Dalilin Da Ya Sa Kula da Girgiza na Gargajiya Ke Ƙara Jinkiri Marar Amfani
A yawancin shigar da compressors, ana saka na’urar saka idanu ta musamman a tsakanin na’urar firikwensin (sensor) da PLC. Wannan na’urar tana sarrafa siginar sannan tana bayar da fitar relay. PLC na ganin “dry contact” ne kawai bayan na’urar saka idanu ta yanke hukuncin cewa akwai matsala. Wannan jerin matakai yana ƙara jinkiri na milisakan 200 zuwa 500. A lokacin wani abin girgiza mai ƙarfi, shaft ɗin na iya motsi dubban microns a cikin wannan lokacin. Haɗa siginar analog kai tsaye yana cire wannan matakin tsaka-tsaki gaba ɗaya.
Tsarin Wayoyi Daga Ƙarshen Probe Zuwa Katin PLC
Bently Nevada 3300 XL probes na kusanci suna buƙatar direba da ake kira proximitor. Direban yana karɓar kebul ɗin probe ɗin sannan yana fitar da sigina biyu. Ɗaya shi ne gap voltage wanda yawanci yake daga -2 zuwa -18 VDC. Na biyu kuma shi ne yanayin 4-20 mA loop da ke wakiltar girman girgiza. Haɗa 4-20 mA loop kai tsaye zuwa module na shigar analog na PLC wanda aka ƙera da ƙuduri 16-bit. Yi amfani da twisted pair shielded cable. Ƙare (terminate) shield ɗin ne kawai a sandar ƙasa ta panel ɗin PLC. Kada a ƙare shi a gefen direba.
Scaling na Siginoni Analog na Asali Cikin Ladder Logic
Yawancin katunan analog na PLC suna maida 4-20 mA zuwa ƙimomin integer. Don kati 16-bit, 4 mA daidai yake da ƙidaya 0, 20 mA kuma daidai yake da 27648 a dandamalin Siemens ko 32767 a tsarin Allen-Bradley. Yi amfani da wannan tsarin lissafi: Vibration = (Raw_Counts - Offset_4mA) raba da (Span_20mA - Offset_4mA) ninka da Full_Scale. Don kewayon 0 zuwa 100 micron peak-to-peak, 12 mA yana haifar da 50 microns. Ajiye wannan ƙimar da aka yi scaling a cikin tag na lamba mai “real”. Aiwatar da wannan lissafin kowane milisakan 50 domin samun isasshen saurin kariya.
Shigar da Proximity Probe Don Samun Daidaitattun Karatu
Tsaftace ramin da aka yi thread a cikin gidajen bearing da tap. Sanya anti-seize compound a kan thread ɗin probe. Juya probe ɗin har sai ƙarfafenta ta kusan ta taɓa shaft. Haɗa voltmeter zuwa fitar direba. Daidaita matsayi na probe har sai gap voltage ya nuna -10.0 VDC da juriya na ±0.2 V. Ɗaure locknut zuwa 10 Nm yayin da kake riƙe jikin probe da spana. Tabbatar cewa voltagen bai canza yayin matsewa ba. Tazarar iska ta ƙarshe ya kamata ta zama kusan 1.5 mm ga probe mai diamita 8 mm.
Shirin Yanke Trip Tare da Jinkirin Lokaci
Kada ka yi trip nan take lokacin da girgiza ta wuce ƙimar ƙofa (threshold). Ɗan tasiri na wucin gadi lokacin farawa ko rikicewar tsarin aiki al’ada ne. Yi amfani da timer-on-delay block a cikin ladder logic ɗinka. Saita preset zuwa sakan 0.5 don yanayin ƙararrawa (alarm) da sakan 1.5 don yanayin trip. Timer ɗin yana farawa ne lokacin da ƙimar girgiza da aka yi scaling ta wuce threshold. Fitarwa (output) zai yi aiki ne kawai bayan timer ya ƙare. Sake saita timer nan take idan girgiza ta faɗi ƙasa da threshold minus kashi 5 cikin 100 na hysteresis band. Wannan yana hana relays na trip yin saurin kunnawa/kashewa akai-akai.
Zaɓin Threshold Bisa Ga Nau’in Compressor
Centrifugal compressors da suke gudu sama da 3000 RPM suna amfani da auna displacement. Al’ada za a sa trip threshold a 80 microns peak-to-peak. Alarm threshold kuma 50 microns. Reciprocating compressors suna amfani da auna velocity. A yi trip a 12 mm/s RMS. A yi alarm a 8 mm/s RMS. Integrally geared compressors suna da ƙayyadaddun tazara masu tsauri. A yi trip a 40 microns. Kullum a fara da duba littafin OEM. Idan bayanan OEM ba su samuwa, yi amfani da ISO 10816-3 a matsayin tunani amma ka yi amfani da ɗan tazara na tsaro kashi 20 cikin 100 ƙasa da iyakar da ka’idar ta bayar.
