CN101818816B - Cathodic protection corrosion-proof valve - Google Patents

Abstract

A cathodic protection anti-corrosion valve, the valve body is made with an inlet a and an outlet b communicating with the cavity of the valve body, a gland is arranged on the side of the inlet a on the valve body, and a valve stem that can rotate around its own axis is arranged in the valve body , the valve stem is provided with a butterfly plate for opening/closing the inlet a, a packing gland and packing are arranged between the top of the valve stem and the valve body, and sacrificial anode pieces are respectively arranged on both sides of the butterfly plate. In the present invention, sacrificial anodes are respectively arranged on both sides of the butterfly plate. When the valve is in use, the set sacrificial anodes and the parts to be protected are all in the liquid, the sacrificial anodes become ions and enter the liquid, and the lost electrons are transferred to zero in the valve body. parts to protect it. Through the function of the sacrificial anode, the internal parts of the valve are in a state of cathodic protection, which protects the valve material from the corrosion of the fluid medium, increases the erosion resistance of the valve, improves the sealing performance of the valve, and prolongs the service life of the valve.

Description

Cathodic protection anti-corrosion valve

technical field

The invention relates to a valve used in liquid pipelines, in particular to a corrosion-resistant valve.

Background technique

As one of the main core components of pressure pipelines, valves are an important part of pressure pipelines. They are widely used in petrochemical, gas, metallurgy, electric power and other important industrial facilities and urban lifeline projects. They play an important role in national economic construction and people's production activities. effect. However, various types of liquid pipeline control valves in use now will produce different degrees of corrosion, which will affect the sealing performance. Valve corrosion will cause material waste, increase energy consumption, cause valve leakage, pollute the environment, cause casualties, and threaten safe production. All of the above situations will bring different degrees of economic losses.

At present, in the existing patented technology, the commonly used corrosion-resistant valves mostly fall into the following three categories:

One is to reduce contact with corrosive fluids by improving the valve structure. The Chinese invention patent with the patent number of 95117085.6 discloses a non-leakage and corrosion-resistant controllable valve, which controls the movement of the valve tongue through magnetic force, thereby controlling the opening or closing of the valve, and is not easy to wear; the Chinese utility model patent with the patent number of 90206833.4 , discloses a corrosion-resistant improved valve, the integral valve stem is changed into two parts, the upper valve stem and the lower valve stem, and the rotating thread at the position below the sealing ring is changed to the upper valve stem, and the upper valve stem is located in the sealing ring The above positions are used to improve the corrosion resistance of the valve.

The other is to use new corrosion-resistant materials to improve the corrosion resistance of the valve. The Chinese invention patent with the patent number 01141067.1 discloses a ceramic valve with a new structure. The valve seat and disc are made of ceramic materials. Change the structure and use corrosion-resistant materials to improve the corrosion resistance of the valve; the Chinese invention patent application number 200710000292.9 discloses a high-temperature and corrosion-resistant high-strength graphite-carbon composite valve, the valve stem and valve core are made of carbon-carbon composite material, and the seat is made of graphite for corrosion resistance.

Another type is to add a lining or coating to the inside of the valve to isolate the corrosive fluid. The Chinese utility model patent No. 90201262.2 discloses a cast stone-lined anti-corrosion valve. A cast stone lining is added to the valve to achieve corrosion resistance; the patent No. is The Chinese utility model patent of 97233920.5 discloses a valve with high temperature resistance, erosion resistance and corrosion resistance. A transition layer is firstly arranged on the surface of the valve cover, the inner cavity of the valve body, the closing member and the valve seat, and a ceramic material and an increaser are arranged on the transition layer. Toughener or self-fluxing alloy working lining.

Although the above-mentioned patents have improved the anti-corrosion ability of valves to varying degrees, each of them has limitations, narrow applicability, poor universality, and some valves have poor anti-corrosion effects.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned valves and provide a cathodic protection anti-corrosion valve with simple structure, good corrosion resistance, strong applicability, good versatility and long service life.

The technical solution adopted to solve the above technical problems is: on the valve body, an inlet a and an outlet b communicating with the cavity of the valve body are made; The rotating valve stem is provided with a butterfly plate for switching the inlet a, a packing gland and packing are arranged between the top of the valve stem and the valve body, and sacrificial anode pieces are respectively arranged on both sides of the butterfly plate.

The sacrificial anode slices arranged on one side of the butterfly plate of the present invention are installed on the center of the butterfly plate or evenly distributed on the same or different circles, and the sacrificial anode slices arranged on the other side of the butterfly plate are connected with the sacrificial anode slices on one side of the butterfly plate. The numbers are the same, and they are set at the center of the circle on the other side of the butterfly plate or evenly distributed on the same circle or different circles.

