Liquid sampling valve maintenance management method and maintenance management apparatus

Abstract

A maintenance management method of a liquid sampling valve 10 including: a drive count acquisition step of acquiring a count of times a piston 17 has been driven after seal material 141 and 142 is newly installed; and a replacement determination step of determining that the seal material 141 and 142 needs to be replaced when the count of times the piston 17 has been driven is equal to or greater than a first replacement threshold, regardless of time elapsed after the seal material 141 and 142 is newly installed.

Description

LIQUID SAMPLING VALVE MAINTENANCE MANAGEMENT METHOD AND MAINTENANCE MANAGEMENT APPARATUSCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to and the benefit of Japanese Patent Application No. 2023-36040 filed March 8, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a liquid sampling valve maintenance management method and maintenance management apparatus.Background

[0003] Conventional liquid sampling valves are known to transport sample gas vaporized from a sample liquid to a detector together with a carrier gas (see, for example, Patent Literature (PTL) 1).

[0004] PTL 1: JP H7-34368 USummary

[0005] (Technical Problem) According to the liquid sampling valve described in Patent Literature 1, sample leakage may occur due to wear of seal material. The maintenance of seal material needs to be appropriately managed.

[0006] In view of the above, it would be helpful to provide a maintenance management method and a maintenance management apparatus able to appropriately manage the maintenance of seal material of a liquid sampling valve. (Solution to Problem)

[0007] (1) A maintenance management method according to at least one embodiment is for managing maintenance of a liquid sampling valve. The liquid sampling valve comprising: a housing including a sampling chamber through which a liquid sample flows and a vaporization chamber in which the liquid sample is vaporized; seal material that separates the sampling chamber from the vaporization chamber; a stem configured to pass in and out of the vaporization chamber through a hole in the seal material; and a piston configured to drive the stem. The maintenance management method comprising: a drive count acquisition step of acquiring a count of times the piston has been driven after the seal material is newly installed; and a replacement determination step of determining that the seal material needs to be replaced when the count of times the piston has been driven is equal to or greater than a first replacement threshold, regardless of time elapsed after the seal material is newly installed.

[0008] Determining the need to replace the seal material based on the count of times the piston has been driven increases the likelihood that seal material in worn condition will be replaced. In other words, seal material not in worn condition is less likely to be replaced. By reducing the replacement of seal material that is not in worn condition, the cost of material or replacement work, lost opportunities due to the shutdown of a gas chromatograph during the period spent on replacement work, and the like are reduced.

[0009] (2) The maintenance management method according to aspect (1) above may further comprise a drive data acquisition step of acquiring at least one of movement speed of the piston or strain of the seal material. In the replacement determination step, determining that the seal material needs to be replaced also occurs in at least one of the following cases: when the movement speed of the piston is equal to or greater than a second replacement threshold, or when the strain of the seal material is equal to or less than a third replacement threshold.

[0010] By determining that the seal material needs to be replaced based on the drive data other than the count of times the piston has been driven, deterioration of the seal material that cannot be ascertained only by the count of times the piston has been driven may be ascertained. As a result, the maintenance of the seal material is appropriately managed.

[0011] (3) The maintenance management method according to aspect (2) above may further comprise a replacement time prediction step of generating extrapolated data predicting a relationship between the count of times the piston has been driven and the movement speed of the piston or the strain of the seal material, and calculating at least one of the count of times the piston is driven when the movement speed of the piston is equal to or greater than the second replacement threshold in the extrapolated data or the count of times the piston is driven when the strain of the seal material is equal to or less than the third replacement threshold in the extrapolated data as a predicted maintenance time until there will be a need to replace the seal material.

[0012] By predicting the maintenance time based on the prediction of the drive data, a user may ascertain when to replace the seal material and may replace the seal material in a planned manner. As a result, the user may develop and implement a plan that incorporates the replacement of the seal material into the analysis work using the gas chromatograph.

[0013] (4) The maintenance management method according to any one of aspects (1) to (3) above may further comprise, before the replacement determination step, a retightening determination step of determining that a nut that applies a load to the seal material needs to be retightened when the count of times the piston has been driven is equal to or greater than a first retightening threshold, regardless of the time elapsed after the seal material is newly installed.

[0014] By performing retightening of the nut before replacing the seal material, the frequency of seal material replacement is reduced. As a result, the cost of material or replacement work, lost opportunities due to the shutdown of the gas chromatograph during the period spent on replacement work, and the like are reduced.

[0015] (5) The maintenance management method according to aspect (4) above, wherein, in the replacement determination step, determining that the seal material needs to be replaced also occurs when retightening of the nut has been performed a defined number of times or more.

[0016] When the seal material is worn or deteriorated, a sufficiently close fit between the seal material and the stem cannot be ensured even when the nut is retightened. By limiting the number of times the retightening of the nut is performed, maintenance work that has little effect is reduced. As a result, the maintenance of the seal material of the liquid sampling valve is appropriately managed.

[0017] (6) A maintenance management apparatus according to at least one embodiment comprises a processor that executes the maintenance management method according to any one of aspects (1) to (5). (Advantageous Effect)

[0018] According to the liquid sampling valve maintenance management method and maintenance management apparatus of the present disclosure, maintenance of the seal material of the liquid sampling valve is appropriately managed.

[0019] In the accompanying drawings: FIG. 1 is a block diagram illustrating an example configuration of a gas chromatograph; FIG. 2 is a cross section view of an example configuration of a liquid sampling valve according to an embodiment, illustrating a state where a sampling groove is positioned in a sampling chamber; FIG. 3 is an enlarged view of the dot-dash frame enclosure A of FIG. 2; FIG. 4 is a cross section view of an example configuration of a liquid sampling valve according to an embodiment, illustrating a state where the sampling groove is positioned in a sample supply passage; FIG. 5 is an enlarged view of the dot-dash frame enclosure B of FIG. 4; FIG. 6 is a cross section view illustrating an example configuration of a liquid sampling valve with an accelerometer and strain sensor attached; FIG. 7 is a flowchart illustrating example procedures of a determination operation of a liquid sampling valve according to an embodiment; FIG. 8 is a flowchart illustrating example procedures of the retightening determination in FIG. 7; FIG. 9 is a flowchart illustrating example procedures of the replacement determination in FIG. 7; FIG. 10 is a graph illustrating an example of predicted piston speed calculated based on measured piston speed; FIG. 11 illustrates an example configuration of a cylinder with an externally attached accelerometer; and FIG. 12 illustrates an example configuration of a cylinder with proximity sensors attached.DETAILED DESCRIPTION

[0020] The present disclosure relates to a liquid sampling valve for use in a gas chromatograph. In gas chromatography, a measured sample of a multi-component mixture collected in a fixed amount is transported to a column with a carrier gas, and the concentration of each component separated in the column is measured and output as a chromatogram. The liquid sampling valve, when the sample to be measured is a liquid sample, enables the gas chromatograph to measure the concentration of the liquid sample by vaporizing the liquid sample and transporting the liquid sample to the column together with the carrier gas.

