JP7593882B2 - Valve maintenance support device and method - Google Patents

Description

The present invention relates to technology that supports maintenance work, and in particular to a valve maintenance support device and method that supports maintenance work for valves equipped with gland packing.

Conventionally, valves used in petrochemical plants and the like (for example, the control valve in FIG. 7) require particular attention to safety, and therefore undergo regular maintenance. The valve 100 shown in FIG. 7 comprises a valve body 101, a positioner 102, and an actuator 103. The actuator 103 moves the valve stem 104 up and down in response to the air output pressure Po supplied from the positioner 102 to adjust the valve opening (the gap between the valve body 105 and the seat ring 106). In other words, it adjusts the flow of the fluid.

The positioner 102 detects the lift position of the valve shaft 104, i.e., the actual opening of the valve, from the rotational angle position of a feedback lever 107 connected to the valve shaft 104, and supplies an air output pressure Po to the actuator 103 according to the difference between the detected actual opening and the set opening.
In the gland portion 108, which slidably holds the valve shaft 104, a gland packing 109 is provided in the gap between the inner wall of the bonnet 111 and the valve shaft 104 to prevent fluid in the valve box 110 from leaking from the gap between the valve shaft 104 and the bonnet 111 provided on the upper part of the valve box 110.

In order to improve the efficiency of valve maintenance work in a plant where a valve 100 like that shown in Figure 7 is installed, a technology has been proposed for determining the hunting state of the valve (see Patent Document 1).

The valve maintenance support device disclosed in Patent Document 1 calculates the accumulated value of the amount of fluctuation in the opening command value to the valve during a predetermined time TX as accumulated fluctuation value A, and the accumulated value of the amount of fluctuation in the actual opening value of the valve during the predetermined time TX as accumulated sliding value B, calculates the difference between accumulated fluctuation value A and accumulated sliding value B as a judgment index, and judges that the valve is in a hunting state when the judgment index exceeds a threshold value. Furthermore, when the valve maintenance support device disclosed in Patent Document 1 judges that the valve is in a hunting state, it corrects the control parameters (PID parameters) of the control device that controls the opening of the valve to the side that makes hunting less likely to occur. By automatically correcting the PID parameters, the hunting state can be eliminated.

The technology disclosed in Patent Document 1 assumes cases where the PID parameters are inappropriately set due to incorrect adjustment of the PID parameters or changes in the valve characteristics. However, since valve hunting is not necessarily caused only by inappropriate PID parameter settings, the technology disclosed in Patent Document 1 may not be able to eliminate valve hunting.

Many valves are used in petrochemical plants and the like. For example, in the example of Figure 8, valves 100-A and 100-M are arranged in flow path 114-1, and valve 100-C is arranged in flow path 114-3. 115-A, 115-C, and 115-M are flow meters, 116 is a tank, and 117 is a pressure transmitter. In plants where many valves are used like this, further improvements in the efficiency of maintenance work are required.

JP 2015-114942 A

The present invention has been made to solve the above problems, and aims to provide a valve maintenance support device and method that can deal with valve hunting that is not caused by inappropriate settings of control parameters and can improve the work efficiency of valve maintenance.

The valve maintenance support device of the present invention is characterized by comprising: an opening command value storage unit configured to store data on the opening command value given to the valve in association with the ID of the valve that sent the data; an opening measurement value storage unit configured to store data on the actual opening value of the valve in association with the ID of the valve that sent the data; a steady-state data extraction unit configured to search for data on the steady-state opening command value that continuously indicates a substantially constant value for the same valve among the opening command values stored in the opening command value storage unit, and extract as diagnostic data the actual opening value of the valve in which the given opening command value has become the steady state and the actual opening value in the time period corresponding to the steady-state opening command value; a hunting determination unit configured to determine whether or not a hunting state has occurred in the diagnostic data, in which the value rises and falls at a substantially constant cycle around the steady-state opening command value; a friction determination unit configured to determine whether or not there is a defect in the gland packing of the valve in which the hunting state has occurred; and a determination result presentation unit configured to present the ID of the valve determined to have a defect in the gland packing.

