apa corrosion monitoring ? pemantauan korosi atau karat

 iki cara ngawasi karat sing biasa di enggo neng perusahaan minyak koyo pertamina lan sanesipun


Apa kuwi pengawasan karat?

neng lapangan ngukur karat, kontrol, lan Nyegah kalebu spektrum banget godhongé amba saka technical aktivitas. Ing bal saka korosi kontrol lan Nyegah, ana technical pilihan kayata cathodic lan anodic pangayoman bahan pilihan, kimia klompok lan aplikasi saka material internal lan eksternal. Pangukuran karat ngandhut macem-macem Techniques kanggo nemtokake cara corrosive lingkungan lan apa mundhut tingkat logam lagi ngalami. Pangukuran karat

iku cara sing jumlah dening kang efektifitas karat kontrol lan Nyegah Techniques bisa mandhiri lan nyedhiyakake saran ngaktifake kontrol korosi lan cara Nyegah supaya optimized.

A macem-macem sudhut karat pangukuran Techniques ana, kalebu:
Non ajurmumur Testing See Chemistry See Chemistry
• ultrasonik testing
• Radiography
• Thermography
• Eddy saiki / Magnetik fluks
• Intelligent babi

• pangukuran PH
• Dipun bibaraken gas (O2, CO2, H2S)
• Metal ion count (Fe2 +, Fe3 +)
• microbiological analisis

Operasional Rambo data elektrokimia
• PH
• mili tingkat (kecepatan)
• meksa
• suhu • pangukuran Potensial
• Potentiostatic pangukuran
• Potentiodynamic pangukuran
• A.C. impedansi

korosi ngawasi
• Bobot mundhut Kupon
• Electrical resistance
• Larikan polarisasi
• hidrogen seng nembus
• galvanik saiki





Sawetara Techniques pangukuran karat bisa digunakake ing baris, saya kapapar ing stream proses, nalika wong nyedhiyani mati-baris pangukuran, kayata sing ditemtokake ing analisis Laboratory. Sawetara Techniques menehi langkah langsung saka mundhut logam utawa karat tingkat, nalika wong sing dipigunakaké kanggo Infer sing lingkungan corrosive uga ana.

Korosi ngawasi punika laku ngukur corrosivity proses stream kahanan dening nggunakake saka "pemeriksaan" kang dilebokake menyang stream proses lan sing terus-terusan kapapar proses stream kawontenan.

Korosi ngawasi "pemeriksaan" bisa dadi mechanical, electrical, utawa elektrokimia piranti.

Korosi ngawasi Techniques piyambak nyedhiyani pangukuran langsung lan online saka logam mundhut / karat tingkat ing industri proses sistem.

Biasane, program pangukuran korosi, pengawasan lan pangopènan digunakake ing sembarang fasilitas industri ora incorporate unsur pangukuran diwenehake dening kombinasi papat on-line/offline, langsung / langsung pangukuran.

     Korosi Ngawasi Direct, On-line
     Non ajurmumur Testing Direct, Off-line
     Analitis Chemistry langsung, Off-line
     Operasional data langsung, On-line

Ing program uga kontrol lan tumata, data saka saben sumber bakal digunakake kanggo tarik migunani Serat bab operasional karat tarif karo sistem proses lan carane iki sing paling èfèktif nyilikake.



Ing Need kanggo karat ngawasi

Tingkat saka korosi dictates suwene sembarang tanduran proses bisa usefully lan aman dilakokno. Takeran saka korosi lan ajeg kanggo obat dhuwur karat tarif ngidini paling biaya efektif operasi tanduran kanggo ngrambah nalika ngurangi biaya urip-siklus digandhengake karo operasi.

Korosi ngawasi Techniques bisa bantuan ing sawetara cara:

     dening nyediakake sawijining bebaya awal sing bakal ngrusak proses kahanan ana kang bisa ngakibataké karat-mlebu Gagal.
     dening sinau korélasi saka owahan ing proses paramèter lan efek ing sistem corrosivity.
     dening diagnosing tartamtu karat masalah, Ngenali sawijining sabab lan tingkat Ngontrol paramèter, kayata meksa, suhu, Ph, aliran tingkat, etc
     dening ngevaluasi efektifitas technique karat kontrol / Nyegah kayata kimia inhibisi lan netepake aplikasi optimal.
     dening nyediakake informasi manajemen hubungane syarat lan pangopènan aktif kawontenan tanduran.