[0021] The liquid sampling valve includes a liquid sample supply section, a liquid sample vaporization section, and seal material separating the supply section and the vaporization section. The liquid sampling valve uses a stem that has a sampling groove to transport a fixed amount of a liquid sample from the supply section to the vaporization section. The liquid sampling valve is able to supply the fixed amount of liquid sample collected in the sampling groove to the vaporizing section by moving the stem so that the sampling groove moves from the supply section through the seal material to the vaporization section. The liquid sampling valve needs to be managed so that no gap occurs between the seal material and the stem, in order to prevent leakage of a liquid sample from the supply section. Specifically, in the liquid sampling valve, sufficient load is applied from the seal material to the stem by tightening the seal material with a nut.

[0022] Here, sample leakage between the seal material and the stem may occur due to wear of the seal material. Sample leakage can change the shape of the chromatogram and cause problems such as poor reproducibility of measurements, destabilization of the chromatogram baseline, and the like.

[0023] In the liquid sampling valve according to a Comparative Example, when a problem occurs, the response is to retighten the nut. However, the method of responding to problems as they arise does not avoid the problems. Further, in order to avoid problems due to wear of the seal material, the seal material is replaced during periodic maintenance regardless of the wear condition of the seal material. Although problems may be avoided by replacing the seal material, the seal material may be replaced when still fully usable, increasing seal material replacement costs.

[0024] Therefore, the present disclosure describes a liquid sampling valve enabling replacement of the seal material at an appropriate time, and a gas chromatograph that uses the liquid sampling valve.

[0025] (Example configuration of gas chromatograph 1) As illustrated in FIG. 1, a gas chromatograph 1 includes a liquid sampling valve 10, a column 20, a detector 30, and a controller 40. The column 20 may also be referred to as a separation tube. The gas chromatograph 1 is an analyzer that, using the liquid sampling valve 10, collects and transports a fixed amount of a multicomponent mixed sample to the column 20 with carrier gas, separates the multicomponent mixed sample into each component by the column 20, detects the concentration of each component by the detector 30, and outputs a detection result as a gas chromatogram by the controller 40.

[0026] The liquid sampling valve 10 includes a fitting labeled "IN" to input the liquid sample and a fitting labeled "OUT" to drain the liquid sample so that the liquid sample flows into the interior. Further, the liquid sampling valve 10 includes a fitting that introduces the carrier gas used to transport the vaporized liquid sample to the column 20. The liquid sampling valve 10 transports sample gas, a mixture of the vaporized liquid sample and the carrier gas, to the column 20.

[0027] The column 20 separates each component in the sample gas. The detector 30 detects the concentration of each component separated by the column 20. The detector 30 includes a fitting that vents sample gas for which component concentration has been detected.

[0028] The controller 40 acquires the detection results of the concentration of each component by the detector 30 and outputs the detection results as a chromatogram. The controller 40 also controls the liquid sampling valve 10 to synchronize the collection of a liquid sample with the detection result by the detector 30.

[0029] The controller 40 may include a processor such as a central processing unit (CPU) or dedicated circuitry such as a field programmable gate array (FPGA), for example. The controller 40 may be configured to execute a program that realizes various functions of the gas chromatograph 1. The controller 40 may include a storage. The storage may store information used in the operation of the controller 40, a program to realize a function of the controller 40, and the like. The storage may function as working memory of the controller 40. The storage may be configured as a semiconductor memory, for example. The storage may be configured as a separate unit from the controller 40.

[0030] The gas chromatograph 1 may further include an interface. Example interfaces include communication interfaces that communicate with external devices by wired or wireless means. The interface may include a display device. Example display devices include various displays such as liquid crystal displays, for example. The interface may include an audio output device such as a speaker. The interface may include an input device that accepts input from a user. Example input devices include keyboards or physical keys, touch panels or touch sensors, and pointing devices such as mice.

[0031] (Example configuration of liquid sampling valve 10) Referring to FIG. 2 to FIG. 5, an example configuration of the liquid sampling valve 10 is described. The liquid sampling valve 10 includes a block 11, a nut 12, a liquid sample block 133, seal material 141 and 142, a stem 15, a piston 17, and a cylinder 18. The block 11, the nut 12, the liquid sample block 133, the stem 15, the piston 17, and the cylinder 18 may be composed of metal material, such as steel use stainless (SUS) steel material, for example, and may include various other materials. The seal material 141 and 142 may be composed of resin material such as rubber, and may include various other materials.

[0032] The block 11, the nut 12, and the liquid sample block 133 are also collectively referred to as the housing of the liquid sampling valve 10. The housing of the liquid sampling valve 10 includes a sampling chamber 152 (see FIG. 3) and a vaporization chamber 161, as described below.

[0033] The liquid sampling valve 10 further includes a pipe 131 through which the liquid sample flows into the sampling chamber 152 (see FIG. 3), which is defined between the liquid sample block 133 and the seal material 141 and 142, and a pipe 132 through which liquid sample flows out of the sampling chamber 152. The sampling chamber 152 forms part of a liquid sample flow path. The seal material 141 has a hole defined by an inner wall 141a. Further, the seal material 142 has a hole defined by an inner wall 142a. The holes in the seal material 141 and 142 are configured to fit the outline of the stem 15, described below, and the stem 15 seals the holes by penetrating through the holes. The seal material 141 and 142 is elastic. By tightening the nut 12 and applying load to the seal material 141 and 142, the inner wall 141a of the seal material 141 and the inner wall 142a of the seal material 142 closely fit to the outer surface of the stem 15. The inner walls 141a and 142a closely fit to the outer surface of the stem 15, which enhances the sealability of the holes in the seal material 141 and 142.

[0034] The seal material 142 separates the sampling chamber 152 from the vaporization chamber 161.

[0035] The liquid sampling valve 10 further includes a pipe 16. The pipe 16 may be constructed as a glass pipe, and may include various other materials. The space inside the pipe 16 is also referred to as the vaporization chamber 161.

[0036] The block 11 of the liquid sampling valve 10 includes an inner wall 114 that defines a carrier gas passage 113 that supplies the carrier gas to the vaporization chamber 161. The block 11 of the liquid sampling valve 10 includes an inner wall 115 (see FIG. 5) that defines a space in which the pipe 16 is accommodated. The space defined by the inner wall 115 connects the carrier gas passage 113 to one end of the pipe 16. The carrier gas is supplied from the carrier gas passage 113 through the space between the pipe 16 and the inner wall 115 to the vaporization chamber 161 from one end of the pipe 16, as illustrated in FIG. 5.

[0037] The block 11 of the liquid sampling valve 10 includes a heater 111 and a temperature sensor 112 in order to control the temperature of the block 11, including the vaporization chamber 161, to a temperature at which the liquid sample vaporizes.

[0038] The stem 15 is a rod-shaped member. The stem 15 includes a sampling groove 151, as illustrated in FIG. 3 and FIG. 5. The sampling groove 151 is configured to have a smaller diameter than other portions of the stem 15, and may also be referred to as a small diameter portion. The stem 15 is configured to be able to pass in and out of the vaporization chamber 161 through the holes in the seal material 141 and 142.

