valve) noma ngokuhlola (isb. i-port yenqubo exhunyiwe). Ukwehluleka kokuqala kuvame ukuxhomeka esikhathini—uma idivayisi noma inhlangano isebenza isikhathi eside, kuba yilapho yonakala khona kakhulu; izimo ezenza kube lula ukwehluleka okungahleliwe ziba namathuba amaningi, ukuxhuma i-port yenqubo noma ukwakheka kwenzwa ngokuhamba kwesikhathi, impilo yokusebenza iphelile, njll. Ngakho-ke, lapho isikhathi sokuhlola ubufakazi siside, kulapho kungenzeka khona ukwehluleka kokuqala noma okuncike esikhathini. Noma yikuphi ukuvikelwa ekuhlulekeni kokuqala nakho kumele kuhlolwe ubufakazi (ukuhlanza i-port, ukulandelela ukushisa, njll.).
Izinqubo kumele zibhalwe ukuze kuhlolwe ubufakazi bokwehluleka okuyingozi (okungatholakali). Imodi yokwehluleka kanye nokuhlaziywa komphumela (FMEA) noma amasu emodi yokwehluleka, ukuhlaziywa komphumela kanye nokuxilonga (FMEDA) angasiza ekuboneni ukwehluleka okuyingozi okungatholakali, kanye nalapho ukumbozwa kokuhlolwa kobufakazi kumele kuthuthukiswe khona.
Izinqubo eziningi zokuhlola ubufakazi zisekelwe kokuhlangenwe nakho okubhaliwe kanye namathempulethi avela ezinqubweni ezikhona. Izinqubo ezintsha kanye nama-SIF ayinkimbinkimbi kakhulu adinga indlela ethuthukisiwe esebenzisa i-FMEA/FMEDA ukuhlaziya ukwehluleka okuyingozi, ukunquma ukuthi inqubo yokuhlola izokuhlola kanjani noma ngeke ikuhlole lokho kwehluleka, kanye nokumbozwa kokuhlolwa. Umdwebo webhulokhi lokuhlaziya imodi yokuhluleka kwezinga elikhulu wenzwa uboniswe kuMfanekiso 2. I-FMEA ngokuvamile idinga ukwenziwa kanye kuphela ngohlobo oluthile lwedivayisi futhi isetshenziswe kabusha kumadivayisi afanayo ngokucabangela isevisi yenqubo yawo, ukufakwa kanye namakhono okuhlola indawo.
Ukuhlaziywa kokuhluleka kwezinga le-macro Umfanekiso 2: Lo mdwebo webhulokhi lokuhlaziya imodi yokuhluleka kwezinga le-macro we-sensor kanye ne-pressure transmitter (PT) ukhombisa imisebenzi emikhulu evame ukuhlukaniswa ibe ukuhlaziywa okuningi kokuhluleka okuncane ukuze kuchazwe ngokugcwele ukwehluleka okungenzeka okuzobhekwana nakho ekuhlolweni komsebenzi.
Umfanekiso 2: Lo mdwebo webhulokhi lokuhlaziya imodi yokuhluleka kwezinga elikhulu le-sensor kanye ne-pressure transmitter (PT) ukhombisa imisebenzi emikhulu evame ukuhlukaniswa ibe ukuhlaziywa okuningi kokuhluleka okuncane ukuze kuchazwe ngokugcwele ukwehluleka okungenzeka okuzobhekwana nakho ekuhlolweni komsebenzi.
Iphesenti lokwehluleka okwaziwayo, okuyingozi, okungatholakali okuvivinywa ubufakazi libizwa ngokuthi ukumbozwa kokuhlolwa kobufakazi (PTC). I-PTC ivame ukusetshenziswa ekubalweni kwe-SIL "ukunxephezela" ukwehluleka kokuhlola ngokugcwele i-SIF. Abantu banenkolelo eyiphutha yokuthi ngenxa yokuthi bacabangele ukuntuleka kokumbozwa kokuhlolwa ekubalweni kwabo kwe-SIL, baklame i-SIF ethembekile. Iqiniso elilula liwukuthi, uma ukumbozwa kokuhlolwa kwakho kungu-75%, futhi uma ulinganise lelo nani ekubalweni kwakho kwe-SIL nezinto ozivivinyayo kakade ozivivinya kaningi, u-25% wokwehluleka okuyingozi kusengenzeka ngokwezibalo. Angifuni neze ukuba kulowo 25%.