Korosi ngawasi Techniques

A nomer akeh karat ngawasi Techniques ana. Details dhaftar Dipuntedahaken Techniques paling umum kang digunakake ing industri aplikasi:

     Korosi Kupon (bobot mundhut pangukuran)
     Electrical Resistance (ER)
     Linear polarisasi Resistance (LPR)
     Galvanik (ZRA) / Potensial
     hidrogen Penetration
     microbial
     Pasir / erosi

Liyane Techniques aja ana, nanging meh kabeh sing sawetara operasi pakar, utawa digunakake ora cekap nggronjal utawa adaptable aplikasi tanduran.

Techniques kadhaptar ndhuwur, karat Kupon, ER, lan LPR mbentuk inti saka industri karat ngawasi sistem. Papat Techniques liyane sing biasane ditemokake ing aplikasi specialized kang rembugan mengko.

Iki karat ngawasi Techniques wis kasil Applied lan dipigunakaké ing sawetara tambah aplikasi amarga:

     Techniques sing gampang mangerténi lan ngleksanakake.
     Peralatan linuwih wis tontonan ing lingkungan lapangan liwat akeh taun saka operasi aplikasi.
     Asil gampang kokwaca.
     Ngukur peralatan bisa digawe Ngrapèkaken aman kanggo bahaya operasi wilayah.
     Kedhaftar wis ngalami entuk manfaat ekonomi pinunjul liwat suda tanduran mudhun wektu lan tanduran urip extension.



Korosi Kupon (Bobot Mundhut)

Ing Bobot Mundhut technique paling misuwur lan paling gampang kabeh Techniques karat ngawasi. Cara melu mbabarake sing spesimené saka materi (coupon) kanggo lingkungan proses kanggo dadi tartamtu, banjur njabut spesimené kanggo analisis. Takeran dhasar kang ditemtokake saka korosi Kupon punika bobot mundhut; mundhut bobot njupuk Panggonan liwat periode cahya kang ditulis minangka karat tingkat.

Gamblang pangukuran ditawani coupon korosi kuwi sing technique kupon Forms metode garis dasar pangukuran ing kathah program karat ngawasi.

Ing technique banget Versatile, wiwit bobot mundhut Kupon bisa fabricated saka sembarang alloy iklan kasedhiya. Uga, nggunakake cocok géometris designs, variétas karat gejala bisa sinau kang kalebu, nanging ora winates:

     Kaku-dibantu karat
     Bimetallic (galvanik) serangan
     diferensial aeration
     Panas-kena pengaruh zona

Kaluwihan saka bobot mundhut Kupon ana sing:

     Technique ditrapake kanggo kabeh lingkungan - gas, cairan, barang padhet / sawetoro aliran.
     Pengawasan visual bisa di tangani.
     Korosi celengan bisa diamati lan dipunanalisis.
     Bobot mundhut bisa siap ditemtokake lan karat tingkat gampang diwilang.
     Localized karat bisa dikenali lan diukur.
     Inhibitor kinerja bisa gampang dinilei.

Ing program ngawasi khas, Kupon sing kapapar kanggo dadi 90-dina sadurunge kang dibusak kanggo analisis Laboratory. Iki menehi dhasar karat tingkat pangukuran ing frekuensi saka papat kaping saben taun. Ing mundhut bobot asil saka sembarang siji pajanan kupon panenan ing "rata-rata" Nilai saka korosi kedadean sak cahya. Kerugian technique kupon iku, menawa ngganggu karat occurs sak periode cahya, kupon piyambak ora bisa kanggo ngenali wektu kedadeyan saka ngganggu, lan gumantung marang Nilai Pucuk ngganggu lan dadi, uga ora malah ndhaftar tambah mundhut kecatet wujud bobot.

