Uvavanyo lobungqina luyinxalenye ebalulekileyo yokugcina ukuthembeka kokhuseleko lweenkqubo zethu zezixhobo zokhuseleko (SIS) kunye neenkqubo ezinxulumene nokhuseleko (umz. ii-alamu ezibalulekileyo, iinkqubo zomlilo negesi, iinkqubo zokudibanisa izixhobo, njl.njl.). Uvavanyo lobungqina luvavanyo oluqhutywa rhoqo ukuze kufunyanwe ukusilela okuyingozi, kuvavanywe ukusebenza okunxulumene nokhuseleko (umz. ukuseta kwakhona, ukugqitha, ii-alamu, ukuxilongwa, ukuvalwa ngesandla, njl.njl.), kunye nokuqinisekisa ukuba inkqubo iyahlangabezana nemigangatho yenkampani kunye neyangaphandle. Iziphumo zovavanyo lobungqina zikwayindlela yokulinganisa ukusebenza kakuhle kwenkqubo yokuthembeka koomatshini be-SIS kunye nokuthembeka kwenkqubo.
Iinkqubo zovavanyo lobungqina zigubungela amanyathelo ovavanyo ukusuka ekufumaneni iimvume, ukwenza izaziso kunye nokukhupha inkqubo kwinkonzo yovavanyo ukuya ekuqinisekiseni uvavanyo olupheleleyo, ukubhala phantsi uvavanyo lobungqina kunye neziphumo zalo, ukubuyisela inkqubo kwinkonzo, kunye nokuvavanya iziphumo zovavanyo lwangoku kunye neziphumo zovavanyo lobungqina bangaphambili.
I-ANSI/ISA/IEC 61511-1, iCandelo 16, ligubungela uvavanyo lobungqina be-SIS. Ingxelo yobugcisa ye-ISA TR84.00.03 – “Ukunyaniseka koMatshini kwiiNkqubo zoKhuseleko (SIS),” igubungela uvavanyo lobungqina kwaye okwangoku iphantsi kohlaziyo kwaye inguqulelo entsha kulindeleke ukuba iphume kungekudala. Ingxelo yobugcisa ye-ISA TR96.05.02 – “Uvavanyo lobungqina obukwindawo yeeValve eziZenzekelayo” ngoku luphantsi kophuhliso.
Ingxelo ye-HSE yase-UK CRR 428/2002 – “Imigaqo yokuvavanya ubungqina beenkqubo ezisebenzisa izixhobo zokhuseleko kushishino lweekhemikhali” inika ulwazi malunga nokuvavanya ubungqina kunye noko kwenziwa ziinkampani e-UK.
Inkqubo yovavanyo lobungqina isekelwe kuhlalutyo lweendlela zokusilela eziyingozi ezaziwayo kwinxalenye nganye kwindlela yokuhamba ye-safety instrumented function (SIF), ukusebenza kwe-SIF njengenkqubo, kunye nendlela (nokuba) yokuvavanya imo yokusilela eyingozi. Uphuhliso lwenkqubo kufuneka luqale kwisigaba soyilo lwe-SIF ngoyilo lwenkqubo, ukukhethwa kwezixhobo, kunye nokumisela ukuba uvavanyo lobungqina luza kuvavanywa nini kwaye njani. Izixhobo ze-SIS zinemigangatho eyahlukeneyo yobunzima bovavanyo lobungqina ekufuneka iqwalaselwe kuyilo, ukusebenza kunye nokugcinwa kwe-SIF. Umzekelo, iimitha ze-orifice kunye nee-pressure transmitters kulula ukuzivavanya kunee-Coriolis mass flowmeters, ii-mag meter okanye ii-sensors ze-radar level radar. Ukusetyenziswa kunye noyilo lwe-valve nako kunokuchaphazela ukuphelela kovavanyo lobungqina be-valve ukuqinisekisa ukuba ukusilela okuyingozi nokuqhubekayo ngenxa yokuwohloka, ukufakelwa okanye ukusilela okuxhomekeke kwixesha akukhokeleli ekusileleni okubalulekileyo ngaphakathi kwexesha lovavanyo elikhethiweyo.
