JPS6339434Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a control device for a multiple reciprocating pump, and more specifically, the invention relates to a control device for a multiple reciprocating pump. This invention relates to a control device for a multiple reciprocating pump that reduces the water hammer phenomenon that occurs when switching to unloading or on-loading.

[Description of Prior Art] Multi-unit reciprocating pumps such as 5-unit, 7-unit, and 9-unit reciprocating pumps are used as descaling pumps used in hot rolling processing in steel mills. This descaling pump is required to frequently adjust and change its discharge flow rate. Methods for changing the discharge flow rate of this pump include, firstly, controlling the drive/stop of the motor, which is the drive source for driving the pump;
Second, the pump's pump function is stopped and activated while the drive source motor is driven to control unload/on-load. Third, a bypass circuit is provided in the pump discharge piping and this bypass circuit is connected. / There is a thing that controls shutoff.

When the discharge flow rate is adjusted frequently, such as in a descaling pump, the device that controls driving/stopping the motor, which is the first driving source, has a problem in that a large load is placed on the motor when starting it up. Moreover, the one that controls communication/cutoff of the third bypass circuit causes energy loss due to the liquid flowing through the bypass circuit, which poses a problem from the viewpoint of energy saving.

Therefore, if the discharge flow rate is adjusted frequently,
The second unload/onload control is most desirable.

This unload/on-load control is achieved by providing an unloading mechanism that forcibly holds open the suction valves provided in each pump that constitutes the multiple reciprocating pump from the outside, and the operation of this unloading mechanism. The suction valve is opened, and the pressure in the cylinder of each pump and the pressure in the suction pipe are made the same pressure. This allows liquid to freely flow in and out of the cylinder and the suction pipe, and each pump idles without discharging liquid from the discharge valve, resulting in unloaded operation. The unloading mechanism is activated in synchronization with the suction stroke of each pump (for example, at the beginning or end of the suction stroke),
This ensures smooth pressure changes within the cylinders of each pump. The structure of such an unloading mechanism is
One example is “Mechanical Engineer’s
Handbook Sixth edition” 1958 McGraw
This is a known technique as described in Hill publications 14-2 to 14-5.

However, in the conventional unload/on-load control described above, while the crankshaft of the multiple reciprocating pump makes one revolution, the unloading mechanism of each pump is activated or deactivated in sequence in the order of the division angle of the crankshaft. One revolution of the crankshaft switches all pumps from unload to on-load or from on-load to unload. For this reason, for example, as shown in Fig. 3A, which shows the change in the discharge flow rate when switching from on-load to unload of a 5-unit reciprocating pump, the discharge flow rate suddenly changes, and The drawback was that a water hammer phenomenon occurred in the pump piping system during switching.

[Purpose of the invention] The purpose of the invention is to eliminate the drawbacks of the prior art described above, and to gradually change the discharge flow rate of a multiple reciprocating pump when switching between unloading and on-loading. An object of the present invention is to provide a control device for a multiple reciprocating pump that reduces the water hammer effect on a plumber.

[Summary of the invention] The control device for a multiple reciprocating pump of the present invention includes an unloading mechanism that maintains the suction valve of each pump constituting the multiple reciprocating pump in an open state, and a control device for a multiple reciprocating pump of the present invention. a sensor that detects the suction stroke of each pump in the order of the division angle of the crankshaft in synchronization with the crankshaft of the pump, and controls the unloading mechanism according to the output signal of the sensor. In the control device for a dynamic pump, a logic circuit section is provided that generates a signal in a different order from the order of dividing angles of the crankshaft based on the output signal of the sensor, and the unloading of each pump is performed according to the signal of the logic circuit section. The present invention is characterized in that a mechanism is controlled to unload or load each of the pumps in an order different from the order of division angles of the crankshaft, thereby slowing down changes in the discharge flow rate of the multiple reciprocating pumps.

[Embodiments of the invention] Hereinafter, the invention will be described based on embodiments shown in the accompanying drawings.

FIG. 1 is a circuit diagram showing a control device for a five-stage reciprocating pump which is an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of the circuit diagram in FIG. FIG. 3 is a diagram showing an example of a change in the discharge flow rate of a five-stage reciprocating pump by the control device of the present invention and a change in the discharge flow rate by a conventional device.

