JPH0334010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for detecting an abnormality in a device, and specifically relates to a reciprocating pump, more specifically a type reciprocatingly driven by pressurized fluid. The present invention relates to a method for detecting an abnormality in a reciprocating pump.

[Prior art and its problems] Among reciprocating pumps, pressurized fluid-driven reciprocating pumps can obtain higher pressure than other types of pumps, so they are used in many fields including cleaning and cutting. ing. Particularly in recent years, as waterjet processing, in which materials are cut by injecting high-pressure water from a nozzle, has come into practical use in various fields, the demand for pressurized fluid-driven reciprocating pumps has rapidly increased. Such pumps generally use a hydraulic system that uses hydraulic oil as the pressurized driving fluid, and an example of this is shown in the circuit diagram of FIG. That is, hydraulic pump 4
The pressurized hydraulic oil is sent to the pressure booster 1 of the pump via the directional control valve 8, and the hydraulic oil presses the piston 2. The piston 2 and the plungers 3, 3' are integrally constructed, and when the piston 2 moves, the plungers 3, 3' also move integrally, so the piston 2 is pushed by hydraulic fluid to the right or left. When the plungers 3, 3' move to the right or left, the liquid in the high pressure chambers 7, 7' is discharged to the outside of the pressure intensifier 1. At this time, due to the pressure receiving area ratio of the large-diameter piston 2 and the small plungers 3, 3', a liquid with a pressure much higher than the hydraulic pressure acting on the piston 2 is created by the plungers 3, 3', and the pressure increases. It is discharged outside the pressure machine 1. The high-pressure liquid is guided to the nozzle 6 via piping means and is injected from the nozzle 6. When the piston 2 is pushed to one side by the hydraulic pressure acting on the piston 2 and reaches the end of movement, the direction control valve 8 is switched to push the piston 2 in the opposite direction. By sequentially switching the direction of hydraulic pressure applied to the piston 2 by the directional control valve 8, the piston 2 is moved left and right, and high-pressure fluid is obtained almost continuously.

However, the high pressure fluid discharged from the pressure intensifier 1 and injected from the nozzle 6 for use in cutting etc. has a high pressure of 100 MPa to 400 MPa, and this pressure is applied not only to the nozzle 6 but also to the discharge check valve 9,
9', suction check valves 10, 10', and high pressure pipes 11, 11', 12, 12'. The problem here is that when the reciprocating pump is operated at the above pressure, among the elements shown in FIG. For some reason, the joints or seals of the discharge check valves 9, 9', nozzle 6, etc. may become wet, making it impossible to achieve the desired performance as a pump.

Conventionally, in cases such as those mentioned above, abnormalities were discovered by visually checking the wetness of the joints or seals, or the desired pressure was reached using a pressure display means such as a pressure gauge installed in the high-pressure system. Monitoring and detection was carried out using extremely primitive methods, such as visually confirming that something was not happening and discovering anomalies. However, if a pump device is incorporated into a product production line and an abnormality in the pump directly affects product defects,
Conventional monitoring and detection methods are often unable to follow the production line, making them very inconvenient to use.

[Objective and Summary of the Invention] In view of the above-mentioned current situation, the present invention provides for early and reliable detection of abnormalities in reciprocating pumps, thereby improving the maintenance of pump equipment and the quality of products when installed on a production line. The aim is to reduce the number of defects.

In order to achieve this objective, the present invention takes the following approach. That is, in a reciprocating pump driven by fluid pressure, the moving direction and moving stroke time of the reciprocating piston are monitored, and the moving stroke time in the same moving direction is compared with a preset set time. An abnormality is detected when the moving stroke time deviates from the set time by a preset number of times. Specifically, if the set time is a larger value than the normal moving stroke time, if the set time is smaller than the normal moving stroke time, or if the set time is smaller than the normal moving stroke time. It is practical to have two values, a large value and a small value.

[Embodiments of the Invention] The present invention will be described in more detail below based on preferred embodiments.

FIG. 1 shows an example of a circuit diagram of a reciprocating pump to which the present invention can be applied, in which 1 is a pressure booster, 2 is a piston, 3 and 3' are plungers, 4 is a hydraulic pump, 5 is a water supply pump, 6 is a nozzle, 7 and 7' are high pressure chambers, 8 is a directional control valve, 9 and 9' are discharge check valves, 10 and 10' are suction check valves, 1
1, 11', 12, 12' high pressure piping, 13 is a stop valve, 14 is a control valve, 15 is a pressure switch, 16
17 is the right end limit switch, and 17 is the left end limit switch.

The connections between the pressure booster 1 and the high pressure pipes 11 and 11', between the high pressure pipe 12 and the high pressure pipe 12', and between the high pressure pipes 12 and 12' and the stop valve are generally constructed by threaded joints. Therefore, high-pressure water may leak from the threaded joint due to loosening of the joint, foreign matter getting caught during assembly, deformation of the sealing part, or the like. In addition, the high pressure system is reduced to zero by reciprocating the plungers 3 and 3' of the pressure booster 1.
- Repeated internal pressure of a predetermined pressure (for example, 100 MPa to 400 MPa) may cause damage due to fatigue life. Furthermore, there are cases where the nozzle 6 becomes worn due to long-term use and the nozzle hole diameter expands, resulting in an increase in the amount of water injected. In such a case,
While the diameters of the plungers 3 and 3' are fixed and the discharge amount per stroke is fixed, the pressure of the hydraulic pressure discharged from the hydraulic pump 4 and pressing the piston 2 is constant, so it is driven by the piston 2. If the amount of high-pressure water that is the secondary fluid discharged by the plunger 3, that is, the amount of water flowing through the high-pressure system, increases compared to the normal state, the reciprocating speed of the plunger 3 and the piston 2 will increase.

