Electric valve rod thrust evaluation method based on electric power detection

Abstract

The invention relates to the technical field of electric valve operation monitoring, in particular to an electric valve rod thrust evaluation method based on power detection, which comprises the following steps of: 1, measuring a reference curve of the valve rod thrust and the active power of an electric valve actuating mechanism motor along with time change under the condition that the front and back pressure difference of a valve is zero; 2, calculating and recording a reference thrust change rate and a reference power change rate; step 3, when the valve is in a zero pressure difference working condition, measuring a curve A of active power of a motor of the electric valve actuating mechanism along with time change; step 4, when the valve is in a pressure difference working condition, measuring a time-varying curve B of the active power of the motor of the electrically operated valve actuating mechanism; 5, acquiring power change rates of the curve A and the curve B; and 6, calculating to obtain thrust under the zero-pressure-difference working condition and thrust under the pressure-difference working condition. According to the method, normalized remote monitoring of the lubrication state and thrust parameters of the electrically operated valve is achieved, and a traditional operation and maintenance mode depending on periodic field testing is changed fundamentally.

Description

Technical Field

[0001] This invention relates to the field of electric valve operation monitoring technology, specifically to a method for evaluating the stem thrust of an electric valve based on electric power detection. Background Technology

[0002] Electric valves are widely used in nuclear industry systems due to their high performance and ease of control. They are generally used for system loop isolation boundaries, and some critical electric valves are closely related to nuclear safety operations, requiring the ability to quickly and reliably shut down the system in the event of an accident or abnormal operating condition. When an electric valve is working, the transmission components within the electric actuator drive the valve stem and valve disc under the influence of the motor. When the output torque of the actuator reaches the torque switch set value, the switch is triggered, cutting off the motor power. To ensure complete valve closure, sufficient valve stem thrust must be provided to overcome resistances such as packing friction, valve stem axial reaction force, and media pressure differential force.

[0003] To ensure reliable valve closure under accident conditions, thrust verification tests must be conducted on-site to confirm that the thrust meets requirements and to periodically retest for thrust reductions that may be caused by factors such as lubrication deterioration. Current on-site thrust verification tests for valves present the following problems: 1. Existing thrust measurements must be performed directly on the valve body. For valves located within the containment or inaccessible areas, testing can typically only be conducted during reactor shutdowns and major overhauls, resulting in a long uncertainty window between tests; 2. During the interval between two on-site tests, personnel cannot remotely monitor changes in lubrication status, nor can they accurately determine whether a thrust reduction is caused by lubrication degradation based solely on thrust measurement data. Therefore, it is difficult to assess the specific impact of lubrication status on valve closure capability. 3. For safety and ease of operation, traditional verification tests are usually conducted under the condition that the pressure difference across the valve is zero. This does not match the actual working condition where there is a pressure difference between the front and back of the valve during actual operation. The actual pressure difference will continuously exert a force on the valve disc during its movement, causing the valve stem thrust to increase slowly before it sits. As a result, for a fixed torque switch setting, the thrust when the switch is triggered is significantly lower than when there is no pressure difference. Summary of the Invention

[0004] This invention provides a method for evaluating the stem thrust of an electric valve based on electrical power detection, which solves the problems of long testing cycles, inability to monitor state degradation in real time, and limited diagnostic information in traditional valve diagnostics in the prior art.

[0005] The technical solution of the present invention is as follows: This invention proposes a method for evaluating the stem thrust of an electric valve based on electrical power detection. The method includes: Step 1: Under the condition that the pressure difference across the valve is zero, perform an on-site benchmark test on the valve, execute the valve closing operation, and measure the benchmark curves of the valve stem thrust and the active power of the electric valve actuator motor over time. Step 2: Analyze the baseline curves of valve stem thrust and electric valve actuator motor active power change over time, calculate and record the baseline thrust change rate and baseline power change rate; Step 3: When evaluating the valve status in the subsequent process, under the condition of zero differential pressure, measure again the curve A of the change in active power of the electric valve actuator motor over time. Step 4: Under differential pressure conditions, measure curve B of the change in active power of the electric valve actuator motor over time; Step 5: Analyze curves A and B to obtain the power change rates of curves A and B; Step 6: Calculate the thrust under zero pressure differential and pressure differential conditions based on the reference thrust change rate; Step 7: Evaluate the degradation of lubrication conditions of the valve stem thread pair based on curve A; Step 8: Evaluate the thrust reduction due to load based on curve B.