Imibiko yokugunyazwa kwe-FMEDA kanye nezincwadi zokuphepha zamadivayisi ngokuvamile zinikeza inqubo yokuhlola ubufakazi obuncane kanye nokumbozwa kokuhlolwa kobufakazi. Lokhu kunikeza isiqondiso kuphela, hhayi zonke izinyathelo zokuhlola ezidingekayo ukuze kuhlolwe ubufakazi obuphelele. Ezinye izinhlobo zokuhlaziya ukwehluleka, njengokuhlaziywa kwesihlahla samaphutha kanye nokugcinwa okugxile ekuthembekeni, nazo zisetshenziselwa ukuhlaziya ukwehluleka okuyingozi.
Ukuhlolwa kobufakazi kungahlukaniswa kube ukuhlolwa kokusebenza okugcwele (ukuqala kusukela ekuqaleni kuya ekugcineni) noma ukuhlolwa kokusebenza okungaphelele (Isithombe 3). Ukuhlolwa kokusebenza okungaphelele kuvame ukwenziwa lapho izingxenye ze-SIF zinezikhawu zokuhlola ezihlukene ekubalweni kwe-SIL ezingahambisani nokuvalwa okuhleliwe noma ukujika. Kubalulekile ukuthi izinqubo zokuhlola ubufakazi bokusebenza okungaphelele zihlangane ukuze ndawonye zihlole konke ukusebenza kokuphepha kwe-SIF. Ngokuhlolwa kokusebenza okungaphelele, kusanconywa ukuthi i-SIF ibe nokuhlolwa kokuqala kobufakazi kusukela ekuqaleni kuya ekugcineni, kanye nokuhlolwa okulandelayo ngesikhathi sokujika.
Ukuhlolwa kobufakazi obungaphelele kufanele kuhlanganiswe Isithombe 3: Ukuhlolwa kobufakazi obungaphelele okuhlanganisiwe (ngezansi) kufanele kufake yonke imisebenzi yokuhlolwa kobufakazi obuphelele obusebenzayo (phezulu).
Umfanekiso 3: Ukuhlolwa kobufakazi obungaphelele okuhlanganisiwe (ngezansi) kufanele kufake yonke imisebenzi yokuhlolwa kobufakazi obusebenzayo obuphelele (phezulu).
Ukuhlolwa kobufakazi obungaphelele kuhlola iphesenti elilodwa kuphela lezindlela zokwehluleka kwedivayisi. Isibonelo esivamile ukuhlolwa kwevalvu yokushaya kancane, lapho ivalvu ishukunyiswa khona inani elincane (10-20%) ukuqinisekisa ukuthi ayibambekile. Lokhu kunomkhawulo wokuhlolwa kobufakazi obuphansi kunokuhlolwa kobufakazi ngesikhathi sokuhlolwa okuyinhloko.
Izinqubo zokuhlola ubufakazi zingahluka ngobunzima ngenxa yobunzima be-SIF kanye nefilosofi yenqubo yokuhlola yenkampani. Ezinye izinkampani zibhala izinqubo zokuhlola zesinyathelo ngesinyathelo ezinemininingwane, kanti ezinye zinezinqubo ezimfushane impela. Izinkomba kwezinye izinqubo, njengokulinganisa okujwayelekile, ngezinye izikhathi zisetshenziselwa ukunciphisa usayizi wenqubo yokuhlola ubufakazi nokusiza ukuqinisekisa ukuvumelana ekuhlolweni. Inqubo yokuhlola ubufakazi enhle kufanele inikeze imininingwane eyanele ukuqinisekisa ukuthi konke ukuhlolwa kufezwe kahle futhi kubhalwe phansi, kodwa hhayi imininingwane eminingi kakhulu engabangela ochwepheshe ukuba bafune ukweqa izinyathelo. Ukuba nochwepheshe, obhekene nokwenza isinyathelo sokuhlola, aqale isinyathelo sokuhlola esiqediwe kungasiza ukuqinisekisa ukuthi ukuhlolwa kuzokwenziwa kahle. Ukusayinwa kokuhlolwa kobufakazi okuqediwe nguMqondisi Wezinsimbi kanye nabamele Imisebenzi kuzogcizelela ukubaluleka futhi kuqinisekise ukuhlolwa kobufakazi okuqediwe kahle.
