JPS6045759B2 - How to operate a water supply device with a pressure tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of operating a water supply system having a pressure tank in which a plurality of pumps are operated in parallel according to the amount of water supplied.

[Background of the Invention] In order to downsize a water supply device equipped with a pressure tank, it is effective to downsize the pressure tank, which occupies the largest volume of the device.

However, if the pressure tank is made smaller, the pump starts more frequently, which is an undesirable phenomenon in terms of continued operation of the device. Recently, in order to reduce the frequency of starting the pump when the pressure tank is made smaller, a method of operating a water supply system has been proposed in which the pump, once started, is forced to continue operating for a predetermined period of time. On the other hand, there is a demand for water supply systems with a relatively large amount of water in the market, and in the operating method of such water supply systems, the total amount of water demand is By dividing the pump into two or three pumps and operating only the necessary number of pumps in parallel, the frequency of pump startup can be reduced, and the shock when starting and stopping the pump can be reduced. The idea is to make it smaller.

An example of such a water supply device is shown in FIG.

Pumps 1 and 2 have the same characteristics, and are connected in parallel to a discharge main pipe 5 communicating with the demand end via check valves 3 and 4, respectively.

A pressure tank 6 has an air reservoir connected to the discharge sides of the pumps 1 and 2, and is equipped with two pressure detectors 7 and 8 for setting the operating ranges of both the pumps 1 and 2, respectively.

In FIG. 2, the horizontal axis represents the pump discharge amount Q, and the vertical axis represents the pump discharge pressure H. A characteristic curve 11 shows the relationship between the discharge amount Q and the discharge pressure H when the pump 1 is operated independently.
Further, the same relationship when pump 1 and pump 2 are operated in parallel is shown as a characteristic curve 12.

That is, the pressure detector 7 detects that the pressure inside the pressure tank 6 is H1.
A command signal is issued, for example, to cause the pump 1 to operate in advance between the pressures H1 and H2 by the action of a contact (not shown) which closes when the pressure drops to H2 and opens when the pressure recovers to H2. In addition, the pressure detector 8 closes when the pressure in the pressure tank 6 drops to a pressure H3 that is slightly lower than the pressure H1, and opens when the pressure H4 recovers to a slightly lower pressure than the pressure H2 due to the function of a contact (not shown). For example, a command signal is issued to cause the pump 2, which starts following the previous pump 1, to operate between the pressure ratio and the pressure H4. Now, even in a water supply device including a plurality of such pumps, consideration must be given to downsizing the device.

However, in such a device, if the operating method described above is adopted and the pressure tank is made smaller, the number of pumps to be operated may not be selected correctly depending on the amount of demand.
The controllability of the water supply system gradually deteriorates, with all pumps starting at once even though the demand for water is small.

Therefore, the inventors of the present invention repeatedly conducted various experiments to investigate this point, and as a result, discovered the following cause. The cause of this
The horizontal axis is the elapsed time T. The operation progress of the water supply system will be explained with reference to FIG. 3, in which pressure H is plotted on the vertical axis. In FIG. 3, the curve m1 is near the outlet of the pump 1 (upstream of the check valve 3), the curve M2 is near the outlet of the pump 2 (upstream of the check valve 4), and the curve M3 is inside the pressure tank 6. These graphs show the pressure change of . Now, when both pumps 1 and 2 are stopped at time a in Fig. 3, a relatively small amount of water is used, and the pressure in the pressure tank 6 decreases and reaches pressure H1 at time b, and the pressure is detected. The pump 1 is started by a command signal from the pump 7. At this time, when pump 1 is started, the pressure near the outlet of pump 1 immediately decreases to H.
However, the pressure inside the pressure tank 6 continues to fall. When the pressure in the pressure tank 6 reaches the pressure H3 at time c, the pump 2 is also started by the command signal from the pressure detector 8. If the demand water amount is relatively small, the two pumps 1,
2 starts parallel operation, oversupply occurs and pressure tank 6
The pressure inside rises to pressure H4 in a short time, and at time d
When the pressure reaches H4, the pump 2 is stopped by the action of the pressure detector 8. In such a conventional operating method of a water supply system, there is a time delay (this is shown as Δt in the figure) for the pressure after the start of the pump 1, which was started earlier, to be transmitted to the pressure tank 6, so the pump 1 is not started. Despite this, the pressure in the pressure tank 6 continued to drop, and the pump 2 started to follow suit. Further, when pumps 1 and 2 are operated simultaneously and there is an oversupply depending on the amount of water demanded, pump 2, which starts following the pump, stops immediately after starting, which causes a so-called chattering phenomenon. j [
Object of the present invention] An object of the present invention is to provide a method of operating a water supply system equipped with a pressure tank that is a combination of a plurality of pumps and a pressure tank, and in which the pumps are started less frequently.

