WO2020087144A1

WO2020087144A1 - Structural arrangement for a sensor/probe for measuring corrosion rate by using electrical resistance

Info

Publication number: WO2020087144A1
Application number: PCT/BR2019/050466
Authority: WO
Inventors: Otavio Carneiro CORREA
Original assignee: Vidya Corrosão Engenharia Ltda
Priority date: 2018-10-29
Filing date: 2019-10-28
Publication date: 2020-05-07
Also published as: BR202018072291U2

Abstract

The utility model patent relates to a structural arrangement for a sensor or probe for measuring corrosion rate by using electrical resistance, applied to the industrial field of systems comprising conduits, pipes and equipment, aiming to achieve greater precision of measurement of corrosion rates and improved results in terms of speed of response, by means of a corrosion electrode (1) and a reference electrode (2) made from the same material and of similar geometry, which will be superposed with a thin insulating layer (3) of polymer between them, thereby achieving advantages in terms of higher speed of measurement, greater precision of measurement, greater reliability in terms of monitoring, simplicity, greater sensitivity to operational changes and to the conditions of the flow, and, furthermore, by using the corrosion rate profile it is possible to influence process variables with a view to minimizing corrosion.

Description

CONSTRUCTIVE ARRANGEMENT

INTRODUCED IN SENSOR / PROBE OF MEASUREMENT OF CORROSION RATE BY ELECTRIC RESISTANCE "

[01] The present utility model patent refers to the constructive arrangement introduced in a sensor or probe for measuring the corrosion rate by electrical resistance applied in the industrial field for systems with ducts, pipes and equipment in order to provide variations in corrosion rates of the system, which aims to obtain greater precision in the measurements of corrosion rates and better result in response speed, with advantages of greater measurement speed, greater measurement accuracy, greater reliability in monitoring, simplicity, sensitivity to operational changes and the flow regime, in addition, through the corrosion rate profile it is possible to act on the process variables to minimize corrosion.

[02] As it is known in the technical field of corrosion sensors today, the sensors are of different materials and geometries and with many interference noises, having a limited measurement, which is often time-consuming and with low precision.

[03] The working principle of this type of device is based on the variation of the electrical resistance of a sensor element in function of its loss of mass caused by corrosion, compensated for the resistivity variations caused by the temperature, through a reference element.

[04] Changes in electrical resistance are measured cumulatively over time, based on the initial measurement of the sensor. In practice, the equipment used makes the automatic conversion of the electrical resistance into loss of mass or thickness of the measurement point. [05] The probe or electrical resistance sensor can be used in any type of medium to determine the uniform corrosion rate, obtaining the accumulated mass loss in the reading period.

[06] Searching the Brazilian and international patent banks, we find the following revelations:

[07] Brazilian patent BR 11 2015 017177 0

“Systems and methods for monitoring and controlling corrosion in hot water systems” The invention concerns systems and methods for monitoring and controlling an oxidation potential - reduction in real time in a hot water system to inhibit corrosion in the hot water system . The method includes defining one or more operational protection zones in the hot water system. One or more of the operational protection zones includes an oxidation potential probe - reduction that is operable to measure an oxidation potential - real-time reduction in the hot water system at operating temperature and pressure. The probe transmits the measured potential in real time to the controller, which evaluates and interprets the transmitted potential to determine whether it conforms to an oxidation - reduction potential setting. If the measured potential is not in accordance with the oxidation-reduction potential setting, the controller is operable to feed or remove one or more active chemical species to the system from the hot water system and additionally operable to change at least one parameter of the system.

[08] US patent 7,061,255 “Corrosion monitoring system”. A system for monitoring corrosion on metal by comparing a test sample exposed to a corrosion-causing environment and a reference sample exposed to a protected environment. An AC voltage source generates a square wave signal oscillating between ground and the voltage Vcc and a filter is positioned to filter the signal to produce a sine wave without a second harmonic component. A voltage driven current source and an inverter amplifier produce a current referenced to 0.5 Vdc to provide an AC current of the driven voltage sinusoidally and symmetrically above and below 0.5 Vdc. A transformer increases the alternating current and then transmits the current through the samples to an amplifier to amplify the current to provide outputs in a proportion that represents the degree of corrosion of the reference sample. The system can operate in situ for on-site measurement and uses relatively low current to allow for long operation.

[09] US patent 8,052,324

“Thin-film ceramic thermocouples” A thin-film ceramic thermocouple (10) having two ceramic thermocouples (12, 14) that are in contact with each other at at least one point to form a joint, and in which each element was prepared in a plasma other than oxygen / nitrogen / argon. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different concentrations of charge carriers. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system with an RTD heat flow sensor can be combined with a thermocouple and a deformation sensor to produce a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that can be used to calibrate optical sensors.