In addition, in one configuration example of the valve maintenance support device of the present invention, when the hunting determination unit determines that a hunting state is occurring in the diagnostic data, the friction determination unit determines whether the friction of the gland packing is too strong based on the hunting speed and the hunting up and down movement range, and the determination result presentation unit presents the ID of the valve for which the friction of the gland packing is determined to be too strong as the ID of a valve having a defect in the gland packing.
In addition, in one configuration example of the valve maintenance support device of the present invention, the friction determination unit is characterized in that it determines that the friction of the gland packing is too strong when the ratio of the hunting speed to the hunting up-down movement width is greater than a first specified value.

In addition, in one configuration example of the valve maintenance support device of the present invention, when the hunting determination unit determines that a hunting state has occurred in the diagnostic data, the friction determination unit determines whether the friction of the gland packing is too weak based on the hunting speed and the hunting up and down movement range, and the determination result presentation unit presents the ID of the valve for which the friction of the gland packing is determined to be too weak as the ID of a valve having a defect in the gland packing.
In addition, in one configuration example of the valve maintenance support device of the present invention, the friction determination unit is characterized in that it determines that the friction of the gland packing is too weak when the ratio between the hunting speed and the hunting up-down movement width is smaller than a second specified value.

The valve maintenance support method of the present invention includes a first step of storing data on the opening command value given to the valve in association with the ID of the valve that sent the data; a second step of storing data on the actual opening value of the valve in association with the ID of the valve that sent the data; a third step of searching for data on the steady-state opening command value that continuously indicates a substantially constant value for the same valve from among the opening command values stored in the first step, and extracting as diagnostic data the actual opening value of the valve for which the given opening command value has reached the steady state and the actual opening value for the time period corresponding to the steady-state opening command value; a fourth step of determining whether or not a hunting state has occurred in the diagnostic data, in which the value fluctuates up and down at a substantially constant cycle around the steady-state opening command value; a fifth step of determining whether or not there is a defect in the gland packing of the valve in which the hunting state has occurred; and a sixth step of presenting the ID of the valve determined to have a defect in the gland packing.

In addition, in one configuration example of the valve maintenance support method of the present invention, the fifth step includes a step of determining whether or not the friction of the gland packing is too strong based on the hunting speed and the hunting up and down movement range when it is determined in the fourth step that a hunting state has occurred in the diagnostic data, and the sixth step includes a step of presenting the ID of the valve for which it has been determined that the friction of the gland packing is too strong as the ID of a valve having a defective gland packing.
In addition, in one configuration example of the valve maintenance support method of the present invention, the fifth step is characterized by including a step of determining that the friction of the gland packing is too strong when the ratio of the hunting speed to the hunting up-down movement width is greater than a first specified value.

In addition, in one configuration example of the valve maintenance support method of the present invention, the fifth step includes a step of determining whether or not the friction of the gland packing is too weak based on the hunting speed and the hunting up and down movement range when it is determined in the fourth step that a hunting state has occurred in the diagnostic data, and the sixth step includes a step of presenting the ID of the valve for which it has been determined that the friction of the gland packing is too weak as the ID of a valve having a defective gland packing.
In addition, in one configuration example of the valve maintenance support method of the present invention, the fifth step is characterized by including a step of determining that the friction of the gland packing is too weak when the ratio between the hunting speed and the hunting up-down movement width is smaller than a second specified value.

According to the present invention, by determining whether or not there is a defect in the gland packing of a valve in which a hunting state is occurring, it is possible to detect a defect in the gland packing and to assist the worker in selecting a valve as a candidate for maintenance. As a result, the present invention can deal with valve hunting that is not caused by inappropriate settings of control parameters, and can improve the work efficiency of valve maintenance.