Nangona iinkqubo zovavanyo lobungqina zihlala ziphuhliswa ngexesha lesigaba sobunjineli be-SIF, kufuneka ziphinde zihlolwe yi-SIS Technical Authority, ii-Operations kunye neengcali zezixhobo eziza kwenza uvavanyo. Uhlalutyo lokhuseleko lomsebenzi (JSA) nalo kufuneka lwenziwe. Kubalulekile ukufumana imvume yesityalo malunga nokuba zeziphi iimvavanyo eziza kwenziwa kwaye nini, kunye nokuba zinokwenzeka na emzimbeni nasempilweni. Umzekelo, akuncedi ukucacisa uvavanyo lwe-partial-stroke xa iqela le-Operations lingavumi ukukwenza. Kukwacetyiswa ukuba iinkqubo zovavanyo lobungqina zihlolwe yingcali ezimeleyo yesifundo (SME). Uvavanyo oluqhelekileyo olufunekayo kuvavanyo lobungqina bomsebenzi opheleleyo luboniswe kuMfanekiso 1.
Iimfuneko zovavanyo olupheleleyo lobungqina bomsebenzi Umfanekiso 1: Inkcazo yovavanyo olupheleleyo lobungqina bomsebenzi wesixhobo sokhuseleko (SIF) kunye nenkqubo yaso yokhuseleko (SIS) kufuneka ichaze okanye ibhekisele kumanyathelo ngokulandelelana ukusuka kumalungiselelo ovavanyo kunye neenkqubo zovavanyo ukuya kwizaziso kunye namaxwebhu.
Umfanekiso 1: Inkcazo epheleleyo yovavanyo olungqina umsebenzi wesixhobo sokhuseleko (SIF) kunye nenkqubo yaso yesixhobo sokhuseleko (SIS) kufuneka ichaze okanye ibhekisele kumanyathelo ngokulandelelana ukusuka kumalungiselelo ovavanyo kunye neenkqubo zovavanyo ukuya kwizaziso kunye namaxwebhu.
Uvavanyo lobungqina sisenzo sokulungisa esicwangcisiweyo ekufuneka senziwe ngabasebenzi abanobuchule abaqeqeshwe kuvavanyo lwe-SIS, inkqubo yobungqina, kunye nee-SIS loops abaza kuzivavanya. Kufuneka kubekho ukucaciswa kwenkqubo ngaphambi kokuba kwenziwe uvavanyo lokuqala lobungqina, kunye nengxelo kwi-SIS Technical Authority emva koko ukuze kuphuculwe okanye kulungiswe.
Kukho iindlela ezimbini eziphambili zokungaphumeleli (ezikhuselekileyo okanye eziyingozi), ezahlulwe zibe ziindlela ezine—ezinobungozi ezingafunyanwanga, ezinobungozi ezifunyenweyo (ngokuxilongwa), ezikhuselekileyo ezingafunyanwanga kunye nezikhuselekileyo. Amagama okusilela angafunyanwanga ayingozi nanobungozi asetyenziswa ngokutshintshana kweli nqaku.
Kuvavanyo lobungqina be-SIF, sinomdla kakhulu kwiindlela zokungaphumeleli ezinobungozi ezingabonwanga, kodwa ukuba kukho iindlela zokuchonga zomsebenzisi ezifumanisa ukungaphumeleli okuyingozi, ezi ndlela zokuchonga kufuneka zivavanywe ubungqina. Qaphela ukuba ngokungafaniyo neendlela zokuchonga zomsebenzisi, iindlela zokuchonga zangaphakathi kwisixhobo azinakuqinisekiswa njengokusebenza ngumsebenzisi, kwaye oku kunokuchaphazela ifilosofi yovavanyo lobungqina. Xa kuthathwa ikhredithi yokuchonga kwiibalo ze-SIL, ii-alamu zokuxilonga (umz. ii-alamu ezingaphandle komgangatho) kufuneka zivavanywe njengenxalenye yovavanyo lobungqina.