The shape of the sacrificial anode sheet of the present invention is circular or rectangular.

The sacrificial anode sheet of the present invention is a magnesium alloy anode sheet, a zinc alloy anode sheet or an aluminum alloy anode sheet.

In the present invention, sacrificial anode pieces are respectively arranged on both sides of the butterfly plate. When the valve is in use, the set sacrificial anode pieces and the components to be protected are all in the liquid, and the sacrificial anode pieces become ions and enter the liquid, and the lost electrons are transferred to zero in the valve body. parts to protect it. Through the function of the sacrificial anode, the internal parts of the valve are in a state of cathodic protection, which protects the valve material from the corrosion of the fluid medium, increases the erosion resistance of the valve, improves the sealing performance of the valve, and prolongs the service life of the valve.

Description of drawings

Fig. 1 is a schematic structural diagram of Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram of the arrangement of sacrificial anode pieces 10 on the butterfly plate 8 in FIG. 1 .

Fig. 3 is a schematic diagram of the arrangement of the sacrificial anode pieces 10 on the butterfly plate 8 according to the second embodiment of the present invention.

Fig. 4 is a schematic diagram of the arrangement of the sacrificial anode pieces 10 on the butterfly plate 8 according to the third embodiment of the present invention.

Fig. 5 is the fitted polarization curve of No. 20 steel and magnesium alloy anodes in recycled water of sewage reuse at 40°C.

Fig. 6 is the curve of the electrode potential of No. 20 steel test tube changing with time.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to these embodiments.

Example 1

In Fig. 1, the cathodic protection anti-corrosion valve of this embodiment consists of a cap 1, a positioning screw 2, a packing gland 3, a packing 4, a valve body 5, a valve stem 6, a gland 7, a butterfly plate 8, a coupling pin 9, The sacrificial anode sheets 10 are connected.

On the valve body 5, an inlet a and an outlet b communicating with the cavity of the valve body 5 are made, and a side of the inlet a on the valve body 5 is fixedly connected with a gland 7 with a threaded fastening connector, and the gland 7 is connected to the valve body 5 A sealing ring is installed between them, and a valve stem 6 is radially installed inside the valve body 5, the valve stem 6 can rotate around its own axis, and a butterfly plate 8 is fixedly installed on the valve stem 6 with two coupling pins 9, the butterfly plate 8 is a circle Shaped sheet structure, the butterfly plate 8 is located in the cavity of the valve body 5, the butterfly plate 8 is used to open or close the inlet a, and the valve stem 6 is rotated, the butterfly plate 8 can close or open the inlet a along with the rotation. The upper end of the valve stem 6 protrudes out of the valve body 5, and three O-shaped rubber rings are installed between the valve stem 6 and the valve body 5, and the packing 4 is installed between the upper part of the valve stem 6 and the valve body 5, and the valve stem 6 is covered with There is a packing gland 3, and the packing 4 is fixed between the valve body 5 and the valve stem 6 through threaded connection between the packing gland 3 and the valve body 5. The upper end of the valve stem 6 is threadedly connected with a positioning screw 2, and the positioning screw 2 can be adjusted to fix the butterfly plate 8 at the fixed position of the inlet a. The upper end of the valve body 5 is provided with a cap 1 through threaded connection, and a rubber ring is installed between the cap 1 and the valve body 5 .

A sacrificial anode piece 10 is respectively welded at the center positions on both sides of the butterfly plate 8 , and the sacrificial anode piece 10 can also be fixedly connected to the center positions on both sides of the butterfly plate 8 by screw fastening connectors. The sacrificial anode sheet 10 of this embodiment is a magnesium alloy anode sheet, and the shape of the sacrificial anode sheet 10 is circular, and the specific number of the sacrificial anode sheet 10 and the size of the sacrificial anode sheet 10 can be protected parts according to the transported medium and requirements The material and the area in contact with the medium are determined according to the specification design.

Example 2

In this embodiment, four sacrificial anode pieces 10 are welded on both sides of the butterfly plate 8 with the center as the center, and are evenly distributed on the circumference of the same radius, and the sacrificial anode pieces 10 can also be fixedly connected to the butterfly plate by screw fastening connectors. On the circumference of the same radius on both sides of the plate 8, the sacrificial anode sheet 10 on one side of the butterfly plate 8 and the sacrificial anode sheet 10 on the other side may or may not overlap on the circumference of the same radius. The sacrificial anode piece 10 in this embodiment is a magnesium alloy anode piece, and the shape of the sacrificial anode piece 10 is a rectangle. Other components and the coupling relationship of the components are the same as in Embodiment 1.