■ [Summary of the invention] That is, the feature of the present invention is that there is a first pump and a second pump, and a pressure tank is connected to the discharge side of these pumps, so that the pressure on the discharge side of the pump is set to the first value. The first pressure detection means detects that the pressure has decreased, and the second pressure is lower than the first value.
and a third value that is higher than the second value and lower than the first value by the second pressure detection means, and starts the first pump based on the signal from the first pressure detection means. It is started by the control means, and the pressure on the discharge side reaches the second value, and the timer starts counting based on the signal of the second value from the second pressure detection means. The second pump start control means, which operates based on the second pump start control means, does not output a start signal for the stopped second pump if the timer is within the operating time even if the second pump start control means receives a signal indicating that the value has decreased to the second value; After the operating time of the timer has elapsed, if the second pressure detection means detects the second value, the stopped second pump is started, and if the second pressure detection means detects the third value, the second pressure detection means detects the third value. An example of this is to operate the stopped second pump without starting it.

Therefore, even if the first pump starts and the pressure increases, there is no possibility that the second pump will follow suit and start.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 4, 5, and 6.
This will be explained based on the diagram.

In these figures, Fig. 4 is a schematic diagram for explaining the mechanical configuration of a water supply system equipped with a pressure tank, Fig. 5 is a diagram for explaining the operating characteristics of the pump, and Fig. 6 is a diagram for explaining the operating characteristics of the pump. It is a sequence diagram for explaining the electrical configuration,
Components denoted by the same reference numerals as those described in the previous step have the same functions, so the description thereof will be omitted. Now, 7 shown in FIG. 4 is a pressure detector having a first pressure detection means, and 8
a is a pressure detector having a second pressure detection means. This pressure detector 8a emits a command signal for the pump to follow and operate, and is provided with a contact 8Sa.
That is, this contact point 8Sa closes when the pressure in the pressure tank 6 drops to the second value of pressure H3, which is slightly lower than the first value of pressure H1 and moreover, the second value of pressure H.
It opens when the pressure is restored to a third value, H5, which is slightly higher than 3. In addition, the contact 8S of the pressure switch 8b
b closes when the pressure in the pressure tank 6 drops to pressure H6, and opens when the pressure recovers to a pressure slightly lower than pressure H2 and slightly higher than pressure H6.

To explain in more detail with reference to FIG. 6, 7S is a contact of the pressure detector 7 that closes when the pressure in the pressure tank 6 drops to the first value H1, and opens when the pressure recovers to the pressure peak;
Pl and P2 are relays for operating pump 1 and pump 2, respectively, and R is a contact point Plb of both relays Pl and P2.
, P2b are both closed, and the contact Rc is moved from the a side to the b side, or from the b side to a
Switch to the side.

T1 is a timer for reducing the frequency of starting the pump that is started in advance, and is set to the shortest time period during which the pump that is started in advance is desired to continue operating. T2 is a timer to prevent the later pumps from starting due to the pumps started earlier, and corresponds to the delay time required for the influence of the pumps started earlier to be sufficiently transmitted to the pressure tank 6. I have set a time limit. Also, T3
is a timer for reducing the frequency of starting the pump that starts following the timer, and sets the shortest time limit for the continuous operation of the pump that starts following the timer. X is a relay to follow and start the pump, and each contact 7S, 8S
a, 8Sb and the contact T2a of the timer T2. That is, this relay is activated when the influence of the pump started by the preceding pump is sufficiently transmitted to the pressure tank 6, and when the pressure in the pressure tank 6 reaches the third value of pressure H.
It assists when the level has not recovered to 5. Next, a method of operating a water supply system equipped with a pressure tank configured as described above will be explained in accordance with the operating order.

First, it is assumed that the pressure in the pressure tank 6 is a pressure H2, and that the contacts are as shown in FIG. In this state, the contact Rc of the ratchet relay R is closed to the b side, so the relationship between both pumps 1 and 2 is selected so that the first pump 1 operates in advance and the second pump 2 follows. . When the pressure in the pressure tank 6 drops to the first value of pressure H1 in response to the water demand 7, the contact 7S closes and the relay P1
energizes, the first pump 1 starts. At this time,
The pressure in the pressure tank 6 instantly drops to the second value of pressure H3, and the contact 8Sa of the pressure detector 8a and the contact 8Sb of the pressure detector 8b, which are the second pressure detection means, are closed and the timer T is activated.
2 is energized, if the pressure H5 recovers to the third value within the time period set by the timer T2, the relay X will not energize and the second pump 2 will not follow up. 6
The pressure inside increases along the characteristic curve 11, and when it reaches the pressure H4, the contact 8Sb of the pressure detector 8b opens. Furthermore, when the pressure inside the pressure tank 6 rises and reaches the pressure tank, the contact 7
S opens. In this state, if the set time limit of the timer T1 is still within the set time limit, the relay P1 continues to be energized by the action of the series circuit between the contact Pla of the relay P1 and the contacts Tla and Tlb of the timer T1 itself. That is, when the set time limit of the timer T1 passes and the contact Tlb opens, if the contact 7S is open, the relay P1 is released and the pump 1 is stopped. When the contact Plb closes due to the release of the relay P1, the ratchet relay R is energized and its contact Rc8b side is switched to the a side. When the pressure in the pressure tank 6 decreases again and becomes less than the second value of pressure H3, the relay P2 is energized this time, so the second pump 2 is started first. Even though the pump 2 has started, the pressure in the pressure tank 6 instantly drops below the second pressure H3, and because the amount of water demanded is large, it recovers to the third value of pressure H5 within the time period set by the timer T2. Otherwise, contact T2a of timer T2 closes and relay X is energized. Due to the energization of relay
When a is energized, relay P1 and timer T3 are energized, and first pump 1 starts following second pump 2. By operating the two pumps 1 and 2 in parallel, the pressure in the pressure tank 6 recovers along the graph 12, and the contacts 8sa1 and 8Sb open one after another.

