JP2000258380A - Method and device for measuring erosion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for accurately measuring the amount of reduced thickness due to erosion accompanied by the flow of fluid on the inner surface of a device. SOLUTION: A method for measuring erosion is provided with first to third electrodes with the same material as that of a metal device in fluid that flows in the metal device, the change in an electrochemical current noise and an electrochemical potential noise when the flow rate of the fluid is changed is measured, and the amount of reduced thickness due to erosion by operation processing is calculated. An erosion- measuring device is provided with first and second electrodes with the same material as that of the metal device, a mounting member for mounting the first to third electrodes to fluid that flows in the metal device, an electrochemical current noise measurement means for measuring the electrochemical current noise between the first and second electrodes, an electrochemical potential noise measurement means for measuring the electrochemical potential noise between the second and third electrodes, a means for changing the flow rate of the fluid, and a means for calculating the amount of reduced thickness due to erosion by arithmetic processing by measuring each change of electrochemical current noise and electrochemical potential noise when a flow rate is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and a device for measuring erosion. More specifically, the present invention relates to a method for electrochemically capturing an oxidation phenomenon due to erosion, and calculating a thinning amount due to erosion based on the measured value, and a measuring device therefor. According to the method of the present invention, it is possible to easily obtain the amount of thinning due to erosion of equipment such as a petrochemical plant and piping equipment.

[0002]

2. Description of the Related Art Various plants, such as petrochemical plants,
It is composed of many devices and piping devices. In order to maintain the soundness of these plants and to ensure stable operation, it is necessary to eliminate damage to these equipment and piping equipment, minimize problems, perform deterioration management and diagnosis, and perform maintenance management. There is a need to. That is, to maintain long-term stable operation under high reliability, planned preventive maintenance is indispensable.

[0003] One of the main deterioration factors of equipment and piping equipment is a thinning phenomenon in which the inner wall of the pipe wall and the inner surface of the equipment is thinned by erosion and corrosion due to internal fluid, that is, corrosion by chemical action (corrosion). ) And erosion due to mechanical action (erosion). Generally, in order to grasp the thinning tendency of these equipment and piping equipment, and to manage the situation, the thickness of the main parts of equipment and piping equipment of a real plant such as a petrochemical plant is regularly measured by ultrasonic thickness measurement. It is being implemented by the total.

[0004]

However, according to the above-mentioned method, it is impossible to measure the thickness only when the apparatus is stopped after the operation for a considerably long time, and it is difficult to measure the amount of thickness reduction by erosion alone. is there. The present invention has been made in view of the above circumstances, and has as its object to provide a method and an apparatus for accurately measuring the amount of wall thinning due to erosion accompanying a fluid flow on the inner surface of the apparatus.

[0005]

The inventor of the present invention has conducted intensive studies on a method of measuring the amount of wall thinning due to erosion caused by an internal fluid in equipment and piping equipment. When the metal electrode of the material is immersed, when the flow velocity of the fluid is changed, the electrochemical current noise and the electrochemical potential noise respectively change, and it is found that the thinning amount by erosion can be measured from the change amount.
The present invention has been completed.

That is, the gist of the present invention is to provide first to third electrodes having the same material as that of a metal device in a fluid flowing through the metal device, and to reduce electrochemical current noise when the flow velocity of the fluid is changed. The method of measuring erosion, characterized in that a change in electrochemical potential noise is measured, and the amount of wall thinning due to erosion is calculated by arithmetic processing, and the first and second electrodes having the same material as the metal device, and A mounting member for mounting the first to third electrodes in a fluid flowing through the metal device, an electrochemical current noise measuring means for measuring electrochemical current noise between the first electrode and the second electrode, Electrochemical potential noise measuring means for measuring electrochemical potential noise between the electrode and the third electrode, means for changing the flow rate of the fluid, electrochemical current noise and electrochemical when the flow rate is changed The change of the potential noise measured respectively, lying in the measuring device, erosion, characterized in comprising means for calculating the thickness reduction due to erosion by the processing.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The mechanism of the occurrence of the wall thinning phenomenon due to the erosion / corrosion of the inner surface of the internal fluid device will be briefly described.
The phenomenon of thinning due to erosion and corrosion is first
Corrosion occurs due to chemical actions such as fluid properties and temperature, which are related to the formation of a protective coating. In addition, erosion is generated by the mechanical force of the mechanical action due to flow velocity and shape, and erosion and
The wall thinning phenomenon due to the corrosion occurs, and the wall thinning phenomenon due to the erosion / corrosion occurs on the pipe wall and the inner surface of the device. The thinning phenomenon and action by the erosion and corrosion will be described in detail.

[0008] The thinning phenomenon due to erosion and corrosion is caused by the interaction between corrosion (corrosion) due to chemical action and erosion (erosion) due to mechanical action.
This is the phenomenon of wall thinning that occurs. That is, when considering metal thinning, the mechanism differs depending on the surrounding fluid conditions (properties, temperature, etc.) and flow conditions (flow speed, shape, etc.). Metals in a corrosive environment are reduced in thickness due to corrosion.However, if the mechanical action is small, such as a low flow velocity of the fluid, single corrosion occurs. As a result, a thinning phenomenon due to erosion and corrosion occurs.