[0039] The stem 15 enters or is withdrawn from the vaporization chamber 161 depending on movement of the piston 17. In other words, the piston 17 drives the stem 15. The stem 15 is configured so that the sampling groove 151 is positioned in the sampling chamber 152 when the piston 17 has moved to a position in the cylinder 18 farthest from the sampling chamber 152, as illustrated in FIG. 2. Further, the stem 15 is configured so that the sampling groove 151 is positioned in the vaporization chamber 161 when the piston 17 has moved to a position closest to the sampling chamber 152 in the cylinder 18, as illustrated in FIG. 4.

[0040] The piston 17 moves when drive air is supplied to the cylinder 18. The piston 17 moves away from the sampling chamber 152 when drive air is supplied to a drive air supply 181 disposed on the side of the cylinder 18 that is closer to the sampling chamber 152. The piston 17 moves toward the sampling chamber 152 when drive air is supplied to a drive air supply 182 disposed on the far side of the cylinder 18 from the sampling chamber 152. As the piston 17 moves toward or away from the sampling chamber 152 as described above, the sampling groove 151 moves between the sampling chamber 152 and the vaporization chamber 161.

[0041] The sampling groove 151 of the stem 15 is filled with liquid sample when positioned in the sampling chamber 152. When the stem 15 moves in the direction from the sampling chamber 152 toward the vaporization chamber 161, the sampling groove 151 filled with liquid sample moves from the sampling chamber 152 to the vaporization chamber 161 through a hole defined by the inner wall 142a of the seal material 142. When the sampling groove 151 moves through the hole in the seal material 142 and into the vaporization chamber 161, only the liquid sample filling the sampling groove 151 is collected in the vaporization chamber 161. The liquid sample filling the sampling groove 151 is also referred to as a collected sample 153. The collected sample 153 vaporizes in the vaporization chamber 161 and turns into sample gas. The sample gas is transported from the vaporization chamber 161 to the column 20 by the carrier gas.

[0042] (Example operation of gas chromatograph 1) The controller 40 of the gas chromatograph 1 is able to cause collection of the collected sample 153 into the vaporization chamber 161 by controlling the movement of the stem 15 of the liquid sampling valve 10. The amount of the collected sample 153 is a fixed amount determined based on the volume of the sampling groove 151. Thus, the gas chromatograph 1 is able to collect a fixed amount of the liquid sample in the vaporization chamber 161. The fixed amount of the liquid sample is vaporized in the vaporization chamber 161 into sample gas, which is transported to the column 20 by the carrier gas. The controller 40 synchronizes the timing of collecting the liquid sample by moving the sampling groove 151 of the stem 15 to the vaporization chamber 161 with the operation of separating each component of the collected sample gas by the column 20. Each component of the sample gas separated in the column 20 is sequentially transported to the detector 30 and detected by the detector 30. The controller 40 generates a chromatogram based on the detection results for each component of the sample gas separated by the column 20.

[0043] In the gas chromatograph 1, each time a liquid sample is collected once to detect the concentration of components in the liquid sample, the piston 17 drives the stem 15 to reciprocate once in the axial direction of the stem 15. A count of times the piston 17 has been driven, also called a drive count, corresponds to the number of analyses by the gas chromatograph 1.

[0044] (Maintenance of liquid sampling valve 10) As has been described above, in the gas chromatograph 1, the stem 15 reciprocates once in the axial direction for each time a liquid sample is collected and analysis is performed. The movement in the axial direction of the stem 15 causes wear on the inner wall 141a of the seal material 141 and the inner wall 142a of the seal material 142 in contact with the stem 15. Wear of the inner wall 141a, 142a increases the likelihood of a gap occurring between the outer surface of the stem 15 and the inner wall 141a, 142a. A gap between the outer surface of the stem 15 and the inner wall 141a or 142a reduces the sealability of the sampling chamber 152 by the seal material 141 or 142. Reduced sealability of the sampling chamber 152 increases the likelihood of a liquid sample leaking into the vaporization chamber 161. When the liquid sample leaks into the vaporization chamber 161, the liquid sample is vaporized and transported to the column 20 even when the sampling groove 151 of the stem 15 has not moved into the vaporization chamber 161. As a result, the amount of sample gas transported to the column 20 becomes unstable. In the liquid sampling valve 10, maintenance of the liquid sampling valve 10 is performed to maintain the sealability of the sampling chamber 152.

[0045] <Replacement of seal material 141 and 142> As maintenance to maintain the sealability of the sampling chamber 152, the seal material 141 and 142 may be replaced. The controller 40 of the gas chromatograph 1 according to the present embodiment determines the need to replace the seal material 141 and 142 based on drive data of the liquid sampling valve 10.

[0046] <<Replacement based on drive count>> The controller 40 of the gas chromatograph 1 accumulates a count of times the piston 17 of the liquid sampling valve 10 has been driven after the seal material 141 and 142 is newly installed in the liquid sampling valve 10, and determines the need for replacement of the seal material 141 and 142 based on the drive count of the piston 17. When the controller 40 determines that the seal material 141 and 142 needs to be replaced, the controller 40 outputs an alarm to prompt a user to replace the seal material 141 and 142. The controller 40 may acquire the drive count of the piston 17 by the controller 40 itself accumulating a total, or by acquiring the drive count accumulated by another device. The operation of acquiring the drive count of the piston 17 may also be referred to as a drive count acquisition step. The operation of determining the need to replace the seal material 141 and 142 may also referred to as a replacement determination step.

[0047] For example, the controller 40 may determine that the seal material 141 and 142 needs to be replaced when the drive count of the piston 17 is equal to or greater than a defined threshold value, and thereupon output an alarm to prompt a user to replace the seal material 141 and 142. The defined threshold value that is compared to the drive count of the piston 17 to determine the need to replace the seal material 141 and 142 may also be referred to as a first replacement threshold. The first replacement threshold may be determined based on a result of wear tests of the seal material 141 and 142, a drive count of the piston 17 at which a problem related to the seal material 141 and 142 occurred during operation of the gas chromatograph 1, or the like. The controller 40 determines the replacement of the seal material 141 and 142 based on the drive count of the piston 17, regardless of the length of time elapsed after the seal material 141 and 142 is newly installed.

[0048] In a case where the seal material 141 and 142 is replaced at the timing of a periodic inspection of the gas chromatograph 1 or the liquid sampling valve 10, the seal material 141 and 142 is replaced based on the time elapsed since the seal material 141 and 142 was newly installed in the liquid sampling valve 10. In other words, the seal material 141 and 142 is replaced only after having been installed in the liquid sampling valve 10 for an extended period of time, regardless of the drive count of the piston 17. Accordingly, the seal material 141 and 142 may be replaced when not in worn condition.