FIG. 1 is a block diagram showing the configuration of a valve maintenance support device according to a first embodiment of the present invention. FIG. 2 is a flowchart illustrating the operation of the valve maintenance support device according to the first embodiment of the present invention. FIG. 3 is a flowchart illustrating the operation of the valve maintenance support device according to the first embodiment of the present invention. FIG. 4 is a diagram showing an example of a hunting state of diagnostic data with a substantially constant period. FIG. 5 is a diagram showing the configuration of a plant and its equipment management system according to a second embodiment of the present invention. FIG. 6 is a block diagram showing an example of the configuration of a computer that realizes the valve maintenance support device according to the first and second embodiments of the present invention. FIG. 7 is a diagram showing an example of a control valve. FIG. 8 is a diagram showing an example of a number of valves used in a tank of a plant.

[Principle of the Invention]
The inventors discovered that in addition to the fact that valve hunting occurs when the friction of the gland packing is too strong, the hunting phenomenon also occurs when the friction of the gland packing is too weak.

Below, the hunting phenomenon related to friction in the gland packing is explained in detail. Here, the symbols in Figure 7 are used to denote the various parts of the valve. In a force balance positioner, which is a typical example of a positioner 102 that automatically adjusts the valve opening, the mechanism related to sensitivity (P operation) is composed of mechanical parts such as cams and springs, so the sensitivity of the positioner is fixed. Therefore, adjustments to the operation of the positioner 102 are mechanical adjustments, such as performing zero-span adjustments of the state of the feedback lever 107 and the state of the air output pressure Po.

Since the adjustment work for the positioner 102 is as described above, if the friction of the gland packing 109 is strong, the valve stem 104 temporarily does not move in response to the opening command value (sticks). In this case, the positioner 102 increases the air output pressure Po to the actuator 103 (in the case of a reverse acting valve). When the air output pressure Po exceeds the friction, the valve stem 104 slips. If the slip of the valve stem 104 causes the feedback opening measurement value to go beyond the opening command value, the positioner 102 lowers the air output pressure Po. When the air output pressure Po exceeds the friction, the valve stem 104 slips.

In this way, when the friction of the gland packing 109 is strong, it repeatedly sticks and slips, causing hunting. Therefore, by reducing the friction of the gland packing 109, the sticking of the valve shaft 104 is eliminated, allowing the valve shaft 104 to move smoothly in response to the opening command value, and as a result, hunting can be eliminated. In other words, if it can be determined that hunting is occurring due to strong friction of the gland packing 109, the operator can make adjustments to resolve the hunting.

On the other hand, suppose that the friction of the gland packing 109 is weakened too much as a result of adjustment work to resolve hunting. In this case, the sensitivity of the positioner 102 and the friction level are not consistent, causing the valve shaft 104 to move too smoothly, resulting in hunting of a different nature.

Therefore, hunting can be eliminated by appropriately increasing the friction of the gland packing 109. In other words, if it can be determined that hunting is occurring due to weak friction of the gland packing 109, the operator can make adjustments to resolve the hunting.

The inventor analyzed the mechanism of occurrence of each type of hunting as described above. He then discovered an indicator for distinguishing between hunting when the friction of the gland packing 109 is strong and hunting when it is weak. Specifically, the relationship between the width of the hunting and the speed of the hunting serves as an indicator for distinction.

When the friction of the gland packing 109 is strong, the static frictional force acts strongly against the propulsive force of the valve shaft 104, making it difficult for the valve shaft 104 to move, and the propulsive force rises temporarily to the force required to exceed the static frictional force. Once the static frictional force is exceeded, the force drops to kinetic friction, but the increased propulsive force causes the valve shaft 104 to move sharply. This makes the hunting speed (maximum speed over several hunting up and down movements) larger than the hunting width.

On the other hand, if the friction of the gland packing 109 is weak, the valve shaft 104 will move too easily, resulting in a force relationship (balance) similar to that of a high gain control target in feedback control, resulting in smooth up-down hunting. As a result, the speed of hunting (maximum speed over several up-down hunting movements) will be smaller than the width of the hunting.

[First embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a valve maintenance support device according to a first embodiment of the present invention. In the following embodiments, in order to simplify the explanation, examples of IDs (identification information) of valves and the like are assumed to be simpler than those used in an actual plant.

The valve maintenance support device includes a valve ID storage unit 1 that stores in advance the IDs of multiple valves that can be candidates for maintenance, an opening acquisition unit 2 that acquires an opening command value given to a valve and an actual opening value of the valve, an opening command value storage unit 3 that stores data on the opening command value in association with the ID of the valve that transmitted the data, an opening measurement value storage unit 4 that stores data on the actual opening value in association with the ID of the valve that transmitted the data, a steady-state data extraction unit 5 that searches for data on steady-state opening command values that continuously indicate a substantially constant value for the same valve from among the opening command values stored in the opening command value storage unit 3, and extracts as diagnostic data the actual opening value of the valve for which the given opening command value has become steady and the actual opening value for the time period corresponding to the steady-state opening command value, and The system includes a hunting determination unit 6 that determines whether a hunting state in which the command value moves up and down at a substantially constant cycle has occurred, a friction determination unit 7 that determines whether the friction of the gland packing is too strong based on the hunting speed and the hunting vertical movement range when the hunting determination unit 6 determines that a hunting state has occurred in the diagnostic data, a friction determination unit 8 that determines whether the friction of the gland packing is too weak based on the hunting speed and the hunting vertical movement range when the hunting determination unit 6 determines that a hunting state has occurred in the diagnostic data, and a determination result presentation unit 9 that presents (displays) the ID of a valve that has been determined to have too strong or too weak friction in the gland packing as the ID of a valve with a defective gland packing.

Figures 2 and 3 are flow charts explaining the operation of the valve maintenance support device of this embodiment. In this embodiment, for example, assume that there are 26 valves in a plant, and that these 26 valves are pre-assigned unique IDs "A", "B", "C", ..., "M", ..., "X", "Y", and "Z". In this embodiment, it is assumed that valves with valve IDs "A", "C", and "M" are selected as the valves with the highest priority for maintenance in a specific regular plant maintenance, and that these IDs "A", "C", and "M" are pre-stored in the valve ID storage unit 1.

The positioner (102 in Fig. 7) used for each valve supplies air pressure to the actuator (103 in Fig. 7) according to the difference between the opening command value SP (stem position command value) given by the higher-level device and the actual opening value PV (stem position measurement value) of the valve.

The opening acquisition unit 2 acquires data on the opening command value SP and actual opening value PV from the positioner of each valve for the valve whose valve ID is registered in the valve ID storage unit 1 (step S100 in Figure 2).

The opening acquisition unit 2 associates the data of the opening command value SP with the ID of the valve that sent the data and information on the time when the data was received, and stores them in the opening command value storage unit 3 (step S101 in Fig. 2). The opening acquisition unit 2 also associates the data of the actual opening value PV with the ID of the valve that sent the data and information on the time when the data was received, and stores them in the opening measurement value storage unit 4 (step S102 in Fig. 2).

The valve ID is acquired by the opening acquisition unit 2 from the valve ID that is added to the data of the opening command value SP and the actual opening value PV by the valve positioner and transmitted. The time information may be added by the valve positioner or by the opening acquisition unit 2.

In this way, by repeating the processing of steps S100 to S102, time series data for the opening command value SP and the actual opening value PV are stored in the opening command value memory unit 3 and the opening measurement value memory unit 4.

Next, the steady-state data extraction unit 5 searches for data on steady-state opening command values SP that continuously indicate a substantially constant value for the same valve among the opening command values SP stored in the opening command value storage unit 3 (step S103 in FIG. 3). Then, the steady-state data extraction unit 5 extracts, from the actual opening values PV stored in the opening measurement value storage unit 4, the actual opening values PV of the valves (valves with the same ID) for which the given opening command value SP has reached a steady state, and for the time period corresponding to the steady-state opening command value SP, as diagnostic data (step S104 in FIG. 3).

A steady state in which the opening command value SP continuously indicates a substantially constant value means, for example, that the opening command value SP is within the range of SPref±α (α is a tolerance range) with respect to the reference value SPref (for example, the most recent average value) for a predetermined time Tconst or more. The actual opening value PV in the time period corresponding to the opening command value SP in the steady state means the actual opening value PV from the start time of the steady state of the opening command value SP to the time when a predetermined time Td has elapsed after the steady state ends. There is a response delay in the valve to the opening command value SP. A time that takes this response delay into account can be set as the above-mentioned predetermined time Td. However, the method of detecting the steady state and the method of extracting diagnostic data in this embodiment are only examples, and it goes without saying that other methods may be adopted.

The hunting determination unit 6 determines whether or not a hunting state in which the steady-state opening command value SP fluctuates up and down at a substantially constant cycle around the steady-state opening command value SP occurs in the diagnostic data extracted for the steady-state opening command value SP (step S105 in FIG. 3).

Figures 4(A) and 4(B) show examples of a hunting state of the diagnostic data (actual opening value PV) at a substantially constant period. Figure 4(A) shows an example of hunting when the friction of the gland packing is strong, and Figure 4(B) shows an example of hunting when the friction of the gland packing is weak.

The hunting determination unit 6 may determine that the diagnostic data is fluctuating up and down when the diagnostic data is changing with an up and down fluctuation range that exceeds a predefined up and down fluctuation threshold. The hunting determination unit 6 may also determine that the period is approximately constant when the time fluctuation rate between up and down fluctuation peaks (maximum and minimum) of the diagnostic data is within a predefined fluctuation rate threshold range. The hunting detection method in this embodiment is just one example, and it goes without saying that other methods may be adopted.

When the hunting determination unit 6 determines that a hunting state with a substantially constant period is occurring in the diagnostic data (YES in step S105), the friction determination unit 7 determines whether the friction of the gland packing is too strong based on the hunting speed and the hunting up and down movement range (step S106 in Figure 3).

Specifically, when the ratio ΔH_max/H of the hunting speed ΔH_max (maximum speed of change in diagnostic data detected by hunting up and down movement) to the hunting up and down movement width H (representative value of several hunting up and down movement widths) is greater than a first specified value T1 (ΔH_max/H>T1), the friction determination unit 7 determines that the friction of the gland packing is too strong (the gland packing is overtightened). An example of the representative value of the hunting up and down movement width (difference between the maximum value and the minimum value) is the average value of several hunting up and down movement widths.

On the other hand, if the hunting determination unit 6 determines that a hunting state with a substantially constant period is occurring in the diagnostic data (YES in step S105), the friction determination unit 8 determines whether the friction of the gland packing is too weak based on the hunting speed and the hunting up and down movement range (step S107 in Figure 3).

Specifically, when the ratio ΔH_max/H of the hunting speed ΔH_max to the hunting up-down movement width H (representative value of several hunting up-down movement widths) is smaller than a second specified value T2 (T1>T2) (ΔH_max/H<T2), the friction determination unit 8 determines that the friction of the gland packing is too weak (the gland packing is too loose).

The judgment result presentation unit 9 presents to the operator the IDs of valves whose valve IDs are registered in the valve ID storage unit 1 and that are judged to have a gland packing defect (friction is too strong or too weak), together with the details of the defect (too strong or too weak) (Figure 3, step S108).

However, the judgment result presentation unit 9 may present (display) any of the following information for all valves whose valve IDs are registered in the valve ID storage unit 1: "The friction of the gland packing is too strong," "The friction of the gland packing is too weak," or "No gland packing defects." In this case, the worker (operator) can check the valve ID even for valves that were found to have no defects as a result of the gland packing judgment.

