SI26200A - Electrical resistance sensor for corrosion monitoring in extreme corrosion conditions - Google Patents

Electrical resistance sensor for corrosion monitoring in extreme corrosion conditions Download PDF

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SI26200A
SI26200A SI202100103A SI202100103A SI26200A SI 26200 A SI26200 A SI 26200A SI 202100103 A SI202100103 A SI 202100103A SI 202100103 A SI202100103 A SI 202100103A SI 26200 A SI26200 A SI 26200A
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measuring
sensor
points
metal element
corrosion
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SI202100103A
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Miha Hren
Branko Belingar
Tadeja Kosec
Viljem Kuhar
Andraž Legat
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DMS, DATA MERILNI SISTEMI, d.o.o
Zavod Za Gradbeništvo Slovenije
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Abstract

Električni uporovni senzor po izumu vključuje kovinski element (1) in izolacijsko ohišje (20), pri čemer je kovinski element (1) izveden ploščato v obliki črke U in je v celoti izdelan iz enega kosa valjane jeklene pločevine, tako da vzdolžna os kovinskega elementa (1) poteka v smeri valjanja pločevine. Del kovinskega elementa (1), ki je neposredno izpostavljen korozivnemu mediju, predstavlja merilno elektrodo, del kovinskega elementa (1), ki je od korozivnega medija izoliran z ohišjem (20), predstavljareferenčno elektrodo. Ker je kovinski element (1) senzorja ploščate oblike, pločevina (jeklo) ni krivljena ali upognjena, je le izrezana v želeno obliko, mikrostruktura jekla ni deformirana, v materialu po izdelavi kovinskega elementa (1) senzorja ni notranjih napetosti, zato ni možnosti za pojav napetostne korozije in zelo malo verjetnosti za pojav interkristalne korozije nerjavnega jekla. Kovinski element (1), torej merilna elektroda in referenčna elektroda, je v celoti izdelan iz enega kosa pločevine,torej iz istega kosa pločevine in na enak način, kar omogoča avtomatsko temperaturno kompenzacijo.The electric resistive sensor according to the invention includes a metal element (1) and an insulating housing (20), wherein the metal element (1) is made flat in the shape of the letter U and is made entirely of one piece of rolled steel sheet, so that the longitudinal axis of the metal element (1) takes place in the direction of sheet metal rolling. The part of the metal element (1) that is directly exposed to the corrosive medium represents the measuring electrode, the part of the metal element (1) that is isolated from the corrosive medium by the casing (20) represents the reference electrode. Since the metal element (1) of the sensor is flat-shaped, the sheet (steel) is not bent or bent, it is only cut into the desired shape, the microstructure of the steel is not deformed, there are no internal stresses in the material after the metal element (1) of the sensor is made, so there is no possibility of occurrence of stress corrosion and very little probability of occurrence of intercrystalline corrosion of stainless steel. The metal element (1), i.e. the measuring electrode and the reference electrode, is completely made from one piece of sheet metal, i.e. from the same piece of sheet metal and in the same way, which enables automatic temperature compensation.

Description

Električni uporovni senzor za korozijski monitoring v ekstremnih korozijskih razmerahElectrical resistance sensor for corrosion monitoring in extreme corrosion conditions

Tehnično področje, na katerega se nanaša izumTechnical field to which the invention relates

Korozijski monitoring, merjenje korozijskih hitrosti nerjavnih jekel v ekstremnih pogojih v hidrometalurgijiCorrosion monitoring, measurement of corrosion rates of stainless steels under extreme conditions in hydrometallurgy

V hidrometalurški industriji predstavlja korozija materialov velik problem. Za natančne ocene degradacije materialov v proizvodnih procesih je potreben nadzor. Običajno se spremlja korozija s korozijskimi vzorci (coupons) iz želenih materialov, ki jih občasno odstranimo iz naprav, pregledamo in tehtamo (gravimetrična metoda). Za spremljane korozije postrojenj v ekstremnih korozijskih razmerah so bili razviti električni uporovni senzorji, v nadaljevanju ER senzorji, iz nerjavnih jekel. Delovanje električnega uporovnega senzorja je preprosto. Z manjšanjem preseka merilnega elementa zaradi korozije se veča njegova električna upornost. Senzor je opremljen s sodobno merilno elektroniko z zajemanjem in brezžičnim prenosom podatkov.Corrosion of materials is a major problem in the hydrometallurgical industry. Accurate assessments of material degradation in manufacturing processes require monitoring. Corrosion is usually monitored with corrosion samples (coupons) from the desired materials, which are periodically removed from the devices, examined and weighed (gravimetric method). Electrical resistance sensors, hereinafter referred to as ER sensors, made of stainless steel were developed for monitored corrosion of plants in extreme corrosion conditions. The operation of an electrical resistive sensor is simple. As the cross-section of the measuring element decreases due to corrosion, its electrical resistance increases. The sensor is equipped with modern measuring electronics with acquisition and wireless data transmission.

Industrijski procesi predelave surovin potekajo v kislih, močno korozivnih kemikalijah pri povišanih temperaturah. Običajno so to raztopine žveplove kisline (okoli 10 % H2SO4), ki vsebujejo tudi kloridne ione (5 g/L NaCI), temperature pa so do 90 °C. Koncentracije kisline, kloridnih ionov v raztopini in temperature se med procesi tudi spreminjajo. V tem okolju so korozijske hitrosti večine kovin in tudi nerjavnih jekel relativno velike, zaradi tega je potrebna optimalna izbira materialov in njihovih dimenzij. Postrojenja so izdelana iz posod (reaktorjev), cevovodov in drugih naprav iz nerjavnih jekel z zelo visoko korozijsko odpornostjo. Večina posod v postrojenjih je izdelana iz pločevin različnih debelin. Zaradi tega je optimalno, da so tudi električni uporovni senzorji za korozijski monitoring izdelani iz pločevin enake kvalitete nerjavnih jekel. Za izdelavo ER senzorjev po izumu sta bili izbrani dve kvaliteti nerjavnih jekel; Cr-Ni-Mo avstenitno nerjavno jeklo AISI 316L in Cr-Mo-Ni avstenitno-feritno nerjavno jeklo duplex 2507 (proizvajalec Outokumpu StainlessAB, Švedska), ki je bilo razvito prav za uporabo v ekstremnih korozijskih okoljih v prisotnosti žveplove kisline, visokih vsebnosti kloridnih ionov in povišanih temperatur.Industrial raw material processing processes take place in acidic, highly corrosive chemicals at elevated temperatures. These are usually sulfuric acid solutions (about 10% H2SO4) that also contain chloride ions (5 g/L NaCI), and temperatures are up to 90 °C. The concentrations of acid, chloride ions in the solution and temperature also change during the processes. In this environment, the corrosion rates of most metals and also stainless steels are relatively high, which is why an optimal choice of materials and their dimensions is necessary. The plants are made of vessels (reactors), pipelines and other devices made of stainless steel with very high corrosion resistance. Most containers in plants are made from sheet metal of various thicknesses. For this reason, it is optimal that the electrical resistance sensors for corrosion monitoring are also made of stainless steel sheets of the same quality. Two grades of stainless steel were chosen for the production of ER sensors according to the invention; Cr-Ni-Mo austenitic stainless steel AISI 316L and Cr-Mo-Ni austenitic-ferritic stainless steel duplex 2507 (manufactured by Outokumpu StainlessAB, Sweden), which was developed precisely for use in extreme corrosion environments in the presence of sulfuric acid, high chloride contents ions and elevated temperatures.

Navedba dosedanjega stanja tehnikeIndication of the current state of the art

Električni uporovni senzorji se uporabljajo za korozijski monitoring od leta 1950 (Dravnieks and Cataldi, 1954; Freedman et al., 1958) [1]. Uporabljajo se na različnih področjih: nuklearna postrojenja, procesna tehnika, petrokemija, naftovodi, monitoring gradbenih konstrukcij in podzemnih objektov itd. Senzorji so lahko iz različnih materialov, oblik in velikosti, predvsem njihova oblika in dimenzija pa določata njihovo uporabnost, ki je povezana s korozijsko hitrostjo kovine ali zlitine v danem okolju.Electrical resistance sensors have been used for corrosion monitoring since 1950 (Dravnieks and Cataldi, 1954; Freedman et al., 1958) [1]. They are used in various fields: nuclear plants, process engineering, petrochemicals, oil pipelines, monitoring of building structures and underground facilities, etc. Sensors can be made of different materials, shapes and sizes, but mainly their shape and dimension determine their usefulness, which is related to the corrosion rate of the metal or alloy in a given environment.

Ameriški proizvajalec COSASCO [2] je izdelal ER senzorje z merilnim elementom iz upognjenega traku in upognjene žice. Senzorje predstavljen na sliki 6, pri čemer je debelina traku 13 0,05 mm, žice pa 0,25 in 0,50 mm. Materiali, iz katerih so izdelani merilni elementi, so izdelani po nekoliko drugačnih metalurških postopkih kot pločevine in imajo drugačno mikrostrukturo. Senzorja sta v uporabi v procesni tehniki in petrokemiji v blagih in zmernih korozijskih razmerah. Prav zaradi deformacije materiala pri upogibanju traku ali žice ostanejo v materialu notranje napetosti, ki so pri nerjavnem jeklu zadostne za pojav napetostne korozije oziroma napetostno-korozijskega pokanja (SCC- stress corrosion cracking) v agresivnih, posebno pa v ekstremnih korozijskih razmerah. Tudi deformirana mikrostruktura merilnega elementa ima nekoliko drugačne lastnosti v primerjavi z nedeformirano. Referenčni element omenjenih senzorjev se nahaja v ohišju 15, ki je izdelano iz nerjavnega jekla (običajno kvalitete AISI 316L) ali zlitine Hastelloy C-276. Tesnjenje je izvedeno s teflonom ali steklom 14.The American manufacturer COSASCO [2] produced ER sensors with a measuring element made of bent tape and bent wire. The sensors are presented in Figure 6, where the thickness of the tape 13 is 0.05 mm, and the wires are 0.25 and 0.50 mm. The materials from which the measuring elements are made are produced by slightly different metallurgical processes than sheet metal and have a different microstructure. The sensors are used in process technology and petrochemicals in mild and moderate corrosion conditions. Due to the deformation of the material when the tape or wire is bent, internal stresses remain in the material, which in the case of stainless steel are sufficient for the occurrence of stress corrosion or stress corrosion cracking (SCC - stress corrosion cracking) in aggressive, and especially in extreme corrosion conditions. Even the deformed microstructure of the measuring element has slightly different properties compared to the undeformed one. The reference element of the mentioned sensors is located in the housing 15, which is made of stainless steel (usually AISI 316L quality) or Hastelloy C-276 alloy. Sealing is done with Teflon or glass 14.