Example 3

In this embodiment, on both sides of the butterfly plate 8 with the center as the center, four sacrificial anode sheets 10 are evenly distributed on one circumference with different radii, and 8 sacrificial anode sheets 10 are evenly distributed on the other circumference with different radii. The anode sheet 10 can also be fixedly connected to the sacrificial anode sheet 10 on the circumference of the same radius on both sides of the butterfly plate 8 with a threaded fastening connector, and the sacrificial anode sheet 10 on one side of the butterfly plate 8 is connected to the sacrificial anode sheet 10 on the other side. On the circumference of the same radius, they can be coincident or not. The sacrificial anode piece 10 in this embodiment is a magnesium alloy anode piece, and the shape of the sacrificial anode piece 10 is a rectangle. Other components and the coupling relationship of the components are the same as in Embodiment 1.

Example 4

In the above embodiments 1-3, the sacrificial anode pieces 10 provided on both sides of the butterfly plate 8 are zinc alloy anode pieces. Other components and the coupling relationship of the components are the same as in Embodiment 1.

Example 5

In the above embodiments 1-3, the sacrificial anode sheets 10 provided on both sides of the butterfly plate 8 are aluminum alloy anode sheets. Other components and the coupling relationship of the components are the same as in Embodiment 1.

The working principle of the present invention is as follows:

By rotating the valve stem 6, the butterfly plate 8 opens or closes the inlet a to open/close the valve. As shown in Figure 1, the valve is in the closed state, and the butterfly plate 8 closes the inlet a. The fluid medium at the inlet a is separated from the fluid medium at the outlet b through the butterfly plate 8 . The sacrificial anode sheet 10 of the present embodiment is arranged at the central position of the left and right sides of the butterfly plate 8, and at the inlet a side, the sacrificial anode sheet 10 and parts are all in the liquid, and the potential of the sacrificial anode sheet 10 is lower than that of this side. The potential of the valve parts gland 7 and butterfly plate 8, the sacrificial anode becomes ions and enters the liquid, and the lost electrons are transmitted to the gland 7 and butterfly plate 8, so that the gland 7 and butterfly plate 8 are in a state of cathodic protection and are not affected by the fluid medium. Corrosion; Similarly, the valve components on the outlet b side: valve body 5, valve stem 6, butterfly plate 8, and connecting pin 9 are also in a cathodic protection state under the protection of the sacrificial anode piece 10, and are not corroded by the fluid medium . Through the function of sacrificial anode, the internal parts of the valve are in the state of cathodic protection, free from corrosion of the fluid medium, increasing the erosion resistance of the valve, improving the sealing performance of the valve, thereby prolonging the service life of the valve.

Through the cathodic protection technology, the internal parts of the valve are in the state of cathodic protection, and are not corroded by the fluid medium, which increases the erosion resistance of the valve and prolongs the service life of the valve. The installation method of the remaining parts of the present invention is exactly the same as that of the prior art, and has strong applicability and good versatility.

In order to verify the beneficial effects of the present invention, the inventor has carried out a large amount of laboratory research experiments, and various experiments are as follows:

1. Determination of corrosion potential and protection potential

Experimental drugs: commercially available acetone and absolute ethanol (both are analytical alcohols, produced by Xi'an Chemical Reagent Factory), recycled water for sewage reuse.

Experimental equipment: HH-4 digital display constant temperature water bath (Changzhou Guohua Instrument Co., Ltd.), Corrtest electrochemical test system (Huazhong University of Science and Technology), the electrolytic cell is a three-electrode electrochemical test system, and the reference electrode and auxiliary electrode are saturated calomel Electrode, platinum electrode (both produced by Shanghai Russell Technology Co., Ltd.).

Prepare No. 20 steel test piece: polish it with 400#, 800# water sandpaper in turn, lead out the wire by welding wire on the other side, seal this surface and the remaining corners with epoxy resin, wipe with acetone to remove oil and absolute ethanol before the experiment. After watering, put it in a desiccator for use, its specification is Φ16×3mm, and the test area is 2.01cm ² .

Prepare the magnesium alloy anode sample: cut a certain length of magnesium alloy sheet as the sacrificial anode material, measure 2cm from one end as the electrode test area, the exposed area is 1.5532cm ² , seal it with epoxy resin to the liquid level of the test solution during the test Above, to prevent waterline corrosion and affect the test results, after the test area is polished to remove scale, the surface is cleaned with acetone and absolute ethanol to remove oil and water, and placed in a desiccator for use.