[10] English patent GB2504214 “Crack corrosion sensor” A sensor for measuring corrosion under the gap of metals immersed in a fluid-containing container, the sensor comprising a cylindrical body and a length of bare metallic wire passing along and in of a groove in the body. The groove can be helical and the sensor can include an inner body of a different diameter with a wire in a corresponding groove. An opening to retain debris in a fluid stream can be included. A method for predicting corrosion in a vessel containing fluid is also described, including the steps of providing a corrosion sensor, immersing at least part of it in the vessel and measuring the electrical resistance of the wire, and the first and second derivatives of the resistance in relation to at time. The vessel can be a pipe or any part of a system that carries fluid in a building, such as heated or chilled water, a sprinkler system or any system that carries fluid, such as in a chemical installation, refinery or desalination plant.

[11] US patent US2009195260

“Low profile electrical resistance corrosion sensor” A thin, narrow electrical resistance corrosion sensor defines the measurement, reference and verification resistances as parts arranged in series of a thin metal resistance element, such as a carbon steel element or ductile iron, with metallurgical properties that combine with a corrosive structure. of interest, like a pipeline buried in the ground. The resistance element is connected to a structural substrate in the thin, long and narrow conductive to which also a bundle of flat cables is attached, which includes conductors connected to the ends of the resistance element and to selected locators of the element between its ends. The resistance element, the substrate, the wire harness and its connections to the resistance element are encapsulated by a non-conductive protective coating, except over the area of the measurement resistor, so that this resistor can be exposed to the surrounding environment. The sensor can be used with conventional corrosion measurement instruments. Arrangements for using multiple sensors to measure corrosion due to direct current in a structure of interest, and to measure corrosion due to alternating currents in that structure, are also described.

[12] US patent US6564620 “Visually, indicating corrosion detection” Corrosion sensors and methods of their use to monitor the corrosion of a material of interest. Corrosion sensors are adapted to be placed in the environment containing the material of interest during the period in which corrosion is occurring. Corrosion sensors include a power source, a visual indicator and an electrode contained in a support. Changes in the electrical resistance of the electrode facilitate the display on the visual indicator, including changes in color or brightness. Some corrosion sensors have energy sources activated by directing a light source or other source of electromagnetic radiation to the corrosion sensor. Some corrosion sensors have visual indicators containing thermochromic or electrochromic materials that respond to changes in voltage drop or current flow through the visual indicator. Some corrosion sensors have tracking devices to provide tracking information about the corrosion sensor. Some corrosion sensors have proximity sensors to inhibit the display of the visual indicator when they are not close to a trigger.

[13] US patent US5627749 “Corrosion monitoring tool” A tool for monitoring corrosion levels within a well is particularly suitable for remote monitoring for long periods. The monitoring tool uses a thin-walled electrical resistance wall corrosion sensor to determine the rate of metal loss within the well. The corrosion sensor is preferably made of the same material as the production pipe or well bore pipe and is positioned to allow the fluid inside the well flows over the sensor at the same speed as the fluid flows over the pipeline. A reference element is incorporated into the corrosion sensor to provide primary temperature compensation. A temperature sensor provides temperature data and allows secondary temperature compensation for the corrosion sensor. A central processing unit reads and stores data from the three sensors in solid-state memory. The probe records data at programmable time intervals. After recovering the probe from the well, the probe can be connected to a computer for downloading the raw data and for further analysis.

[14] US patent US6946855 “Electrical resistance sensor and corrosion monitoring devices x” An apparatus (1) is revealed to monitor the effect on a material exposed to a fluid and thereby monitor the effect on a section of the tube (9) to transport the fluid. The apparatus includes a sensor element (51) exposed to the fluid and formed as a ring of the material coaxially mounted inside, but electrically isolated from the tube section (9). Changes in the electrical resistance of the sensor element (51) are monitored. Preferably, the apparatus also includes a reference element (31) electrically isolated from the tube (9), electrically connected in series to the sensor element (51) and protected from exposure to the fluid. The elements can both be made of the same material as the tube (9) and, as they are contained within it, experience the same temperature and pressure variations as the tube (9). In this way, a change in the resistance of the sensor element (51) caused by corrosion / erosion by the fluid accurately indicates the degree of corrosion / erosion of the tube (9) that carries the fluid.

[15] Japanese patent JPS58178246 “Corrosion monitoring probe” OBJECTIVE: To locate the flow current distribution within a pit and to know the corrosion rate or its polarization resistance to detect local corrosion progressing under the probe, through the constitution of a special shaped probe by some electrodes. CONSTITUTION: It is necessary that the surface area of an opposite insoluble electrode 2 be greater than at least one corrosion or similar to be measured. It is desirable to select the surface area of the paired electrode to be not less than 10 cm2, since a cavity to be measured has a maximum diameter of about 3 cm. A paired electrode chamber 3 in an electrical insulating container 1 is desirably a container with a volume of not less than 60 ml. A 4 minute hole is provided on the surface of the container wall corresponding to the paired electrode. The reduction of the minimum diameter of 4 in diameter makes it possible to obtain an excellent resolving power. The diameter is preferably 0.05-1 mm. in consideration of practicality. For a reference electrode 7, any material can be used, as long as it is stable in seawater and in another environment. The performance of a corrosion speed monitoring according to the polarization resistance method by using this probe makes it possible to directly detect corrosion in a structure corroded by sea water or other liquid.