[0006] In some embodiments, step one specifically includes: Step 1.1: Install a thrust sensor on the valve yoke, and install a voltage probe and a current probe on the electric valve actuator. The voltage probe and current probe measure the motor electrical parameters of the electric valve actuator. Step 1.2: Start the valve and perform the closing operation. Measure the valve stem thrust signal and the three-phase voltage and current signals of the motor. Calculate the active power of the motor using the three-phase voltage and current signals to obtain the reference curves of valve stem thrust and active power over time.

[0007] In some embodiments, step two specifically includes: identifying the valve disc seating start point A1 and the control switch tripping point B1 on the reference curve of valve stem thrust changing with time, calculating the time interval t1 between the two points and the thrust change F1 during the time interval; determining the power change P1 between the valve disc seating start point A1 and the control switch tripping point B1 on the reference curve of active power changing with time, with the reference thrust change rate being F1 / t1 and the reference power change rate being P1 / t1.

[0008] In some embodiments, step three specifically includes: ensuring that the valve is under zero differential pressure conditions, conducting valve testing in the electrical workshop, connecting voltage and current probes to the motor control center of the valve's electric valve actuator, collecting electrical signals during the valve closing process, and calculating the curve of the motor's active power changing over time.

[0009] In some embodiments, step four specifically includes: the valve being subjected to actual working pressure difference, valve testing being conducted in the electrical workshop, voltage and current probes being connected to the motor control center of the valve's electric valve actuator, collecting electrical signals during the valve closing process, and calculating the curve of the motor's active power changing over time.

[0010] In some embodiments, step five specifically includes: identifying the valve disc seating start point A2 and the control switch tripping point B2 on curve A; measuring the time interval t2 between the two points on curve A and the control switch tripping point B2, and the power change P2 during this time interval; and calculating the power change rate of curve A as P2 / t2; identifying the valve disc seating start point A3 and the control switch tripping point B3 on curve B; measuring the time interval t3 between the two points on curve B and the control switch tripping point B3, and the power change P3 during this time interval; and calculating the power change rate of curve B as P3 / t3.

[0011] In some embodiments, step six specifically includes: multiplying the reference thrust change rate determined in step 2 by the time interval t2 between the valve disc seating start point A2 and the control switch trip point B2 on curve A to obtain the thrust under zero differential pressure conditions; and multiplying the reference thrust change rate determined in step 2 by the time interval t3 between the valve disc seating start point A3 and the control switch trip point B3 on curve B to obtain the thrust under differential pressure conditions.

[0012] In some embodiments, step seven specifically includes: calculating the ratio of the power change rate in the benchmark test curve to the power change rate P2 / t2 of curve A, the ratio being used to evaluate the deterioration of the lubrication conditions of the valve stem thread pair.

[0013] In some embodiments, step seven specifically includes: evaluating the thrust reduction caused by the load by calculating the ratio of the power change rate of curve A to the power change rate of curve B.

[0014] The implementation of this invention has the following beneficial effects: 1. This invention proposes a method for evaluating the stem thrust of an electric valve based on electrical power detection. This method, by connecting voltage and current probes to the motor control center, collects electrical signals from the valve, enabling routine remote monitoring of the lubrication status and thrust parameters of the electric valve. This fundamentally changes the traditional operation and maintenance model that relies on periodic on-site testing. Testing personnel no longer need to visit the valve body multiple times for data collection, significantly reducing radiation dose and greatly improving the efficiency of electric valve status detection.

[0015] 2. This invention proposes a method for evaluating the thrust of an electric valve stem based on electric power detection. By measuring differential pressure conditions and zero differential pressure conditions, this method can effectively separate and quantify the two different mechanisms that lead to a decrease in thrust: lubrication degradation and differential pressure effects. This provides an accurate basis for implementing targeted maintenance and avoids misjudgment and ineffective maintenance.