Ƙara Kula da Gap Voltage Don Lafiyar Probe
Gap voltage yana nuna nisan tsayawar probe daga samfurin (standoff distance). Canjin kwatsam na 0.5 VDC yana nuna yiwuwar prob ɗin ya yi laushi ko lalacewar saman target. Yi amfani da tashar shigar analog ta biyu don karanta gap voltage. Yi scaling na -2 VDC zuwa ƙidaya 0, -18 VDC zuwa cikakken ƙidaya. Karatun al’ada ya kamata ya zama -10 VDC. Shirya gargadi idan gap voltage ya wuce -9 VDC ko ya faɗi ƙasa da -11 VDC. Shirya block na kashewa gaba ɗaya idan gap voltage ya kai -1 VDC wanda yake nuna probe ɗin na taɓa shaft ko -20 VDC wanda yake nuna probe ɗin ya yanke.
Misalin Aiki a Fage: Shukar Ethylene da Ta Rage Lokacin Tsayawa da Kashi 87
Wata masana’antar ethylene a Gulf Coast tana sarrafa compressors centrifugal uku don cracked gas. Kowace injin na da racks na Bently Nevada 3500 dabam da Honeywell DCS dabam. Tsarukan biyu ba sa musayar bayanan girgiza. Masu aiki ba za su iya ganin motsin shaft kai tsaye yayin canjin load ba. Shukar ta sake wayoyi ta yadda kowanne probe ya tafi kai tsaye zuwa Siemens S7-1500 PLC. Suka yi shirin graduated load shedding. Lokacin da girgiza ta kai 60 microns, PLC ɗin ya rage matsin lamba na suction da kashi 5 cikin 100. A 70 microns, load ya faɗi da ƙarin kashi 10. A 80 microns, injin ya yi trip. Kafin canjin, ana samun unplanned shutdown guda takwas a shekara. Bayan canjin, an samu shutdown guda ɗaya kawai a cikin watanni 18. Lokacin tsayawa ya faɗi daga sa’o’i 112 zuwa sa’o’i 14 a shekara. Ajiyar kuɗi ya wuce dala miliyan 4 a shekara.
Misalin Aiki a Fage: Nitrogen Rejection Unit Ta Hana Mummunan Lalacewa
Wata masana’antar sarrafa iskar gas a Kanada tana da high-speed integrally geared compressor da ke gudu a 28000 RPM. OEM ta bayar da sauƙaƙƙen vibration switch kawai wanda ke yin trip a 100 microns. Babu bayanan trend da za a iya nazari. Injiniyoyi suka ƙara wani saiti na probes 3300 XL da aka haɗa zuwa CompactLogix PLC. Watanni shida bayan shigarwa, trend na PLC ya nuna girgiza ta tashi daga 35 microns zuwa 55 microns a cikin makonni biyu. Tsarin ya nuna ɓangaren 1X tare da ƙaramin 2X wanda ke nuna rashin balance. A lokacin shutdown da aka tsara, an gano impeller ya tsage. Farashin sauyawa ya kasance $180,000. Mummunar lalacewa za ta lalata gearbox gaba ɗaya ta kuma kai kuɗi $1.7 miliyan banda watanni uku na tsayawa.
Aiwar da Alarmin Frequency Band Ba Tare da Spectrum Analyzer Ba
PLCs na al’ada ba za su iya yin FFT analysis a cikinsu ba. Amma duk da haka za ka iya gano takamaiman fault frequencies ta amfani da analog filtering. Sanya external bandpass filters tsakanin direba da shigar analog na PLC. 1X tracking filter yana bi gudun injin. 2X filter yana gano yanayin misalignment. High-pass filter sama da 500 Hz yana kama matsalolin bearing. Aika kowace sigina da aka tace zuwa shigar analog daban. Kwatanta kowace band da threshold ɗinta mai zaman kanta. Wannan dabara tana kashe kuɗi ƙasa da cikakken spectrum analyzer amma tana bayar da bayanan ganewar asali masu amfani.
Gwajin Tsarin da Aka Haɗe Kafin a Kaddamar da Compressor
Kada ka dogara da software simulation kaɗai don tabbatarwa. Yi amfani da handheld signal calibrator wanda ke fitar da 4-20 mA. Cire shigar probe a direba ka haɗa calibrator. Saka 4 mA ka tabbatar PLC ɗin ya karanta 0 microns. Saka 12 mA ka tabbatar kashi 50 cikin 100 na full scale. Saka 20 mA ka tabbatar full scale. Ɗaga siginar daga 4 mA zuwa 20 mA a cikin sakan 30. Tabbatar kowace ƙararrawa da trip sun yi aiki a madaidaicin ƙimar milliampere. Auna lokaci daga wucewar threshold zuwa fitar relay ta amfani da oscilloscope. Jinkiri da za a iya yarda da shi ƙasa ne da milisakan 100 ƙari da jinkirin lokaci na timer da ka shirya.