Mulane, kupon ngawasi paling migunani ing lingkungan ngendi karat tarif ora Ngartekno ngganti liwat dawa wektu. Nanging, dheweke bisa nyedhiyani gathukane migunani karo Techniques liyane kayata ER lan LPR pangukuran.



Electrical Reistance (ER) ngawasi

ER pemeriksaan bisa panginten kang minangka "elektronik" karat Kupon. Kaya Kupon, ER pemeriksaan nyedhiyani pangukuran dhasar saka mundhut logam, nanging kados Kupon, ing Nilai saka mundhut logam bisa diukur ing sembarang wektu, minangka kerep minangka dibutuhake, nalika satelit ing-situ lan permanen kapapar ing stream proses.

Korosi ngawasi Pambuka

Daur ulang kabel dituduhake punika anyar karo menehi gunggung diameter 40 Mils (gunggung migunani satelit gesang 10 Mils).

Kene elemen wis ngalami babagan 5 Mils seng nembus utawa babagan setengah saka sawijining urip migunani. Tambah electrical resistance ing unsur bakal ndhaftar minangka 5 Mils logam seng nembus menyang pipo utawa proses sistem.

Kene elemen wis diukur 10 Mils saka seng nembus lan mbutuhake panggantos.

Technique ER ngukur pangowahan ing Ohmic resistance saka corroding logam unsur kapapar ing stream proses. Padamelan karat ing lumahing unsur mrodhuksi nyuda ing sawijining salib-bagean wilayah karo Tambah korespondensi ing sawijining electrical resistance. Tambah ing resistance bisa duwé pranala langsung menyang mundhut logam lan mundhut logam minangka fungsi saka wektu iku dening definisi tingkat korosi. Senajan isih wektu averaged technique, wektu nanggepi kanggo ER ngawasi iku adoh luwih cendhek tinimbang sing kanggo bobot mundhut Kupon. Ing grafik ngisor nuduhake khas nanggepi tambahan.

Korosi ngawasi Pambuka

ER pemeriksaan duwe kabeh kaluwihan saka Kupon, plus:

     Lagi ditrapake kanggo kabeh lingkungan apa gas, cairan, barang padhet, sawetoro mili.
     Langsung karat tarif bisa dipikolehi.
     Satelit tetep diinstal ing-line nganti operasi urip wis kesel.
     Padha nanggapi kanthi cepet kanggo karat upsets lan bisa digunakake kanggo micu weker.

ER pemeriksaan kasedhiya ing macem-macem unsur géomètri, metallurgies lan sensitivities lan bisa diatur kanggo disegerne maneh sing soyo tambah kuwi sing pigging operasi bisa njupuk Panggonan tanpa kabutuhan kanggo mbusak pemeriksaan. Ing sawetara sensitivities ngidini operator kanggo milih respon paling dinamis konsisten karo proses syarat.


Linear polarisasi Resistance (LPR) ngawasi

Technique LPR adhedhasar téori panitahan-kimia komplèks. Tujuane aplikasi pangukuran industri lagi simplified kanggo konsep banget dhasar. Ing dhasar istilah, voltase cilik (utawa polarisasi potensial) wis Applied menyang elektroda ing solusi. Saiki perlu kanggo njaga tartamtu voltase shift (biasane 10 MV) langsung gegandhengan karo korosi ing lumahing elektroda ing solusi. Kanthi ngukur saiki, tingkat karat bisa asalé.

Ing kauntungan saka technique LPR iku pangukuran karat tingkat digawe instantaneously. Iki alat luwih kuat ketimbang Kupon utawa ER ngendi pangukuran ing dhasar punika mundhut logam lan ngendi sawetara periode pajanan dibutuhake kanggo nemtokake karat tingkat. Kerugian menyang technique LPR iku mung bisa kasil dileksanakake ing relatif resik banyu lingkungan Electrolytic. LPR ora bisa ing gas utawa emulsions banyu / lenga ngendi fouling saka elektrods bakal nyegah pangukuran kang digawe.