First, the structure will be explained. In the figure, 1
is the first pump constituting a 5-unit reciprocating pump (the 5-unit reciprocating pump is composed of the first to fifth pumps, but the second to fifth pumps are not shown) ), a plunger (or piston) 3 that moves up and down as the crankshaft 2 rotates
is arranged inside the cylinder 4. In this cylinder 4, there is a suction valve 6 connected to the suction pipe 5,
A discharge valve 8 connected to the discharge pipe 7 is provided. Further, each pump is provided with an unloading mechanism 9 for forcibly holding the suction valve 6 in an open state from the outside. This unloading mechanism 9 includes an actuator 11 that contracts the rod against the elasticity of an elastic member using air pressure from an air source 10, and a solenoid valve MV (hereinafter referred to as The solenoid valves MV corresponding to the first to fifth pumps are the first to fifth solenoid valves, respectively.
(referred to as MV _{1 to 5} ). Furthermore, a suction position detector 12 is provided at the tip of the extended shaft of the crankshaft 2 to detect the suction stroke of each pump. This suction position detector 12 is provided such that a disc 14 in which one slit 13 is bored rotates in synchronization with the crankshaft.
Five sensors S _{1 to 5} , consisting of a light emitting element and a light receiving element sandwiching 4, are arranged at equal angles (72
degree). The first to fifth sensors S1 _{to S5} correspond to each of the first to fifth pumps, and the plunger 3 of each pump generates an output signal at the top dead center at the beginning of the suction stroke. Therefore, when the crankshaft 2 rotates once, each sensor
_S1-5 sequentially generate output signals.

The control panel 15 receives the output signals of the sensors S _{1 to 5} and controls the first to fifth solenoid valves MV _{1 to} 5 of the unloading mechanism 9 of each pump. A logic circuit section 17 that calculates the output of the pulse input section 16 which receives output signals _{1 to 5} as input.
and an unload/on-load switch that provides a signal for switching the unload or on-load to this logic circuit section 17.
An on-road switching unit 18 and a solenoid valve drive unit 19 that controls each solenoid valve MV 1 to MV ₅ with a signal from the logic circuit unit 17.
and a power supply section 20 that supplies operating voltage to each circuit section. Each of the above circuit sections will be explained in detail below.

The output signals of the first to fifth sensors S _{1 to} 5 are:
They are applied to the pulse input section 16 as parallel signals, each waveform-shaped by the NOT circuit group NOT, and
Given to the input terminal of the OR circuit OR. This OR circuit OR applies the output signals from each sensor S _{1 to S 5} as a pulse train to the frequency divider 21 of the logic circuit section 17 . This frequency divider 21 divides the frequency of the pulse train using a frequency division ratio set by a frequency division ratio setter 22 and supplies the divided pulse train to a one-shot multi 23 . This one-shot multi 23 is triggered by the rising edge of the signal applied from the frequency divider 21 and generates a narrow pulse, which is sent to one input terminal of each of the 11th and 12th AND circuits AND ₁₁ and ₁₂ . give to The other input terminals of the eleventh and twelfth AND circuits AND ₁₁ and ₁₂ are connected to the Q terminal output and the terminal output of the sixth flip-flop FF ₆ controlled by the unload/on-load switching section 18. Given. Furthermore, the logic circuit section 17 includes each solenoid valve of the unloading mechanism 9.
First to fifth flip-flops FF1 to _FF5 are provided corresponding to MV1 to _MV5 . And the first
The set terminal S of the flip-flop _FF1 is supplied with the output of the first AND circuit _AND1 , and the reset terminal R thereof is supplied with the output of the second AND circuit _AND2 . And, one input terminal of each of these first and second AND circuits AND ₁ and ₂ is
An output signal of the first sensor S ₁ is provided. Similarly, the set terminal S of the second flip-flop _FF2
is given the output of the third AND circuit _AND3 , and the reset terminal R is given the output of the fourth AND circuit AND3.
The output of AND ₄ is given. And these third
The output signal of the second sensor _S2 is applied to one input terminal of each of the fourth AND circuits _AND3 and _AND4 . 3rd to 5th flip-flop
FFs _{3 to 5} are similarly given the outputs of the fifth to tenth AND circuits AND _{5 to 10} , and the input terminals of these fifth to tenth AND circuits AND _{5 to 10} are as follows:
Output signals of third to fifth sensors _S3-5 are given. Furthermore, the set terminals S of the first to fifth flip-flops FF ₁ to FF are connected to first, third, fifth, seventh, and ninth AND circuits _AND1 , ₃ ,
The output of the eleventh AND circuit _AND11 is commonly given to the other input terminal of each of circuits ₅ , ₇ , and ₉ .
In addition, the second, _fourth , and
A twelfth AND circuit is connected to the other input terminal of each of the AND circuits AND ₂ , ₄ , ₆ , ₈ , _{and 10} of 6, 8, and 10.
The output of AND ₁₂ is given in common. The electromagnetic valve drive section 19 includes first to fifth power transistors T1 to _T5 corresponding to the respective electromagnetic valves MV1 to _MV5 . Each power transistor _T1-5 has its base terminal connected to the Q output terminal of the corresponding first to fifth flip-flop _FF1-5 , its emitter terminal grounded, and its collector terminal connected to each corresponding solenoid valve.
It is connected to the excitation coils of MV _{1 to 5} . The unload/on-load switching unit 18 includes a first light emitting diode PD 1 that emits light in response to an unload command, a first phototransistor PT ₁ that becomes conductive in response to the light emitted, and a second phototransistor PT ₁ that emits light in response to an on-load command. It consists of a light emitting diode PD ₂ and a second phototransistor PT ₂ which becomes conductive in response to this light emission. The collector voltage of the first phototransistor PT ₁ is applied to the set terminal S of the sixth flip-flop FF ₆ of the logic circuit section 17 via the NOT circuit, and the collector voltage of the second phototransistor PT ₂ is applied to the NOT circuit. It is applied to the reset terminal R via a circuit. Note that the switch SW ₁ provided outside the control panel 15 is operated by an unload command generated externally depending on various conditions such as flow rate, pressure, and water level on the discharge side of the pump, and switches the first light emitting diode. It is for making PD ₁ emit light,
The switch SW ₂ is similarly operated by an on-load command to cause the second light emitting diode PD ₂ to emit light.