[0049] On the other hand, as in the liquid sampling valve 10 according to the present embodiment, by replacing the seal material 141 and 142 when the drive count of the piston 17 is equal to or greater than the first replacement threshold, regardless of the time elapsed after the seal material 141 and 142 is newly installed, the seal material 141 and 142 is more likely to be worn at the time of replacement. Accordingly, the replacement of the seal material 141 and 142 is appropriately managed.

[0050] In a case where a user waits until a problem occurs in the gas chromatograph 1 to replace the seal material 141 and 142, the user is unable to ascertain when to replace the seal material 141 and 142 and is unable replace the seal material 141 and 142 in a planned manner. In such a case, the implementation of analytical work using the gas chromatograph 1 is negatively affected.

[0051] On the other hand, as in the liquid sampling valve 10 according to the present embodiment, the seal material 141 and 142 is replaced when the drive count of the piston 17 is equal to or greater than the first replacement threshold, and therefore a user is able to ascertain when to replace the seal material 141 and 142 and is able to replace the seal material 141 and 142 in a planned manner. As a result, the user may develop and implement a plan that incorporates replacement work of the gas chromatograph 1 into the analysis work using the gas chromatograph 1.

[0052] Appropriate management of when to replace the seal material 141 and 142, or the implementation of planned work, reduces the cost of materials and work spent on replacing the seal material 141 and 142, or reduces loss incurred by reduced availability of analytical work using the gas chromatograph 1.

[0053] <<Replacement based on speed of piston 17>> As illustrated in FIG. 6, the liquid sampling valve 10 may include an accelerometer 171 attached to the piston 17. The accelerometer 171 is able to measure acceleration as the piston 17 moves in the axial direction of the stem 15. The controller 40 of the gas chromatograph 1 may be communicatively connected to the accelerometer 171 via a cable 172. The controller 40 may be communicatively connected to the accelerometer 171 by wireless means.

[0054] The controller 40 acquires the acceleration of the piston 17 from the accelerometer 171 and calculates the movement speed of the piston 17 when driving the piston 17. The controller 40 may acquire the movement speed of the piston 17 by calculating the movement speed, or the movement speed of the piston 17 may be acquired from another device. The movement speed of the piston 17 matches the movement speed in the axial direction of the stem 15. When the closeness of fit between at least one of the seal material 141 or 142 and the stem 15 decreases due to wear of the seal material 141 or 142, the frictional force received from the seal material 141 or 142 when the stem 15 moves in the axial direction decreases. Under the assumption that the pressure of the drive air that drives the piston 17 is constant, the lower the frictional force received by the stem 15, the faster the stem 15 moves in the axial direction, and thus the faster the piston 17 moves. The controller 40 is able to evaluate the closeness of fit between at least one of the seal material 141 or 142 and the stem 15 based on the calculated movement speed of the piston 17 and thereby determine the need for replacement of the seal material 141 and 142.

[0055] Specifically, the controller 40 may output an alarm to prompt a user to replace the seal material 141 and 142 when the movement speed of the piston 17 is equal to or greater than a defined threshold value. The defined threshold value that is compared to the movement speed of the piston 17 to determine the replacement of the seal material 141 and 142 may also be referred to as a second replacement threshold. The second replacement threshold may be determined based on an actual value of movement speed of the piston 17 at which a problem related to the seal material 141 and 142 occurred during operation of the gas chromatograph 1, or the like.

[0056] According to the present embodiment, even when the controller 40 determines that there is no need to replace the seal material 141 and 142 based on the drive count of the piston 17, the controller 40 may further determine the need to replace the seal material 141 and 142 based on the movement speed of the piston 17. By executing a determination based on the movement speed of the piston 17 in addition to a determination based on the drive count of the piston 17, deterioration of the seal material 141 or 142 that cannot be ascertained only by the drive count of the piston 17 may be ascertained. As a result, the replacement of the seal material 141 and 142 is appropriately managed.

[0057] The controller 40 may confirm that the piston 17 has completed movement in the cylinder 18 by acquiring the measurement result of the accelerometer 171. On the other hand, in the liquid sampling valve 10, by providing drive air from the drive air supply 182 for a sufficiently long time, the piston 17 completing movement in the direction from the sampling chamber 152 to the vaporization chamber 161 is ensured. The accelerometer 171 is utilized in management of the seal material 141 and 142, even when the accelerometer 171 need not be used to confirm completion of movement of the piston 17.

[0058] <<Replacement based on strain of seal material 141 or 142>> As illustrated in FIG. 6, the liquid sampling valve 10 may include a strain sensor 143 attached to the seal material 142. The strain sensor 143 may be configured to measure compressive strain caused by the seal material 142 being pushed outward from the inner wall 142a. The strain sensor 143 may be configured to measure shear strain in the seal material 142 caused by frictional force acting against the inner wall 142a of the seal material 142 from the stem 15 moving in the axial direction. The controller 40 of the gas chromatograph 1 may be communicatively connected to the strain sensor 143 via a cable 144. The controller 40 may be communicatively connected to the strain sensor 143 by wireless means.

[0059] The controller 40 acquires strain of the seal material 142 from the strain sensor 143. When the inner diameter of the hole defined by the inner wall 142a increases due to wear of the seal material 142, the compressive force acting on the inner wall 142a of the seal material 142 from the stem 15 becomes smaller. Further, when closeness of fit between the seal material 142 and the stem 15 decreases due to wear of the seal material 142, the frictional force that the seal material 142 receives from the stem 15 decreases, under the assumption that the pressure of the drive air that drives the piston 17 remains constant. The lower the frictional force to which the seal material 142 is subjected, the smaller the shear strain on the seal material 142. Accordingly, whether the strain sensor 143 measures either compressive strain or shear strain, the controller 40 is able to evaluate the wear of the seal material 142 and determine the need to replace the seal material 142 based on the strain of the seal material 142 measured by the strain sensor 143.

[0060] The strain sensor 143 may also be attached to the seal material 141. When the strain sensor 143 is attached to the seal material 141, the controller 40 is able to evaluate the wear of the seal material 141 and determine the need to replace the seal material 141 based on the strain of the seal material 141 measured by the strain sensor 143.

[0061] The strain sensor 143 may be replaced by a load sensor such as a pressure sensor or load cell when measuring the compressive force acting from the stem 15 on the seal material 141 or 142.

[0062] Specifically, the controller 40 may output an alarm to prompt a user to replace the seal material 141 and 142 when the strain of the seal material 141 or 142 is equal to or less than a defined threshold value. The defined threshold that is compared to the strain of the seal material 141 or 142 to determine the replacement of the seal material 141 and 142 may also be referred to as a third replacement threshold. The third replacement threshold may be determined based on an actual value of strain of the seal material 141 or 142 at which a problem related to the seal material 141 and 142 occurred during operation of the gas chromatograph 1, or the like.

[0063] According to the present embodiment, even when the controller 40 determines that there is no need to replace the seal material 141 and 142 based on the drive count of the piston 17, the controller 40 may further determine the need to replace the seal material 141 and 142 based on the strain of the seal material 141 or 142. By executing a determination based on the strain of the seal material 141 or 142 in addition to a determination based on the drive count of the piston 17, deterioration of the seal material 141 or 142 that cannot be ascertained only by the drive count of the piston 17 may be ascertained. As a result, the replacement of the seal material 141 or 142 is appropriately managed.