Za meritve korozijskih hitrosti v simuliranih pogojih toplotnega izmenjevalca s hladilno tekočino v primarnem sistemu nuklearne elektrarne je bil razvit ER senzor v obliki cevi [3]. Za merilni element je bil uporabljen podoben material, kot so cevi toplotnega izmenjevalca (nerjavno jeklo), vendar v obliki tanke cevi z notranjim premerom 1 mm. Notranja površina cevi predstavlja izpostavljeno površino merilnega elementa. Pogoji delovanja so kot v jedrskem reaktorju (temperatura 310 °C, tlak 10,1 MPa, hitrost pretoka tekočine 2,1 m/s). Pri spremembi pH hladilne tekočine iz pH 9 na pH 3 (z dodajanjem žveplove kisline) je dobro vidno tanjšanje debeline stene cevi.A pipe-shaped ER sensor was developed for measurements of corrosion rates under simulated conditions of a heat exchanger with coolant in the primary system of a nuclear power plant [3]. A similar material as the heat exchanger tubes (stainless steel) was used for the measuring element, but in the form of a thin tube with an inner diameter of 1 mm. The inner surface of the tube represents the exposed surface of the measuring element. The operating conditions are the same as in a nuclear reactor (temperature 310 °C, pressure 10.1 MPa, liquid flow rate 2.1 m/s). When changing the pH of the coolant from pH 9 to pH 3 (by adding sulfuric acid), the thinning of the pipe wall thickness is clearly visible.

Literaturni vir [4] navaja uporabne podatke o specifični električni upornosti (p) nerjavnih jekel pri različnih temperaturah, tudi za avstenitno nerjavno jeklo AISI 316L. Rezultati so prikazani numerično in grafično. Podatki so za konstruiranje ER senzorja pomembni, ker temperaturni koeficient električne upornosti (a) pri vseh temperaturah ni enak. Zaradi tega mora imeti uporovni senzor referenčni element, ki je izpostavljen enaki temperaturi kot merilni element, mora pa biti zaščiten pred korozijo.Reference source [4] provides useful data on the specific electrical resistivity (p) of stainless steels at different temperatures, also for austenitic stainless steel AISI 316L. The results are shown numerically and graphically. The data are important for designing the ER sensor because the temperature coefficient of electrical resistance (a) is not the same at all temperatures. For this reason, a resistive sensor must have a reference element that is exposed to the same temperature as the measuring element and must be protected against corrosion.

[1] Electrical Resistance Probe, https://www.sciencedirect.com/topics/engineering/electricalresistance-probe[1] Electrical Resistance Probe, https://www.sciencedirect.com/topics/engineering/electricalresistance-probe

[2] COSASCO (ER) Electrical Resistance Probes ER-Probe-Accessories-DS rev-Rev. Date: 05/17/2016[2] COSASCO (ER) Electrical Resistance Probes ER-Probe-Accessories-DS rev-Rev. Date: 05/17/2016

[3] L. Yang, K.T. Chiang, On-line and real-time corrosion monitoring techniques of metals and alloys in nuclear power plants and laboratories, Understanding and Mitigating Ageing in Nuclear Power Plants, 2010[3] L. Yang, K.T. Chiang, On-line and real-time corrosion monitoring techniques of metals and alloys in nuclear power plants and laboratories, Understanding and Mitigating Aging in Nuclear Power Plants, 2010

[4] C.y. Ho, T.K. Chu, Electrical Resistivity and Conductivity of selected AISI Stainless Steel, CINDAS Report 45, sept 1977, http://www.inductor-jmag.ru/files/content/al29160.pdf[4] C.y. Ho, T.K. Chu, Electrical Resistivity and Conductivity of selected AISI Stainless Steel, CINDAS Report 45, Sept 1977, http://www.inductor-jmag.ru/files/content/al29160.pdf

Tehnični problemTechnical problem

Za izdelavo ustreznih ER senzorjev, ki omogočajo realno oceno korozijskega monitoringa v ekstremnih korozijskih razmerah, je pomembnih več faktorjev.Several factors are important for the production of suitable ER sensors that enable a realistic evaluation of corrosion monitoring in extreme corrosion conditions.

Izbira in obdelava materiala, to je pločevine, iz katere je izdelan kovinski del ER senzorja, je pomembna zaradi korozijskih lastnosti materiala. Zaželeno je, da je uporabljen material isti kot je material uporabljen za izdelavo postrojenj, kjer se bo izvajal korozijski monitoring, in daje pločevina izdelana po enakem postopku. Na ta način se izognemo uporabi referenčnih materialov, kot je znano iz stanja tehnike, hkrati pa je zagotovljena enaka mikrostruktura materiala.The choice and processing of the material, i.e. the sheet metal from which the metal part of the ER sensor is made, is important due to the corrosion properties of the material. It is desirable that the material used is the same as the material used for the production of plants where corrosion monitoring will be carried out, and that the sheet metal is produced according to the same process. In this way, we avoid the use of reference materials, as is known from the state of the art, and at the same time, the same microstructure of the material is ensured.

Mikrostruktura valjane pločevine iz katere je izdelan kovinski del ER senzorja, je v različnih smereh glede na smer valjanja različna, kar ima velik vpliv na vrsto in stopnjo korozije. Zato je zaželeno, da so ER senzorji za merjenje korozijskih hitrosti nerjavnih jekel izdelani tako, da so vplivi korozijsko občutljivih prerezov čim manjši.The microstructure of the rolled sheet, from which the metal part of the ER sensor is made, is different in different directions depending on the direction of rolling, which has a great influence on the type and degree of corrosion. Therefore, it is desirable that ER sensors for measuring the corrosion rates of stainless steels are made in such a way that the effects of corrosion-sensitive cross-sections are as small as possible.

Postopki izdelave oblike pločevinastega električnega uporovnega senzorja iz pločevine lahko v veliki meri vplivajo na korozijske lastnosti materiala (pločevine). Zaradi tega se je potrebno izogibati postopkov, ki povzročajo deformacijo mikrostrukture zaradi mehanske obdelave (work hardening), spremembe mikrostrukture zaradi vpliva povišanih temperatur, raztrganine, mikrorazpoke in hrapavo površino.The manufacturing processes of the sheet metal electrical resistive sensor form can greatly affect the corrosion properties of the material (sheet metal). For this reason, it is necessary to avoid processes that cause deformation of the microstructure due to mechanical processing (work hardening), changes in the microstructure due to the influence of elevated temperatures, tears, microcracks and a rough surface.

Dimenzije ER senzorja so omejene zaradi prostora za vgradnjo. ER senzorji so vgrajeni v naprave (reaktorje) s tekočino. Predvideno je vstavljanje skozi odprtino na zgornji strani reaktorja, pri čemer skozi odprtino potekajo tudi vsi povezovalni kabli, zato je največji premer lahko do 40 mm in dolžina do 250 mm. Dimenzije kovinskega dela ER senzorja so pomembne, ker je mogoče le pri določenih razmerjih debeline pločevine, širine vodnikov in dolžine vodnikov zagotoviti ustrezno električno upornost vodnikov, da so pri prehodu relativno majhnega električnega toka skozi vodnike padci napetosti zadostni za meritve z zadostno ločljivostjo.The dimensions of the ER sensor are limited by the installation space. ER sensors are built into devices (reactors) with liquid. It is intended to be inserted through the opening on the upper side of the reactor, whereby all connecting cables also pass through the opening, so the maximum diameter can be up to 40 mm and the length can be up to 250 mm. The dimensions of the metal part of the ER sensor are important because only with certain ratios of sheet thickness, conductor width and conductor length can the adequate electrical resistance of the conductors be ensured, so that when a relatively small electric current passes through the conductors, the voltage drops are sufficient for measurements with sufficient resolution.

Ker so kovine dobri električni prevodniki, je zaželeno, da je prerez vodnikov majhen, vodniki pa dovolj dolgi. Zaradi tega pločevina ne sme biti predebela, istočasno pa je zaželeno, da je dimenzija vodnikov ER senzorja taka, da dopušča zanesljive meritve električne upornosti električnih uporov senzorja z današnjo dostopno elektroniko (zadostna električna upornost).Since metals are good electrical conductors, it is desirable that the cross section of the conductors is small and the conductors are long enough. For this reason, the sheet must not be too thick, but at the same time it is desirable that the dimension of the conductors of the ER sensor is such that it allows reliable measurements of the electrical resistance of the electrical resistances of the sensor with today's available electronics (sufficient electrical resistance).

Zaželeno je, da je ER senzor izdelan tako, da spremembe temperature in spremembe koncentracije kemikalij v čim manjši meri vplivajo na natančnost meritev.It is desirable that the ER sensor is made in such a way that changes in temperature and changes in the concentration of chemicals affect the accuracy of the measurements as little as possible.

Kovinski del električnega uporovnega senzorja, ki predstavlja električni upor, je neposredno izpostavljen korozivnemu in električno prevodnemu mediju, zato je zaželeno, da je oblika kovinskega dela ER senzorja taka, da je vpliv parazitne upornosti čim manjši.The metal part of the electrical resistance sensor, which represents the electrical resistance, is directly exposed to the corrosive and electrically conductive medium, so it is desirable that the shape of the metal part of the ER sensor is such that the influence of the parasitic resistance is as small as possible.

Elementi senzorja, ki so izpostavljeni v korozivnem mediju, so oblikovani tako, da so mehansko odporni na vpliv mešanja tekočega medija. Korozijsko izpostavljeni del, to je merilni element, je izveden kot samonosna konstrukcija, saj se ne sme dotikati drugih materialov zaradi možnosti nastanka špranjske korozije. ER senzor namreč lahko poda zanesljive meritve v primeru enakomerne korozije, kjer se prerez lahko enakomerno manjša. Lokalizirano, jamičasto in napetostno korozijo ER senzor nepravilno zazna, zato je zaželeno, da je kovinski del senzorja preproste oblike in da v materialu ni notranjih napetosti, ki bi nastale pri izdelavi.Sensor elements that are exposed in a corrosive medium are designed to be mechanically resistant to the influence of liquid medium mixing. The part exposed to corrosion, i.e. the measuring element, is designed as a self-supporting structure, as it must not touch other materials due to the possibility of crevice corrosion. The ER sensor can provide reliable measurements in the case of uniform corrosion, where the cross-section can be uniformly reduced. Localized, pitting and stress corrosion are incorrectly detected by the ER sensor, so it is desirable that the metal part of the sensor is simple in shape and that there are no internal stresses in the material that would arise during manufacturing.