Galvanik / Potensial ngawasi

     Ing galvanik technique ngawasi, uga dikenal minangka Zero Resistance Ammetry (ZRA) liya elektrokimia technique ukur. Kanthi ZRA pemeriksaan, rong medium sing béda saka elektrods logam sing kapapar adi proses. Nalika nyemplungaken ing solusi, voltase alam (potensial) prabédan tumuju antarane elektrods. Saiki kui amarga iki prabédan potensial hubungane kanggo tingkat saka korosi sing kedadean ing luwih aktif saka pasangan elektroda.

     Galvanik / Potensial ngawasi ditrapake kanggo ing ngisor iki elektroda pasangan:
     Bimetallic karat
     Crevice lan pitting serangan
     Korosi dibantu gawe
     Korosi dening Highly oxidizing spesies
     Weld bosok

Ukuran saiki galvanik wis nemokake sawijining palng aplikasi ing sistem banyu injeksi ngendi larut oksigen konsentrasi sing badhan utama. Oksigen bocor menyang sistem kuwi nemen mundhak galvanik sapunika lan kanthi mangkono tingkat karat baja proses komponen. Galvanik ngawasi sistem digunakake kanggo nyedhiyani pratondo oksigen bisa invading injeksi Waters liwat bocor gaskets utawa deaeration sistem.


specialized ngawasi

biologi ngawasi
Biologi ngawasi lan analisis umumé nggoleki kanggo ngenali ngarsane sulphate Ngurangi Bakteri - SRB kang. Iki kelas anaerobic bakteri kang nganggo sulphate saka stream proses lan nguripake asam sulfur, a corrosive kang nyerang tanduran produksi bahan.

Pasir / erosi ngawasi
Iki piranti kang dirancang kanggo ngukur erosi ing sistem milinipun. Padha golek sudhut aplikasi ing sistem lenga / gas produksi ngendi sawetoro prakara iku saiki.

Hidrogen Penetration ngawasi
Ing ngandhut asam proses lingkungan, hidrogen punika kanthi-produk saka reaksi korosi. Hidrogen kui ing kuwi reaksi bisa digunakke dening baja utamané nalika ngambah ing sulphide utawa cyanide sing saiki. Iki uga kanggo mimpin hidrogen mlebu Gagal dening siji utawa luwih saka saperangan mekanisme. Konsep hidrogen pemeriksaan kanggo ndeteksi jumlah hidrogen permeating liwat baja kanthi pangukuran mechanical utawa elektrokimia lan nggunakake minangka pratondo kwalitase saka korosi tingkat.

instrumen

Ana macem-macem opsi piranti gadhah maneka Techniques karat ngawasi. Telung klasifikasi punika:

     hotspot
     Suwine Single Kanal
     Suwine Multi-Channel

Ing sawetara aplikasi kayata iku ngalami ing lenga / gas produksi lan panyulingan, instrumen dibutuhake supaya certified dienggo ing "wilayah bahaya". Kanggo hotspot instruments iki paling asring ngrambah dening gadhah peralatan certified minangka "Ngrapèkaken aman" dening panguwasa dikenali kayata BASEEFA (UK), UL (U.S.A.), utawa CENELEC (Eropah). Kanggo hardwired suwine ngawasi electronics, hubungan alangan bisa digunakake kanggo mesthekake yen, ing acara saka kondisi fault, ora cukup energi iki ditularaké menyang bahaya lapangan wilayah supaya sing narik mbledhos ora bisa diprodhuksi.


Satelit fitting Gaya

Ana rong dhasar fitting gaya kanggo karat pemeriksaan: tetep lan saged dipindhah ing meksa.

Telpon gaya saka pemeriksaan / sensor duwe biasane sing Utas utawa flanged lampiran kanggo tanduran proses. Kanggo telpon gaya saka sensor, aman mung bisa tuntas sak sistem mati utawa dening ora duwe hubungan lan depressurization saka lokasi sensor.

Saka wektu kanggo wektu, karat Kupon lan pemeriksaan sing aman lan panggantos. Iku kadhangkala luwih trep kanggo bisa mbusak lan nginstal sensor nalika sistem proses operasional. Kanggo nggampangake iki, ana loro sistem béda kang ngidini aman / instalasi ing meksa.