When the contact 8Sb opens, if it is still within the set time limit of the timer T3, the contact T3 of the timer T3 is closed, and the pump 1 continues to operate. In other words, if contact 8Sb opens and remains open when the set time limit of timer T3 has passed,
Relay X is deenergized, relay P1 is released, and first pump 1 is stopped. As is clear from the above explanation, in this embodiment, the contact point of the pressure detector that determines the operating range of the pump to be followed and started is replaced with the contact point 8Sa for taking out the command signal for starting the pump, and the contact point 8Sa for taking out the command signal for starting the pump. Even if the contact 8Sa is closed, should the pump be followed up and started until the transient state period in which the preceding pump started (the period indicated by Δt explained in Fig. 3) has passed? The vehicle is operated without making any judgments. In addition, although the described embodiment has been described in which two pumps having the same characteristics are combined with a small-capacity pressure tank, the operating method of the present invention is also applicable to the combination of three or more pumps. It can also be applied to the operation of water supply systems connected in parallel and controlled in number, and if necessary, pumps with different characteristics can be combined. When combining such pumps with different water supply capacities, it is best to operate the pumps in order of decreasing capacity. [Effects of the Invention] As is clear from the above description, the present invention provides a signal from a pressure detector for a follow-up pump attached to a pressure tank so as to avoid the transient period of a pump that starts in advance. This controls the temporary cancellation.

Therefore, according to the present invention, the starting frequency of the follow-up pump can be controlled even if the volume of the pressure tank is reduced.
Further, since the operation of the pumps is stable and an appropriate number of pumps can be selected according to the amount of water demanded, the water supply device can be downsized.

[Brief explanation of the drawings] Fig. 1 is a schematic diagram showing the mechanical configuration of a conventional water supply system equipped with a pressure tank, and Fig. 2 is a discharge pump with the horizontal axis representing the discharge flow rate and the vertical axis representing the discharge pressure H. FIG. 3 is a diagram for explaining the characteristics, and FIG. 3 is a diagram for explaining the operating state of the water supply device with elapsed time on the horizontal axis and discharge pressure H on the vertical axis. FIG. 4 is an example of the present invention. FIG. 5 is a diagram for explaining the operation of the present invention, with the horizontal axis representing the discharge flow rate and the vertical axis representing the discharge pressure H. FIG. 6 shows the electrical configuration of the same embodiment. It is a sequence diagram for explanation. 1 and 2 are first and second pumps, 6i is a pressure tank, 7 is a pressure detector having a first pressure detection means,
8a is a pressure detector having a second pressure detection means, T2 is a timer, X is a relay, and Δt is a delay time required for the pressure in the pressure tank to come under the influence of the pump started earlier.

Claims (1)

[Claims] 1. There is a first pump and a second pump, a pressure tank is connected to the discharge side of these pumps, and a first pressure detection means detects that the pressure on the discharge side of the pump has decreased to a first value. detecting a second value lower than the first value;
and a third value higher than the value of and lower than the first value by a second pressure detection means, and a first pump start control means for controlling the first pump based on a signal from the first pressure detection means. When the pressure on the discharge side reaches the second value, the pressure at the second value increases.
A timer starts counting based on a signal based on the second value of the pressure sensing means, and a second pump start control means that operates based on the timer and a signal from the second pressure sensing means starts counting based on the signal from the second value. Even if it receives a signal indicating that the pressure has decreased to 100%, if it is still within the operating time of the timer, it will not output a starting signal for the stopped pump, and after the operating time of the timer has elapsed, the second pressure will not be output. If the detection means detects the second value, the stopped pump is started, and if the second pressure detection means detects the third value, the stopped pump is not started. A method of operating a water supply device equipped with a pressure tank characterized by: