WO1993019317A1

WO1993019317A1 - Process and device for testing the operability of a valve or fitting driven a motor element

Info

Publication number: WO1993019317A1
Application number: PCT/EP1993/000641
Authority: WO
Inventors: Klaus Fischer
Original assignee: Elektro-Mechanik Gmbh
Priority date: 1992-03-18
Filing date: 1993-03-18
Publication date: 1993-09-30
Also published as: DE4224902A1

Abstract

In a valve or fitting with a spindle which is adjustable by a motor element via a torque, the operability of the valve or fitting is tested by applying an additional test force. The coefficients of friction of the valve or fitting are found from the different torque or driving force required at different test forces for driving the spindle.

Description

Method and device for checking the functionality of a valve driven by an actuator

The invention relates to a method and a device for checking the functionality of a valve, in particular for determining the coefficient of friction and the forces that occur on a valve stem; which is adjustable by an actuator by means of a torque.

In nuclear power plants, fittings such as valves, slides and flaps are required to shut off lines, the fitting having to work reliably for safety reasons when required. When converting the drive torque into the spindle longitudinal force required to actuate, for example, the valve plate of a valve, the state of the stuffing box, which surrounds and seals the spindle, the state of the spindle nut to which the drive torque acts, and the remote actuator efficiency for valves with remote control play a significant role Role.

If the stuffing box is clamped too tightly, such a great frictional force can arise that the valve works without malfunction during recurring tests, but under certain circumstances sufficient actuating force is not available when the line pressure is high. Spindle nut friction is also of great importance. If the coefficient of friction of the spindle nut is too low, the valve can be damaged by the torque increase occurring when the torque switch of the actuator motor responds when it switches off when the set torque is reached. If the friction coefficients of the spindle nut and the stuffing box are too high, there is a risk that the valve will not work reliably if required.

The invention is based on the object of proposing a method by means of which the functionality of a valve can be checked and in particular the coefficients of friction can be determined, and an apparatus for carrying out the method.

This object is achieved according to the invention by a method in which a test force is applied to the spindle during the adjustment movement of the valve of the valve, the different torque or the different drive power being used for the different test forces for the Drive the spindle is required, the coefficient of friction of the valve or the force actually acting on the spindle are determined.

Depending on the results of such a test of a valve, remedial measures can be carried out on the valve in good time so that there is no longer any risk of malfunction in the event of a request.

Advantageous embodiments of the invention are specified in the claims and in the description below.

For example, embodiments of the invention are explained in more detail below with reference to the drawing. Show it

Fig. 1 shows schematically an armature with an inventive

Measuring device, Fig. 2 shows the course of drive torque, test force and

3 shows another embodiment of the measuring device, FIG. 4 shows a diagram of drive power and test force, FIG. 5 shows a further representation of the test force in connection with the reserve force, and Fig. 6 shows another embodiment of the measuring device.

In Fig. 1, a valve 2 arranged in a pipeline 1 is shown schematically as a fitting, the spindle 5 of which can be adjusted by an actuator 3 into the open or closed position shown. The spindle 5 of this fitting is provided with a thread with which a spindle nut 4 is engaged. The spindle nut 4 is set in rotation by an electric motor (not shown) of the actuator 3 via a gear, so that the spindle 5 is adjusted in the axial direction. A stuffing box 6, in which the spindle 5 is displaceable, seals the pipeline 1 from the outside area. This structure of a valve is known per se.

According to the invention, a measuring device 7 is attached to such a fitting, which in the exemplary embodiment shown comprises a piston 8 attached to the free end of the spindle 5, which can be displaced in a cylinder 9 filled with hydraulic fluid, which at a fixed point 10 has a force measurement ¬ device 11 is supported. A connecting line 12 is provided between the upper and lower cylinder spaces 13 and 14, in which a throttle valve 15 is arranged, the throttle cross section of which can be changed by an adjusting device 20.

At 16, a signal output of the force measuring device 11 is indicated, which is connected to a display device 17, for example a storage oscilloscope. The signal output 16 is also expediently connected to a data processing device 18 which is connected to a memory 21 and the adjusting device 20. The actuator 3 is connected to a device 22 for measuring the torque exerted by the actuator, which is also connected to a memory 23.