Ing refinery lan proses tanduran lingkungan ngendi tekanan sing biasane kurang saka 1500 psi, sistem Retractable digunakake. Iki kasusun saka kelenjar diinget (stuffing kothak) lan tutup noto. Kanggo lingkungan kayata iku ngalami ing lenga / gas produksi ngendi tekanan sawetara ewu psi sing ngalami, khusus Dhuwur Meksa Akses Sistem digunakake. Iki ngidini aman lan gampang instalasi / aman saka korosi ngawasi piranti apa tekanan nganti 3600 psi.


Aplikasi saka korosi ngawasi Techniques

Korosi ngawasi punika biasane digunakake ing kahanan ing ngisor iki:

     Ngendi risiko dhuwur - tekanan dhuwur, suhu dhuwur, flammable, mbledhos, racun pangolahan.
     Ngendi proses upsets bisa nimbulaké dhuwur corrosivity.
     Ngendi owahan ing kahanan operasi bisa nimbulaké owah-owahan wujud ing korosi tingkat.
     Ngendi karat Inhibitor sing dienggo.
     Ing kumpulan pangolahan, ngendi corrosive konstituen sing klempakan amargi bola muter.
     Ngendi proses feedstock diganti.
     Ngendi tanduran output utawa operasi paramèter sing diganti saka desain spesifikasine.
     Ing evaluasi karat prilaku manéka warna wesi.
     Ngendi mlebu potensial Nggeser digunakake kanggo nglindhungi sistem lan / utawa struktur.
     Ngendi ketularan produk amargi karat iku badhan penting.

Korosi ngawasi uga digunakake ing sakbenere sembarang industri ngendi karat Nyegah punika requirement utama. Sawetara conto industri lan wilayah tartamtu saka kapentingan klebu, nanging ora winates:
Lenga / Gas Produksi

     Flowlines
     ngumpul Systems
     transportasi Pipeline
     Banyu Injeksi Fasilitas
     prau
     Processing
     banyu Systems
     Kimia Injeksi Systems
     Ngebur Mud Systems
     Banyu wisuh Systems
     Desalters

panyulingan

     Crude Overheads
     Visbreakers
     vakum Towers
     Asem banyu Strippers
     amine Systems
     cooling Systems

Pulp lan Paper

     Digesters
     putih Omben-omben
     ketel Systems

keperluan

     cooling Systems
     Effluent Systems
     Priksa-Up banyu Systems
     Ketel banyu Systems

Petrochemicals / Kimia / Processing

     proses Systems
     cooling Systems



Ing sembarang sistem karat ngawasi, iku umum kanggo nggoleki loro utawa luwih saka Techniques digabungake kanggo nyedhiyani basa sudhut kanggo ngumpul data. Techniques pas kang bisa digunakake gumantung adi proses nyata, logam campuran sistem, lan paramèter operasi.

Korosi ngawasi nawakake jawaban kanggo pitakonan saka apa maneh karat punika kedadean dina minangka dibandhingake wingi. Nganggo informasi iki iku bisa kanggo nduweni sabab korosi lan ngundhakke sawijining pengaruh. Korosi ngawasi tetep gegaman terkenal ing perang nglawan korosi, mangkono nyediakake entuk manfaat ekonomi substansial menyang user....