Impendulo yochwepheshe kufanele ihlale imenywa ukusiza ekuthuthukiseni inqubo. Impumelelo yenqubo yokuhlola ubufakazi isezandleni zochwepheshe, ngakho-ke umzamo wokubambisana unconywa kakhulu.
Ukuhlolwa kobufakazi okuningi kuvame ukwenziwa ngaphandle kwe-inthanethi ngesikhathi sokuvala noma sokuguqula. Kwezinye izimo, ukuhlolwa kobufakazi kungadingeka kwenziwe ku-inthanethi ngenkathi kusetshenziswa ukuze kuhlangatshezwane nezibalo ze-SIL noma ezinye izidingo. Ukuhlolwa ku-inthanethi kudinga ukuhlela nokuxhumana ne-Operations ukuze kuvunyelwe ukuhlolwa kobufakazi kwenziwe ngokuphephile, ngaphandle kokuphazamiseka kwenqubo, futhi ngaphandle kokubangela uhambo olungamanga. Kuthatha uhambo olulodwa kuphela olungamanga ukusebenzisa wonke ama-attaboy akho. Phakathi nalolu hlobo lokuhlolwa, lapho i-SIF ingatholakali ngokugcwele ukwenza umsebenzi wayo wokuphepha, 61511-1, Isigaba 11.8.5, sithi “Izinyathelo zokubuyisela eziqinisekisa ukuqhubeka kokusebenza okuphephile zizonikezwa ngokuhambisana no-11.3 lapho i-SIS idlula (ukulungiswa noma ukuhlolwa).” Inqubo yokuphatha isimo esingajwayelekile kufanele ihambisane nenqubo yokuhlola ubufakazi ukusiza ukuqinisekisa ukuthi lokhu kwenziwa kahle.
I-SIF ivame ukuhlukaniswa ibe izingxenye ezintathu eziyinhloko: izinzwa, izixazululi ze-logic kanye nezinto zokugcina. Ngokuvamile kukhona namadivayisi asizayo angahlotshaniswa ngaphakathi kwengxenye ngayinye yalezi zingxenye ezintathu (isb. izithiyo ze-IS, ama-trip amps, ama-interposing relay, ama-solenoid, njll.) okumele ahlolwe futhi. Izici ezibalulekile zokuhlola ubufakazi ngayinye yalezi zobuchwepheshe zingatholakala kubha eseceleni, “Izinzwa zokuhlola, izixazululi ze-logic kanye nezinto zokugcina” (ngezansi).
Ezinye izinto kulula ukuzihlola kunezinye. Ubuchwepheshe obuningi bokugeleza kanye nezinga besimanje kanye nobuchwepheshe obumbalwa obudala busesigabeni esinzima kakhulu. Lokhu kufaka phakathi ama-flowmeter e-Coriolis, ama-vortex metres, ama-mag metres, i-radar yasemoyeni, izinga le-ultrasonic, kanye nokushintsha kwenqubo ngaphakathi, ukubala okumbalwa. Ngenhlanhla, eziningi zalezi manje zinezindlela zokuxilonga ezithuthukisiwe ezivumela ukuhlolwa okuthuthukisiwe.
Ubunzima bokuhlola ubufakazi kudivayisi enjalo ensimini kumele bucatshangelwe ekwakhiweni kwe-SIF. Kulula ngobunjiniyela ukukhetha amadivayisi e-SIF ngaphandle kokucabanga ngokujulile ngalokho okungadingeka ukuze kuhlolwe ubufakazi bedivayisi, njengoba bengeke babe ngabantu abawahlolayo. Lokhu kuyiqiniso nangokuhlolwa kwe-partial-stroke, okuyindlela evamile yokuthuthukisa isilinganiso se-SIF amathuba okwehluleka uma kudingeka (PFDavg), kodwa kamuva i-Plant Operations ayifuni ukukwenza, futhi izikhathi eziningi ingase ingafuni. Njalo nikeza isitshalo ukwengamela ubunjiniyela be-SIF maqondana nokuhlolwa kobufakazi.
Ukuhlolwa kobufakazi kufanele kufake ukuhlolwa kokufakwa nokulungiswa kwe-SIF njengoba kudingeka ukuze kuhlangatshezwane no-61511-1, Isigaba 16.3.2. Kufanele kube nokuhlolwa kokugcina ukuqinisekisa ukuthi konke kufakwe izinkinobho, kanye nokuhlola kabili ukuthi i-SIF ibuyiselwe kahle yini enkonzweni yenqubo.