If the valve 2 by a torque acting on the spindle nut 4 of the actuator .; 3 is opened, the Piston 8 hydraulic fluid from the cylinder space 13 via the throttle 15 in the line 12 into the cylinder space 14. The cylinder 9 is pressed against the fixed point 10 with a certain pressure force, depending on the degree of opening of the throttle 15. This pressure force with which the cylinder 9 is pressed against the fixed point 10 can be set via the throttle 15 and the force measuring device 11 can be measured. This compressive force corresponds to a test force P which acts coaxially on the spindle 5.

During the measuring process, if the operating pressure prevails in line 1, preferably in the vicinity of the open position of the valve from a point in time _x to a point in time t _2, on the one hand, the torque M exerted by the actuator 3 as a measuring function M = M (t) from the device 22 measured and stored in the memory 23, while on the other hand the test force P is displayed as a measuring function P = P (t) on the display device 17 via the signal output 16 and is stored in the memory 21 via the data processing device 18. During the adjustment movement of the piston 8 in the cylinder 9, a change in the throttle opening in the throttle 15 changes the test force P in accordance with a predetermined measuring function P = P (t), which can be read from a file 19 into the data processing device 18, which adjusts the throttle 15 in a corresponding manner via the adjusting device 20. Such a predetermined measuring function can be compared with the measuring function P = P (t) during the measuring process. If this measurement function deviates from the specified test force characteristic beyond a specified tolerance, the measurement function P = P (t) can be corrected by the data processing device 18 via the adjusting device 20 and the throttle 15.

Since the torque M and the test force P are known, with an overpressure = 0 in the pipeline 1, the spindle coefficient C can

M _x

Spindle force F _sp = - = R + P _x (1) and

C M,

= R + P, (2)

about

M ₂ - M ₁

C = (4)

P ₂ - P,

can be determined, where R is the bushing force required to overcome the friction of the stuffing box.

Out

2 • C • n • d _F • cosγ ^{~ d} _F • h • cosγ μ = (5) π • d _F ² + 2 - C • h

the coefficient of friction μ of the spindle nut 4 can be determined, where d _{F is} the flank diameter of the thread, h is the thread pitch and cosγ corresponds to half the flank angle of the thread.

2 schematically shows the course of the test force P and the torque M over time t and the friction coefficient μ of the spindle nut 4 and the stuffing box friction force R determined in this way. While the stuffing box friction at different test forces P is essentially constant results, the spindle nut friction changes depending on the test force. It depends on the surface load and the lubrication status of the thread.

To determine the magnitude of the coefficient of friction of the spindle nut, it may be sufficient if two in succession different test forces are created, or the required torque is measured with a certain test force and without test force.

The evaluation can take place in the data processing device 18 on the basis of the measured values stored in the memories 21 and 23 or on the basis of the stored measured values in a separate data processing device.

When determining the coefficient of friction of the spindle nut, the specified boundary conditions, such as pressure in line 1 and weight of spindle 5, are taken into account for the various test forces P.

According to an expedient embodiment, the change in the test force P during an adjustment stroke of the valve can be measured in short time intervals, whereupon the individual measurement signals are stored and / or displayed as a control function. This makes it possible to achieve a reliable detection and storage of the measured values forming the control function within the predetermined measuring time despite a limited data processing speed of the data processing device 18.

Instead of a piston 8 with a cylinder 9, a spring can be arranged between the spindle end and the force measuring device 11. During the adjustment movement of the spindle 5 by the actuator 3, a test force P results as a function of the path or the time, which can be measured via the signal output 16 of the force measuring device 11, in accordance with the characteristic curve of the spring or a corresponding spring assembly.

A plurality of cylinders 9 or a plurality of spring assemblies can be arranged around the spindle between the stuffing box and the actuator, each cylinder or spring assembly being assigned a force measuring device. In this embodiment, the cylinders or springs are arranged around the spindle so that the resulting test force P lies on the spindle axis. The spring packs can be exchangeable to change the test force. The range of spring characteristics can be changed by a spring adjustment device.

Fig. 3 shows another embodiment of the measuring device, wherein the cylinder 9 is supported directly at the fixed point 10 and a pressure gauge 24 is provided on both sides of the throttle 15. The two pressure gauges are connected to the data processing device 18, so that the test force P can be determined via the pressure determined in the two cylinder spaces 13 and 14.

FIG. 3 shows a slide 2 with a slide plate 25 immersed in the pipeline 1 instead of the valve disk shown in FIG. 1. Furthermore, a spring key is shown at 26, by means of which the spindle nut 4 is connected to the actuator 3 and which can be removed to release this connection.

At 27, the electric drive motor of the actuator 3 is schematically indicated, which is connected to a device 28 for measuring the power of the drive motor. This device 28 is connected to a data processing device 29. A switch for switching off the power supply of the drive motor 27 is shown at 30. Between the drive motor 27 and the actuator 3, a torque switch 31 is provided, which is set to a specific torque value, upon reaching which the drive motor 27 is switched off via the switch 30.

3 instead of the torque M, the drive power L = L (t) of the drive motor 27 is measured as a function of time at 28. While the torque is being measured on the valve, the drive power can be far removed from the Valve can be measured in the control room. To measure the stuffing box friction force, the drive power L _{0 of} the drive motor is first measured without connection to the spindle nut 4 by removing the spring key 26, that is to say the idling power. Then the drive power ^ is measured when the actuator 3 is connected by the spring key 26 to the spindle nut 4 and no test force is applied. The drive power L _{2 is then} measured when a test force P ₂ loads the spindle, which is in the order of the stuffing box friction force. In this area of little change in the test force, the spindle nut friction coefficient can be regarded as constant.

4 shows at L ₀ the drive power of the drive motor without spindle nut 4, which runs constantly over time, and at ^ the drive power ^ with spindle nut 4 when the spindle nut 4 is connected to the actuator 3 and the test force P _x = 0 . At t _2, a test load P attacks _2, which increases the drive power to _L2.

If there is no pressure in the pipeline 1 and the flow medium is at rest, the difference L ^ - L _{0 is} a measure of the stuffing box friction force in the axial direction of the spindle. In order to be able to convert this performance value L- _L -L ₀ into the stuffing box friction force, the test force P ₂ is applied in such a way that a performance increase from L _x to L ₂ equals ^ - L ₀ . The increase in performance from _L to L ₂ is proportional to the increase in test force from P _x to P ₂ . If the idle power is subtracted, the power value L = L _{j ^} + (L _{j ^} - L ₀ ) corresponds to a test force P _x that corresponds to the gland friction force sought, as shown in FIG. 4. The spindle nut efficiency is not taken into account here, since it is the same for L _x and L ₂ . The total longitudinal force acting on the spindle is composed of the stuffing box friction force and the test force, the stuffing box friction force being determined by a value of the drive power which is required to overcome the stuffing box friction force. This performance value is expressed in the form of a corresponding test force. After determining the stuffing box friction force, the friction coefficient μ of the spindle nut 4 can be determined by equations 1 and 5 with the aid of the switch-off torque of the torque switch 31 and the associated test force P.

5 explains how safety-relevant fittings can be checked, whether they are correctly designed when required. The actuating force reserve F _st running parallel to the time axis t is the force available at point 32 on the lower edge of the stuffing box 6. The reserve force is essentially equal to the test force P that occurs when the torque switch switches off at a line pressure of 0 and a stationary line medium. The actuating force reseve F _st is obtained by setting the torque switch 31, which opens the switch 30 for the power supply of the drive motor 27 when the maximum permissible torque occurs, to the maximum permissible torque, which is the weakest at the one known from the strength calculation Link of the drive chain may attack. A torque switch set in this way prevents the functionality of the valve from being jeopardized during recurring tests if, for example, a travel limit switch (not shown), which is usually connected upstream of the torque switch 31 and fails to switch off the motor when the valve reaches a certain stroke position.