Iindlela zokusilela zinokwahlulwahlulwa zibe zezo zivavanyiweyo ngexesha lovavanyo lobungqina, ezo zingavavanywanga, kunye nokusilela okuqalekayo okanye ukusilela okuxhomekeke kwixesha. Ezinye iindlela zokusilela eziyingozi zisenokungavavanywa ngokuthe ngqo ngezizathu ezahlukeneyo (umz. ubunzima, ubunjineli okanye isigqibo sokusebenza, ukungazi, ukungakwazi, ukushiywa okanye ukwenza iimpazamo zenkqubo, amathuba aphantsi okwenzeka, njl.njl.). Ukuba kukho iindlela zokusilela ezaziwayo ezingayi kuvavanywa, kufuneka kwenziwe imbuyekezo kuyilo lwesixhobo, inkqubo yovavanyo, ukutshintshwa kwesixhobo rhoqo okanye ukwakhiwa kwakhona, kunye/okanye uvavanyo oluqikelelweyo kufuneka lwenziwe ukunciphisa impembelelo kwi-SIF ingqibelelo yokungavavanywa.
Ukusilela kokuqala yimeko okanye imeko ethobayo kangangokuba ukusilela okubalulekileyo nokuyingozi kunokulindeleka ukuba amanyathelo okulungisa athathwa ngexesha elifanelekileyo. Zihlala zibonwa ngokuthelekisa ukusebenza novavanyo lobungqina bokuqala okanye lwamva nje (umz. iisiginitsha zevalvu okanye amaxesha okuphendula kwevalvu) okanye ngokuhlola (umz. i-plugged process port). Ukusilela kokuqala kudla ngokuxhomekeka kwixesha—okukhona isixhobo okanye i-assembly isebenza ixesha elide, kokukhona isonakala ngakumbi; iimeko ezenza kube lula ukusilela ngokungacwangciswanga ziba nokwenzeka ngakumbi, ukufakelwa kwe-process port okanye ukwakheka kwe-sensor ngokuhamba kwexesha, ubomi obuluncedo buphelile, njl.njl. Ke ngoko, okukhona ixesha elide lovavanyo lobungqina, kokukhona kunokwenzeka ukuba ukusilela kokuqala okanye okuxhomekeke kwixesha. Naluphi na ukhuseleko ekusileleni kokuqala kufuneka luvavanywe ubungqina (ukucoca i-port, ukulandelwa kobushushu, njl.njl.).
Iinkqubo mazibhalwe ukuze kuhlolwe ubungqina bokusilela okuyingozi (okungabonwayo). Iindlela zovavanyo lokusilela kunye nohlalutyo lweziphumo (FMEA) okanye iindlela zokusilela, uhlalutyo lweziphumo kunye novavanyo (FMEDA) zinokunceda ekuchongeni ukusilela okuyingozi okungabonwayo, kwaye apho kufuneka kuphuculwe khona ukugubungela uvavanyo lobungqina.
Iinkqubo ezininzi zovavanyo lobungqina zisekelwe kumava abhaliweyo kunye neetemplate ezivela kwiinkqubo ezikhoyo. Iinkqubo ezintsha kunye nee-SIF ezintsonkothileyo zifuna indlela enobuchule ngakumbi esebenzisa i-FMEA/FMEDA ukuhlalutya ukungaphumeleli okuyingozi, ukumisela indlela inkqubo yovavanyo eza kuvavanya okanye engayi kuvavanya ngayo ezo mpazamo, kunye nokugubungela iimvavanyo. Umzobo webhloko yohlalutyo lwendlela yokusilela kwenqanaba elikhulu le-sensor uboniswe kuMfanekiso 2. I-FMEA idla ngokufuna ukwenziwa kube kanye kuphela kuhlobo oluthile lwesixhobo kwaye isetyenziswe kwakhona kwizixhobo ezifanayo kuqwalaselwa inkonzo yazo yenkqubo, ukufakelwa kunye nobuchule bokuvavanya indawo.