[16] The current and patented sensors have drawbacks, limitations and disadvantages of: slower measurement speed; lower measurement accuracy; limitation of corrosion monitoring by making only qualitative measurements; many of today's sensors / devices measure inaccurate corrosion rates, serving only as an indication of internal corrosion processes and requiring validation using other methods; lack of reliability in monitoring; and low speed of response to small corrosion rates.

[17] “Constitutive provision introduced in sensor / probe for measuring corrosion rate by electrical resistance”, object of the present patent, was developed to overcome the limitations, the inconveniences and the disadvantages of the current sensors and probes, through a new configuration of the electrodes with which it was possible to significantly reduce the measurement noise caused by the effects of temperature differentials and consequently increase the sensitivity in the measurement of the corrosion rate and bringing advantages of greater measurement speed, greater measurement accuracy, greater reliability in monitoring, simplicity, sensitivity to operational changes and the flow regime, in addition, through the corrosion rate profile is possible to act on the process variables to minimize corrosion.

[18] With overlapping geometrically equal corrosion detection and reference electrodes separated by a thin layer of polymer as an electrical insulator, with the possibility of obtaining heat transfer rate or equal temperature gain between the detection and reference electrodes when the fluid temperature of the equipment being measured the corrosion varies, increasing the sensor's corrosion rate detection resolution and decreasing the measurement noise.

[19] Current electrical resistance corrosion rate sensors and probes present the following technical problems that have been solved by the present invention as follows:

[20] A) Current sensors detect variations in the corrosion rate with low speed and low sensitivity, limiting the measurement of lower corrosion rates to longer measurement periods, ie low reading speed, requiring measurement days for correction operational parameters that influence corrosion, such as the injection of corrosion inhibitors. Resolved by this invention through a new configuration with overlapping corrosion detection and reference electrodes geometrically equal separated by a thin layer of polymer as an electrical insulator, with which it was possible to obtain an equal heat transfer rate between the reference detection electrode and the fluid of the equipment, in which the corrosion is being measured, and increasing the resolution of detection of the corrosion rate of the sensor and reducing the noise.

[21] B) Process variables of the fluid contained in industrial systems, such as ducts, pipes and equipment, where variations in corrosion rates are measured, are not detected quickly because of the low sensitivity and low corrosion measurement speed in the sensors current. Solved by the present invention through an approximation of the corrosion and reference electrodes, both having the same heat transfer with the working fluid, thus reducing the interference noise of the measurement and consequently increasing the sensitivity.

[22] For better understanding of the present invention, the following drawings are attached: †

[23] FIGURE 1., which shows the side view of the electrodes together with the polymer film between them;

[24] FIGURE 2., which shows the perspective view of the two separate electrodes and the polymer film; and

[25] FIGURE 3., which represents the operation of the circuit, with the electrodes connected in the way they are arranged in the patent. [26] The invention of the present patent consists of two electrodes of the same material and similar geometries, which will be overlaid with a thin layer of polymer between them.

[27] The reference electrode provides the data as parameters for the measurement of corrosion, in the system in question.

[28] The corrosion detection electrode will be subject to corrosion thereby generating a resistance difference in relation to the reference electrode which will not suffer corrosion, thus giving the expected results.

[29] According to the figures, more specifically the invention consists of a reference electrode (2) of optimized shape; corrosion detection electrode (1) with an optimized shape similar to the electrode (2); insulating layer (3) in polymer for example (PTFE, PoliTetraFluorEtilene, or Teflon) with volumetric electrical resistivity of at least 1.0E + 18 (I, OcIO ¹⁸ ) ohm.cm and with thermal conductivity of at least 0.2W / mK of the same geometric shape as the electrodes, with a maximum thickness of 200pm.

[30] The operating process of the invention of the present patent takes place in the following sequence:

[31] a) The corrosion sensor or probe is installed in the piping, the electrode being in contact with the fluid being worked on;

[32] b) The initial parameters are registered automatically in the device's memory for later comparison;

[33] c) The temperature is detected by the reference electrode that will compensate for the resistivity variation; [34] d) The corrosion electrode is exposed to the system fluid where corrosion occurs, which causes the resistance variation of the circuit; and

[35] e) With the resistance variation over time, compared to the initial parameters, corrosion caused by the operation fluid is determined.

Claims

CLAIM

1. “CONSTRUCTIVE ARRANGEMENT

INTRODUCED INTO A CORROSION RATE MEASUREMENT PROBE BY ELECTRIC RESISTANCE ”, consisting of a reference electrode (2) of optimized shape, and a corrosion detection electrode (1) of optimized shape similar to that of the electrode (2) , characterized by an insulating layer (3) between the electrodes, in polymer with volumetric electrical resistivity, of at least 1.0E + 18 (I, OcIO ¹⁸ ) ohm. cm and with thermal conductivity of at least 0.2W / mK of the same geometric shape as the electrodes, with a maximum thickness of 200pm.