By this measure it can be achieved that fittings which are important in terms of safety technology and are also already in operation are not overloaded with regard to their strength.

If limit switch failure is also to be investigated, a solenoid valve 33 arranged in line with the throttle valve 15 in line 12 can be provided to simulate the end stop of the valve or to simulate a stroke limitation, by means of which line 12 can be shut off. so that the piston 8 can no longer displace hydraulic fluid through the line 12 and is held in position by a stop. In this case, the set by the The maximum possible torque, which is decisive for the strength and acts on the spindle, is measured via the pressure gauge 24 or the force measuring device 11.

3, the coefficient of friction of the slide plate 25 of the slide 2 can be determined if there is a known pressure difference Δp on both sides of the slide plate 25 in the pipeline 1. For this purpose, the measuring functions of the actuating force reserve F _εt , the test force P (t) and the differential pressure Δp (t) are used.

The difference between the reserve force F _εt and the test force P at a time t _x about 5 to 10% before the end of the stroke when the torque switch 31 responds is the frictional force in the longitudinal direction of the spindle on the slide plate 25 at the existing differential pressure Δp ( t _x ). Taking into account the boundary conditions of the accident, this frictional force is a measure of the functionality of the valve when required.

The plate friction results from

F _εt - P (t _x ) - F _AÜF = plate _{friction force} F _p = d _D ² a / 4 • Δp (t _x ) • μ _plate

where d _{D is} the sealing diameter of the sealing plate and

^F _ΛUF = ^ Spi _n de _l ² * ^π / ⁴ * ^p S, i.e. the pressure force that acts on the spindle in the opening direction due to the line pressure PS.

6 schematically shows a further embodiment of the measuring device for a fitting, in which a valve flap, not shown, is slowly pivoted by the rotating spindle. A lever 35 is attached to the spindle 5 and acts on the piston 8 with its free end. Here, the torque M occurring on the spindle 5 can be determined from the test force P times the length of the lever 35. The test force can be measured as in Fig. 1 by a force measuring device or as in Fig. 3 by the pressure in the cylinder chambers. In this measuring device according to FIG. 6, the test force is increased until the torque switch 31 responds. As a result, the torque actually occurring on the valve spindle can be measured, regardless of the efficiency of a gearbox of the actuator 3.

Instead of the piston 8 with the cylinder 9, a spring with a force measuring device 11 can also be provided for applying a test force.

Claims

Expectations

1. A method for testing the functionality of a valve with a spindle that is adjustable by an actuator by means of a torque, characterized in that an additional test force is applied to the spindle, and that from the different torque or the different drive power, the or The friction coefficients of the valve are determined which are required for driving the spindle with different test forces.

2. The method according to claim 1, characterized in that the test force is changed continuously or step by step and the required drive torque or the required drive power is recorded continuously or stepwise.

3. The method according to claim 1, characterized in that the test force is increased until the torque switch of the valve switches off, and the test force occurring is measured.

4. The method according to claim 1, characterized in that the test force is applied coaxially to the spindle axis.

5. Ver ears according to claim 1, characterized in that the test raft across a lever transverse to the spindle longitudinal axis is applied as torque.

6. Device for performing the method according to claim

1, characterized in that a device (9; 35) is provided on the spindle (5) of the valve for exerting a variable test force on the spindle, and in that a device for measuring the test force and a

Device for measuring the drive power or the torque required for the spindle movement is provided.

7. The device according to claim 6, characterized in that the spindle is connected to at least one piston (8) which is displaceable in a cylinder filled with hydraulic fluid (9), the cylinder chambers on both sides of the piston via a line ( 12) are connected to a throttle (15), and that the cylinder (9) is supported at a fixed point (10).

8. The device according to claim 7, characterized in that a force measuring device (11) is provided between the cylinder (9) and fixed point (10).

9. The device according to claim 7, characterized in that pressure gauges (24) on the line (12) are provided for determining the test force on the pressure in the cylinder.

10. The device according to claim 6, characterized in that between the spindle (5) and a fixed point (10) at least one spring is provided, which is supported via a force measuring device at the fixed point (10).