Kurakuran Shigarwa da Aka Fi Yi da Yadda Za a Guje Musu
Kuskure 1: Amfani da kebul mara shielded don 4-20 mA loop. Wannan yana ɗaukar hayaniyar variable frequency drive. Kullum yi amfani da Belden 8762 ko shielded cable makamancin haka. Kuskure 2: Saita trip threshold da yawa kusa da girgizar aiki na yau da kullum. Tazarar kashi 10 cikin 100 yana haifar da nuisance trips. Yi amfani da mafi ƙaranci tazara kashi 30 cikin 100. Kuskure 3: Manta kunna wire break detection. Waya da ta yanke tana kama da 0 mA wanda PLC ke fassara shi a matsayin girgiza sifili. Shirya module na shigar analog ya saita fault bit idan current ya faɗi ƙasa da 3 mA. Kuskure 4: Daurawa direba a wuri mai zafi sama da digiri 85 Celsius. Lantarkin direba yana yin drift da zafi. Sanya drivers a cikin akwati (enclosure) mai sanyi dabam.
Kwatancen Kuɗi: Direct Wiring Da Traditional Monitor Rack
| Kayan aiki | Traditional System | Direct PLC Integration |
|---|---|---|
| Probes da drivers | $4,500 | $4,500 |
| Vibration monitor don tashoshi 4 | $12,000 | $0 |
| Katin shigar analog na PLC | $0 already present | $1,200 |
| Injiniyoyi da shirye-shirye | $8,000 | $6,000 |
| Jimla ga kowane compressor | $24,500 | $11,700 |
Direct integration yana adana $12,800 ga kowane layin compressor. Ga shuka da compressors goma, ajiyar ta wuce $120,000 a kayan aiki kaɗai. Kuɗin kula da kayan aiki ma ya ragu domin babu wani monitor rack dabam da ke buƙatar calibration lokaci-lokaci.
Tambayoyin da Injiniyoyin Fage Kan Yawan Yi
Q1: Shin direct wiring yana cika buƙatun API 670 don kariyar injuna?
A1: API 670 na buƙatar tsarin kariya na musamman da ke da takamaiman lokutan amsawa da iyawar gano matsala. PLC da aka shirya da kyau tare da isolated analog inputs da redundant power supplies na iya cika nufin ka’idar. Amma wasu masu inshora har yanzu suna buƙatar certified monitors. Tabbatar ka tuntubi mai inshorarka kafin ka cire racks na kariya da ke akwai yanzu.
Q2: Wane PLC scan time ne ya isa sauri don kariyar girgiza?
A2: Matsakaicin jinkiri da za a iya yarda daga firikwensin zuwa trip relay shi ne milisakan 200 ga yawancin compressors. PLC na zamani da ke gudu a cyclic task na milisakan 50 tare da sauƙaƙƙen ladder logic zai iya cimma wannan sauƙin. Ka guji amfani da general PLC scan da ke ɗauke da dogayen shirin. Ƙirƙiri dedicated high-priority interrupt task na tashoshin girgiza kaɗai.
Q3: Ta yaya zan sarrafa redundancy na probes biyu a cikin shirin PLC?
A3: Sanya probes biyu da tazarar digiri 90 a kan bearing ɗaya. Karanta duka ƙimomin cikin PLC. Yi trip ga compressor idan kowanne daga cikin probes ya wuce threshold na tsawon sakan 1.5. Don alarm, yi amfani da tsarin zabe (voting scheme). Ƙaddamar da sanarwar kulawa idan duk probes biyu sun wuce kashi 80 cikin 100 na threshold. Ƙaddamar da gaggawar alarm idan probe ɗaya ya wuce kashi 120 cikin 100 na threshold ba tare da la’akari da timer delay ba.
Takaitaccen Bayanai na Injiniya Don Masu Aikin Automation
Direct wiring na Bently Nevada 3300 XL probes zuwa shigar analog na PLC yana kawar da kayan aiki marasa amfani kuma yana rage jinkiri. Yi amfani da 4-20 mA loops tare da twisted shielded cable. Yi scaling na sigina a cikin PLC ta amfani da tsarin lissafi na linear. Shirya jinkirin lokaci na sakan 0.5 zuwa 1.5 don guje wa nuisance trips. Ƙara kula da gap voltage domin gano lafiyar probe. Gwada kowace tashar da signal calibrator kafin commissioning. Misalan aiki daga shuke-shuken ethylene da wuraren sarrafa gas sun nuna raguwar unplanned downtime da kashi 80 zuwa 90 tare da lokacin dawowa da jari (payback) ƙasa da watanni shida.