Zaščiteni del kovinskega senzorja mora biti zaščiten z materiali, ki so dobri električni izolatorji in so kemijsko obstojni v raztopini žveplove kisline (okoli 10 %) pri temperaturi do 90 °C. Ohišje ER senzorja ne sme biti izdelano iz kovine.The protected part of the metal sensor must be protected by materials that are good electrical insulators and are chemically stable in sulfuric acid solution (around 10%) at a temperature of up to 90 °C. The housing of the ER sensor must not be made of metal.

Vsi ostali električno-izolacijski materiali in kabli morajo biti izdelani iz materialov, ki so dolgočasovno obstojni v omenjenih pogojih.All other electrical insulating materials and cables must be made of materials that are long-lasting under the mentioned conditions.

Opis izumaDescription of the invention

Navedeni tehnični problemi so rešeni z električnim uporovnim senzorjem po izumu, ki je opisan v nadaljevanju in predstavljen na slikah, ki prikazujejo:The stated technical problems are solved with an electrical resistive sensor according to the invention, which is described below and presented in the pictures showing:

Slika 1 prikazuje kovinski del ER senzorja;Figure 1 shows the metal part of the ER sensor;

Slika 2 prikazuje lokacije uporov ER senzorja in mesta priključkov električnih vodnikov na kovinskem delu;Figure 2 shows the locations of the ER sensor resistors and the locations of the electrical conductor connections on the metal part;

Slika 3 prikazuje sestavne elemente ER senzorja z izolacijskim ohišjem - razstavljeno, pogled v perspektivi;Figure 3 shows the components of an ER sensor with an insulating housing - disassembled, perspective view;

Slika 4 prikazuje ER senzor z izolacijskim ohišjem - sestavljeno, pogled v perspektivi;Figure 4 shows an ER sensor with an insulating housing - assembled, perspective view;

Slika 5 prikazuje detajlni pogled spojke na spodnjem in zgornjem pokrovu izolacijskega ohišja;Figure 5 shows a detailed view of the coupling on the lower and upper covers of the insulating housing;

Slika 6 prikazuje stanje tehnike, in sicer ER senzor ameriškega proizvajalca z merilnim elementom iz upognjenega traku;Figure 6 shows the state of the art, namely an ER sensor from an American manufacturer with a bent tape measuring element;

Slika 7 prikazuje diagram kompenzacije merilne elektrode zaradi vpliva temperatureFigure 7 shows the compensation diagram of the measuring electrode due to the effect of temperature

Električni uporovni senzor po izumu vključuje kovinski element 1 in izolacijsko ohišje 20, pri čemer je kovinski element 1 izveden ploščato v obliki črke U in je v celoti izdelan iz enega kosa valjane jeklene pločevine, tako da vzdolžna os kovinskega elementa 1 poteka v smeri valjanja pločevine, pri čemer del kovinskega elementa 1, ki je neposredno izpostavljen korozivnemu mediju, predstavlja merilno elektrodo 2, in del kovinskega elementa 1, ki je od korozivnega medija izoliran z ohišjem 20, predstavlja referenčno elektrodo 2a, in je ohišje 20 izvedeno iz zgornjega 7 in spodnjega 8 pokrova, pri čemer je notranjost pokrovov 7, 8 prirejena za sprejem referenčne elektrode 2a in priključnega kabla 9, ki vključuje zunanje električne vodnike, in sta oba pokrova 7, 8 med sabo oblikosklepno fiksno povezana preko povezovalnih elementov 30.The electric resistive sensor according to the invention includes a metal element 1 and an insulating housing 20, wherein the metal element 1 is made flat in the shape of the letter U and is made entirely of one piece of rolled steel sheet, so that the longitudinal axis of the metal element 1 runs in the direction of rolling the sheet , where the part of the metal element 1 that is directly exposed to the corrosive medium represents the measuring electrode 2, and the part of the metal element 1 that is isolated from the corrosive medium by the housing 20 represents the reference electrode 2a, and the housing 20 is made from the above 7 and of the lower 8 cover, whereby the inside of the covers 7, 8 is adapted to receive the reference electrode 2a and the connecting cable 9, which includes external electrical conductors, and both covers 7, 8 are fixedly connected to each other via connecting elements 30.

Merilna elektroda 2 je izvedena v obliki črke U, tako da sta tvorjena dva med sabo v bistvu vzporedna merilna trakova 21, 22, ki se nadaljujeta v referenčno elektrodo 2a. Referenčna elektroda 2a je izvedena iz dveh referenčnih trakov 3,4, tako da se merilni trak 21 merilne elektrode 2 nadaljuje v referenčni trak 3 in se merilni trak 22 merilne elektrode 2 nadaljuje v referenčni trak 4. Vsak od referenčnih trakov 3, 4 je v delu, kjer se merilna trakova 21, 22 nadaljujeta v referenčna trakova 3, 4, povezana s pomožnima vodnikoma 5, 6, in sicer referenčni trak 3 s pomožnim vodnikom 5 in referenčni trak 4 s pomožnim vodnikom 6, ki sta uporabljena kot električna vodnika od stičišča referenčnega traku 3 s pomožnim vodnikom 5 (to je točke B) in stičišča referenčnega traku 4 s pomožnim vodnikom 6 (to je točke C) do mest označenih s točkami A, D, E, F za priključitev zunanjih električnih vodnikov.The measuring electrode 2 is made in the shape of the letter U, so that two essentially parallel measuring strips 21, 22 are formed, which continue into the reference electrode 2a. The reference electrode 2a is made of two reference strips 3, 4, so that the measuring strip 21 of the measuring electrode 2 continues into the reference strip 3 and the measuring strip 22 of the measuring electrode 2 continues into the reference strip 4. Each of the reference strips 3, 4 is in part, where the measuring tapes 21, 22 continue into the reference tapes 3, 4, connected to the auxiliary conductors 5, 6, namely the reference tape 3 with the auxiliary conductor 5 and the reference tape 4 with the auxiliary conductor 6, which are used as electrical conductors from the junction of the reference strip 3 with the auxiliary conductor 5 (that is, point B) and the junction of the reference strip 4 with the auxiliary conductor 6 (that is, point C) to the places marked with points A, D, E, F for the connection of external electrical conductors.

Ploščata izvedba kovinskega elementa 1 v oblik črke U omogoča doseganje največje možne električne upornost pri dani dimenziji, oziroma pri razmerju dimenzij debeline pločevine, dolžine in širine merilnih trakov 21, 22 in referenčnih trakov 3,4. Merilna elektroda 2 bolj komplicirane oblike npr. večkrat zavit trak v nasprotni smeri bi lahko imela večjo električno upornost, imela pa bi tudi več korozijsko bolj občutljivih mest in manjšo mehansko togost.The flat design of the metal element 1 in the shape of the letter U enables the maximum possible electrical resistance to be achieved for a given dimension, i.e. for the ratio of dimensions of sheet thickness, length and width of measuring tapes 21, 22 and reference tapes 3,4. Measuring electrode 2 of a more complicated shape, e.g. a strip wrapped several times in the opposite direction could have a higher electrical resistance, but it would also have more corrosion-sensitive spots and less mechanical stiffness.

Ker vzdolžna os kovinskega elementa 1 poteka v smeri valjanja pločevine, je površina vzdolžnih in prečnih korozijsko bolj občutljivih prerezov pločevine majhna. Korozijsko najbolj občutljiv prečni prerez je tako le na zunanjem in notranjem radiju polkrožnega dela oblike črke U merilne elektrode 2. Na primer za ER senzorje iz Cr-Ni-Mo avstenitnega nerjavnega jekla kvalitete AISI 316L je izbrana pločevina debeline 1 mm in 0,5 mm, za ER senzorje iz Cr-Mo-Ni avstenitno-feritnega nerjavnega jeklo kvalitete duplex 2507 pa pločevina debeline 0,5 mm. Pri širini merilnih trakov 21, 22 ER senzorja 5 mm je pri senzorju, ki je izdelan iz pločevine debeline 1,0 mm, delež površine korozijsko bolj občutljivih vzdolžnih in prečnih prerezov le 16,67 %, pri senzorju, ki je izdelan iz pločevine debeline 0,5 mm, pa 9,09 % .Since the longitudinal axis of the metal element 1 runs in the direction of the rolling of the sheet, the area of the longitudinal and transverse sections of the sheet, which are more susceptible to corrosion, is small. The most corrosion-sensitive cross-section is thus only on the outer and inner radius of the semicircular part of the U-shaped measuring electrode 2. For example, for ER sensors made of Cr-Ni-Mo austenitic stainless steel of AISI 316L quality, sheet thicknesses of 1 mm and 0.5 mm are selected , and for ER sensors made of Cr-Mo-Ni austenitic-ferritic stainless steel duplex 2507, a 0.5 mm thick sheet. When the width of the measuring strips 21, 22 of the ER sensor is 5 mm, for a sensor made of sheet metal 1.0 mm thick, the share of the area of more corrosion-sensitive longitudinal and cross-sections is only 16.67%, for a sensor made of sheet metal thick 0.5 mm, and 9.09%.

Kovinski element 1, torej merilna elektroda 2 in referenčna elektroda 2a, je v celoti izdelan iz enega kosa pločevine, torej iz istega kosa pločevine in na enak način. Zaradi tega je specifična električna upornost materiala (p) obeh elektrod enaka in temperaturni koeficient električne upornosti (a) enak.The metal element 1, i.e. the measuring electrode 2 and the reference electrode 2a, is completely made from one piece of sheet metal, i.e. from the same piece of sheet metal and in the same way. As a result, the specific electrical resistivity of the material (p) of the two electrodes is the same and the temperature coefficient of electrical resistance (a) is the same.