Ukubhala nokusebenzisa inqubo yokuhlola enhle kuyisinyathelo esibalulekile sokuqinisekisa ubuqotho be-SIF phakathi nesikhathi sayo sokuphila. Inqubo yokuhlola kufanele inikeze imininingwane eyanele ukuqinisekisa ukuthi ukuhlolwa okudingekayo kwenziwa njalo nangokuphepha futhi kubhalwe phansi. Ukwehluleka okuyingozi okungahlolwanga ngokuhlolwa kobufakazi kufanele kunxeshezelwe ukuqinisekisa ukuthi ubuqotho bokuphepha be-SIF bugcinwa ngokwanele phakathi nesikhathi sayo sokuphila.
Ukubhala inqubo enhle yokuhlola ubufakazi kudinga indlela enengqondo yokuhlaziya ubunjiniyela bokwehluleka okungaba yingozi, ukukhetha izindlela, nokubhala izinyathelo zokuhlola ubufakazi ezingaphakathi kwamandla okuhlola esitshalo. Endleleni, thola ukwamukelwa kwesitshalo kuzo zonke izigaba zokuhlolwa, bese uqeqesha ochwepheshe ukwenza nokubhala phansi ukuhlolwa kobufakazi kanye nokuqonda ukubaluleka kokuhlolwa. Bhala imiyalelo njengokungathi unguchwepheshe wezinsimbi okuzodingeka enze umsebenzi, nokuthi izimpilo zincike ekutholeni ukuhlolwa okufanele, ngoba bayakwenza.
Testing sensors, logic solvers and final elements A SIF is typically divided up into three main parts, sensors, logic solvers and final elements. There also typically are auxiliary devices that can be associated within each of these three parts (e.g. I.S. barriers, trip amps, interposing relays, solenoids, etc.) that must also be tested.Sensor proof tests: The sensor proof test must ensure that the sensor can sense the process variable over its full range and transmit the proper signal to the SIS logic solver for evaluation. While not inclusive, some of the things to consider in creating the sensor portion of the proof test procedure are given in Table 1. Table 1: Sensor proof test considerations Process ports clean/process interface check, significant buildup noted Internal diagnostics check, run extended diagnostics if available Sensor calibration (5 point) with simulated process input to sensor, verified through to the DCS, drift check Trip point check High/High-High/Low/Low-Low alarms Redundancy, voting degradation Out of range, deviation, diagnostic alarms Bypass and alarms, restrike User diagnostics Transmitter Fail Safe configuration verified Test associated systems (e.g. purge, heat tracing, etc.) and auxiliary components Physical inspection Complete as-found and as-left documentation Logic solver proof test: When full-function proof testing is done, the logic solver’s part in accomplishing the SIF’s safety action and related actions (e.g. alarms, reset, bypasses, user diagnostics, redundancies, HMI, etc.) are tested. Partial or piecemeal function proof tests must accomplish all these tests as part of the individual overlapping proof tests. The logic solver manufacturer should have a recommended proof test procedure in the device safety manual. If not and as a minimum, the logic solver power should be cycled, and the logic solver diagnostic registers, status lights, power supply voltages, communication links and redundancy should be checked. These checks should be done prior to the full-function proof test.Don’t make the assumption that the software is good forever and the logic need not be tested after the initial proof test as undocumented, unauthorized and untested software and hardware changes and software updates can creep into systems over time and must be factored into your overall proof test philosophy. The management of change, maintenance, and revision logs should be reviewed to ensure they are up to date and properly maintained, and if capable, the application program should be compared to the latest backup.Care should also be taken to test all the user logic solver auxiliary and diagnostic functions (e.g. watchdogs, communication links, cybersecurity appliances, etc.).Final element proof test: Most final elements are valves, however, rotating equipment motor starters, variable-speed drives and other electrical components such as contactors and circuit breakers are also used as final elements and their failure modes must be analyzed and proof tested.The primary failure modes for valves are being stuck, response time too slow or too fast, and leakage, all of which are affected by the valve’s operating process interface at trip time. While testing the valve at operating conditions is the most desirable case, Operations would generally be opposed to tripping the SIF while the plant is operating. Most SIS valves are typically tested while the plant is down at zero differential pressure, which is the least demanding of operating conditions. The user should be aware of the worst-case operational differential pressure and the valve and process degradation effects, which should be factored into the valve and actuator design and sizing.Commonly, to compensate for not testing at process operating conditions, additional safety pressure/thrust/torque