In this way, the processing of steps S100 to S108 in FIG. 3 is performed periodically. Note that it is also possible to omit the processing of either the friction determination unit 7 or the friction determination unit 8, and present (display) the result of the determination performed by either one of them.

In this embodiment, by monitoring the valve hunting phenomenon, it is possible to detect malfunctions in the gland packing and assist workers in selecting valves as candidates for maintenance.

[Second embodiment]
Next, a second embodiment of the present invention will be described. This embodiment describes an implementation example of the first embodiment. Fig. 5 is a diagram showing the configuration of a plant and its equipment management system, and the same components as those in Fig. 8 are given the same reference numerals.

In equipment management systems for petroleum and chemical plants, a management device 10 is provided to control and manage each piece of equipment in the plant. The valve ID storage unit 1, opening acquisition unit 2, opening command value storage unit 3, and opening measurement value storage unit 4 described in the first embodiment handle a huge amount of plant-specific information, so it is preferable that they are implemented in the management device 10.

Meanwhile, the steady-state data extraction unit 5, the hunting judgment unit 6, the friction judgment units 7 and 8, and the judgment result presentation unit 9 provide processing that is required in principle only when judging whether valve maintenance is required. Also, the maintenance implementer (the worker at the maintenance contracted company) generally carries out plant maintenance on behalf of the plant owner company. Therefore, assuming that an unspecified number of plants will be the target, it is preferable to implement the steady-state data extraction unit 5, the hunting judgment unit 6, the friction judgment units 7 and 8, and the judgment result presentation unit 9 in a portable computer 11 carried around by the worker (operator) at the maintenance contracted company.

The plant management device 10 and the computer 11 are temporarily connected to each other using a communication function such as Ethernet (registered trademark) when maintenance work is performed.
When an operator starts the application software on the computer 11, the CPU (Central Processing Unit) of the computer 11 executes processing according to the program stored in the memory, and realizes the functions of a steady-state data extraction unit 5, a hunting judgment unit 6, friction judgment units 7 and 8, and a judgment result presentation unit 9.

The judgment result presentation unit 9 reads the valve ID from the valve ID storage unit 1 on the management device 10, reads the judgment results from the friction judgment units 7 and 8, and displays the judgment results on the display of the computer 11 (Figure 3, step S108).

The operator checks the valves that require particular attention for inspection of the gland packing based on the displayed valve ID. After checking the displayed items, the operator disconnects the computer 11 from the management device 10.
In this manner, the valve maintenance support device described in the first embodiment can be applied to an actual plant.

The valve maintenance support device described in the first and second embodiments can be realized by a computer equipped with a CPU, a storage device, and an interface, and a program for controlling these hardware resources. An example of the configuration of this computer is shown in Fig. 6. The computer is equipped with a CPU 300, a storage device 301, and an interface device (I/F) 302. For example, a valve, a management device, a display, etc. are connected to the I/F 302. In such a computer, a program for realizing the valve maintenance support method of the present invention is stored in the storage device 301. The CPU 300 executes the processing described in the first and second embodiments in accordance with the program stored in the storage device 301.
When the valve maintenance support device is implemented separately in the management device 10 and the computer 11 as in the second embodiment, each of them may be realized with the configuration shown in FIG.

The present invention can be applied to technology that assists in valve maintenance work.

1... Valve ID storage unit, 2... Opening degree acquisition unit, 3... Opening degree command value storage unit, 4... Opening degree measurement value storage unit, 5... Steady-state data extraction unit, 6... Hunting determination unit, 7, 8... Friction determination unit, 9... Determination result presentation unit, 10... Management device, 11... Computer.