sing asli ne koyo ngene

What is Corrosion Monitoring? The field of corrosion measurement, control, and prevention covers a very broad spectrum of technical activities. Within the sphere of corrosion control and prevention, there are technical options such as cathodic and anodic protection, materials selection, chemical dosing and the application of internal and external coatings. Corrosion measurement employs a variety of techniques to determine how corrosive the environment is and at what rate metal loss is being experienced. Corrosion measurement is the quantitative method by which the effectiveness of corrosion control and prevention techniques can be evaluated and provides the feedback to enable corrosion control and prevention methods to be optimized. A wide variety of corrosion measurement techniques exists, including: Non Destructive Testing Analytical Chemistry Analytical Chemistry • Ultrasonic testing • Radiography • Thermography • Eddy current/magnetic flux • Intelligent pigs • pH measurement • Dissolved gas (O2, CO2, H2S) • Metal ion count (Fe2+, Fe3+) • Microbiological analysis Operational Data Fluid Electrochemistry • pH • Flow rate (velocity) • Pressure • Temperature • Potential measurement • Potentiostatic measurements • Potentiodynamic measurements • A.C. impedance Corrosion Monitoring • Weight loss coupons • Electrical resistance • Linear polarization • Hydrogen penetration • Galvanic current Some corrosion measurement techniques can be used on-line, constantly exposed to the process stream, while others provide off-line measurement, such as that determined in a laboratory analysis. Some techniques give a direct measure of metal loss or corrosion rate, while others are used to infer that a corrosive environment may exist. Corrosion monitoring is the practice of measuring the corrosivity of process stream conditions by the use of "probes" which are inserted into the process stream and which are continuously exposed to the process stream condition. Corrosion monitoring "probes" can be mechanical, electrical, or electrochemical devices. Corrosion monitoring techniques alone provide direct and online measurement of metal loss/corrosion rate in industrial process systems. Typically, a corrosion measurement, inspection and maintenance program used in any industrial facility will incorporate the measurement elements provided by the four combinations of on-line/offline, direct/indirect measurements. Corrosion Monitoring Direct, On-line Non Destructive Testing Direct, Off-line Analytical Chemistry Indirect, Off-line Operational Data Indirect, On-line In a well controlled and coordinated program, data from each source will be used to draw meaningful conclusions about the operational corrosion rates with the process system and how these are most effectively minimized.

The Need for Corrosion Monitoring The rate of corrosion dictates how long any process plant can be usefully and safely operated. The measurement of corrosion and the action to remedy high corrosion rates permits the most cost effective plant operation to be achieved while reducing the life-cycle costs associated with the operation. Corrosion monitoring techniques can help in several ways: by providing an early warning that damaging process conditions exist which may result in a corrosion-induced failure. by studying the correlation of changes in process parameters and their effect on system corrosivity. by diagnosing a particular corrosion problem, identifying its cause and the rate controlling parameters, such as pressure, temperature, pH, flow rate, etc. by evaluating the effectiveness of a corrosion control/prevention technique such as chemical inhibition and the determination of optimal applications. by providing management information relating to the maintenance requirements and ongoing condition of plant.

Corrosion Monitoring Techniques A large number of corrosion monitoring techniques exist. The following list details the most common techniques which are used in industrial applications: Corrosion Coupons (weight loss measurements) Electrical Resistance (ER) Linear Polarization Resistance (LPR) Galvanic (ZRA) / Potential Hydrogen Penetration Microbial Sand/Erosion Other techniques do exist, but almost all require some expert operation, or otherwise are not sufficiently rugged or adaptable to plant applications. Of the techniques listed above, corrosion coupons, ER, and LPR form the core of industrial corrosion monitoring systems. The four other techniques are normally found in specialized applications which are discussed later. These corrosion monitoring techniques have been successfully applied and are used in an increasing range of applications because: The techniques are easy to understand and implement. Equipment reliability has been demonstrated in the field environment over many years of operational application. Results are easy to interpret. Measuring equipment can be made intrinsically safe for hazardous area operation. Users have experienced significant economic benefit through reduced plant down time and plant life extension.

Corrosion Coupons (Weight Loss) The Weight Loss technique is the best known and simplest of all corrosion monitoring techniques. The method involves exposing a specimen of material (the coupon) to a process environment for a given duration, then removing the specimen for analysis. The basic measurement which is determined from corrosion coupons is weight loss; the weight loss taking place over the period of exposure being expressed as corrosion rate. The simplicity of the measurement offered by the corrosion coupon is such that the coupon technique forms the baseline method of measurement in many corrosion monitoring programs. The technique is extremely versatile, since weight loss coupons can be fabricated from any commercially available alloy. Also, using appropriate geometric designs, a wide variety of corrosion phenomena may be studied which includes, but is not limited to: Stress-assisted corrosion Bimetallic (galvanic) attack Differential aeration Heat-affected zones Advantages of weight loss coupons are that: The technique is applicable to all environments - gases, liquids, solids/particulate flow. Visual inspection can be undertaken. Corrosion deposits can be observed and analyzed. Weight loss can be readily determined and corrosion rate easily calculated. Localized corrosion can be identified and measured. Inhibitor performance can be easily assessed. In a typical monitoring program, coupons are exposed for a 90-day duration before being removed for a laboratory analysis. This gives basic corrosion rate measurements at a frequency of four times per year. The weight loss resulting from any single coupon exposure yields the "average" value of corrosion occurring during that exposure. The disadvantage of the coupon technique is that, if a corrosion upset occurs during the period of exposure, the coupon alone will not be able to identify the time of occurrence of the upset, and depending upon the peak value of the upset and its duration, may not even register a statistically significant increased weight loss. Therefore, coupon monitoring is most useful in environments where corrosion rates do not significantly change over long time periods. However, they can provide a useful correlation with other techniques such as ER and LPR measurements.