Uhlalutyo lokusilela kwenqanaba le-Macro Umfanekiso 2: Lo mzobo webhloko yohlalutyo lwendlela yokusilela kwenqanaba le-macro yesixhobo sokudlulisa uxinzelelo (i-PT) ubonisa imisebenzi ephambili eya kwahlulwahlulwa ibe zii-micro failure analysis ezininzi ukuchaza ngokupheleleyo ukusilela okunokwenzeka okuza kulungiswa kwiimvavanyo zomsebenzi.
Umfanekiso 2: Lo mzobo webhloko yohlalutyo lwendlela yokusilela kwenqanaba elikhulu le-sensor kunye ne-pressure transmitter (PT) ubonisa imisebenzi ephambili eya kwahlulwahlulwa ibe zii-micro failure analysis ezininzi ukuchaza ngokupheleleyo iintsilelo ezinokubakho eziza kulungiswa kwiimvavanyo zomsebenzi.
Ipesenti yokusilela okwaziwayo, okuyingozi, nokungabonwayo okuvavanyiweyo kubungqina ibizwa ngokuba yi-proof test coverage (PTC). I-PTC isetyenziswa rhoqo kwizibalo ze-SIL "ukuhlawula" ukusilela kokuvavanya ngokupheleleyo i-SIF. Abantu banenkolelo ephosakeleyo yokuba kuba beqwalasele ukungabikho kwe-test coverage kwi-SIL calculation yabo, bayila i-SIF ethembekileyo. Inyani elula kukuba, ukuba i-test coverage yakho yi-75%, kwaye ukuba ulinganise elo nani kwi-SIL calculation yakho kwaye uvavanya izinto osele uzivavanya rhoqo, i-25% ye-failure eyingozi isenokwenzeka ngokwezibalo. Andifuni ukuba kuloo 25%.
Iingxelo zokuvunywa kwe-FMEDA kunye neencwadana zokhuseleko zezixhobo zihlala zibonelela ngenkqubo yovavanyo lobungqina obuncinci kunye nokugubungela uvavanyo lobungqina. Ezi zibonelela ngesikhokelo kuphela, hayi onke amanyathelo ovavanyo afunekayo kwinkqubo yovavanyo lobungqina obupheleleyo. Ezinye iintlobo zohlalutyo lokusilela, ezinje ngohlalutyo lomthi wempazamo kunye nokugcinwa okugxile ekuthembekeni, nazo zisetyenziselwa ukuhlalutya ukusilela okuyingozi.
Uvavanyo lobungqina lunokwahlulwa lube luvavanyo olusebenzayo olupheleleyo (uvavanyo oluvela ekupheleni ukuya ekupheleni) okanye uvavanyo olusebenzayo olungaphelelanga (Umfanekiso 3). Uvavanyo olusebenzayo olungaphelelanga lwenziwa rhoqo xa izinto ze-SIF zinexesha lovavanyo elahlukileyo kubalo lwe-SIL ezingahambelani nokuvalwa okucwangcisiweyo okanye ukujika. Kubalulekile ukuba iinkqubo zovavanyo lobungqina obusebenzayo olungaphelelanga zihambelane ukuze xa zizonke zivavanye yonke imisebenzi yokhuseleko ye-SIF. Ngovavanyo olusebenzayo olungaphelelanga, kusacetyiswa ukuba i-SIF ibe novavanyo lokuqala lobungqina oluvela ekupheleni ukuya ekupheleni, kunye novavanyo olulandelayo ngexesha lokujika.
Uvavanyo lobungqina obungaphelelanga kufuneka ludibane Umfanekiso 3: Uvavanyo lobungqina obungaphelelanga oludibeneyo (ezantsi) lufanele lugubungele yonke imisebenzi yovavanyo lobungqina obupheleleyo olusebenzayo (phezulu).
Umfanekiso 3: Uvavanyo oludibeneyo lobungqina obungaphelelanga (ezantsi) lufanele lugubungele yonke imisebenzi yovavanyo olupheleleyo lobungqina obusebenzayo (phezulu).