[0016] 3. This invention proposes a method for evaluating the thrust of an electric valve stem based on electric power detection. By deeply analyzing the motor power curve and combining it with the initial thrust benchmark, this invention can remotely approximate the thrust of the electric valve without the need for subsequent on-site thrust testing, greatly expanding the dimensions and practicality of condition assessment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an electric valve structure according to an embodiment of the present invention, which provides a method for evaluating the stem thrust of an electric valve based on electric power detection. Figure 2 This is a graph showing the change of valve stem thrust over time during the closing process of an electric valve, based on an electric power detection-based method for evaluating the valve stem thrust of an electric valve, as proposed in an embodiment of the present invention. Figure 3 The curve showing the change of motor power over time during the closing process of the electric actuator in an electric valve stem thrust evaluation method based on electric power detection, as proposed in an embodiment of the present invention. Explanation of reference numerals in the attached diagram: 1. Valve body; 2. Valve seat; 3. Valve disc; 4. Valve stem; 5. Gasket; 6. Packing; 7. Valve cover; 8. Valve stem nut; 9. Electric actuator; 10. Thrust measuring point; 11. Current measuring point; 12. Voltage measuring point. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figures 1 to 3As shown, this invention proposes a method for evaluating the stem thrust of an electric valve based on electrical power detection. This method is applied to an electric valve, which includes a valve body, valve seat, valve disc, valve stem, gasket, packing, valve cover, valve stem nut, and electric actuator. The valve body is the main body of the valve, serving as the fluid passage and supporting all internal components. The valve seat is fixed within the valve body's flow channel, acting as the valve's sealing element. The valve disc is mounted on the valve seat, and its contact or separation with the seat controls the valve's opening and closing, thus cutting off or allowing media flow. The valve stem is the core transmission component of the electric valve, equipped with a thrust measuring point. Its upper end connects to the electric actuator, and its lower end connects to the valve disc. Driven by the valve stem, it moves up and down, contacting or separating from the valve seat. Its core function is to convert the rotational motion generated by the drive mechanism into linear motion, driving the valve disc to move up and down, thereby opening and closing the valve. The valve stem has a valve yoke, which provides stable support for the valve stem, ensuring its linear motion. The valve stem nut is connected to the output shaft and valve stem of the electric actuator. The electric actuator connects to current and voltage measuring points. During benchmark testing of this method, wiring is led from the electric actuator to connect the current and voltage probes. During remote testing of this method, wiring is led from the motor control center to connect the current and voltage probes. When the electric actuator drives the valve stem nut to rotate, the valve stem, which is threaded to it, will perform a vertical linear motion. The valve cover is located at the top of the valve body, and the packing is located inside the valve cover, tightly wrapping the valve stem to achieve a dynamic seal.

[0020] This invention proposes a method for evaluating the stem thrust of an electric valve based on electrical power detection. The method includes: Step 1: After confirming that the valve is in good condition (e.g., after new lubrication is completed), Step 2: Under the condition that the pressure difference across the valve is zero, perform a field benchmark test on the valve, perform the valve closing operation, and measure the curves of valve stem thrust and the active power of the electric valve actuator motor changing over time. Step 1.1: Install a thrust sensor on the valve yoke, and install a voltage probe and a current probe on the electric valve actuator. The voltage probe and current probe measure the motor electrical parameters of the electric valve actuator. Step 1.2: Start the valve and perform the closing operation. Synchronously and at high speed, acquire the valve stem thrust signal and the three-phase voltage and current signals of the motor throughout the closing process. Calculate the active power of the motor using the three-phase voltage and current signals to obtain a set of synchronous "thrust-time" curves and "power-time" curves, which will serve as the benchmark for all subsequent analyses of the valve.

[0021] Step 2: Analyze the two baseline curves obtained in Step 1. Identify the valve seat starting point A1 and the control switch tripping point B1 on the "thrust-time" curve, and calculate the time interval t1 between the two points and the thrust change F1 during this time interval; on the corresponding "power-time" curve, determine the power change P1 during the same time interval; based on the above analysis, calculate and record two core baseline parameters: the baseline thrust change rate (i.e., the average change in thrust per unit time from seating to tripping) F1 / t1 and the baseline power change rate (i.e., the average change in power per unit time during the same period) P1 / t1. Figure 2 and Figure 3 As shown, A1, A2, and A3 are the starting points for the electric valve to sit, and B1, B2, and B3 are the tripping points for the control switch.