Next, the operation will be explained with reference to the time chart shown in FIG. The suction stroke and compression stroke of each of the first to fifth pumps of the five-unit reciprocating pump are shown in FIGS. 2a to 2e. The first to fifth sensors are activated in synchronization with the initial stage of the suction stroke of each pump.
Output signals from S1 _{to S5} are sequentially outputted as shown in FIG. 2, f to j. This output signal of f~j is an OR circuit
The speed is changed by OR to the pulse train shown in FIG. 2k, and the frequency is further divided by the frequency divider 21, resulting in the output shown in FIG. 2l. The output shown in FIG. 2I is obtained when the frequency division ratio of the frequency divider 21 is set to "2". If the frequency division ratio is set to "0", the same output as in Fig. 2 k will be obtained from the frequency divider 2.
Output from 1. At the rising edge of the output l of the frequency divider 21, the one-shot multiplier 23 is triggered and produces a narrow output as shown in FIG. 2m. The output of this one shot multi 23 is OR circuit OR
For the output k of , it is every other output.

Here, if an unload command is given at time _T1 during pump operation, _an output as shown in _FIG . The output of the one-shot multi 23 is allowed to pass through. First, the output of the one-shot multi 23 that has passed through the eleventh AND circuit _AND11 matches the output signal of the second sensor _S2 , and the output signal of the one-shot multi ₂₃ that has passed through the eleventh AND circuit AND11 matches the output signal of the second sensor S2. The flip-flop _FF2 is set, the second solenoid valve _MV2 is energized as shown in FIG. 2q, and the second pump is unloaded. Next, the sensor that matches the output of One Shot Multi 23
The output signals of S1 _{to S5} are the output signals of the fourth sensor _S4 , and the fourth flip-flop _FF4 is set to the set state via the seventh AND circuit _AND7 .
As shown in Figure s, the fourth solenoid valve MV ₄ is energized to unload the fourth pump. Similarly, the first, third, and fifth pumps are unloaded as shown in FIG. 2, p, r, and t, and the five-unit reciprocating pump is unloaded. In this way, the unloading of each pump is not done in the order of the dividing angle of the crankshaft of each pump, but by sequentially unloading every other pump, as shown in Figure 3B, the discharge of the 5-unit reciprocating pump is The flow rate can be gradually reduced gradually during two revolutions of the crankshaft.

Next, if an on-load command is given at time T ₂ during unload operation, the sixth flip-flop FF ₆ is inverted and produces an output at the terminal as shown in Figure 2 o, and the twelfth AND circuit AND ₁₂ allows the output of the one-shot multi 23 to pass through. This 12th
The output of the one-shot multi 23 that has passed through the AND circuit AND ₁₂ and the fourth sensor
The output signal of S ₄ matches, and the 8th AND circuit
The fourth flip-flop FF ₄ is set to the reset state via AND ₈ , and the fourth solenoid valve MV ₄ is set to the reset state in FIG.
Demagnetize the pump as shown below and put the fourth pump on-load. Next, the output signals of sensors S _{1 to 5} that match the output of the one-shot multi 23 are sent to the first sensor S ₁
This is _the output _{signal of} is on-road. In the same way, as shown in Figure 2 r, t, and q, the third, fifth, and second pumps are set to on-load.
On-load the 5-bar reciprocating pump. In this way, the on-load of each pump is not done in the order of the division angle of the crankshaft of each pump, but by sequentially on-loading every other pump, the discharge flow rate of the 5-unit reciprocating pump can be controlled during two rotations of the crankshaft. can be increased slowly in stages.