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Senzorje ploščate oblike, pločevina (jeklo) ni krivljena ali upognjena, je le izrezana v želeno obliko. Tako mikrostruktura jekla ni deformirana, v materialu po izdelavi kovinskega elementa 1 senzorja m notranjih napetosti. Zaradi tega ni možnosti za pojav napetostne korozije in zelo malo verjetnosti za pojav interkristalne korozije nerjavnega jekla. Oblika kovinskega elementa 1 ER senzorja in način izdelave tako predstavljata bistveno prednost pred že znanim stanjem tehnike. V že znanem stanju tehnike sta bila izdelana ER senzorja ameriškega proizvajalca z merilno elektrodo iz upognjenega traku in upognjene žice. Prav zaradi deformacije materiala pri upogibanju traku ali žice ostanejo v materialu notranje napetosti, ki so pri nerjavnih jeklih običajno zadostne za pojav napetostne korozije oziroma napetostno-korozijskega pokanja (SCC - stress corrosion cracking) v agresivnih, posebno pa v ekstremnih korozijskih razmerah. Dodatno ima deformirana mikrostruktura merilne elektrode nekoliko drugačne korozijske lastnosti v primerjavi z nedeformirano. Dimenzije (debelina) merilnih elektrod že znanega proizvajalca so premajhne. Materiali, iz katerih so izdelane merilne elektrode iz stanja tehnike, so izdelani po drugačnih metalurških postopkih kot pločevine in imajo tudi drugačno mikrostrukturo.Flat-shaped sensors, the sheet metal (steel) is not bent or bent, it is only cut into the desired shape. Thus, the microstructure of the steel is not deformed, in the material after the manufacture of the metal element 1 sensor m internal stresses. As a result, there is no chance of stress corrosion cracking and very little chance of intergranular corrosion of stainless steel. The shape of the metal element 1 of the ER sensor and the method of production thus represent a significant advantage over the already known state of the art. In the already known state of the art, ER sensors from an American manufacturer were made with a measuring electrode made of a bent tape and a bent wire. It is precisely because of the deformation of the material when the tape or wire is bent that internal stresses remain in the material, which in the case of stainless steels are usually sufficient to cause stress corrosion or stress corrosion cracking (SCC - stress corrosion cracking) in aggressive, and especially in extreme corrosion conditions. Additionally, the deformed microstructure of the measuring electrode has slightly different corrosion properties compared to the undeformed one. The dimensions (thickness) of the measuring electrodes of an already known manufacturer are too small. The materials from which the measuring electrodes from the state of the art are made are produced by different metallurgical processes than sheet metal and also have a different microstructure.

Dodatna prednost tega, da je kovinski element 1 v celoti izdelan iz enega kosa pločevine, je možnost avtomatske temperaturne kompenzacije. Namreč, ker se električna upornost korozijsko izpostavljene merilne elektrode 2 veča s temperaturo, potrebujemo tudi referenčno elektrodo 2a iz enakega materiala, ki je izpostavljena enaki temperaturi, in je v celoti protikorozijsko zaščitena. Razmerje električne upornosti med merilno elektrodo 2 in referenčno elektrodo 2a na ta način s spremembo temperature ostane nespremenjeno. Uporaba obeh elektrod 2, 2a predstavlja avtomatsko temperaturno kompenzacijo.An additional advantage of the fact that the metal element 1 is completely made from one piece of sheet metal is the possibility of automatic temperature compensation. Namely, since the electrical resistance of the measuring electrode 2 exposed to corrosion increases with temperature, we also need a reference electrode 2a made of the same material, which is exposed to the same temperature and is fully corrosion-protected. In this way, the electrical resistance ratio between the measuring electrode 2 and the reference electrode 2a remains unchanged with a change in temperature. The use of both electrodes 2, 2a represents automatic temperature compensation.

Kovinski element 1 ER senzorja predstavlja električni upor, ki ga zaradi oblike razdelimo na več uporov in delov, kot je prikazano na sliki 2:The metal element 1 of the ER sensor represents an electrical resistor, which is divided into several resistors and parts due to its shape, as shown in Figure 2:

- korozijsko aktivni del senzorja, to je merilna elektroda 2 (merilni upor Ri), je nezaščitena pločevina med točkama B in C v obliki črke U;- the corrosion-active part of the sensor, i.e. measuring electrode 2 (measuring resistor Ri), is an unprotected U-shaped sheet between points B and C;

referenčni upor predstavljata korozijsko zaščitena dela senzorja med točkama A in B (referenčni trak 3; referenčni upor R2) in med točkama C in D (referenčni trak 4; referenčni upor R3), ki se nahajata v izolacijskem ohišju 20;the reference resistance is represented by the corrosion-protected parts of the sensor between points A and B (reference strip 3; reference resistance R 2 ) and between points C and D (reference strip 4; reference resistance R 3 ), which are located in the insulating housing 20;

- pomožna vodnika 5, 6 med točkama B in E ter med točkama C in F sta uporabljena kot pomožna električna vodnika in se nahajata v izolacijskem ohišju 20;- auxiliary conductors 5, 6 between points B and E and between points C and F are used as auxiliary electrical conductors and are located in the insulating housing 20;

ena stran, prednostno zgornja stran referenčnih trakov 3,4 in pomožnih vodnikov 5,6 je v točkah A, E, F in D namenjena spajkanju priključnih kablov, to je zunanjih električnih vodnikov.one side, preferably the upper side of the reference strips 3,4 and the auxiliary conductors 5,6 is intended at points A, E, F and D for soldering connection cables, i.e. external electrical conductors.

Ker je električna upornost merilne elektrode 2 in referenčne elektrode 2a ER senzorja zelo majhna, morajo biti zunanji električni vodniki ločeni po parih. Ločeni pari električnih vodnikov priključnega kabla 9 so namenjeni za napajanje senzorja s konstantnim tokom in za merjenje padca napetosti na merilni elektrodi 2 (merilnem uporu) in referenčni elektrodi 2a (referenčnima uporoma). Mesta so označena na sliki 2.Since the electrical resistance of the measuring electrode 2 and the reference electrode 2a of the ER sensor is very small, the external electrical conductors must be separated in pairs. The separate pairs of electrical conductors of the connection cable 9 are intended for supplying the sensor with a constant current and for measuring the voltage drop on the measuring electrode 2 (measuring resistor) and the reference electrode 2a (reference resistors). The locations are marked in Figure 2.

prvi par: točki A in D sta predvideni za priključitev zunanjih električnih vodnikov za napajanje senzorja s konstantnim tokom (istočasno teče enak električni tok skozi merilno elektrodo 2 in referenčno elektrodo 2a). Na točki A in D je poleg prvega para lahko lotan tudi tretji par zunanjih električnih vodnikov. V tem slučaju se lahko istočasno meri padec napetosti (U2 in U3) na referenčnih trakovih 3,4 ter padec napetosti (Ux) na merilni elektrodi 2 (merilnih trakovih 21, 22) senzorja. V danem primeru priključitve električnih vodnikov je skupna električna upornost vseh uporov na ER senzorju Ri + R2 + R3. Padec napetosti na obeh referenčnih uporih (U2 + U3) = (U2 + U3) - Ui.the first pair: points A and D are intended for connecting external electrical conductors to supply the sensor with a constant current (the same electrical current flows through the measuring electrode 2 and the reference electrode 2a at the same time). At points A and D, in addition to the first pair, a third pair of external electrical conductors can also be soldered. In this case, the voltage drop (U 2 and U 3 ) on the reference strips 3,4 and the voltage drop (U x ) on the measuring electrode 2 (measuring strips 21, 22) of the sensor can be measured at the same time. In the given case of connecting electrical conductors, the total electrical resistance of all resistors on the ER sensor is Ri + R 2 + R 3 . Voltage drop across both reference resistors (U 2 + U 3 ) = (U 2 + U 3 ) - Ui.

drugi par: točki E in F sta predvideni za priključitev zunanjih električnih vodnikov za merjenje padca napetosti (Ui) na merilni elektrodi 2 senzorja (merilnem uporu Rx) med točkama B in C;the second pair: points E and F are provided for the connection of external electrical conductors for measuring the voltage drop (Ui) on the measuring electrode 2 of the sensor (measuring resistor R x ) between points B and C;

tretji par (alternativna varianta): točki A in E in točki F in D sta predvideni za priključitev zunanjih električnih vodnikov za merjenje padca napetosti U2 (ali U3) na posameznem referenčnem traku 3, 4 (referenčnem uporu R2 ali R3), in sicer sta točki A in E namenjeni za priključka električnih vodnikov za merjenje padca napetosti U2 na referenčnem traku 3 (za referenčni upor R2), točki F in D sta namenjeni za priključka zunanjih električnih vodnikov za merjenje padca napetosti U3 na referenčnem traku 4 (za referenčni upor R3).third pair (alternative variant): points A and E and points F and D are intended for connecting external electrical conductors for measuring the voltage drop U 2 (or U 3 ) on a single reference strip 3, 4 (reference resistance R 2 or R 3 ) , namely points A and E are intended for the connection of electrical conductors for measuring the voltage drop U 2 on the reference strip 3 (for the reference resistor R 2 ), points F and D are intended for the connection of external electrical conductors for measuring the voltage drop U 3 on the reference of strip 4 (for reference resistance R 3 ).

Merilna elektroda 2, ki predstavlja električni upor, je neposredno izpostavljena korozivnemu in električno prevodnemu mediju. Vpliva parazitne upornosti električno prevodnega medija, v katerem se merilna elektroda 2 nahaja, ni mogoče v celoti izključiti. Lahko pa se po potrebi zmanjša vpliv parazitne upornosti medija med vzdolžnim delom, to je med merilnima trakovoma 21, 22 merilne elektrode 2, ki je v obliki črke U. V ta namen lahko ER senzor opcijsko vključuje mehansko pregrado 10, ki je izvedena v obliki tanke plošče, ki je postavljena vzdolžno med merilna trakova 21, merilne elektrode 2. Pregrada 10 je vstavljena v režo 7a izvedeno v zgornjem pokrovu 7 ohišja 20 in dodatno pritrjena s tesnilno maso na silikonski osnovi. Pregrada 10 poveča razdaljo med merilnima trakovoma 21, 22 merilne elektrode 2 v električno prevodnem mediju in s tem zmanjša vpliv parazitne upornosti.Measuring electrode 2, which represents electrical resistance, is directly exposed to a corrosive and electrically conductive medium. The influence of the parasitic resistance of the electrically conductive medium in which the measuring electrode 2 is located cannot be completely excluded. However, if necessary, the influence of the parasitic resistance of the medium can be reduced during the longitudinal part, i.e. between the measuring strips 21, 22 of the measuring electrode 2, which is in the shape of the letter U. For this purpose, the ER sensor can optionally include a mechanical barrier 10, which is made in the form thin plate, which is placed longitudinally between the measuring tape 21, the measuring electrode 2. The barrier 10 is inserted into the slot 7a made in the upper cover 7 of the housing 20 and additionally fixed with a silicone-based sealant. The barrier 10 increases the distance between the measuring tapes 21, 22 of the measuring electrode 2 in the electrically conductive medium and thereby reduces the influence of parasitic resistance.