margin is added to the valve actuator and inferential performance testing is done utilizing baseline testing. Examples of these inferential tests are where the valve response time is timed, a smart positioner or digital valve controller is used to record a valve pressure/position curve or signature, or advance diagnostics are done during the proof test and compared with previous test results or baselines to detect valve performance degradation, indicating a potential incipient failure. Also, if tight shut off (TSO) is a requirement, simply stroking the valve will not test for leakage and a periodic valve leak test will have to be performed. ISA TR96.05.02 is intended to provide guidance on four different levels of testing of SIS valves and their typical proof test coverage, based on how the test is instrumented. People (particularly users) are encouraged to participate in the development of this technical report (contact crobinson@isa.org).Ambient temperatures can also affect valve friction loads, so that testing valves in warm weather will generally be the least demanding friction load when compared to cold weather operation. As a result, proof testing of valves at a consistent temperature should be considered to provide consistent data for inferential testing for the determination of valve performance degradation.Valves with smart positioners or a digital valve controller generally have capability to create a valve signature that can be used to monitor degradation in valve performance. A baseline valve signature can be requested as part of your purchase order or you can create one during the initial proof test to serve as a baseline. The valve signature should be done for both opening and closing of the valve. Advanced valve diagnostic should also be used if available. This can help tell you if your valve performance is deteriorating by comparing subsequent proof test valve signatures and diagnostics with your baseline. This type of test can help compensate for not testing the valve at worst case operating pressures.The valve signature during a proof test may also be able to record the response time with time stamps, removing the need for a stopwatch. Increased response time is a sign of valve deterioration and increased friction load to move the valve. While there are no standards regarding changes in valve response time, a negative pattern of changes from proof test to proof test is indicative of the potential loss of the valve’s safety margin and performance. Modern SIS valve proof testing should include a valve signature as a matter of good engineering practice.The valve instrument air supply pressure should be measured during a proof test. While the valve spring for a spring-return valve is what closes the valve, the force or torque involved is determined by how much the valve spring is compressed by the valve supply pressure (per Hooke’s Law, F = kX). If your supply pressure is low, the spring will not compress as much, hence less force will be available to move the valve when needed. While not inclusive, some of the things to consider in creating the valve portion of the proof test procedure are given in Table 2. Table 2: Final element valve assembly considerations Test valve safety action at process operating pressure (best but typically not done), and time the valve’s response time. Verify redundancy Test valve safety action at zero differential pressure and time valve’s response time. Verify redundancy Run valve signature and diagnostics as part of proof test and compare to baseline and previous test Visually observe valve action (proper action without unusual vibration or noise, etc.). Verify the valve field and position indication on the DCS Fully stroke the valve a minimum of five times during the proof test to help ensure valve reliability. (This is not intended to fix significant degradation effects or incipient failures). Review valve maintenance records to ensure any changes meet the required valve SRS specifications Test diagnostics for energize-to-trip systems Leak test if Tight Shut Off (TSO) is required Verify the command disagree alarm functionality Inspect valve assembly and internals Remove, test and rebuild as necessary Complete as-found and as-left documentation Solenoids Evaluate venting to provide required response time Evaluate solenoid performance by a digital valve controller or smart positioner Verify redundant solenoid performance (e.g. 1oo2, 2oo3) Interposing Relays Verify correct operation, redundancy Device inspection
I-SIF ivame ukuhlukaniswa ibe izingxenye ezintathu eziyinhloko, izinzwa, izixazululi ze-logic kanye nezinto zokugcina. Ngokuvamile kukhona namadivayisi asekelayo angahlotshaniswa ngaphakathi kwengxenye ngayinye yalezi zingxenye ezintathu (isb. izithiyo ze-IS, ama-trip amps, ama-interposing relay, ama-solenoid, njll.) okumele nawo ahlolwe.