[0064] The movement speed of the piston 17 and the strain of the seal material 141 or 142 may also be referred to as drive data. In other words, the drive data includes at least one of the movement speed of the piston 17 or the strain of the seal material 141 or 142. The drive data may include the drive count of the piston 17. The controller 40 may determine the need to replace the seal material 141 and 142 based on the drive data. The operation of acquiring the drive data may also be referred to as a drive data acquisition step.

[0065] <Retighten nut 12> As a maintenance operation to maintain the sealability of the sampling chamber 152, retightening of the nut 12 may be performed so that sufficient load is applied to the seal material 141 and 142 to ensure a close fit between the seal material 141 and 142 and the stem 15. By retightening the nut 12 as maintenance work before replacing the seal material 141 and 142, the cost of material or replacement work, lost opportunities due to the shutdown of the gas chromatograph 1 during the period spent on replacement work, and the like are reduced. The controller 40 of the gas chromatograph 1 according to the present embodiment determines the need to retighten the nut 12 based on the drive data of the liquid sampling valve 10.

[0066] The controller 40 may accumulate the drive count of the piston 17 of the liquid sampling valve 10 and determine the need to retighten the nut 12 based on the drive count. When the controller 40 determines that there is a need to retighten the nut 12, the controller 40 may output an alarm to prompt a user to retighten the nut 12. The operation of determining the need to retighten the nut 12 may also be referred to as a retightening determination step.

[0067] For example, the controller 40 may determine that the nut 12 needs to be retightened when the drive count of the piston 17 is equal to or greater than a defined threshold value, and thereupon output an alarm to prompt a user to retighten the nut 12. The defined threshold value that is compared to the drive count of the piston 17 to determine the retightening of the nut 12 may also be referred to as a first retightening threshold. The first retightening threshold may be determined based on a result of wear tests of the seal material 141 and 142, a drive count of the piston 17 at which a problem related to the seal material 141 and 142 occurred during operation of the gas chromatograph 1, or the like. The controller 40 determines the retightening of nut 12 based on the drive count of the piston 17, regardless of the length of time elapsed after the seal material 141 and 142 is newly installed.

[0068] The controller 40 may output an alarm to prompt a user to retighten the nut 12 when the movement speed of the piston 17 of the liquid sampling valve 10 is equal to or greater than a defined threshold value. The defined threshold value that is compared to the movement speed of the piston 17 to determine the retightening of nut 12 may also be referred to as a second retightening threshold. The second retightening threshold may be determined based on an actual value of movement speed of the piston 17 at which a problem related to the seal material 141 and 142 occurred during operation of the gas chromatograph 1, or the like.

[0069] The controller 40 may output an alarm to prompt a user to retighten the nut 12 when the strain on the seal material 141 or 142 of the liquid sampling valve 10 is equal to or less than a defined threshold value. The defined threshold value that is compared to the strain of the seal material 141 or 142 to determine retightening of the nut 12 may also be referred to as a third retightening threshold. The third retightening threshold may be determined based on an actual value of strain of the seal material 141 or 142 at which a problem related to the seal material 141 and 142 occurred during operation of the gas chromatograph 1, or the like.

[0070] According to the present embodiment, even when the controller 40 determines that there is no need to retighten the nut 12 based on the drive count of the piston 17, the controller 40 may further determine the need to retighten the nut 12 based on the movement speed of the piston 17 or the strain of the seal material 141 or 142. By executing a determination based on the movement speed of the piston 17 or a determination based on the strain of the seal material 141 or 142 in addition to a determination based on the drive count of the piston 17, deterioration of the seal material 141 or 142 that cannot be ascertained only by the drive count of the piston 17 may be ascertained. As a result, retightening of the nut 12 is appropriately managed.

[0071] When the seal material 141 or 142 is worn or deteriorated, a sufficiently close fit between the seal material 141 or 142 and the stem 15 cannot be ensured even when the nut 12 is retightened. The controller 40 of the gas chromatograph 1 may manage the liquid sampling valve 10 so that the number of times the nut 12 is retightened is less than a defined number. The defined number of times may be determined based on a correlation between the number of times the nut 12 has been retightened and an actual frequency of occurrence of problems related to the seal material 141 and 142. The controller 40 may set the defined number of times to one, or to two or more. When the defined number of times is set to zero, the controller 40 does not determine the need for retightening the nut 12, but rather determines the need for replacing the seal material 141 and 142 from the beginning.

[0072] When the retightening of the nut 12 does not ensure a sufficiently close fit between the seal material 141 or 142 and the stem 15, there is little maintenance benefit to be gained by retightening the nut 12. By limiting the number of times the retightening of the nut 12 is performed, maintenance work that has little effect is reduced. As a result, the maintenance of the liquid sampling valve 10 is appropriately managed.

[0073] The controller 40 of the gas chromatograph 1 according to the present embodiment determines the need for replacing the seal material 141 and 142 after retightening the nut 12 the defined number of times. In other words, the controller 40 of the gas chromatograph 1 according to the present embodiment does not determine the need for replacing the seal material 141 and 142 until the nut 12 is retightened the defined number of times. The determination of the need for retightening the nut 12 and the determination of the need for replacing the seal material 141 and 142 are not limited to the combinations described above, and may be performed in combinations modified as appropriate.

[0074] <Example procedures of maintenance management method of liquid sampling valve 10> The controller 40 of the gas chromatograph 1 may execute the maintenance management method of the liquid sampling valve 10, including the example procedures of the flowcharts illustrated in FIG. 7, FIG. 8, and FIG. 9. The maintenance management method of the liquid sampling valve 10 may be realized as a maintenance management program to be executed by a processor constituting the controller 40 of the gas chromatograph 1. The maintenance management program may be stored on a non-transitory computer-readable storage medium.

[0075] The controller 40 acquires the drive data of the gas chromatograph 1 (step S1). The drive data includes the drive count of the piston 17. The drive data may include measurements of the acceleration or speed of the piston 17 when driven. The drive data may include measurements of the compressive strain of the seal material 141 or 142, or the compressive force acting on the seal material 141 or 142 from the stem 15. The drive data may include measurements of the shear strain in the seal material 141 or 142 when the piston 17 is driven.

[0076] The controller 40 determines whether the number of times the nut 12 has been retightened after newly replacing the seal material 141 and 142 is equal to or greater than the defined number (step S2). When the number of times the nut 12 has been retightened is not equal to or greater than the defined number (step S2: NO), that is, when the number of times the nut 12 has been retightened is less than the defined number, the controller 40 proceeds to step S3, the procedure for retightening determination of the nut 12, and executes the procedures of the flowchart illustrated in FIG. 8. When the number of times the nut 12 has been retightened is equal to or greater than the defined number of times (step S2: YES), the controller 40 proceeds to the procedure of step S4, the procedure for replacement determination of the seal material 141 and 142, and executes the procedures of the flowchart illustrated in FIG. 9. After executing the procedures of the flowchart illustrated in FIG. 8 or FIG. 9 as step S3 or S4, the controller 40 ends execution of the procedures of the flowchart illustrated in FIG. 7.