[0022] Step 3: When evaluating the valve status later, under the condition of zero differential pressure, measure the curve A of the change of active power of the electric valve actuator motor over time again; at any subsequent time point, when it is necessary to evaluate the valve status, conduct tests at the electrical plant to ensure that the valve is under the condition of zero differential pressure. By using voltage and current probes connected to the motor control center, collect electrical signals during the valve closing process and generate a "power-time" curve.

[0023] Step 4: With the valve operating under differential pressure, measure curve B, which shows the change in active power of the electric valve actuator motor over time. To further evaluate the valve's performance under actual operating conditions, a differential pressure test can be conducted at the electrical control room when the system allows and the time is close to that of Step 3. During the test at the electrical control room, the valve must withstand the actual operating differential pressure. Voltage and current probes connected to the motor control center are used to collect electrical signals during the valve closing process, obtaining another "power-time" curve under actual differential pressure conditions. This curve is used to analyze the impact of differential pressure on the valve stem thrust.

[0024] Step 5: Analyze curves A and B to obtain the power change rates of curves A and B; identify the valve seat starting points A2 and A3 and the control switch tripping points B2 and B3 on curves A and B; accurately measure the time intervals t2 and t3 between these two points on the two curves, as well as the power changes P2 and P3 within the corresponding time intervals; and calculate the power change rates P2 / t2 and P3 / t3 under zero differential pressure conditions and under differential pressure conditions, respectively.

[0025] Step 6: Calculate the thrust under zero differential pressure and differential pressure conditions based on the reference thrust change rate. Multiply the reference thrust change rate F1 / t1 determined in Step 2 by the time intervals t2 and t3 measured from the remote zero differential pressure or differential pressure curve, respectively, to obtain an estimated value of the thrust that the valve can generate from the start of seating to tripping under the current condition. This value is the thrust under the current condition. Specifically: Multiply the reference thrust change rate determined in Step 2 by the time interval t2 between the valve seating start point A2 and the control switch tripping point B2 on curve A to obtain the thrust under zero differential pressure conditions; multiply the reference thrust change rate determined in Step 2 by the time interval t3 between the valve seating start point A3 and the control switch tripping point B3 on curve B to obtain the thrust under differential pressure conditions.

[0026] Step 7: By calculating the ratio of the power change rate P1 / t1 in the benchmark test curve to the power change rate P2 / t2 in the remote test curve A under zero differential pressure conditions, the deterioration of the lubrication conditions of the valve stem thread pair can be assessed. Since the lubrication conditions of the electric valve stem deteriorate, more power is required to establish the same thrust under the same zero differential pressure conditions. This means the ratio of power change to thrust change increases during the time interval from the starting point of the valve to the control switch. Dividing both the initial and final values ​​by the change time gives the ratio of the power change rate to the thrust change rate. Comparing the ratios of the two power change rates to the thrust change rates reflects the lubrication degradation during the two tests. Furthermore, because the thrust change rate is determined by the mechanical structure of the electric valve and its value is essentially constant, the ratio of the two power change rates reflects the lubrication degradation.

[0027] Step 8: By calculating the ratio of the power change rate P2 / t2 under zero differential pressure conditions to the power change rate P3 / t3 under differential pressure conditions (curve B), the thrust reduction caused by the load can be assessed, thus decomposing the thrust change into two parts: lubrication degradation and the effect of differential pressure. Since the intervals between the two tests are similar, the lubrication conditions can be considered essentially unchanged. The differential pressure condition requires more power to establish the same thrust; therefore, the ratio of the two power change rates reflects the effect of differential pressure.

[0028] Overall, this invention, based on the remote acquisition and analysis of electrical signals from electric valves, enables effective assessment of the critical operating status of electric valves. It provides timely and objective status data for power plant operation and maintenance personnel, helping to rationally arrange maintenance cycles, reduce operation and maintenance costs, and minimize unnecessary downtime while ensuring the safe and reliable operation of the system.