Mikrostruktura valjane pločevine je v različnih smereh glede na smer valjanja različna, kar ima velik vpliv na vrsto in hitrost korozije. Razlike v korozijskih hitrosti med zunanjo površino pločevine in vzdolžnim in prečnim prerezom je velika zaradi mikrostrukturnih značilnosti in napak na prerezih, na primer zaradi nekovinskih vključkov, napetostnih linij in usmerjenosti kristalnih zrn. Na pločevini debeline 1 mm iz avstenitnega nerjavnega jekla AISI 316L v preizkusnih pogojih (raztopina žveplove kisline 10 % H2SO4, 5 g/L NaCI pri temperaturi 90 °C) so korozijske hitrosti različne, in sicer so na zunanji površini približno 1,4 mm/leto, na vzdolžnem prerezu približno 4,2 mm/leto, na prečnem prerezu pa > 4,2 mm/leto. Razmerje korozijskih hitrosti je tako 1 : 3 : >3 (povprečni rezultati preliminarnih preiskav, prerezi so bili pregledani in izmerjeni metalografsko). Da bi se v čim večji meri izognili vplivu korozijsko bolj občutljivih prerezov, so kovinski elementi 1 ER senzorjev po izumu iz pločevine izdelani tako, da je njihova vzdolžna os poteka v smeri valjanja pločevine.The microstructure of the rolled sheet is different in different directions according to the rolling direction, which has a great influence on the type and rate of corrosion. Differences in corrosion rates between the outer surface of the sheet and the longitudinal and transverse sections are large due to microstructural features and cross-sectional defects, such as non-metallic inclusions, stress lines and crystal grain orientation. On a 1 mm thick sheet made of AISI 316L austenitic stainless steel under test conditions (sulfuric acid solution 10% H 2 SO 4 , 5 g/L NaCI at a temperature of 90 °C), the corrosion rates are different, namely on the outer surface they are approximately 1, 4 mm/year, on the longitudinal section about 4.2 mm/year, and on the transverse section > 4.2 mm/year. The ratio of corrosion rates is thus 1 : 3 : >3 (average results of preliminary investigations, cross-sections were inspected and measured metallographically). In order to avoid as much as possible the influence of sections that are more sensitive to corrosion, the metal elements 1 of the ER sensors according to the invention are made of sheet metal so that their longitudinal axis runs in the direction of rolling of the sheet metal.

Kovinski element 1 ER senzorja je mogoče iz nerjavne pločevine tanjših debelin, prednostno debeline 1 mm in 0.5 mm, in da se v čim večji meri izognemo deformaciji mikrostrukture, izdelati na več načinov, na primer z rezanjem z abrazivnim vodnim curkom ali z laserskim rezanjem v atmosferi zaščitnega plina. Oba postopka teoretično omogočata relativno natančno izdelavo (pri dimenzijah kovinskega elementa 1 ER senzorja ±0,1 mm). Metalografski pregled prečni prerezov izrezanih kovinskih elementov 1 ER senzorjev je pokazal, da je prednostno najprimernejša izdelava z laserskim rezanjem v atmosferi zaščitnega plina. Postopek rezanja z abrazivnim vodnim curkom povzroči zaobljen zgornji rob (r = od 10 do 30 pm) in ostre poškodbe na zgornji površini do 200 pm od reza. Odrezane stranice so vidno poševne, mikrostruktura pa je ob rezu rahlo deformirana do globine 10 pm pri obeh nerjavnih jeklih. Spodnji rob je oster in deformiran navzdol. Spodnje robove bi bilo tako potrebno popraviti z ročnim brušenjem.The metal element 1 of the ER sensor can be made from stainless steel sheet of thinner thicknesses, preferably 1 mm and 0.5 mm thick, and in order to avoid deformation of the microstructure as much as possible, it can be produced in several ways, for example by cutting with an abrasive water jet or by laser cutting in protective gas atmosphere. Both processes theoretically enable relatively accurate production (with the dimensions of the metal element 1 ER sensor ±0.1 mm). A metallographic examination of the cross-sections of the cut metal elements of 1 ER sensors showed that it is preferably manufactured by laser cutting in a shielding gas atmosphere. The cutting process with an abrasive water jet causes a rounded upper edge (r = from 10 to 30 pm) and sharp damage on the upper surface up to 200 pm from the cut. The cut sides are visibly bevelled, and the microstructure is slightly deformed upon cutting to a depth of 10 pm in both stainless steels. The lower edge is sharp and deformed downwards. The lower edges would thus need to be repaired by manual sanding.

Pri laserskem rezanju je zgornji rob rahlo zaobljen (nekaj pm). Toplotne spremembe mikrostrukture ob rezu so zanemarljivo majhne in segajo od 2 pm do 10 pm v globino le na zgornjem robu reza. Površina reza je zataljena in gladka, na površini po rezanju ni bilo ostankov visokotemperaturnih oksidov. Po rezanju ni potrebnih nobenih dodatnih obdelav.In laser cutting, the upper edge is slightly rounded (a few pm). The thermal changes of the microstructure at the cut are negligible and range from 2 pm to 10 pm in depth only at the upper edge of the cut. The cut surface is sealed and smooth, there were no residues of high-temperature oxides on the surface after cutting. No additional processing is required after cutting.

Rezkanje ni primerno, ker je tanko pločevino težko stabilno vpeti, rezkanje nerjavnega jekla pa povzroča deformacijo mikrostrukture.Milling is not suitable because thin sheet metal is difficult to clamp stably, and milling stainless steel causes deformation of the microstructure.

Ustreznost različnih nekovinskih izolacijskih materialov smo preverili z dolgo-časovno laboratorijsko izpostavitvijo. Ohišje 20 ER senzorja, torej zgornji 7 in spodnji 8 pokrov, sta prednostno izvedena iz ABS plastike (akrilonitril butadien stiren) in izdelana s 3D tiskom. Mehanska pregrada 10 za zmanjšanje vpliva parazitnih tokov je prednostno prav tako izdelana s 3D tiskom in iz enakega materiala. Vsi deli so s kovinskim elementom 1 ER senzorja medsebojno zlepljeni s tesnilno maso na silikonski osnovi, ki je odporna proti povišanim temperaturam. Tesnilna masa popolnoma zapolni bazen v spodnjem pokrovu 8 ohišja 20. Silikonska tesnilna masa, ki se nerjavnega jekla zelo dobro oprime, preprečuje nastanek »špranjske korozije« nerjavnega jekla v notranjosti ohišja 20 na prehodu merilne elektrode 2 (korozijsko nezaščiten del) v referenčno elektrodo 2a (korozijsko zaščiten del). Dodatno sta oba pokrova 7, 8 izolativnega ohišja 20 mehansko pritrjena s pritrdilnimi elementi 30, ki so prednostno spojke 11, 12 za preprečevanje razprtja obeh pokrovov 7, 8 med uporabo.The adequacy of various non-metallic insulating materials was verified by long-term laboratory exposure. The housing 20 of the ER sensor, i.e. the upper 7 and lower 8 covers, are preferably made of ABS plastic (acrylonitrile butadiene styrene) and manufactured by 3D printing. The mechanical barrier 10 for reducing the influence of parasitic currents is preferably also produced by 3D printing and from the same material. All parts are glued together with the metal element 1 of the ER sensor with a silicone-based sealant that is resistant to elevated temperatures. The sealing compound completely fills the pool in the lower cover 8 of the housing 20. The silicone sealing compound, which adheres very well to the stainless steel, prevents the formation of "crevice corrosion" of the stainless steel inside the housing 20 at the transition of the measuring electrode 2 (non-corrosion-protected part) to the reference electrode 2a (corrosion protected part). In addition, the two covers 7, 8 of the insulating housing 20 are mechanically attached with fasteners 30, which are preferably couplings 11, 12 to prevent the two covers 7, 8 from opening during use.

Zunanji električni vodniki so na ustrezna mesta, točke A, E, F in D prednostno lotani z mehkim lotom (SnAg3) po predhodnem brušenju mest za spajkanje in obdelavi z dezoksidacijskim sredstvom. Lotana mesta in del kablov so dodatno zaščitena s termokrčljivimi cevmi v več plasteh, na zunanji strani, kjer priključni kabel 9 vstopa v ohišje 20, pa tudi s tesnilno maso na silikonski osnovi. Prednostno so električni vodniki trikrat zviti par (tvvisted pair) bakrenih posrebrenih vodnikov s prerezom 0,5 mm2 z oplaščenjem na posameznih parih. Izolacija vodnikov je prednostno izdelana iz FEP (fluorirani etilen propilen).The external electrical conductors are preferably soldered to the appropriate places, points A, E, F and D, with soft solder (SnAg 3 ) after preliminary grinding of the soldering places and treatment with a deoxidizing agent. The soldered places and part of the cables are additionally protected with heat-shrinkable tubes in several layers, on the outside, where the connecting cable 9 enters the housing 20, as well as with silicone-based sealant. Preferably, the electrical conductors are a three-twisted pair of silver-plated copper conductors with a cross-section of 0.5 mm 2 with coating on individual pairs. Conductor insulation is preferably made of FEP (fluorinated ethylene propylene).

Izvedben primerA workable example

Za ER senzorje iz Cr-Ni-Mo avstenitnega nerjavnega jekla kvalitete AISI 316L smo izbrali pločevino debeline 0,5 mm (pločevina proizvajalca jekla, ki je namenjena za preiskave korozijske obstojnosti nerjavnega jekla v hidrometalurških procesih je formata 210 mm χ 297 mm). Smer valjanja pločevine poteka v smeri daljše stranice.For the ER sensors made of AISI 316L quality Cr-Ni-Mo austenitic stainless steel, we chose a sheet with a thickness of 0.5 mm (the sheet of the steel manufacturer, which is intended for investigations of the corrosion resistance of stainless steel in hydrometallurgical processes, has a format of 210 mm x 297 mm). The sheet rolling direction is in the direction of the longer side.

