JPH08233211A - Method and device for controlling/preventing overheating of water supplying pump for deaeration device - Google Patents

Abstract

PURPOSE: To improve a controlling technology for keeping a flow rate passing through a water supplying pump for a deaeration device more than a minimum limit value in order to prevent over-heating of this pump. CONSTITUTION: A water supplying circulation line 9 branched from a water supplying line 1 at an outlet of a water supplying pump 5 and returning back to a water supplying tank 4 is provided with a circulation flow rate adjusting valve 16. This adjusting valve 16 is controlled under a utilization of an opening degree signal sent from a water level adjusting meter 7 of the deaeration device 2 to a water level adjusting valve (a water supplying adjuster valve) 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and a control device applied to prevent overheating of a deaerator feed water pump.

[0002]

2. Description of the Related Art FIG. 3 is a system diagram showing an example of a conventional deaerator water supply system. In this figure, (1) is a deaerator (2)
It is a water supply line which sends out water supply from a water supply tank (4) by a deaerator water supply pump (5) in order to supply water supply to. In order to keep the water level (3) of the deaerator (2) constant, the water level transmitter (6) and the water level controller (7) measure the water level control valve (water supply control valve) (8) opening. To control.
For example, when the water level (3) rises (falls), the opening of the water level control valve (8) is moved in the closing direction (opening direction). The relationship between the output signal of the water level controller (7) and the opening of the water level control valve (8) is shown in Fig. 2 (a). As shown in this figure, when the output signal of the water level gauge controller (7) becomes 0, the water level control valve (8) is fully closed, so that the outlet of the deaerator feed water pump (5) is blocked.

On the other hand, in the deaerator water supply pump (5), it is necessary to ensure a minimum flow rate (pump flow rate) for the purpose of preventing overheating. In order to allow the deaerator feed water pump (5) to have a minimum flow rate for preventing overheating, in the example shown in FIG. 3, the deaerator feed water pump (5) is branched from the discharge part to the water supply tank (4). A water supply circulation line (9) is provided, and a fixed orifice (10) is installed in the water supply circulation line (9).
The water supply at the outlet of the deaerator water supply pump (5) is constantly returned to the water supply tank (4). However, in the case of such a constant circulation system, the water supply is circulated even in the pump operation range where overheat prevention (securing the minimum flow rate) is not required, so that there is a drawback that the pump power cost becomes high.

Therefore, an on / off control system using an automatic valve as shown in FIG. 4 is also implemented. In this method, a flow meter (11) is installed in the discharge line of the deaerator water supply pump (5), and a monitor that detects that the detected flow rate value is smaller than the minimum overheat prevention flow rate (αT / H) Switch (12) and reset flow rate (βT /
A monitor switch (13) for detecting that the size is larger than H) is provided. And for the overheat prevention valve (15) (on / off valve) provided in the water supply circulation line (9),
The interlock circuit (14) outputs a fully open command when the detected flow rate <α and a fully closed command when the detected flow rate> β,
The minimum flow rate for preventing overheating of the deaerator water supply pump (5) is returned to the water supply tank (4) through the overheat prevention valve (15).

[0005]

In the constant circulation system with the fixed orifice shown in FIG. 3, the water supply is always circulated even in the pump operation range where it is not necessary to secure the minimum flow rate for preventing overheating as described above, and the pump power cost becomes high. was there.

Further, in the on / off control system using the automatic valve of FIG. 4, an on / off valve for preventing overheating is installed in order to reduce the power cost of the pump, but the conditions necessary for opening and closing the valve are taken out. Therefore, it is necessary to separately install a flow meter that detects the pump discharge amount.