Claims (10)

an opening command value storage unit configured to store data of an opening command value given to a valve in association with an ID of a valve that is a transmission source of the data;
an opening measurement value storage unit configured to store data of an actual opening value of a valve in association with an ID of a valve that is a source of the data;
a steady-state data extraction unit configured to search for data on steady-state opening command values which continuously indicate a substantially constant value for the same valve from among the opening command values stored in the opening command value storage unit, and to extract, as diagnostic data, an actual opening value of the valve in which a given opening command value has reached the steady state and an actual opening value in a time period which corresponds to the steady-state opening command value;
a hunting determination unit configured to determine whether or not a hunting state in which the diagnostic data fluctuates up and down at a substantially constant period around the opening command value in the steady state occurs;
a friction determination unit configured to determine whether or not there is a defect in a gland packing of the valve in which the hunting state occurs;
and a determination result presentation unit configured to present the ID of a valve determined to have a defective gland packing. 2. The valve maintenance support device according to claim 1,
the friction determination unit, when the hunting determination unit determines that a hunting state occurs in the diagnostic data, determines whether or not the friction of the gland packing is too strong based on a hunting speed and a hunting up-down movement width;
The valve maintenance support device is characterized in that the judgment result presentation unit presents the ID of a valve for which the friction of the gland packing is determined to be too strong as the ID of a valve having a defect in the gland packing. 3. The valve maintenance support device according to claim 2,
The friction determination unit determines that the friction of the gland packing is too strong when a ratio between the hunting speed and the hunting up-down movement width is greater than a first specified value. 2. The valve maintenance support device according to claim 1,
the friction determination unit, when the hunting determination unit determines that a hunting state occurs in the diagnostic data, determines whether or not the friction of the gland packing is too weak based on a hunting speed and a hunting up-down movement range;
The valve maintenance support device is characterized in that the judgment result presentation unit presents the ID of a valve for which the friction of the gland packing is judged to be too weak as the ID of a valve having a defect in the gland packing. 5. The valve maintenance support device according to claim 4,
The friction determination unit determines that the friction of the gland packing is too weak when the ratio between the hunting speed and the hunting up-and-down movement width is smaller than a second specified value. A first step of storing data of an opening command value given to a valve in association with an ID of a valve that is a sender of the data;
a second step of storing the data of the actual valve opening value in association with the ID of the valve that transmitted the data;
a third step of searching for data on steady-state opening command values which continuously indicate a substantially constant value for the same valve from among the opening command values stored in the first step, and extracting, as diagnostic data, an actual opening value of the valve in the steady state where a given opening command value is given and an actual opening value in a time period corresponding to the steady-state opening command value;
a fourth step of determining whether or not a hunting state in which the diagnostic data fluctuates up and down at a substantially constant period around the opening command value in the steady state is occurring;
a fifth step of determining whether or not there is a defect in the gland packing of the valve in which the hunting state occurs;
and a sixth step of presenting the ID of the valve determined to have a defective gland packing. 7. The valve maintenance support method according to claim 6,
the fifth step includes a step of determining whether or not the friction of the gland packing is too strong based on a hunting speed and a hunting up-down movement range when it is determined in the fourth step that a hunting state occurs in the diagnostic data,
The valve maintenance support method according to the present invention, wherein the sixth step includes a step of presenting the ID of a valve for which it has been determined that the friction of the gland packing is too strong as the ID of a valve having a defect in the gland packing. The valve maintenance support method according to claim 7,
The valve maintenance support method according to the present invention, characterized in that the fifth step includes a step of determining that the friction of the gland packing is too strong when a ratio between the hunting speed and the hunting up-down movement width is greater than a first specified value. 7. The valve maintenance support method according to claim 6,
the fifth step includes a step of determining whether or not the friction of the gland packing is too weak based on a hunting speed and a hunting up-down movement range when it is determined in the fourth step that a hunting state occurs in the diagnostic data,
The valve maintenance support method according to the present invention, wherein the sixth step includes a step of presenting the ID of a valve whose gland packing friction is determined to be too weak as the ID of a valve whose gland packing is defective. The valve maintenance support method according to claim 9,
The valve maintenance support method according to the present invention, characterized in that the fifth step includes a step of determining that the friction of the gland packing is too weak when a ratio between the hunting speed and the hunting up-down movement width is smaller than a second specified value.

Images