Električna upornost ER senzorja pri omejenih dimenzijah (največji premer okoli 40 mm in dolžina okoli 250 mm) mora biti čim večja, zato smo se odločili kovinski element 1 ER senzorja izdelati ploščato v obliki črke U. Istočasno je oblika dovolj preprosta, da omogoča natančno izdelavo iz nerjavne pločevine. Dolžina korozijsko izpostavljenega dela, to je merilne elektrode 2, je prednostno 100 mm, kar zagotavlja tudi zadostno mehansko togost merilne elektrode 2 v tekočini. Dolžina celotnega kovinskega elementa 1 ER senzorja je prednostno 200 mm, širina je prednostno 20 mm. Širina posameznega merilnega traku 21, 22 in širina posameznega referenčnega traku 3, 4 je prednostno 5 mm, tako da je prerez posameznega merilnega traku 21, 22 in posameznega referenčnega traku 3, 4 Ao = 5 mm2 za pločevino debeline 1 mm in 2,5 mm2 za pločevino debeline 0,5 mm. Skupna dolžina ER senzorja z ohišjem 20 iz električno izolacijskega materiala je prednostno okoli 240 mm, širina prednostno okoli 30 mm in višina prednostno okoli 10 mm. Oblika senzorja omogoča montažo vseh zunanjih električnih vodnikov in priključnega kabla 9 na eno stran. V reaktorju je senzor z izolacijskim ohišjem 20 vred potopljen v korozivni medij, priključni kabel 9 je speljan navzven skozi pripravljeno odprtino na zgornji strani reaktorja.The electrical resistance of the ER sensor with its limited dimensions (maximum diameter around 40 mm and length around 250 mm) must be as high as possible, so we decided to make the metal element 1 of the ER sensor flat in the shape of the letter U. At the same time, the shape is simple enough to allow for accurate manufacturing made of stainless steel. The length of the part exposed to corrosion, i.e. the measuring electrode 2, is preferably 100 mm, which also ensures sufficient mechanical rigidity of the measuring electrode 2 in the liquid. The length of the entire metal element 1 of the ER sensor is preferably 200 mm, the width is preferably 20 mm. The width of the individual measuring tape 21, 22 and the width of the individual reference tape 3, 4 is preferably 5 mm, so that the cross-section of the individual measuring tape 21, 22 and the individual reference tape 3, 4 is A o = 5 mm 2 for a sheet of thickness 1 mm and 2 .5 mm 2 for sheet metal with a thickness of 0.5 mm. The total length of the ER sensor with the housing 20 made of electrically insulating material is preferably about 240 mm, the width is preferably about 30 mm and the height is preferably about 10 mm. The shape of the sensor allows mounting of all external electrical conductors and connecting cable 9 on one side. In the reactor, the sensor with the insulating housing 20 is immersed in a corrosive medium, the connecting cable 9 is led outwards through the prepared opening on the upper side of the reactor.

Kovinski element 1 ER senzorja navedene oblike in dimenzij je bil izdelan z laserskim razrezom v zaščitni atmosferi. Vzorci kovinskih elementov 1 ER senzorja so bili izrezani tako, da je njihova vzdolžna os poteka v smeri valjanja pločevine. Po razrezu smo naredili vizualni pregled vseh robov in preverili dimenzije. Robove smo pregledali z video-mikroskopom. Površina reza je zataljena in gladka, na površini po rezanju ni bilo ostankov visokotemperaturnih oksidov. Po rezanju ni bilo potrebnih nobenih dodatnih obdelav.The metal element 1 of the ER sensor of the specified shape and dimensions was produced by laser cutting in a protective atmosphere. Samples of metal elements 1 ER sensor were cut so that their longitudinal axis runs in the direction of sheet metal rolling. After cutting, we made a visual inspection of all edges and checked the dimensions. The edges were examined with a video microscope. The cut surface is sealed and smooth, there were no residues of high-temperature oxides on the surface after cutting. No further processing was required after cutting.

Površino mest A, E, F in D, ki so namenjena spajkanju zunanjih električnih vodnikov, smo na dolžini okoli 5 mm rahlo obrusili z brusnim papirjem granulacije P 600 in obdelali z dezoksidacijskim sredstvom nemudoma pred spajkanjem električnih vodnikov. Uporabili smo kabel 3x tvvisted pair bakrenih posrebrenih vodnikov s prerezom 0,5 mm2, z oplaščenjem po parih in s FEP izolacijo. Električni vodniki so bili na nerjavno jeklo lotani z mehkim lotom (SnAg3), s tališčem 230 °C, s temperaturo okoli 260 °C.The surface of places A, E, F and D, which are intended for the soldering of external electrical conductors, was lightly sanded for a length of about 5 mm with P 600 grit sandpaper and treated with a deoxidizing agent immediately before soldering the electrical conductors. We used a cable of 3x tvvisted pair of silver-plated copper conductors with a cross-section of 0.5 mm 2 , sheathed in pairs and with FEP insulation. The electrical conductors were soldered to stainless steel with soft solder (SnAg3), with a melting point of 230 °C, with a temperature of around 260 °C.

Lotana mesta in del zunanjih električnih vodnikov s FEP izolacijo so dodatno zaščitena s termokrčljivimi cevmi z notranjim lepilom in v več plasteh. Najprej posamezne vodnike, nato še okoli vseh vodnikov, tako, da so kabli in mesta lotov popolnoma električno izolirani. Na zunanji strani ohišja, kjer v ohišje 20 vstopa priključni kabel 9, smo izvedli tudi izolacijo s tesnilno maso za visoke temperature na silikonski osnovi.The soldered places and part of the external electrical conductors with FEP insulation are additionally protected by heat-shrinkable tubes with internal glue and in several layers. First individual conductors, then around all conductors, so that the cables and lot locations are completely electrically isolated. On the outside of the housing, where the connecting cable 9 enters the housing 20, we also insulated it with a silicone-based sealant for high temperatures.

Električni vodniki so na površino mest, na točke A, E, F in D kovinskega dela 1 ER senzorja lotani: - prvi par: točki A in D sta namenjeni napajanju senzorja s konstantnim tokom (istočasno teče enak električni tok skozi merilno elektrodo 2 in referenčno elektrodo 2a). Na točki A in D je poleg prvega para lotan tudi tretji par električnih vodnikov, v tem slučaju se lahko istočasno meri padec napetosti (U2 in U3) na referenčnih trakovih 3, 4 (referenčnih uporih R2 in R3) ter padec napetosti (Ui) na merilni elektrodi 2 senzorja.Electrical conductors are soldered to the surface of the sites, to points A, E, F and D of the metal part 1 of the ER sensor: - the first pair: points A and D are intended to supply the sensor with a constant current (at the same time, the same electric current flows through the measuring electrode 2 and the reference electrode 2a). At points A and D, in addition to the first pair, a third pair of electrical conductors is soldered, in this case the voltage drop (U 2 and U 3 ) on the reference strips 3, 4 (reference resistors R 2 and R 3 ) and the voltage drop can be measured at the same time (Ui) on measuring electrode 2 of the sensor.

- drugi par: točki E in F sta namenjeni za priključka električnih vodnikov za merjenje padca napetosti (Ui) na merilni elektrodi 2 senzorja (uporu Ri) med točkama B in C.- the second pair: points E and F are intended for the connection of electrical conductors for measuring the voltage drop (Ui) on the measuring electrode 2 of the sensor (resistor Ri) between points B and C.

V danem primeru priključitve zunanjih električnih vodnikov je skupna električna upornost vseh uporov na ER senzorju R1+ R2 + R3. Padec napetosti na obeh referenčnih uporih (U2 + U3) = (U2 + U3) - Ui.In the given case of connecting external electrical conductors, the total electrical resistance of all resistors on the ER sensor is R1+ R2 + R3. Voltage drop across both reference resistors (U 2 + U 3 ) = (U 2 + U 3 ) - Ui.

Dimenzije in material kovinskega elementa 1 ER senzorja vplivajo na električne lastnosti ER senzorja.The dimensions and material of the metal element 1 of the ER sensor affect the electrical properties of the ER sensor.

Temperaturni koeficient električne upornosti (a) pri različnih temperaturah ni enak. Specifična električna upornost materiala ER senzorja (p) je pri različnih temperaturah različna, in sicer je pri 293 K (20 °C) 77,1 xl0‘7 Ωπί, pri 350 °K (77 °C) je 81,5 xl0'7 Qm, pri 400 °K (127 °C) je 85,2 xl0'7 Om. Pri temperaturi 90 °C, kar je predvidena maksimalna temperatura med izpostavitvijo ER senzorja, je p 83.0 xl0’7 Om. Omenjeno vrednost smo izbrali za izračune upornosti ER senzorja.The temperature coefficient of electrical resistance (a) is not the same at different temperatures. The specific electrical resistance of the ER sensor material (p) is different at different temperatures, namely at 293 K (20 °C) it is 77.1 xl0' 7 Ωπί, at 350 °K (77 °C) it is 81.5 xl0' 7 Qm, at 400 °K (127 °C) is 85.2 xl0' 7 Ohm. At a temperature of 90 °C, which is the expected maximum temperature during exposure of the ER sensor, p 83.0 xl0' 7 Ohm. We chose the mentioned value for the calculations of the resistance of the ER sensor.

Upornost je izračunana po enačbi: R = p , pri čemer je p specifična električna upornost, 1 je dolžina vodnika in s je prerez vodnika.The resistance is calculated according to the equation: R = p , where p is the specific electrical resistance, 1 is the length of the conductor and s is the cross section of the conductor.

Med električnima kontaktoma - točki A in D (merilna elektroda 2 in oba referenčna trakova 3 in 4) je dolžina 393,6 mm, presek pa 2,5 mm2. Električna upornost vseh (Rx + R2 + r3) je 130,68 mO.Between the two electrical contacts - points A and D (measuring electrode 2 and both reference strips 3 and 4), the length is 393.6 mm, and the cross-section is 2.5 mm 2 . The electrical resistance of all (R x + R 2 + r 3 ) is 130.68 mO.

Med točkama B in C (merilna elektroda 2) je dolžina 205,6 mm, električna upornost Ri je 68,26 mQ. Električna upornost Rise z manjšanjem prereza zaradi korozije sčasoma veča, zaradi sprememb temperature pa nekoliko spreminja.Between points B and C (measuring electrode 2) the length is 205.6 mm, the electrical resistance Ri is 68.26 mQ. The electrical resistivity of Rise increases over time as the cross-section decreases due to corrosion, but changes slightly due to temperature changes.

Med točkama A in B ter C in D (oba referenčna trakova 3 in 4 skupaj) je skupna dolžina 190 mm, električna upornost R2 +R3 je 63,08 mQ. Vrednosti R2 +R3semed meritvami spreminjajo le zaradi nihanja temperature.Between points A and B and C and D (both reference strips 3 and 4 together) the total length is 190 mm, the electrical resistance R 2 +R3 is 63.08 mQ. The values of R 2 +R 3 change during measurements only due to temperature fluctuations.

Vrednosti električne upornosti merilne elektrode 2 in referenčnih trakov 3, 4 so pomembne zaradi temperaturne kompenzacije in projektiranja analogne merilne elektronike ER senzorja.The electrical resistance values of the measuring electrode 2 and the reference strips 3, 4 are important due to the temperature compensation and the design of the analog measuring electronics of the ER sensor.