Uvavanyo lobungqina obungaphelelanga luvavanya ipesenti kuphela yeendlela zokusilela kwesixhobo. Umzekelo oqhelekileyo luvavanyo lwevalvu yestroke engaphelelanga, apho ivalvu ishukunyiswa kancinci (10-20%) ukuqinisekisa ukuba ayibambekanga. Oku kunovavanyo lobungqina oluphantsi kunovavanyo lobungqina kwisithuba sovavanyo lokuqala.
Iinkqubo zovavanyo lobungqina zinokwahluka ngobunzima ngenxa yobunzima be-SIF kunye nefilosofi yenkqubo yovavanyo lwenkampani. Ezinye iinkampani zibhala iinkqubo zovavanyo ezineenkcukacha ngenyathelo ngenyathelo, ngelixa ezinye zineenkqubo ezimfutshane. Iingxelo kwezinye iinkqubo, ezifana nokulinganisa okuqhelekileyo, ngamanye amaxesha zisetyenziselwa ukunciphisa ubungakanani benkqubo yovavanyo lobungqina kunye nokunceda ukuqinisekisa ukuhambelana kovavanyo. Inkqubo yovavanyo lobungqina elungileyo kufuneka inike iinkcukacha ezaneleyo ukuqinisekisa ukuba lonke uvavanyo lwenziwe ngokufanelekileyo kwaye lubhalwe phantsi, kodwa kungabi neenkcukacha ezininzi ezinokubangela ukuba iingcali zifune ukutsiba amanyathelo. Ukuba nengcali, enoxanduva lokwenza inyathelo lovavanyo, iqale inyathelo lovavanyo olugqityiweyo kunokunceda ukuqinisekisa ukuba uvavanyo luya kwenziwa ngokuchanekileyo. Ukusayinwa kovavanyo lobungqina olugqityiweyo yi-Instrument Supervisor kunye nabameli beMisebenzi kuya kugxininisa ukubaluleka kwaye kuqinisekise uvavanyo lobungqina olugqityiweyo ngokufanelekileyo.
Ingxelo yeengcali kufuneka ihlale icelwa ukunceda ukuphucula inkqubo. Impumelelo yenkqubo yovavanyo lobungqina ixhomekeke kakhulu kwizandla zeengcali, ngoko ke umzamo wokubambisana uyacetyiswa kakhulu.
Uninzi lovavanyo lobungqina ludla ngokwenziwa ngaphandle kwe-intanethi ngexesha lokuvalwa okanye ukutshintshwa. Kwezinye iimeko, uvavanyo lobungqina lunokufuneka lwenziwe kwi-intanethi ngelixa luqhutywa ukuze kuhlangatyezwane nezibalo ze-SIL okanye ezinye iimfuno. Uvavanyo lwe-intanethi lufuna ucwangciso kunye nokulungelelaniswa neMisebenzi ukuvumela uvavanyo lobungqina lwenziwe ngokukhuselekileyo, ngaphandle kokuphazamiseka kwenkqubo, kwaye ngaphandle kokubangela uhambo olungeyonyani. Kuthatha uhambo olunye kuphela olungeyonyani ukusebenzisa zonke izixhobo zakho. Ngexesha lolu hlobo lovavanyo, xa i-SIF ingekho ngokupheleleyo ukwenza umsebenzi wayo wokhuseleko, 61511-1, iCandelo 11.8.5, lithi “Amanyathelo okuhlawula aqinisekisa ukuqhubeka nokusebenza ngokukhuselekileyo aya kubonelelwa ngokuhambelana ne-11.3 xa i-SIS ikwi-passpass (ukulungiswa okanye uvavanyo).” Inkqubo yolawulo lwemeko engaqhelekanga kufuneka ihambe nenkqubo yovavanyo lobungqina ukunceda ukuqinisekisa ukuba oku kwenziwa ngokufanelekileyo.
I-SIF idla ngokwahlulwahlulwa ibe ziinxalenye ezintathu eziphambili: ii-sensors, ii-logic solvers kunye nee-final elements. Kukwakho nezixhobo ezincedisayo ezinokudibaniswa ngaphakathi kwenxalenye nganye kwezi zintathu (umz. ii-IS barriers, ii-trip amps, ii-interposing relay, ii-solenoids, njl.njl.) ekufuneka zivavanywe. Izinto ezibalulekileyo zokuvavanya ubungqina nganye kwezi teknoloji zinokufumaneka kwi-sidebar, "Ii-test sensors, ii-logic solvers kunye nee-final elements" (ngezantsi).