[0029] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for evaluating the stem thrust of an electric valve based on electrical power detection, characterized in that, The method includes: Step 1: Under the condition that the pressure difference across the valve is zero, perform an on-site benchmark test on the valve, execute the valve closing operation, and measure the benchmark curves of the valve stem thrust and the active power of the electric valve actuator motor over time. Step 2: Analyze the baseline curves of valve stem thrust and electric valve actuator motor active power change over time, calculate and record the baseline thrust change rate and baseline power change rate; Step 3: When evaluating the valve status in the subsequent process, under the condition of zero differential pressure, measure again the curve A of the change in active power of the electric valve actuator motor over time. Step 4: Under differential pressure conditions, measure curve B of the change in active power of the electric valve actuator motor over time; Step 5: Analyze curves A and B to obtain the power change rates of curves A and B; Step 6: Calculate the thrust under zero pressure differential and pressure differential conditions based on the reference thrust change rate; Step 7: Evaluate the degradation of lubrication conditions of the valve stem thread pair based on curve A; Step 8: Evaluate the thrust reduction due to load based on curve B.

2. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 1, characterized in that, Step one specifically includes: Step 1.1: Install a thrust sensor on the valve yoke, and install a voltage probe and a current probe on the electric valve actuator. The voltage probe and current probe measure the motor electrical parameters of the electric valve actuator. Step 1.2: Start the valve and perform the closing operation. Measure the valve stem thrust signal and the three-phase voltage and current signals of the motor. Calculate the active power of the motor using the three-phase voltage and current signals to obtain the reference curves of valve stem thrust and active power over time.

3. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 2, characterized in that, Step two specifically includes: identifying the valve disc seating start point A1 and the control switch tripping point B1 on the reference curve of valve stem thrust changing with time, calculating the time interval t1 between the two points and the thrust change F1 during this time interval; determining the power change P1 between the valve disc seating start point A1 and the control switch tripping point B1 on the reference curve of active power changing with time, with the reference thrust change rate being F1 / t1 and the reference power change rate being P1 / t1.

4. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 3, characterized in that, Step three specifically includes: ensuring the valve is in a zero differential pressure condition, conducting valve testing in the electrical workshop, connecting voltage and current probes to the motor control center of the valve's electric valve actuator, collecting electrical signals during the valve closing process, and calculating the curve of the motor's active power changing over time.

5. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 4, characterized in that, Step four specifically includes: the valve being subjected to actual working pressure difference, valve testing being conducted in the electrical workshop, voltage and current probes being connected to the motor control center of the valve's electric valve actuator to collect electrical signals during the valve closing process, and the curve of the motor's active power changing over time being calculated.

6. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 5, characterized in that, Step five specifically includes: identifying the valve seat starting point A2 and the control switch tripping point B2 on curve A; measuring the time interval t2 between the two points on curve A; measuring the power change P2 within the time interval t2; and calculating the power change rate of curve A as P2 / t2. Similarly, identifying the valve seat starting point A3 and the control switch tripping point B3 on curve B; measuring the time interval t3 between the two points on curve B; measuring the power change P3 within the time interval t3; and calculating the power change rate of curve B as P3 / t3.

7. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 6, characterized in that, Step six specifically includes: multiplying the reference thrust change rate determined in step 2 by the time interval t2 between the valve disc seating start point A2 and the control switch trip point B2 on curve A to obtain the thrust under zero differential pressure conditions; and multiplying the reference thrust change rate determined in step 2 by the time interval t3 between the valve disc seating start point A3 and the control switch trip point B3 on curve B to obtain the thrust under differential pressure conditions.

8. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 7, characterized in that, Step seven specifically includes: calculating the ratio of the power change rate in the benchmark test curve to the power change rate P2 / t2 of curve A, the ratio being used to evaluate the degradation of lubrication conditions of the valve stem thread pair.

9. The method for evaluating the stem thrust of an electric valve based on electrical power detection according to claim 8, characterized in that, Step seven specifically includes: evaluating the thrust reduction caused by the load by calculating the ratio of the power change rate of curve A to the power change rate of curve B.

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