Protikorozijsko ni zaščitena le merilna elektroda 2 ER senzorja. Zaščitene so vse ostale površine, ki se nahajajo v pravokotniku s črtkano črto, kot je prikazano na sliki 2.Only the measuring electrode 2 of the ER sensor is not protected against corrosion. All other surfaces located within the dashed rectangle as shown in Figure 2 are protected.

Zaščiteni del EP senzorja (referenčna elektroda 2a) smo izolirali z ohišjem 20, ki je izvedeno iz zgornjega 7 in spodnjega 8 pokrova. Vsi deli ohišja 20 so izdelani iz ABS plastike in so s kovinskim elementom 1 ER senzorja vred medsebojno zlepljeni s tesnilno maso na silikonski osnovi, ki je odporna proti povišanim temperaturam. V režo 7a izvedeno na zgornjem pokrovu 7 se lahko opcijsko vstavili tudi pregrado 10 za manjšanje parazitnih upornosti.The protected part of the EP sensor (reference electrode 2a) was isolated with a housing 20, which is made of the upper 7 and lower 8 covers. All parts of the housing 20 are made of ABS plastic and are glued together with the metal element 1 of the ER sensor with a silicone-based sealant that is resistant to elevated temperatures. A barrier 10 can also optionally be inserted into the slot 7a on the upper cover 7 to reduce parasitic resistances.

Na drugo stran priključnega kabla 9 dolžine 2m je spojen vodotesni konektor, ki se vklopi v ohišje z napajalno in merilno analogno elektroniko (constant current source, precision low noise operational amplifier), analogno-digitalnim pretvornikom (ADC), data-loggerjem z mikroračunalnikom in RF oddajnikom.A waterproof connector is connected to the other side of the connecting cable 9 of 2m length, which is plugged into the housing with power supply and measuring analog electronics (constant current source, precision low noise operational amplifier), analog-to-digital converter (ADC), data-logger with microcomputer and to RF transmitters.

Čas izvedbe meritve je 100 do 1500ms v odvisnosti od zahtevane točnosti meritve. Zaželeno je, da se meritve izvajajo v intervalih, saj se s tem prepreči morebitno dodatno segrevanje elektrod. Čas med posameznimi meritvami se izbere v računalniškem programu.The measurement execution time is 100 to 1500 ms, depending on the required measurement accuracy. It is desirable that the measurements be carried out at intervals, as this prevents possible additional heating of the electrodes. The time between individual measurements is selected in the computer program.

Prototip ER senzorja je bil izpostavljen v realnem ekstremnem okolju v hidrometalurškem reaktorju toliko časa, da je skorodiralo vsaj 50 % prereza merilnega elementa. Prerezi so bili zatem metalografsko pregledani in rezultati primerjani z rezultati električnih meritev senzorja (Tabela 1).The ER sensor prototype was exposed to a realistic extreme environment in a hydrometallurgical reactor for such a time that at least 50% of the cross-section of the measuring element corroded. The sections were then metallographically examined and the results compared with the results of electrical measurements of the sensor (Table 1).

Tabela 1. poškodbe na senzorju po izpostavi, izmerjene iz metalurškega obrusa in izračunane iz meritev ER senzorja.Table 1. Sensor damage by exposure measured from metallurgical cloth and calculated from ER sensor measurements.

Poškodbe Injuries Metalurški obrus Metallurgical tablecloth ER senzor ER sensor V smeri normalno na prerez In the direction normal to the section 25 pm 25 pm 27 pm 27 pm V prečni smeri prereza In the cross section direction 160 pm 160 p.m 165 pm 165 p.m

Postopek izvedbe temperaturne kompenzacije:Temperature compensation implementation procedure:

Re......Električna upornost merilne elektrode 2Re......Electrical resistance of measuring electrode 2

Rk......Električna upornost referenčne elektrode 2aRk......Electrical resistance of reference electrode 2a

Rek....Kompenzirana vrednost električne upornosti merilne elektrode 2Rek...Compensated value of electrical resistance of measuring electrode 2

ReO....Električna upornost merilne elektrode 2 pri referenčni temperaturiReO....Electrical resistance of measuring electrode 2 at reference temperature

RkO.... Električna upornost referenčne elektrode 2a pri referenčni temperaturiRkO.... Electrical resistance of the reference electrode 2a at the reference temperature

Tref....Referenčna temperaturaTref....Reference temperature

Tamb..Temperatura medija v katerega je postavljen ER senzorTamb..The temperature of the medium in which the ER sensor is placed

Rref....Referenčni merilni upor (na podlagi vrednosti Rref se izračuna vrednost električne upornosti merilne 2 ter referenčne elektrode 2a)Rref....Reference measuring resistance (based on the value of Rref, the electrical resistance value of measuring 2 and reference electrode 2a is calculated)

Temperaturna kompenzacija merilne elektrode 2 med točkama BC je izvedena s pomočjo matematičnega preračuna električne upornosti Re merilne elektrode 2 na osnovi spremembe električne upornosti Rk referenčne elektrode 2a med točkami AB ter CD pod pogojem, da sta obe elektrodi na enaki oz. podobni temperaturi.The temperature compensation of the measuring electrode 2 between the points BC is carried out with the help of a mathematical calculation of the electrical resistance Re of the measuring electrode 2 based on the change in the electrical resistance Rk of the reference electrode 2a between the points AB and CD under the condition that both electrodes are at the same or similar temperature.

Referenčno elektrodo 2a predstavlja podaljšek merilne elektrode 2 v izolacijskem ohišju 20, ki obenem služi za priklop električnih vodnikov, s katerimi napajamo ER senzor ter merimo električno upornost Re merilne elektrode 2 ter električno upornost Rk referenčne elektrode 2a. Ker je referenčna elektroda 2a izolirana pred korozijskimi procesi z izolacijskim ohišjem 20, na spremembo njene električne upornosti Rk vpliva samo sprememba temperature medija (Tamb). Če je temperatura elektrod 2 ter 2a podobna ali enaka, lahko s preprosto matematično operacijo izvedemo temperaturno kompenzacijo električne upornosti Rek merilne elektrode 2.The reference electrode 2a is an extension of the measuring electrode 2 in the insulating housing 20, which also serves to connect the electrical conductors with which we feed the ER sensor and measure the electrical resistance Re of the measuring electrode 2 and the electrical resistance Rk of the reference electrode 2a. Since the reference electrode 2a is isolated from corrosion processes by the insulating housing 20, the change in its electrical resistance Rk is only affected by the change in the temperature of the medium (Tamb). If the temperature of electrodes 2 and 2a is similar or the same, a simple mathematical operation can be used to perform a temperature compensation of the electrical resistance Rek of measuring electrode 2.

Izračun temperaturne kompenzacije merilne elektrode:Calculation of the temperature compensation of the measuring electrode:

Rek=Rk/RkO*ReRek=Rk/RkO*Re

Uspešnost kompenzacije spremembe upornosti zaradi temperature je prikazana na sliki 7.The performance of compensating the resistance change due to temperature is shown in Figure 7.

Prednosti ER senzorja po izumu so sledeče:The advantages of the ER sensor according to the invention are as follows:

- temperaturna kompenzacija ali popravek vrednosti električne upornosti merilne elektrode je izvedena s pomočjo temperaturne spremembe električne upornosti referenčne elektrode v izolacijskem ohišju ER senzorja;- temperature compensation or correction of the value of the electrical resistance of the measuring electrode is carried out with the help of the temperature change of the electrical resistance of the reference electrode in the insulating housing of the ER sensor;

- referenčno elektrodo predstavlja podaljšek merilne elektrode v izolirano ohišje, ki služi za električni priklop in izvedbo meritev upornosti merilne elektrode;- the reference electrode is an extension of the measuring electrode into an insulated housing, which serves for electrical connection and performance of resistance measurements of the measuring electrode;

- merilna in referenčna elektroda skupaj s priključnimi kontakti sta izvedeni iz istega monolitnega kosa metalnega traku.- the measuring and reference electrodes together with the connecting contacts are made from the same monolithic piece of metal tape.

Claims (10)