[0077] The controller 40 executes the procedures of the flowchart of the retightening determination illustrated in FIG. 8 as the procedure of step S3 in FIG. 7. The controller 40 determines whether the drive count of the piston 17 is equal to or greater than the first retightening threshold (step S31). When the drive count of the piston 17 is equal to or greater than the first retightening threshold (step S31: YES), the controller 40 proceeds to step S34.

[0078] When the drive count of the piston 17 is not equal to or greater than the first retightening threshold (step S31: NO), that is, when the drive count of the piston 17 is less than the first retightening threshold, the controller 40 determines whether the movement speed of the piston 17 is equal to or greater than the second retightening threshold (step S32). When the movement speed of the piston 17 is equal to or greater than the second retightening threshold (step S32: YES), the controller 40 proceeds to step S34.

[0079] When the movement speed of the piston 17 is not equal to or greater than the second retightening threshold (step S32: NO), that is, when the movement speed of the piston 17 is less than the second retightening threshold, the controller 40 determines whether the strain of the seal material 141 or 142 is equal to or less than the third retightening threshold (step S33). When the strain of the seal material 141 or 142 is equal to or less than the third retightening threshold (step S33: YES), the controller 40 proceeds to step S34. When the strain of the seal material 141 or 142 is not equal to or less than the third retightening threshold (step S33: NO), that is, when the strain of the seal material 141 or 142 is greater than the third retightening threshold, the controller 40 determines that there is no need to retighten the nut 12 and ends execution of the procedures of the flowchart illustrated in FIG. 8.

[0080] When at least one of the following cases is true: the drive count of the piston 17 is determined to be equal to or greater than the first retightening threshold (step S31: YES), the movement speed of the piston 17 is determined to be equal to or greater than the second retightening threshold (step S32: YES), or the strain of the seal material 141 or 142 is determined to be equal to or less than the third retightening threshold (step S33: YES), the controller 40 determines that retightening of the nut 12 is necessary and outputs a retightening alarm to prompt a user to retighten the nut 12 (step S34). After execution of the procedure in step S34, the controller 40 ends execution of the procedures of the flowchart in FIG. 8.

[0081] The controller 40 executes the procedures of the flowchart of replacement determination illustrated in FIG. 9 as the procedure of step S4 in FIG. 7. The controller 40 determines whether the drive count of the piston 17 is equal to or greater than the first replacement threshold (step S41). When the drive count of the piston 17 is equal to or greater than the first replacement threshold (step S41: YES), the controller 40 proceeds to step S44.

[0082] When the drive count of the piston 17 is not equal to or greater than the first replacement threshold (step S41: NO), that is, the drive count of the piston 17 is less than the first replacement threshold, the controller 40 determines whether the movement speed of the piston 17 is equal to or greater than the second replacement threshold (step S42). When the movement speed of the piston 17 is equal to or greater than the second replacement threshold (step S42: YES), the controller 40 proceeds to step S44.

[0083] When the movement speed of the piston 17 is not equal to or greater than the second replacement threshold (step S42: NO), that is, when the movement speed of the piston 17 is less than the second replacement threshold, the controller 40 determines whether the strain of the seal material 141 or 142 is equal to or less than the third replacement threshold (step S43). When the strain of the seal material 141 or 142 is equal to or less than the third replacement threshold (step S43: YES), the controller 40 proceeds to step S44. When the strain of the seal material 141 or 142 is not equal to or less than the third replacement threshold (step S43: NO), that is, when the strain of the seal material 141 or 142 is greater than the third replacement threshold, the controller 40 determines that there is no need to replace the seal material 141 and 142 and ends execution of the procedures of the flowchart illustrated in FIG. 8.

[0084] When at least one of the following cases is true: the drive count of the piston 17 is determined to be equal to or greater than the first replacement threshold (step S41: YES), the movement speed of the piston 17 is determined to be equal to or greater than the second replacement threshold (step S42: YES), or the strain of the seal material 141 or 142 is determined to be equal to or less than the third replacement threshold (step S43: YES), the controller 40 determines that replacement of the seal material 141 and 142 is necessary and outputs a replacement alarm to prompt a user to replace the seal material 141 and 142 (step S44). After execution of the procedure in step S44, the controller 40 ends execution of the procedures of the flowchart in FIG. 8.

[0085] (Review) As described above, according to the maintenance management method of the gas chromatograph 1 of the present embodiment, the replacement of the seal material 141 and 142 is managed based on the drive count of the piston 17 of the liquid sampling valve 10. By managing the replacement of the seal material 141 and 142 based on the drive count of the piston 17, there is a greater likelihood that the seal material 141 and 142 is replaced in a worn condition. In other words, the seal material 141 and 142 not in worn condition is less likely to be replaced. By reducing the replacement of the seal material 141 and 142 that is not in worn condition, the cost of material or replacement work, lost opportunities due to the shutdown of the gas chromatograph 1 during the period spent on replacement work, and the like are reduced.

[0086] Further, as a maintenance operation for the liquid sampling valve 10, retightening of the nut 12 may be performed based on the drive count of the piston 17 before replacement of the seal material 141 and 142. By retightening the nut 12 before replacing the seal material 141 and 142, the cost of material or replacement work, lost opportunities due to the shutdown of the gas chromatograph 1 during the period spent on replacement work, and the like are reduced.

[0087] As maintenance work for the liquid sampling valve 10, the seal material 141 and 142 is replaced or the nut 12 is retightened based on the drive count of the piston 17, in order to appropriately manage maintenance of the seal material 141 and 142.

[0088] Further, by managing the maintenance of the seal material 141 and 142 based on the drive count of the piston 17, a user may ascertain when to maintain the seal material 141 and 142 and is able to replace the seal material 141 and 142 and retighten the nut 12 in a planned manner. As a result, the user may develop and implement a plan that incorporates management work of the gas chromatograph 1 into the analysis work using the gas chromatograph 1.

[0089] According to the gas chromatograph 1 and the liquid sampling valve 10 of the present embodiment, appropriate management of maintenance timing of the seal material 141 and 142, or planned work, may be implemented. As a result, the cost of materials and work spent on the maintenance of the seal material 141 and 142, or loss incurred by reduced availability of analytical work using the gas chromatograph 1, are reduced.

[0090] Further, maintenance of the seal material 141 and 142 may be managed based on movement speed of the piston 17 or strain of the seal material 141 or 142. By managing the maintenance of the seal material 141 and 142 based not only on the drive count of the piston 17, but also on other drive data of the liquid sampling valve 10, deterioration of the seal material 141 or 142 that cannot be ascertained only by the drive count of the piston 17 may be ascertained. As a result, the maintenance of the seal material 141 or 142 is appropriately managed.

[0091] (Other embodiments) The following is a description of other embodiments of the gas chromatograph 1 and the liquid sampling valve 10.