Ezinye izinto kulula ukuzivavanya kunezinye. Iiteknoloji ezininzi zanamhlanje kunye nezinye ezindala zokugeleza kunye nezinga zikwicandelo elinzima ngakumbi. Ezi ziquka iiCoriolis flowmeters, iivortex metres, iimag metres, i-radar yomoya, i-ultrasonic level, kunye neeswitshi zenkqubo ezikwindawo ethile, ukukhankanya ezimbalwa. Ngethamsanqa, uninzi lwazo ngoku luneendlela zokuchonga eziphuculweyo ezivumela uvavanyo oluphuculweyo.
Ubunzima bokuvavanya ubungqina besixhobo esinjalo kwicandelo kufuneka buqwalaselwe kuyilo lwe-SIF. Kulula ukuba ubunjineli bukhethe izixhobo ze-SIF ngaphandle kokucinga nzulu ngoko kuya kufunekayo ukuvavanya ubungqina besixhobo, kuba abayi kuba ngabantu abazivavanyayo. Oku kukwanjalo novavanyo lwe-partial-stroke, oluyindlela eqhelekileyo yokuphucula amathuba aphakathi e-SIF okusilela xa kufuneka (PFDavg), kodwa kamva i-plant Operations ayifuni ukukwenza oko, kwaye amaxesha amaninzi ayinakukwenza oko. Soloko ubonelela ngeliso lobunjineli be-SIF malunga novavanyo lobungqina.
Uvavanyo lobungqina kufuneka luquke ukuhlolwa kofakelo lwe-SIF kunye nokulungiswa njengoko kufuneka ukuze kuhlangatyezwane ne-61511-1, iCandelo 16.3.2. Kufuneka kubekho uhlolo lokugqibela ukuqinisekisa ukuba yonke into icinezelwe, kunye nokujonga kabini ukuba i-SIF ibuyiselwe ngokufanelekileyo kwinkonzo yenkqubo.
Ukubhala nokusebenzisa inkqubo yovavanyo elungileyo linyathelo elibalulekileyo ukuqinisekisa ukuthembeka kwe-SIF ebomini bayo bonke. Inkqubo yovavanyo kufuneka inike iinkcukacha ezaneleyo ukuqinisekisa ukuba iimvavanyo ezifunekayo zenziwa ngokukhuselekileyo nangokungaguquguqukiyo kwaye zibhalwe phantsi. Ukusilela okuyingozi okungavavanywanga ngovavanyo lobungqina kufuneka kuhlawulwe ukuqinisekisa ukuba ukuthembeka kokhuseleko lwe-SIF kugcinwa ngokwaneleyo ubomi bayo bonke.
Ukubhala inkqubo yovavanyo lobungqina obuhle kufuna indlela enengqondo yohlalutyo lobunjineli lokusilela okunokuba yingozi, ukukhetha iindlela, nokubhala amanyathelo ovavanyo lobungqina akwizakhono zovavanyo lwesityalo. Endleleni, fumana imvume yesityalo kuwo onke amanqanaba ovavanyo, kwaye uqeqeshe iingcali ukuba zenze kwaye zibhale phantsi uvavanyo lobungqina kunye nokuqonda ukubaluleka kovavanyo. Bhala imiyalelo ngokungathi ungumchwephesha wezixhobo oza kufuneka enze umsebenzi, kwaye ubomi buxhomekeke ekufumaneni uvavanyo olufanelekileyo, kuba benza njalo.
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 idla ngokwahlulwahlulwa ibe ziinxalenye ezintathu eziphambili, ii-sensors, i-logic solvers kunye nee-final elements. Kukwakho nezixhobo ezincedisayo ezinokudibaniswa ngaphakathi kwenxalenye nganye kwezi zintathu (umz. i-IS barriers, i-trip amps, i-interposing relay, i-solenoids, njl.njl.) ekufuneka zivavanywe.