The present invention is characterized in that the amount of wall thinning due to erosion is measured by the change in the amount of wall thinning due to erosion / corrosion when the flow velocity of the fluid flowing through the tube wall of the metal device or the inner surface of the equipment is changed. It is. That is,
When the flow velocity of the fluid is small and the mechanical action is small, the single corrosion due to the corrosion occurs. On the other hand, when the flow velocity of the fluid is increased, the thinning phenomenon occurs due to both the erosion and the corrosion. The difference between the two is measured by the electrochemical noise method, and the amount of thinning due to erosion is measured.

Next, a method for measuring corrosion of a metal material by the electrochemical noise method is described in Japanese Patent Application Laid-Open No. 9-297117. In FIG. 1, three measurement electrodes of the same material on a metal surface to be measured for corrosion are immersed in a corrosive solution to be measured. A current measuring circuit having substantially zero internal resistance, that is, a so-called non-resistance ammeter 4 is connected between the first electrode 1 and the second electrode 2, and the second electrode 3 and the third electrode 3 are connected.
Between them, an electrometer 5 capable of measuring a signal voltage without affecting the electrode side is connected.

In this state, between the electrode 1 and the electrode 2,
A coupling current corresponding to the degree of progress of corrosion on each electrode surface is generated, and the coupling current is measured by the ammeter 4. The potential difference between the electrodes 2 and 3 is measured by the electrometer 5. FIG. 2 shows changes in current and potential measured by the ammeter 4 and the electrometer 5. From these measurement results, the corrosion rate is calculated by the following equation.

[0012]

(Equation 1)

Here, ΔE is the amount of change in potential, ΔI is the amount of change in current, and R is the electrochemical resistance of corrosion.

[0014]

[Equation 2] Corrosion rate = K × R

Here, K is a coefficient determined by the metal material and the fluid property, and can be obtained by calculating backward from the corrosion loss of the metal test piece or by measurement. In the present invention, the erosion measuring device shown in FIG. 3 was used in the fluid flow shown in FIG. 4 to change the flow velocity of the fluid using the erosion measuring device shown in FIG. 3 utilizing the principle of the above-described corrosion measurement (electrochemical noise method). The change in electrochemical current noise and electrochemical potential noise at that time is measured to measure the amount of thinning due to erosion.

In FIG. 3, reference numerals 1 to 3 denote metal electrodes made of the same material as the inner surface of the equipment or the pipe, and the space between the electrodes is sealed with an insulator 4 '. The electrode 2 is provided with an orifice 6 which forms a narrow portion in the fluid flow direction in order to change the flow velocity of the flowing fluid, and the erosion measuring device 7 has mounting members (flange members) 8 provided on both sides thereof.
Attached to piping or equipment.

FIG. 4 shows a state in which the above-mentioned erosion measuring device is mounted in a pipe flow for discharging steam drain, and a valve 9 is provided.
Of the method of measuring the electrochemical current noise and the electrochemical potential noise when the flow rate of the fluid (steam) in the orifice section 6 is changed by adjusting the valve opening degree of the valve to calculate the amount of wall thinning due to erosion FIG. 5 shows changes in the electrochemical current noise and the electrochemical potential noise. From these data, the erosion thinning amount is calculated by the following equation.

[0018]

[Equation 3] ER = EK * CR

Here, ER is the erosion amount calculated from the thickness of the orifice, EK is the coefficient obtained from the measurement result, and CR is the sum of the corrosion amounts calculated by the corrosion measuring device.

[0020]

According to the present invention, the oxidation phenomenon due to erosion in the apparatus is electrochemically detected and measured, whereby the thickness loss due to erosion can be easily calculated.

[Brief description of the drawings]

FIG. 1 shows the principle of an electrochemical measurement method of corrosion of a metallic material.

FIG. 2 is a diagram showing changes in current and potential.

FIG. 3 is a sectional view of the erosion measuring device of the present invention.

FIG. 4 is a flowchart of an example of the erosion measurement method of the present invention.

FIG. 5 is a diagram showing changes in current noise and potential noise in the erosion measurement method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 electrode 2 electrode 3 electrode 4 ammeter 4 ′ insulator 5 electrometer 6 orifice 7 erosion measuring device 8 mounting member 9 valve

Claims (2)

[Claims] 1. A method according to claim 1, wherein the first to third electrodes having the same material as that of the metal device are provided in the fluid flowing through the metal device to reduce the electrochemical current noise and the electrochemical potential noise when the flow rate of the fluid is changed. A method for measuring erosion, characterized in that each change is measured and the amount of wall thinning due to erosion is calculated by arithmetic processing. 2. A first and a second electrode having the same material as a metal device, a mounting member for mounting the first to third electrodes in a fluid flowing through the metal device, and a mounting member for connecting the first and second electrodes. Electrochemical current noise measuring means for measuring electrochemical current noise between the electrodes; electrochemical potential noise measuring means for measuring electrochemical potential noise between the second electrode and the third electrode; Erosion characterized by comprising means for changing, and means for measuring changes in electrochemical current noise and electrochemical potential noise when the flow rate is changed, and calculating the erosion thinning amount by arithmetic processing. Measuring device.