Patentni zahtevkiPatent claims 1. Električni uporovni senzor za korozijski monitoring v ekstremnih korozijskih razmerah, pri čemer električni uporovni senzor vključuje kovinski element (1) in izolacijsko ohišje (20), označen s tem, da je kovinski element (1) izveden ploščato v obliki črke U in je v celoti izdelan iz enega kosa valjane jeklene pločevine, tako da vzdolžna os kovinskega elementa (1) poteka v smeri valjanja pločevine, pri čemer del kovinskega elementa (1), ki je neposredno izpostavljen korozivnemu mediju, predstavlja merilno elektrodo (2), in del kovinskega elementa (1), ki je od korozivnega medija izoliran z ohišjem (20), predstavlja referenčno elektrodo (2a), pri čemer je merilna elektroda (2) izvedena v obliki črke U, tako da sta tvorjena dva med sabo v bistvu vzporedna merilna trakova (21, 22), ki se nadaljujeta v referenčno elektrodo (2a) in je referenčna elektroda (2a) izvedena iz dveh referenčnih trakov (3, 4), tako da se merilni trak (21) merilne elektrode (2) nadaljuje v referenčni trak (3) in se merilni trak (22) merilne elektrode (2) nadaljuje v referenčni trak (4), pri čemer je vsak od referenčnih trakov (3, 4) v delu, kjer se merilna trakova (21, 22) nadaljujeta v referenčna trakova (3,4), povezana s pomožnima vodnikoma (5, 6), ki sta uporabljena kot električna vodnika od stičišča referenčnega traku (3) s pomožnim vodnikom (5), to je točke (B), in stičišča referenčnega traku (4) s pomožnim vodnikom (6), to je točke (C), do točk (A, E, F in D) za priključitev zunanjih električnih vodnikov, in je ohišje (20) izvedeno iz zgornjega (7) in spodnjega (8) pokrova, pri čemer je notranjost pokrovov (7, 8) prirejena za sprejem referenčne elektrode (2a) in priključnega kabla (9) in sta oba pokrova (7, 8) med sabo oblikosklepno fiksno povezana preko povezovalnih elementov (30).1. An electrical resistance sensor for corrosion monitoring in extreme corrosion conditions, wherein the electrical resistance sensor includes a metal element (1) and an insulating housing (20), characterized by the fact that the metal element (1) is made flat in the shape of the letter U and is completely made of one piece of rolled steel sheet, so that the longitudinal axis of the metal element (1) runs in the direction of rolling of the sheet, whereby the part of the metal element (1) which is directly exposed to the corrosive medium represents the measuring electrode (2), and part of the metal element (1), which is isolated from the corrosive medium by the housing (20), represents the reference electrode (2a), whereby the measuring electrode (2) is designed in the shape of the letter U, so that two essentially parallel measuring electrodes are formed of strips (21, 22), which continue into the reference electrode (2a) and the reference electrode (2a) is made of two reference strips (3, 4), so that the measuring strip (21) of the measuring electrode (2) continues into the reference strip (3) and the measuring strip (22) of the measuring electrode (2) continues into the reference strip (4), each of the reference strips (3, 4) being in the part where the measuring strips (21, 22) continue into the reference strips (3, 4), connected to auxiliary conductors (5, 6), which are used as electrical conductors from the junction of the reference strip (3) with the auxiliary conductor (5), i.e. point (B), and the junction of the reference strip (4) with the auxiliary conductor (6), i.e. points (C), to points (A, E, F and D) for the connection of external electrical conductors, and the housing (20) is made of the upper (7) and lower (8) covers, whereby the inside of the covers (7, 8) is adapted to receive the reference electrode (2a) and the connecting cable (9) and both covers (7, 8) are fixedly connected to each other via connecting elements (30). 2. Električni uporovni senzor po zahtevku 1, označen s tem, da kovinski element (1) senzorja predstavlja električni upor razdeljen na več uporov in delov, in sicer:2. Electric resistance sensor according to claim 1, characterized in that the metal element (1) of the sensor represents an electric resistance divided into several resistances and parts, namely: korozijsko aktivni del senzorja, to je merilna elektroda (2), ki predstavlja merilni upor (Ri), je nezaščitena pločevina med točkama (B) in (C) v obliki črke U;the corrosion-active part of the sensor, i.e. the measuring electrode (2), representing the measuring resistance (Ri), is an unprotected sheet between points (B) and (C) in the shape of the letter U; referenčni upor predstavljata korozijsko zaščitena dela senzorja med točkama (A) in (B), to je referenčni trak (3), ki predstavlja referenčni upor (R2), in med točkama (C) in (D), to je referenčni trak (4), ki predstavlja referenčni upor (R3), ki se nahajata v izolacijskem ohišju (20);the reference resistance is represented by the corrosion-protected parts of the sensor between points (A) and (B), i.e. the reference strip (3), which represents the reference resistance (R 2 ), and between points (C) and (D), i.e. the reference strip ( 4), which represents the reference resistance (R 3 ), which are located in the insulating housing (20); - pomožna vodnika (5, 6) med točkama (B) in (E) ter med točkama (C) in (F) sta uporabljena kot pomožna električna vodnika in se nahajata v izolacijskem ohišju (20), pri čemer je ena stran, prednostno zgornja stran, referenčnih trakov (3,4) in pomožnih vodnikov (5,6) namenjena spajkanju zunanjih električnih vodnikov v točkah (A, E, F in D).- the auxiliary conductors (5, 6) between points (B) and (E) and between points (C) and (F) are used as auxiliary electrical conductors and are located in the insulating housing (20), with one side preferably the upper side, reference strips (3,4) and auxiliary conductors (5,6) intended for soldering external electrical conductors at points (A, E, F and D). 3. Električni uporovni senzor po zahtevkih 1 in 2, označen s tem, da so zunanji električni vodniki ločen po parih, pri čemer je:3. Electrical resistive sensor according to claims 1 and 2, characterized in that the external electrical conductors are separated in pairs, whereby: - prvi par, to sta točki (A) in (D), predviden za priključitev zunanjih električnih vodnikov za napajanje senzorja s konstantnim tokom, pri čemer istočasno teče enak električni tok skozi merilno elektrodo (2) in referenčno elektrodo (2a);- the first pair, i.e. points (A) and (D), intended for the connection of external electrical conductors for powering the sensor with a constant current, with the same electrical current flowing simultaneously through the measuring electrode (2) and the reference electrode (2a); - drugi par, to sta točki (E) in (F), predviden za priključitev zunanjih električnih vodnikov za merjenje padca napetosti (Ui) na merilni elektrodi (2) senzorja, to je na merilnem uporu (Rx), med točkama (B) in (C) in- the second pair, i.e. points (E) and (F), intended for connecting external electrical conductors for measuring the voltage drop (Ui) on the measuring electrode (2) of the sensor, i.e. on the measuring resistor (R x ), between points (B ) and (C) and - tretji par, to sta točki (A) in (E) in točki (F) in (D), predviden za priključitev zunanjih električnih vodnikov za merjenje padca napetosti (U2) ali (U3) na posameznem referenčnem traku (3, 4), to je na referenčnem uporu (R2) ali (R3), pri čemer sta točki (A) in (E) prevideni za priključitev zunanjih električnih vodnikov za merjenje padca napetosti (U2) na referenčnem traku (3) in sta točki (F) in (D) predvideni za priključitev zunanjih električnih vodnikov za merjenje padca napetosti (U3) na referenčnem traku (4).- the third pair, i.e. points (A) and (E) and points (F) and (D), intended for the connection of external electrical conductors for measuring the voltage drop (U2) or (U3) on a single reference strip (3, 4) , i.e. on the reference resistor (R2) or (R3), where points (A) and (E) are provided for the connection of external electrical conductors for measuring the voltage drop (U 2 ) on the reference strip (3) and are points (F ) and (D) provided for the connection of external electrical conductors for measuring the voltage drop (U 3 ) on the reference strip (4). 4. Električni uporovni senzor po zahtevku 3, označen s tem, da je na točki (A) in (D) poleg prvega para lahko lotan tudi tretji par zunanjih električnih vodnikov za omogočanje istočasnega merjenja padca napetosti (U2 in U3) na referenčnih trakovih (3,4) ter padca napetosti (U1) na merilni elektrodi (2), to je na merilnih trakovih (21, 22) senzorja.4. The electrical resistive sensor according to claim 3, characterized by the fact that at points (A) and (D) in addition to the first pair, a third pair of external electrical conductors can also be soldered to enable simultaneous measurement of the voltage drop (U 2 and U 3 ) on the reference of the strips (3,4) and the voltage drop (U1) on the measuring electrode (2), i.e. on the measuring strips (21, 22) of the sensor. 5. Električni uporovni senzor po predhodnih zahtevkih, označen s tem, da senzor opcijsko vključuje mehansko pregrado (10), ki je izvedena v obliki tanke plošče, ki je postavljena vzdolžno med merilna trakova (21, 22) merilne elektrode (2) za zmanjšanje vpliva parazitne upornosti medija med vzdolžnim delom, to je med merilnima trakovoma (21, 22) merilne elektrode (2).5. Electrical resistive sensor according to the preceding claims, characterized in that the sensor optionally includes a mechanical barrier (10), which is made in the form of a thin plate, which is placed longitudinally between the measuring strips (21, 22) of the measuring electrodes (2) to reduce the influence of the parasitic resistance of the medium during the longitudinal part, i.e. between the measuring strips (21, 22) of the measuring electrode (2). 6. Električni uporovni senzor po zahtevku 5, označen s tem, da je pregrada (10) vstavljena v režo (7a) izvedeno v zgornjem pokrovu (7) ohišja (20) in dodatno pritrjena s tesnilno maso na silikonski osnovi.6. Electrical resistive sensor according to claim 5, characterized by the fact that the partition (10) is inserted into the slot (7a) made in the upper cover (7) of the housing (20) and additionally fixed with a silicone-based sealant. 7. Električni uporovni senzor po predhodnih zahtevkih, označen s tem, da so zgornji (7) pokrov, spodnji (8) pokrov in mehanska pregrada (10) prednostno izvedeni iz ABS plastike in so navedeni deli s kovinskim elementom (1) senzorja medsebojno zlepljeni s tesnilno maso na silikonski osnovi, ki je odporna proti povišanim temperaturam, pri čemer tesnilna masa popolnoma zapolni bazen v spodnjem pokrovu (8) ohišja (20), s čimer se prepreči nastanek »špranjske korozije« nerjavnega jekla v notranjosti ohišja (20) na prehodu merilne elektrode (2) v referenčno elektrodo (2a).7. Electrical resistive sensor according to the preceding claims, characterized in that the upper (7) cover, lower (8) cover and mechanical barrier (10) are preferably made of ABS plastic and the mentioned parts with the metal element (1) of the sensor are glued to each other with a silicone-based sealant resistant to elevated temperatures, the sealant completely filling the basin in the lower cover (8) of the housing (20), thereby preventing the formation of "crevice corrosion" of the stainless steel inside the housing (20) on transition of the measuring electrode (2) to the reference electrode (2a). 8. Električni uporovni senzor po predhodnih zahtevkih, označen s tem, da so zunanji električni vodniki na točke (A, E, F in D) prednostno lotani z mehkim lotom (SnAg3) in so lotana mesta in del vodnikov dodatno zaščitena s termokrčljivimi cevmi v več plasteh, na zunanji strani, kjer priključni kabel (9) vstopa v ohišje (20), pa tudi s tesnilno maso na silikonski osnovi.8. Electrical resistance sensor according to the preceding claims, characterized by the fact that the external electrical conductors at points (A, E, F and D) are preferably soldered with soft solder (SnAg3) and the soldered points and part of the conductors are additionally protected by heat-shrinkable tubes in several layers, on the outside where the connection cable (9) enters the housing (20), as well as with a silicone-based sealant. 9. Električni uporovni senzor po predhodnih zahtevkih, označen s tem, da so zunanji električni vodniki trikrat zviti par bakrenih posrebrenih vodnikov s prerezom 0,5 mm2 z oplaščenjem na posameznih parih in je izolacija vodnikov prednostno izdelana iz fluoriranega etilen propilena.9. Electrical resistance sensor according to the previous claims, characterized by the fact that the external electrical conductors are a triple twisted pair of silver-plated copper conductors with a cross-section of 0.5 mm 2 with coating on individual pairs and the insulation of the conductors is preferably made of fluorinated ethylene propylene. 10. Električni uporovni senzor po predhodnih zahtevkih, označen s tem, da je kovinski element (1) senzorja iz nerjavne pločevine tanjših debelin, prednostno debeline 1 mm in 0.5 mm, izdelan z rezanjem z abrazivnim vodnim curkom ali z laserskim rezanjem v atmosferi zaščitnega plina.10. Electrical resistance sensor according to the previous claims, characterized by the fact that the metal element (1) of the sensor is made of stainless steel sheet of thinner thicknesses, preferably 1 mm and 0.5 mm thick, made by cutting with an abrasive water jet or by laser cutting in an atmosphere of protective gas .
SI202100103A 2021-05-14 2021-05-14 Electrical resistance sensor for corrosion monitoring in extreme corrosion conditions SI26200A (en)

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