Uvavanyo lokumelana nezivamvo: Uvavanyo lokumelana nezivamvo kufuneka luqinisekise ukuba izivamvo zinokuva utshintsho lwenkqubo kuluhlu lwazo olupheleleyo kwaye zidlulisele isignali efanelekileyo kwisisombululo se-SIS logic ukuze sivavanywe. Nangona zingabandakanyi, ezinye zezinto ekufuneka ziqwalaselwe ekudaleni inxalenye yezivamvo kwinkqubo yovavanyo lokumelana nezivamvo zinikwe kwiTheyibhile 1.
Uvavanyo lobungqina bokusombulula ingxaki yeLogic: Xa uvavanyo lobungqina bokusebenza ngokupheleleyo lwenziwe, indima yomsombululi weLogic ekufezekiseni isenzo sokhuseleko se-SIF kunye nezenzo ezinxulumene noko (umz. ii-alamu, ukuseta kwakhona, ii-bypasses, ukuxilongwa komsebenzisi, ukuphinda kusebenze, i-HMI, njl.njl.) ziyavavanywa. Uvavanyo lobungqina bokusebenza okungaphelelanga okanye okuncinci kufuneka lufezekise zonke ezi mvavanyo njengenxalenye yovavanyo lobungqina obuhambelanayo. Umenzi we-logic solver kufuneka abe nenkqubo yovavanyo lobungqina ecetyiswayo kwincwadi yokhuseleko lwesixhobo. Ukuba akunjalo kwaye ubuncinane, amandla e-logic solver kufuneka ajikeleziswe, kwaye iirejista zokuxilonga ze-logic solver, izibane zesimo, ii-voltages zombane, amakhonkco onxibelelwano kunye nokuphinda kusebenze kufuneka zihlolwe. Olu hlolo kufuneka lwenziwe ngaphambi kovavanyo lobungqina bokusebenza ngokupheleleyo.
Musa ukucinga ukuba isoftware ilungile ngonaphakade kwaye ingqiqo akufuneki ivavanywe emva kovavanyo lokuqala lobungqina njengoko utshintsho lwesoftware kunye nehardware olungabhalwanga phantsi, olungagunyaziswanga nolungavavanywanga kunye nohlaziyo lwesoftware lunokungena kwiinkqubo ngokuhamba kwexesha kwaye kufuneka lufakwe kwifilosofi yakho yovavanyo lobungqina. Ulawulo lweerekhodi zotshintsho, ulondolozo, kunye nohlaziyo kufuneka luhlolwe ukuqinisekisa ukuba zihlaziyiwe kwaye zigcinwe ngokufanelekileyo, kwaye ukuba ziyakwazi, inkqubo yesicelo kufuneka ithelekiswe ne-backup yamva nje.
Kufuneka kuqatshelwe ukuvavanya yonke imisebenzi yokuncedisa kunye neyokuxilonga yesisombululo se-logic somsebenzisi (umz. ii-watchdog, amakhonkco onxibelelwano, izixhobo zokhuseleko lwe-cyber, njl.njl.).
Uvavanyo lokugqibela lokumelana nezinto: Uninzi lwezinto zokugqibela ziivalvu, nangona kunjalo, iziqalisi zeemoto zezixhobo ezijikelezayo, ii-variable-speed drives kunye nezinye izinto zombane ezifana neecontactors kunye nee-circuit breakers nazo zisetyenziswa njengezinto zokugqibela kwaye iindlela zazo zokusilela kufuneka zihlalutywe kwaye uvavanyo lobungqina luvavanywe.
Iindlela eziphambili zokusilela kweevalvu ziyabambeka, ixesha lokuphendula licotha kakhulu okanye likhawuleza kakhulu, kunye nokuvuza, konke oku kuchaphazeleka yindlela yokusebenza kwevalvu ngexesha lokuhamba. Nangona ukuvavanya ivalvu kwiimeko zokusebenza yeyona meko ifunekayo, imisebenzi ngokubanzi iya kuchasene nokukhubeka kweSIF ngelixa isityalo sisebenza. Uninzi lweevalvu zeSIS zihlala zivavanywa ngelixa isityalo siphantsi koxinzelelo lomahluko, oluya kuba lolona lunzima kakhulu kwiimeko zokusebenza. Umsebenzisi kufuneka azi ngoxinzelelo lomahluko wokusebenza olubi kakhulu kunye neziphumo zokuwohloka kwevalvu kunye nenkqubo, ekufuneka zifakwe kuyilo kunye nobungakanani bevalvu kunye 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).