Experimental method: Insert the No. 20 steel test piece and the auxiliary electrode into the electrolytic cell, and put the reference electrode into the sleeve salt bridge. The connection process of the salt bridge is as follows: First, the solution to be tested is sucked into the outer tube of the salt bridge through the ear washing ball from the latex tube mouth and filled; 3mL saturated KCl solution is injected into the inner tube of the salt bridge; the reference The electrodes are first inserted into the mouth of the latex tube, and then plugged into the inner casing of the salt bridge and made tight; the solution in the inner hole is prevented from leaking through the porous sand core through negative pressure.

The polarization curve of the No. 20 steel test piece was measured by the potentiodynamic scanning polarization curve measurement test method. Before the experiment, the power was turned on to preheat the instrument for 20 minutes, and the three-electrode system was connected to the corrosion test system. Immerse the test surface of the polished No. 20 steel test piece into 0.5-1cm below the surface of the circulating water of sewage reuse, and place it in a water bath to maintain the temperature at 40°C. After standing for 10 minutes, the dynamic potential scan was started after the No. 20 steel specimen reached a stable self-corrosion potential. Turn on the analog low-pass filter and digital filter in the potentiostat settings, and set the delay time to 20 s. The No. 20 steel test piece was set with an initial potential of -100mV, an end potential of 800mV (both relative to the open circuit potential), and a scan rate of 3mV/s.

Using the potentiodynamic scanning polarization curve measurement test method to measure the polarization curve of the magnesium alloy anode sample is the same as that of the No. 20 steel test piece. The initial potential of the magnesium alloy anode sample is set to -800mV, and the termination potential is 100mV (both relative to the open circuit potential) , the scan rate is 3mV/s.

The curve was fitted with the Cview software of the Corrtest electrochemical test system to obtain the protection potential and protection current density.

Experimental results: The experimental results are shown in Figure 5. Figure 5 shows the fitted polarization curves of No. 20 steel and magnesium alloy anodes in sewage reuse circulating water at 40°C. From the polarization curves of No. 20 steel and magnesium alloy anodes It can be seen that the intersection of the two polarization curves is the minimum protection potential and the minimum protection current, where the minimum protection potential is -1.412V (relative to the saturated calomel electrode), and the minimum protection current density is 2564.2μA/cm ² .

2. Determination of working potential and weight loss

Experimental drugs: commercially available acetone and absolute ethanol (both are analytical alcohols, produced by Xi'an Chemical Reagent Factory), recycled water for sewage reuse.

Experimental instruments: portable Cu/saturated CuSO ₄ reference electrode (Shandong Dongying Kete Anticorrosion Engineering Co., Ltd.), TG328A analytical balance (Shanghai Tianping Instrument Factory), HH S-4B electric heating constant temperature water bath (Beijing Changfeng Instrument Company), new handheld digital multimeter UT33D (Shenzhen Hengkeda Testing Instrument Co., Ltd.).

Prepare the sample: take the processed No. 20 steel half-section pipe sample (the specification is Φ19mm×2mm×50mm) and use chemical methods to derust and clean it, rinse it with distilled water, clean the surface with acetone and absolute ethanol, and remove oil stains and moisture, placed in a desiccator for later use. Solder the lead wire at the hanging hole, bend the magnesium alloy anode and connect it to the treated test tube, make it conduct with the end far away from the hanging hole, and insulate it from the hanging hole end, leaving a 2cm working area in the middle. The rest and the wiring connection points are sealed with epoxy resin.

(1) Test method: Take 4 prepared No. 20 steel test tubes, numbered No. 1, No. 2, and No. 3 No. 20 steel test tubes for soaking, and the other No. 20 steel test tube is used as a blank control sample. No. 20 steel test tubes numbered 1, 2, and 3 were respectively connected to the wires drawn from the Cu/saturated CuSO ₄ reference electrode and a digital multimeter, soaked at a constant temperature of 40°C for 15 days, and recorded the potential value every day. The No. 20 steel test tube and the magnesium alloy anode sample before and after immersion were removed from the corrosion products, weighed after drying, and the corrosion rate was calculated according to the following formula.