Electrical Reistance (ER) Monitoring ER probes can be thought of as "electronic" corrosion coupons. Like coupons, ER probes provide a basic measurement of metal loss, but unlike coupons, the value of metal loss can be measured at any time, as frequently as required, while the probe is in-situ and permanently exposed to the process stream.

The wire loop represented here is new with its total diameter of 40 mils (total useful probe life of 10 mils). Here the element has experienced about 5 mils penetration or about half of its useful life. The increased electrical resistance of the element will register as 5 mils metal penetration into the piping or process system. Here the element has measured 10 mils of penetration and requires replacement.

The ER technique measures the change in Ohmic resistance of a corroding metal element exposed to the process stream. The action of corrosion on the surface of the element produces a decrease in its cross-sectional area with a corresponding increase in its electrical resistance. The increase in resistance can be related directly to metal loss and the metal loss as a function of time is by definition the corrosion rate. Although still a time averaged technique, the response time for ER monitoring is far shorter than that for weight loss coupons. The graph below shows typical response times.

ER probes have all the advantages of coupons, plus: They are applicable to all working environments gases, liquids, solids, particulate flows. Direct corrosion rates can be obtained. Probe remains installed in-line until operational life has been exhausted. They respond quickly to corrosion upsets and can be used to trigger an alarm. ER probes are available in a variety of element geometries, metallurgies and sensitivities and can be configured for flush mounting such that pigging operations can take place without the necessity to remove probes. The range of sensitivities allows the operator to select the most dynamic response consistent with process requirements.

Linear Polarization Resistance (LPR) Monitoring The LPR technique is based on complex electro-chemical theory. For purposes of industrial measurement applications it is simplified to a very basic concept. In fundamental terms, a small voltage (or polarization potential) is applied to an electrode in solution. The current needed to maintain a specific voltage shift (typically 10 mV) is directly related to the corrosion on the surface of the electrode in the solution. By measuring the current, a corrosion rate can be derived. The advantage of the LPR technique is that the measurement of corrosion rate is made instantaneously. This is a more powerful tool than either coupons or ER where the fundamental measurement is metal loss and where some period of exposure is required to determine corrosion rate. The disadvantage to the LPR technique is that it can only be successfully performed in relatively clean aqueous electrolytic environments. LPR will not work in gases or water/oil emulsions where fouling of the electrodes will prevent measurements being made.

Galvanic/Potential Monitoring The galvanic monitoring technique, also known as Zero Resistance Ammetry (ZRA) is another electrochemical measuring technique. With ZRA probes, two electrodes of dissimilar metals are exposed to the process fluid. When immersed in solution, a natural voltage (potential) difference exits between the electrodes. The current generated due to this potential difference relates to the rate of corrosion which is occurring on the more active of the electrode couple. Galvanic/Potential monitoring is applicable to the following electrode couples: Bimetallic corrosion Crevice and pitting attack Corrosion assisted cracking Corrosion by highly oxidizing species Weld decay Galvanic current measurement has found its widest applications in water injection systems where dissolved oxygen concentrations are a primary concern. Oxygen leaking into such systems greatly increases galvanic currents and thus the corrosion rate of steel process components. Galvanic monitoring systems are used to provide an indication that oxygen may be invading injection waters through leaking gaskets or deaeration systems.