[0092] <Prediction of maintenance time based on changes in drive data> In the liquid sampling valve 10, the seal material 141 or 142 wears as the drive count of the piston 17 increases. The more the seal material 141 or 142 wears, the faster the piston 17 moves. The more the seal material 141 or 142 wears, the smaller the strain on the seal material 141 or 142. In other words, the drive count of the piston 17 correlates with the drive data such as the movement speed of the piston 17, the strain on the seal material 141 or 142, and the like.

[0093] For example, FIG. 10 illustrates a graph that indicates the correlation between the drive count of the piston 17 and the movement speed of the piston 17. In the graph of FIG. 10, the horizontal axis represents the drive count. The vertical axis represents the movement speed of the piston 17. The actual measured data of the movement speed of the piston 17 acquired for the liquid sampling valve 10 is indicated as a solid circle. A trend for the movement speed of the piston 17 to increase with the drive count of the piston 17 can be seen.

[0094] The relationship between the drive count of the piston 17 and the movement speed of the piston 17 may be formulated, for example, by a linear approximation. In the graph of FIG. 10, extrapolated data that is a linear approximation of the measured data of the movement speed of the piston 17 is indicated by a dotted line. The extrapolated data of the movement speed of the piston 17 extends the relationship between the drive count of the piston 17 and the movement speed of the piston 17 to a range of times the piston 17 has not yet actually been driven, and is used to predict the movement speed of the piston 17 assuming an increase in the drive count of the piston 17. By generating extrapolated data based on the measured data of the movement speed of the piston 17, the controller 40 of the gas chromatograph 1 is able to predict the movement speed of the piston 17 when the drive count of the piston 17 is set to a number not actually yet reached.

[0095] Using the extrapolated data of the movement speed of the piston 17, the controller 40 is able to predict the drive count of the piston 17 when the predicted value of the movement speed of the piston 17 will be equal to or greater than the second retightening threshold or the second replacement threshold as a predicted maintenance time when maintenance such as retightening the nut 12 or replacing the seal material 141 and 142 will be required. In the graph of FIG. 10, the threshold of the movement speed of the piston 17 is represented by a dashed line extending in the horizontal direction. The maintenance time is represented by a dashed line extending in the vertical direction. When the controller 40 drives the piston 17 at a constant cycle, the controller 40 is able to calculate the date and time when a maintenance time will be reached by calculating the product of the number of times until the drive count corresponding to the maintenance time is reached and the drive cycle of the piston 17.

[0096] The drive count of the piston 17 also correlates with the strain on the seal material 141 or 142. The controller 40 may generate extrapolated data by approximating the measured data of the strain of the seal material 141 or 142 with respect to the drive count of the piston 17. The extrapolated data for the strain of the seal material 141 or 142 extends the relationship between the drive count of the piston 17 and the strain of the seal material 141 or 142 to a range of times the piston 17 has not yet actually been driven, and is used to predict the strain of the seal material 141 or 142 assuming an increase in the drive count of the piston 17. By generating extrapolated data based on the measured data of the strain of the seal material 141 or 142, the controller 40 is able to predict the strain of the seal material 141 or 142 when the drive count of the piston 17 is set to a number not actually yet reached.

[0097] Using the extrapolated data of the strain of the seal material 141 and 142, the controller 40 is able to predict the drive count of the piston 17 when the predicted value of the strain of the seal material 141 and 142 will be equal to or greater than the third retightening threshold or the third replacement threshold as a predicted maintenance time when maintenance such as retightening the nut 12 or replacing the seal material 141 and 142 will be required.

[0098] The controller 40 is not limited to linear approximation, and may perform various other approximations, such as polynomial approximation, to generate extrapolated data for the drive data.

[0099] As mentioned above, the controller 40 is able to predict maintenance timing based on predictions of drive data. Predicted maintenance timing may also be referred to as predicted maintenance time. A user may ascertain when to replace the seal material 141 and 142 based on the predicted maintenance time and is able to replace the seal material 141 and 142 in a planned manner. Further, a user is also able to plan to retighten the nut 12 based on the predicted maintenance time. As a result, the user may develop and implement a plan that incorporates maintenance work on the liquid sampling valve 10 into analysis work using the gas chromatograph 1. The operation of predicting maintenance timing may also be referred to as a maintenance time prediction step. The operation of predicting when to replace the seal material 141 and 142 may also be referred to as a replacement time prediction step. The operation of predicting when to retighten the nut 12 may also be referred to as a retightening time prediction step.

[0100] <Other ways to calculate movement speed of piston 17> According to the embodiments described above, the movement speed of the piston 17 is calculated based on the acceleration measured by the accelerometer 171 attached to the piston 17. Other ways of calculating the movement speed of the piston 17 are described below.

[0101] As illustrated in FIG. 11, the accelerometer 171 may be attached to the cylinder 18 instead of the piston 17. The controller 40 of the gas chromatograph 1 may be communicatively connected to the accelerometer 171 via the cable 172. The controller 40 may be communicatively connected to the accelerometer 171 by wireless means.

[0102] When the piston 17 moves in a direction that pushes the stem 15 from the sampling chamber 152 toward the vaporization chamber 161, the piston 17 moves until hitting the wall of the cylinder 18 near the sampling chamber 152. Conversely, when the piston 17 moves in a direction that pulls the stem 15 from the vaporization chamber 161 toward the sampling chamber 152, the piston 17 moves until hitting the wall on the far side of the cylinder 18 from the sampling chamber 152. The accelerometer 171 attached to the cylinder 18 detects acceleration that occurs in the cylinder 18 when the piston 17 hits a wall of the cylinder 18.

[0103] The controller 40 of the gas chromatograph 1 acquires the time when the accelerometer 171 detects acceleration as the time when the piston 17 hits a wall of the cylinder 18. The controller 40 calculates the time from a time when drive air is supplied to the drive air supply 181 or 182 to start driving the piston 17 to a time when the piston 17 hits a wall of the cylinder 18 as the travel time of the piston 17. The controller 40 is able to calculate the movement speed of the piston 17 by acquiring known information about the distance the piston 17 moves in the cylinder 18 and dividing the distance traveled by the piston 17 by the movement time.

[0104] By allowing the speed of the piston 17 to be calculated simply by attaching the accelerometer 171 to the cylinder 18, the configuration required to calculate the movement speed of the piston 17 is easily added to the liquid sampling valve 10 when already present.

[0105] As illustrated in FIG. 12, a proximity sensor 173 or 175 may be attached to the cylinder 18. The proximity sensor 175 may be attached to the wall of the cylinder 18, on the side closer to the sampling chamber 152. The proximity sensor 173 may be attached to the wall of the cylinder 18, on the far side from the sampling chamber 152. The controller 40 of the gas chromatograph 1 may be communicatively connected to the proximity sensor 173 via a cable 174. The controller 40 may be communicatively connected to the proximity sensor 175 via a cable 176. The controller 40 may be communicatively connected to the proximity sensor 173 or 175 by wireless means.