In this way, since each pump is unloaded or loaded every other pump rather than in the order of the crankshaft's division angle, the change in the discharge flow rate is gradual and the water hammer effect on the pump piping system can be reduced. can. In addition, in the above embodiment, the operation was explained assuming that the frequency division ratio of the frequency divider 21 is "2", but by changing the frequency division ratio, the change in the discharge flow rate of the multiple reciprocating pump can be made more gradual. It can also be made into something. Furthermore, in the above embodiment, since the control device is configured with a non-contact logic circuit, its lifespan is semi-permanent and the response speed is high, so the discharge flow rate of the pump can be adjusted according to external conditions. Changes and adjustments can be made quickly.

In the above embodiment, a light emitting diode and a phototransistor are used as the sensor, but the sensor is not limited to this, and the rotational position of the crankshaft may be detected by an electromagnetic sensor, a mechanical cam switch, or even an encoder. Good too. Furthermore, if the frequency division ratio is fixed to "2" in advance, a bistable multivibrator may be used as the frequency divider. Furthermore, a counter may be used instead of the frequency divider.

In the above embodiment, for the 5-unit reciprocating pump,
Since the frequency division ratio is set to 2, each pump (1st, 3rd, 5th, 2nd, 4th, etc.) is sequentially unloaded or onloaded in the order of the crankshaft division angle, and all pumps are unloaded or loaded in order. are controlled sequentially. However,
If the division ratio is set to 2 for an 8-unit reciprocating pump, the first, third, fifth, and seventh pumps will be controlled every other pump in the order of the crankshaft division angle. , the second, fourth, sixth, and eighth pumps will not be controlled. In such a case, as shown in FIG. 4, which shows a main circuit with a part of the circuit diagram in FIG. ₂ to the frequency divider 21, and the output of the OR circuit to the counter 24.
and the delay circuit 25 in series to form a second OR circuit.
Configure it to feed into the input of OR ₂ . Counter 24
generates one output by counting the number of output signals output from the sensor during one revolution of the crankshaft. The frequency divider 21, which receives this output via the delay circuit 25, receives an input equal to the output signal from the sensor plus 1 in one revolution of the crankshaft, and when the one-shot multi 23 outputs shifts each time the crankshaft rotates,
The first, third, fifth, and seventh pumps match the second sensor output signal, and the fourth, sixth, and eighth pumps are controlled in this order. Thus, all individual pumps can be controlled.

[Effect of the invention] As explained above, according to the control device for a multiple reciprocating pump having the above structure, each pump constituting the multiple reciprocating pump can be operated in different orders according to the division angle of the crankshaft. This is an excellent feature that can be unloaded or on-loaded, which allows for gradual changes in the discharge flow rate of multiple reciprocating pumps, and reduces the water hammer effect on the pump piping system caused by changes in the discharge flow rate. It's effective.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the control device for a multiple reciprocating pump of the present invention, FIG. 2 is a time chart for explaining the operation of the circuit diagram in FIG. 1, and FIG. 4 is a diagram showing an example of a change in the discharge flow rate of a five-stage reciprocating pump caused by the control device of the present invention and a change in the discharge flow rate by a conventional device. FIG. FIG. 1...Pump constituting a multiple reciprocating pump,
6... Suction valve, 9... Unloading mechanism, 2... Crankshaft, S _{1 to 5} ... Sensor, 17... Logic circuit section, 21... Frequency divider, 23... One shot multi, AND _{1 ~10} ...and circuit.

Claims (1)

[Claims for Utility Model Registration] 1. An unloading mechanism that maintains the suction valves of each pump constituting the multiple reciprocating pump in an open state;
a sensor that detects the suction stroke of each pump in the order of the division angle of the crankshaft in synchronization with the crankshaft of the multiple reciprocating pump,
In a control device for a multiple reciprocating pump that controls the unloading mechanism according to an output signal of the sensor, a logic circuit section generates a signal in a different order from the order of division angles of the crankshaft based on the output signal of the sensor. is provided, and the unloading mechanism of each of the pumps is controlled in accordance with a signal from the logic circuit unit, so that each of the pumps is unloaded or loaded in an order different from the dividing angle order of the crankshaft. A control device for a multiple reciprocating pump characterized by: 2. A frequency divider that inputs the pulse train of the output signal of the sensor to the logic circuit section, and a one-shot multiplier triggered by the output of the frequency divider;
an AND circuit that generates an output when the output of the one-shot multi and the output signal of the sensor match, and the output of the AND circuit controls the unloading mechanism of each pump, and the frequency division According to the frequency division ratio of the pump, each of the pumps is unloaded or loaded every other pump or pumps in the order of the dividing angle of the crankshaft. A control device for a multiple reciprocating pump according to item 1.