$\mathrm{<span\; class="notranslate">\; \&upsi;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; St.</span>}}$

In the formula, υ is the corrosion rate, g/(m ² h) (if it is converted into mm/a, it needs to be multiplied by 8.76/ρ, ρ is the density of the material, the density of iron is 7.85g/cm ³ , W ₀ is Initial weight (g), W ₁ is the weight (g) after cleaning the corrosion products, S is the exposed area of the sample (m ² ), and t is the corrosion time (hours).

The blank control sample was not subjected to the immersion test.

(2) Experimental results

Working potential: The potential of No. 20 steel test tube alone in the sewage circulating water is -0.730V. The obtained No. 20 steel test tube and the Cu/saturated CuSO ₄ reference electrode data are plotted as electrode potential versus time curves, as shown in Figure 6a, Figure 6b, and Figure 6c. Figure 6a is the No. 20 steel test tube electrode numbered 1 The potential change curve with time, Figure 6b is the time-varying curve of the electrode potential of the No. 20 steel test tube numbered 2, and Figure 6c is the time-varying curve of the electrode potential of the No. 20 steel test tube numbered 3. It can be seen from Figure 6 that the potential of No. 20 steel test tube tends to be stable and fluctuates between -1.200 ~ -1.350V (relative to the saturated CuSO ₄ electrode). The working potential is within the normal range, and the protected No. 20 steel test tube can be effectively protected against corrosion. The No. 20 steel test tube is protected by the magnesium alloy anode.

Weight loss measurement: No. 20 steel test tube has a black-gray film layer on the surface, which is easy to remove, and no rust layer appears. The weight loss of the blank test tube, m = 0.00136g, was weighed after treatment, and the corrosion rate of the No. 20 steel test tube was obtained to be 0.0331 mm/a. The experimental results are shown in Table 1.

Table 120 No. Steel Test Tube Weighing Record Form

serial number Mass before immersion m ₀ (g) Mass after immersion m ₁ (g) Weight loss Δm=m ₀ -m ₁ -m' Corrosion rate (mm/a) 1 20.02406 20.00522 0.01748 0.0325 2 20.37845 20.34729 0.01116 0.0311 3 20.53760 20.50270 0.01490 0.0356

It can be seen from Table 1 that the corrosion rate of No. 20 steel test tube is small, and the magnesium alloy anode is effectively protected, but the anode is consumed quickly, and the protection degree Z is 75.11%.

3. Conclusion

(1) From the measurement of corrosion potential and protection potential, it can be known that the minimum protection potential of No. 20 steel is -1.412V and the minimum protection current density is 2564.2μA/cm ² (relative to saturated calomel electrode) when it is protected by magnesium alloy anode.

(2) From the measurement of working potential and weight loss, it can be seen that magnesium alloy is used as sacrificial anode to protect No. 20 steel test tube, and its working potential is between -1.200～-1.350V (relative to saturated CuSO ₄ electrode);

(3) The corrosion rate of No. 20 steel is 0.0331mm/a, and the protection degree is 75.11%. The magnesium alloy anode plays a protective role.

Claims (3)

1. A cathodic protection anti-corrosion valve, on the valve body (5), an inlet (a) and an outlet (b) connected with the valve body (5) cavity are made, and the inlet (a) on the valve body (5)- A gland (7) is arranged on the side, and a valve stem (6) that can rotate around its own axis is arranged inside the valve body (5), and a butterfly plate (8) that switches the inlet (a) is arranged on the valve stem (6) , the two sides of the butterfly plate (8) are respectively provided with sacrificial anode pieces (10), the top of the valve stem (6) and the valve body (5) are provided with a packing gland (3) and packing (4), and the valve stem (6) ) is installed with a set screw (2) through threaded connection, adjust the set screw (2), and the butterfly plate (8) can be fixed at the fixed position of the inlet (a); the upper end of the valve body (5) is installed with a cap through threaded connection (1), a rubber ring is installed between the cap (1) and the valve body (5), and it is characterized in that: the sacrificial anode piece (10) arranged on one side of the butterfly plate (8) is installed at the center of the butterfly plate (8) Or evenly distributed on the same circumference or different circumferences, the number of sacrificial anode pieces (10) on the other side of the butterfly plate (8) is the same as that of the sacrificial anode pieces (10) on one side, and the number of sacrificial anode pieces (10) on the butterfly plate (8) On the other side, the centers of circles are evenly distributed on the same circle or on different circles. 2. The cathodic protection anti-corrosion valve according to claim 1, characterized in that: said sacrificial anode piece (10) is circular or rectangular in shape. 3. The cathodic protection anti-corrosion valve according to claim 1, characterized in that: said sacrificial anode (10) is a magnesium alloy anode, a zinc alloy anode or an aluminum alloy anode. the

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