[0106] When the piston 17 moves in a direction that pushes the stem 15 from the sampling chamber 152 toward the vaporization chamber 161, the piston 17 moves until hitting the wall of the cylinder 18 near the sampling chamber 152. The proximity sensor 175 detects when the piston 17 hits the wall of the cylinder 18 near the sampling chamber 152. Conversely, when the piston 17 moves in a direction that pulls the stem 15 from the vaporization chamber 161 toward the sampling chamber 152, the piston 17 moves until hitting the wall on the far side of the cylinder 18 from the sampling chamber 152. The proximity sensor 173 detects when the piston 17 hits the wall on the far side of the cylinder 18 from the sampling chamber 152.

[0107] The controller 40 of the gas chromatograph 1 acquires the time when the proximity sensor 173 or 175 detects that the piston 17 has hit the wall of the cylinder 18 as the time when the piston 17 hits the wall of the cylinder 18. The controller 40 calculates the time from a time when drive air is supplied to the drive air supply 181 or 182 to start driving the piston 17 to a time when the piston 17 hits a wall of the cylinder 18 as the travel time of the piston 17. The controller 40 is able to calculate the movement speed of the piston 17 by acquiring known information about the distance the piston 17 moves in the cylinder 18 and dividing the distance traveled by the piston 17 by the movement time.

[0108] By being able to calculate the movement speed of the piston 17 using the proximity sensor 173 or 175, the movement speed of the piston 17 may be calculated in a simple or inexpensive configuration.

[0109] <Determination considering pressure fluctuation of drive air> The controller 40 of the gas chromatograph 1 is able to determine the need for replacing the seal material 141 or 142 by comparing the movement speed of the piston 17 with the second replacement threshold under the assumption that the pressure of the drive air supplied into the cylinder 18 from the drive air supply 181 or 182 to drive the piston 17 is constant. When the pressure of the drive air varies, the controller 40 may change the second replacement threshold according to the pressure of the drive air. For example, the higher the pressure of the drive air, the faster the movement speed of the piston 17. Therefore, the higher the pressure of the drive air, the greater the second exchange threshold may be. The higher the pressure of the drive air, the greater the third replacement threshold may be, compared to the strain of the seal material 141 or 142.

[0110] The controller 40 may change the second retightening threshold used to determine the need for retightening the nut 12 according to the pressure of the drive air. For example, the higher the pressure of the drive air, the greater the second retightening threshold may be. The higher the pressure of the drive air, the greater the third retightening threshold may be.

[0111] The controller 40 may correct the drive data according to the pressure of the drive air. For example, when the pressure of the drive air is higher than a reference pressure, the controller 40 may calculate a corrected value for the movement speed of the piston 17 when the pressure of the drive air is the reference pressure, based on the measured movement speed of the piston 17 and the pressure of the drive air, and compare the corrected value to the second replacement threshold or the second retightening threshold. Further, when the pressure of the drive air is higher than the reference pressure, the controller 40 may calculate a corrected value for the strain of the seal material 141 or 142 when the pressure of the drive air is the reference pressure, based on the measured strain of the seal material 141 or 142 and the pressure of the drive air, and compare the corrected value to the third replacement threshold or the third retightening threshold .

[0112] As described above, the controller 40 is able to change the determination reference depending on the pressure of the drive air. The accuracy of determining the need for maintenance is enhanced when the pressure of the drive air is taken into account.

[0113] <Other aspects of maintenance management> As described above, the maintenance management method for determining whether to output an alarm about the maintenance of the liquid sampling valve 10 is described as being executed by the controller 40 of the gas chromatograph 1. The liquid sampling valve 10 may include a processor that implements the maintenance management method of the liquid sampling valve 10. In other words, the maintenance management method or maintenance management program described above may be executed by the processor of the liquid sampling valve 10, not just by the controller 40 of the gas chromatograph 1.

[0114] The gas chromatograph 1 may include a maintenance management apparatus that executes the maintenance management method of the liquid sampling valve 10, which may be different from the controller 40 and the processor of liquid sampling valve 10. The controller 40 of the gas chromatograph 1 or the processor of the liquid sampling valve 10 may each also be referred to as a maintenance management apparatus when provided with the function of executing the maintenance management method.

[0115] The above description of embodiments according to the present disclosure is provided with reference to the drawings. Specific configurations are not limited to the embodiments described, and variations are included without departing from the scope of the present disclosure.

[0116] 1 gas chromatograph (20: column, 30: detector, 40: controller) 10 liquid sampling valve 11 block (111: heater, 112: temperature sensor, 113: carrier gas passage, 114, 115: inner wall) 12 nut 131, 132 pipe 133 liquid sample block 141, 142 seal material (141a, 142a: inner wall) 143 strain sensor 144 cable 15 stem (151: sampling groove, 153: liquid sample) 152 sampling chamber 16 pipe 161 vaporization chamber 17 piston 171 accelerometer 173, 175 proximity sensor 172, 174, 176 cable 18 cylinder (181, 182: drive air supply)

Claims

1. A maintenance management method for a liquid sampling valve comprising: a housing including a sampling chamber through which a liquid sample flows and a vaporization chamber in which the liquid sample is vaporized; seal material that separates the sampling chamber from the vaporization chamber; a stem configured to be able to pass in and out of the vaporization chamber through a hole in the seal material; and a piston configured to drive the stem, the maintenance management method comprising: a drive count acquisition step of acquiring a count of times the piston has been driven after the seal material is newly installed; and a replacement determination step of determining that the seal material needs to be replaced when the count of times the piston has been driven is equal to or greater than a first replacement threshold, regardless of time elapsed after the seal material is newly installed.

2. The maintenance management method according to claim 1, further comprising a drive data acquisition step of acquiring at least one of movement speed of the piston or strain of the seal material, wherein in the replacement determination step, determining that the seal material needs to be replaced also occurs in at least one of the following cases: when the movement speed of the piston is equal to or greater than a second replacement threshold, or when the strain of the seal material is equal to or less than a third replacement threshold.

3. The maintenance management method according to claim 2, further comprising a replacement time prediction step of generating extrapolated data predicting a relationship between the count of times the piston has been driven and the movement speed of the piston or the strain of the seal material, and calculating, as a predicted maintenance time until there will be a need to replace the seal material, at least one of (i) the count of times the piston is driven when the movement speed of the piston is equal to or greater than the second replacement threshold in the extrapolated data or (ii) the count of times the piston is driven when the strain of the seal material is equal to or less than the third replacement threshold in the extrapolated data.

4. The maintenance management method according to any one of claims 1 to 3, further comprising, before the replacement determination step, a retightening determination step of determining that a nut that applies a load to the seal material needs to be retightened when the count of times the piston has been driven is equal to or greater than a first retightening threshold, regardless of the time elapsed after the seal material is newly installed.

5. The maintenance management method according to claim 4, wherein, in the replacement determination step, determining that the seal material needs to be replaced also occurs when retightening of the nut has been performed a defined number of times or more.

6. A maintenance management apparatus comprising a processor that executes the maintenance management method according to any one of claims 1 to 3.

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