Ukuhlolwa kokuvikela inzwa: Ukuhlolwa kokuvikela inzwa kumele kuqinisekise ukuthi inzwa iyakwazi ukuzwa ukuguquguquka kwenqubo kulo lonke ububanzi bayo futhi idlulisele isignali efanele ku-SIS logic solver ukuze ihlolwe. Nakuba kungabandakanyi, ezinye zezinto okufanele uzicabangele ekudaleni ingxenye yenzwa yenqubo yokuhlola ubufakazi zinikezwe kuThebula 1.
Ukuhlolwa kobufakazi bokuxazulula izinkinga nge-logic: Uma kwenziwa ukuhlolwa kobufakazi bokusebenza okugcwele, indima yomxazululi we-logic ekufezeni isenzo sokuphepha se-SIF kanye nezenzo ezihlobene (isb. ama-alamu, ukusetha kabusha, ukunqamula, ukuxilongwa komsebenzisi, ukuphinda kusebenze, i-HMI, njll.) kuyahlolwa. Ukuhlolwa kobufakazi bokusebenza okuyingxenye noma okuyingxenye kumele kufeze zonke lezi zivivinyo njengengxenye yokuhlolwa kobufakazi obuhambisanayo. Umenzi we-logic solver kufanele abe nenqubo yokuhlola ubufakazi enconyiwe encwadini yokuphepha yedivayisi. Uma kungenjalo futhi okungenani, amandla e-logic solver kufanele ajikelezwe, futhi amarejista okuxilonga e-logic solver, izibani zesimo, ama-voltage okunikezwa kwamandla, izixhumanisi zokuxhumana kanye nokuphindaphinda kufanele kuhlolwe. Lokhu kuhlola kufanele kwenziwe ngaphambi kokuhlolwa kobufakazi bokusebenza okugcwele.
Ungacabangi ukuthi isofthiwe ilungile unomphela futhi i-logic akudingeki ihlolwe ngemva kokuhlolwa kokuqala kobufakazi njengoba izinguquko zesofthiwe nehadiwe ezingabhalisiwe, ezingagunyaziwe nezingahlolwanga kanye nezibuyekezo zesofthiwe zingangena ezinhlelweni ngokuhamba kwesikhathi futhi kumele zifakwe kufilosofi yakho yokuhlola ubufakazi iyonke. Ukuphathwa kwamalogi okushintsha, ukugcinwa, kanye nokubuyekezwa kufanele kubuyekezwe ukuqinisekisa ukuthi asesikhathini futhi agcinwe kahle, futhi uma ekwazi, uhlelo lokusebenza kufanele luqhathaniswe nekhophi yakamuva.
Kufanele futhi kuqashelwe ukuhlola yonke imisebenzi yokusiza kanye neyokuxilonga yokuxazulula izinkinga zomsebenzisi (isib. abaqaphi, izixhumanisi zokuxhumana, izinto zokuphepha kwe-cyber, njll.).
Ukuhlolwa kokugcina kokuvikela izakhi: Izinto eziningi zokugcina zingama-valve, nokho, iziqalisi zezimoto zemishini ejikelezayo, ama-drive anejubane eliguquguqukayo kanye nezinye izingxenye zikagesi ezifana nama-contactor nama-circuit breaker nazo zisetshenziswa njengezinto zokugcina futhi izindlela zazo zokwehluleka kumele zihlaziywe futhi kuhlolwe ubufakazi.
Izindlela eziyinhloko zokwehluleka kwama-valve ziyabambeka, isikhathi sokuphendula sihamba kancane noma sishesha kakhulu, kanye nokuvuza, konke okuthintwa yi-interface yenqubo yokusebenza kwe-valve ngesikhathi sokuhamba. Ngenkathi ukuhlola i-valve ezimweni zokusebenza kuyisimo esifiseleka kakhulu, Ukusebenza ngokuvamile kuzophikisana nokukhubeka kwe-SIF ngenkathi isitshalo sisebenza. Ama-valve amaningi e-SIS avame ukuhlolwa ngenkathi isitshalo siphansi ku-zero differential pressure, okuyinto engadingi kakhulu izimo zokusebenza. Umsebenzisi kufanele aqaphele ingcindezi yokusebenza ehluke kakhulu kanye nemiphumela yokuwohloka kwe-valve kanye nenqubo, okufanele ifakwe ekwakhiweni nasekulinganisweni kwe-valve kanye ne-actuator.