Amaqondo obushushu aphakathi anokuchaphazela nemithwalo yokungqubana kweevalvu, ukuze iivalvu zokuvavanya kwimozulu efudumeleyo ngokubanzi zibe ngumthwalo wokungqubana ongenzima kangako xa kuthelekiswa nokusebenza kwimozulu ebandayo. Ngenxa yoko, uvavanyo lobungqina beevalvu kwiqondo lobushushu elihambelanayo kufuneka luqwalaselwe ukuze kubonelelwe ngedatha ehambelanayo yovavanyo oluqikelelweyo lokufumanisa ukuhla kokusebenza kweevalvu.
Iivalvu ezineendawo ezihlakaniphileyo okanye isilawuli sevalvu yedijithali ngokubanzi ziyakwazi ukwenza utyikityo lwevalvu olunokusetyenziselwa ukujonga ukuwohloka kokusebenza kwevalvu. Utyikityo lwevalvu olusisiseko lungacelwa njengenxalenye yeodolo yakho yokuthenga okanye ungenza olunye ngexesha lovavanyo lokuqala lobungqina ukuze lusebenze njengesiseko. Utyikityo lwevalvu kufuneka lwenziwe zombini ukuvulwa nokuvalwa kwevalvu. Ukuxilongwa kwevalvu okuphambili kufuneka kusetyenziswe ukuba kuyafumaneka. Oku kunokukunceda ukukuxelela ukuba ukusebenza kwevalvu yakho kuyohloka ngokuthelekisa utyikityo lwevalvu yovavanyo lobungqina olulandelayo kunye nokuxilongwa kunye nesiseko sakho. Olu hlobo lovavanyo lunokunceda ekuhlawuleni ukungavavanyi ivalvu kwiimeko ezinzima zokusebenza.
Isiginitsha yevalvu ngexesha lovavanyo lobungqina inokukwazi ukurekhoda ixesha lokuphendula ngezitampu zexesha, isusa isidingo sestopwotch. Ixesha elongezelelweyo lokuphendula luphawu lokuwohloka kwevalvu kunye nomthwalo okhulayo wokungqubana ukuhambisa ivalvu. Nangona kungekho migangatho malunga notshintsho kwixesha lokuphendula kwevalvu, iphethini engalunganga yotshintsho ukusuka kuvavanyo lobungqina ukuya kuvavanyo lobungqina ibonisa ukulahleka okunokwenzeka komda wokhuseleko lwevalvu kunye nokusebenza kwayo. Uvavanyo lwanamhlanje lobungqina bevalvu ye-SIS kufuneka lubandakanye isiginitsha yevalvu njengomcimbi wobugcisa obuhle.
Uxinzelelo lomoya wesixhobo sevalvu kufuneka lulinganiswe ngexesha lovavanyo lobungqina. Nangona intwasahlobo yevalvu yevalvu yokubuyisela intwasahlobo iyeyona ivala ivalvu, amandla okanye i-torque ebandakanyekayo imiselwa kukuba intwasahlobo yevalvu icinezelwe kangakanani luxinzelelo lonikezelo lwevalvu (ngokoMthetho kaHooke, F = kX). Ukuba uxinzelelo lwakho lonikezelo luphantsi, intwasahlobo ayizukucinezelwa kangako, ngoko ke kuya kubakho amandla amancinci okushukumisa ivalvu xa kufuneka. Nangona ingabandakanyi, ezinye zezinto ekufuneka ziqwalaselwe ekudaleni inxalenye yevalvu yenkqubo yovavanyo lobungqina zinikwe kwiTheyibhile 2.
Ixesha lokuthumela: Novemba-13-2019