Therefore, if there is no abnormality such as wetting of the high pressure system, the stroke time T _N of the piston 2 or plunger 3, 3' during operation of the reciprocating pump in the so-called normal state is measured in advance, and this stroke time T _N is used as a reference. Set by some means. That is, in the circuit diagram of FIG. 1, when the plunger 3 reaches the right end from the illustrated state and the right end limit switch 16 detects the stroke end of the plunger 3, the directional control valve 8 is switched in the opposite direction to that illustrated. Then, the piston 2 and plungers 3, 3' move to the left, and finally the plunger 3' reaches the left end and the left end limit switch 17 is activated.
detects the stroke end of the plunger 3' and opens the directional control valve 8.
Switch back to the state shown. The same operation is repeated thereafter. In such an operation, the time from when the right end limit switch 16 detects the stroke end of the plunger 3 until the left end limit switch 17 detects the stroke end of the plunger 3', or when the left end limit switch 17 detects the stroke end of the plunger 3' The time from detection until the right end limit switch 16 detects the stroke end of the plunger 3, or the average value of the two types of time, is defined as the normal stroke time T _N.

Next, if the high-pressure system gets wet or the nozzle 6 wears out and the hole diameter expands as described above,
As described above, the stroke time of the plunger 3 is shorter than the normal stroke time T _N. The travel time at this time
Let it be T _A. Similarly, the stroke time of plunger 3' is T _B
shall be. Regarding the relationship between T _A and T _B , depending on the location where the abnormality occurs in the high pressure system, T _A ≒ T _B ,
T _A > T _B and T _A < T _B. In other words, if there is an abnormality in the system from discharge check valves 9, 9' to nozzle 6, generally T _A ≒ T _B , and suction check valve 10 is not sealed properly or high pressure piping 11 is wet. It can be easily understood from Fig. 1 that T _A < T _B in such cases, and T _A > T _B in cases such as poor sealing of the suction check valve 10' or wetness of the high pressure piping 11'. Probably. In either case, T _N > T _A and T _N > T _B.

Here, in the abnormal operating state, the stroke time
If T _N , T _A , and T _B are directly compared, conditions for abnormal operation may be _met depending on the temperature of the hydraulic oil, changes in mechanical resistance, and other disturbance conditions. The above-mentioned reduction can be avoided by adding the offset value to the set time to be compared. Let this value be Tn. To further ensure accuracy, a condition is provided in which the abnormal operation state occurs continuously over a plurality of strokes.

In this way, for example, if the offset value added to T _N is a negative value, T _N > Tn, and the reciprocating speed of the plunger 3 or 3' increases due to the abnormality, resulting in stroke times T _A and T _B becomes small, and when this phenomenon occurs a plurality of times, preferably twice, an abnormality signal is generated.

To explain based on the figures, when an abnormality occurs in _{the high} voltage circuit in Figs. and Tb, and the Ta,
The occurrence of an abnormality is confirmed when Tb becomes smaller than the value of Tn. Then, when the abnormal state continues over a plurality of preset strokes of two or more strokes, it is detected as an abnormality. Figure 2 shows normal operation, where Tn＜T _A ≒T _B
, and Figure 3 shows that during abnormal operation, Tn>Ta≒
Tb, and Figure 4 shows T _B > Tn > during abnormal operation.
Ta, and Figure 5 shows that during abnormal operation, T _A > Tn
> This indicates the operating status of Tb.

Contrary to what has been explained above, if, for example, a foreign object gets stuck in the hole of the nozzle 6 and is blocked, or the stop valve 13 is clogged with a foreign object, the case shown in FIGS. 2 to 5 will not occur. Conversely, the time during abnormal operation is longer than the time during normal operation. In this case, set the offset value added to T _N to be a positive value, set Tn' so that T _N <Tn', and set the stroke times Ta and Tb at the time of abnormality to the set values.
An abnormality is detected when a state in which the value exceeds Tn' continues over a plurality of preset strokes of two or more strokes. An example of such a case is shown in FIG.

In practice, it is effective to configure the device so that it has both the functions of detecting as an abnormality when Tn>Ta, Tb and also detecting as an abnormality when Tn′<Ta, Tb. .

[Effects of the Invention] As detailed above, according to the present invention,
Not only can abnormal conditions of the pump equipment be detected reliably, but the detected abnormality can be output as a signal, and the signal can be used to turn on an indicator light, stop the operation of the pump equipment, or perform other functions. It can also be configured to control the operation of related equipment, making maintenance management of the pump equipment easier and reducing product defects caused by pump abnormalities on the product manufacturing line. The effects in this field are extremely significant.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a reciprocating pump, and FIGS. 2 to 6 are time charts showing different cases of the reciprocating pump to which the present invention is applied.

Claims (1)

[Claims] 1. In a reciprocating pump driven by fluid pressure, the moving direction and moving stroke time of a reciprocating piston are monitored, and the moving stroke time in the same moving direction and a preset setting time are In comparison, an abnormality detection method for a reciprocating pump characterized in that an abnormality is detected when the travel stroke time deviates from the set time for a preset number of times. 2. The abnormality detection method for a reciprocating pump according to claim 1, wherein the set time is a value larger than the normal moving stroke time. 3. The abnormality detection method for a reciprocating pump according to claim 1, wherein the set time is a value smaller than the normal moving stroke time. 4. The abnormality detection method for a reciprocating pump according to claim 1, wherein the set time has two values, one larger and one smaller than the normal moving stroke time.