Commonly, to compensate for not testing at process operating conditions, additional safety pressure/thrust/torque margin is added to the valve actuator and inferential performance testing is done utilizing baseline testing. Examples of these inferential tests are where the valve response time is timed, a smart positioner or digital valve controller is used to record a valve pressure/position curve or signature, or advance diagnostics are done during the proof test and compared with previous test results or baselines to detect valve performance degradation, indicating a potential incipient failure. Also, if tight shut off (TSO) is a requirement, simply stroking the valve will not test for leakage and a periodic valve leak test will have to be performed. ISA TR96.05.02 is intended to provide guidance on four different levels of testing of SIS valves and their typical proof test coverage, based on how the test is instrumented. People (particularly users) are encouraged to participate in the development of this technical report (contact crobinson@isa.org).
Amazinga okushisa asezingeni eliphezulu angathinta nemithwalo yokungqubuzana kwama-valve, ukuze ama-valve okuhlola esimweni sezulu esifudumele ngokuvamile abe umthwalo wokungqubuzana odinga kancane uma kuqhathaniswa nokusebenza kwesimo sezulu esibandayo. Ngenxa yalokho, ukuhlolwa kobufakazi bama-valve ekushiseni okulinganayo kufanele kucatshangelwe ukuhlinzeka ngedatha ehambisanayo yokuhlolwa kokuqagela ukuze kunqunywe ukuwohloka kokusebenza kwama-valve.
Amavalvu anezindawo ezihlakaniphile noma isilawuli se-valve yedijithali ngokuvamile anekhono lokudala isiginesha se-valve esingasetshenziswa ukuqapha ukwehla kokusebenza kwe-valve. Isiginesha se-valve esiyisisekelo singacelwa njengengxenye ye-oda lakho lokuthenga noma ungadala esisodwa ngesikhathi sokuhlolwa kokuqala kobufakazi ukuze sisebenze njengesisekelo. Isiginesha se-valve kufanele senziwe kokubili ukuvulwa nokuvalwa kwe-valve. Ukuxilongwa kwe-valve okuthuthukisiwe kufanele futhi kusetshenziswe uma kutholakala. Lokhu kungakusiza ukukutshela ukuthi ukusebenza kwe-valve yakho kuyawohloka yini ngokuqhathanisa iziginesha ze-valve yokuhlola ubufakazi okulandelayo kanye nokuxilongwa nesisekelo sakho. Lolu hlobo lokuhlola lungasiza ekubuyiseleni ukungalihloli i-valve ezingcindezini zokusebenza ezimbi kakhulu.
Isiginesha se-valve ngesikhathi sokuhlolwa kobufakazi singase sikwazi ukurekhoda isikhathi sokuphendula ngezitembu zesikhathi, kususwe isidingo sewashi lokumisa. Isikhathi sokuphendula esengeziwe siyisibonakaliso sokuwohloka kwe-valve kanye nomthwalo wokungqubuzana owandisiwe wokuhambisa i-valve. Nakuba kungekho zindinganiso mayelana nezinguquko esikhathini sokuphendula kwe-valve, iphethini engemihle yezinguquko kusukela ekuhlolweni kobufakazi kuya ekuhlolweni kobufakazi ikhombisa ukulahlekelwa okungenzeka komkhawulo wokuphepha kwe-valve kanye nokusebenza kwayo. Ukuhlolwa kobufakazi be-valve ye-SIS yesimanje kufanele kufake isiginesha se-valve njengendaba yomkhuba omuhle wobunjiniyela.
Umfutho womoya wethuluzi le-valve kufanele ulinganiswe ngesikhathi sokuhlolwa kobufakazi. Nakuba intwasahlobo ye-valve ye-valve yokubuyisela intwasahlobo iyona evala i-valve, amandla noma i-torque ehilelekile inqunywa ukuthi intwasahlobo ye-valve icindezelwe kangakanani yingcindezi yokunikezwa kwe-valve (ngokoMthetho kaHooke, F = kX). Uma umfutho wakho wokunikezwa uphansi, intwasahlobo ngeke icindezeleke kakhulu, ngakho-ke kuzoba namandla amancane okuhambisa i-valve uma kudingeka. Nakuba kungabandakanyi, ezinye zezinto okufanele uzicabangele ekudaleni ingxenye ye-valve yenqubo yokuhlola ubufakazi zinikezwe kuThebula 2.
Isikhathi sokuthunyelwe: Novemba-13-2019