Specialized Monitoring Biological Monitoring Biological monitoring and analysis generally seeks to identify the presence of Sulphate Reducing Bacteria - SRB's. This is a class of anaerobic bacteria which consume sulphate from the process stream and generate sulphuric acid, a corrosive which attacks production plant materials. Sand / Erosion Monitoring These are devices which are designed to measure erosion in a flowing system. They find wide application in oil/gas production systems where particulate matter is present. Hydrogen Penetration Monitoring In acidic process environments, hydrogen is a by-product of the corrosion reaction. Hydrogen generated in such a reaction can be absorbed by steel particularly when traces of sulphide or cyanide are present. This may lead to hydrogen induced failure by one or more of several mechanisms. The concept of hydrogen probes is to detect the amount of hydrogen permeating through the steel by mechanical or electrochemical measurement and to use this as a qualitative indication of corrosion rate.

Instrumentation There exists a variety of instrument options associated with the various corrosion monitoring techniques. Three classifications are: Portable Continuous Single Channel Continuous Multi-Channel In some applications such as those experienced in oil/gas production and refining, instrumentation is required to be certified for use in "hazardous areas". For portable instruments this is most often achieved by having the equipment certified as "intrinsically safe" by a recognized authority such as BASEEFA (U.K.), U.L. (U.S.A.), or CENELEC (Europe). For hardwired continuous monitoring electronics, isolation barriers can be used to ensure that, in the event of a fault condition, insufficient energy is transmitted to the hazardous field area so that an explosive spark cannot be produced.

Probe Fitting Styles There are two fundamental fitting styles for corrosion probes: fixed and removable under pressure. Fixed styles of probes/sensors have typically a threaded or flanged attachment to the process plant. For fixed styles of sensors, removal can only be accomplished during system shut down or by isolation and depressurization of the sensor location. From time to time, corrosion coupons and probes require removal and replacement. It is sometimes more convenient to be able to remove and install sensors while the process system is operational. To facilitate this, there are two distinct systems which permit removal/installation under pressure. In refinery and process plant environments where pressures are normally less than 1500 psi, a Retractable System is used. This consists of a packing gland (stuffing box) and valve arrangement. For environments such as those experienced in oil/gas production where pressures of several thousand psi are experienced, a special High Pressure Access System is used. This permits the safe and easy installation/removal of corrosion monitoring devices at working pressures up to 3600 psi.

Applications of Corrosion Monitoring Techniques Corrosion monitoring is typically used in the following situations: Where risks are high - high pressure, high temperature, flammable, explosive, toxic processes. Where process upsets can cause high corrosivity. Where changes in operating conditions can cause significant changes in corrosion rate. Where corrosion inhibitors are in use. In batch processes, where corrosive constituents are concentrated due to repeated cycling. Where process feedstock is changed. Where plant output or operating parameters are changed from design specifications. In the evaluation of corrosion behavior of various alloys. Where induced potential shifts are used to protect systems and/or structures. Where product contamination due to corrosion is a vital concern. Corrosion monitoring may be used in virtually any industry where corrosion prevention is a primary requirement. Some examples of industries and specific areas of interest include, but are not limited to: Oil/Gas Production Flowlines Gathering Systems Transport Pipelines Water Injection Facilities Vessels Processing Water Systems Chemical Injection Systems Drilling Mud Systems Water Wash Systems Desalters Refining Crude Overheads Visbreakers Vacuum Towers Sour Water Strippers Amine Systems Cooling Systems Pulp and Paper Digesters White Liquor Boiler Systems Utilities Cooling Systems Effluent Systems Make-Up Water Systems Boiler Water Systems Petrochemicals/Chemicals/Processing Process Systems Cooling Systems In any corrosion monitoring system, it is common to find two or more of the techniques combined to provide a wide base for data gathering. The exact techniques which can be used depend on the actual process fluid, alloy system, and operating parameters. Corrosion monitoring offers an answer to the question of whether more corrosion is occurring today as compared to yesterday. Using this information it is possible to qualify the cause of corrosion and quantify its effect. Corrosion monitoring remains a valuable weapon in the fight against corrosion, thereby providing substantial economic benefit to the user.