[0007]

In order to solve the above-mentioned conventional problems, the present inventor has provided a deaerator, a water supply tank connected to the deaerator via a water supply line, and a water supply line. A water supply pump provided, a water supply control valve provided downstream of the water supply pump in the water supply line, and the water supply control valve according to the deaerator water level in order to keep the water level of the deaerator at a specified value. In the water supply system of the deaerator having a water level controller sending an opening signal to the water supply line, and a water supply circulation line branching from the middle of the water supply pump of the water supply line and the water supply control valve to the water supply tank, A deaerator feed water pump overheat prevention control method characterized by controlling a circulation flow control valve provided in a circulation line based on an opening signal sent from the water level controller to the water feed control valve; Supply to the air system and the deaerator A water tank connected via a line, a water supply pump provided on the water supply line, a water supply control valve provided on the downstream side of the water supply pump on the water supply line, and a water level of the deaerator to a specified value. Water level controller that sends an opening signal to the water supply control valve according to the water level of the deaerator in order to maintain the water level, and water supply that branches from the middle of the water supply pump and the water supply control valve of the water supply line to the water supply tank. In a water supply system of a deaerator having a circulation line, a circulation flow rate control valve provided in the water supply circulation line and an opening signal sent from the water level controller to the water supply control valve prevent overheating of the water supply pump. Function to send an opening signal to the circulating flow rate control valve so that the sum of the flow rates passing through the feed water control valve and the circulating flow rate control valve becomes equal to or more than the minimum flow rate after reaching the minimum flow rate required for With vessels It proposes a deaerator feed water pump overheat prevention control device being characterized in that comprises.

[0008]

In the first solving means, the circulation flow rate control valve provided in the water supply circulation line is controlled based on the opening signal sent from the water level controller to the water supply control valve. Therefore, the water supply line and the water supply circulation are controlled. The total flow rate flowing through the line can always be greater than or equal to the minimum flow rate for preventing overheating of the water supply pump.

In the second solving means, the circulation flow rate control valve provided in the water supply circulation line and the opening signal sent from the water level controller to the water supply control valve prevent overheating of the water supply pump. Function to send an opening signal to the circulating flow rate control valve so that the sum of the flow rates passing through the feed water control valve and the circulating flow rate control valve becomes equal to or more than the minimum flow rate after reaching the minimum flow rate required for Since it is equipped with a vessel, it is possible to prevent overheating of the water supply pump without installing extra equipment such as a flow meter, increasing the pump power, and a simple control system.

[0010]

FIG. 1 is a system diagram showing an embodiment of the present invention. In this figure, the same parts as those of the conventional one described with reference to FIGS. 3 and 4 are given the same reference numerals to avoid redundancy, and detailed description thereof is omitted.

In this embodiment, the deaerator water supply pump (5) is prevented from overheating in the water supply circulation line (9) that branches from the wake of the deaerator water supply pump (5) and returns to the water supply tank (4). A circulation flow rate control valve (16) having a flow rate characteristic higher than the flow rate is provided. Then, the function generator (17) performs signal matching so that the circulation flow rate control valve (16) has the opening shown in FIG. 2 (b) with respect to the output signal of the water level controller (7), and the control is performed. Make up the system. The output signal x% of the water level controller (7) at which it is necessary to start opening the circulation flow rate control valve (16) is determined by the water level (water supply) control valve (8) opening x'corresponding to the overheat prevention flow rate. As a result, the total flow rate of the water supply circulation line (9) and the water supply line (1) can always be equal to or higher than the minimum flow rate for preventing overheating, so that overheat protection for the deaerator feed water pump (5) is achieved.

[0012]

According to the present invention, overheat prevention control of the deaerator feed pump can be realized while satisfying the following conditions.

1) No extra equipment (flow meter, etc.) needs to be installed.

2) Simplification of the control system.

3) Reduction of pump power.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between an output signal of a water level controller and the opening degrees of a water supply control valve (water level control valve) and a circulation flow rate control valve.

FIG. 3 is a system diagram showing an example of a conventional deaerator water supply system.

FIG. 4 is a system diagram showing another example of a conventional deaerator water supply system.

[Explanation of symbols]

 (1) Water supply line (2) Deaerator (3) Deaerator water level (4) Water tank (5) Deaerator water supply pump (6) Water level transmitter (7) Water level controller (8) Water level control valve ( Water supply control valve) (9) Water supply circulation line (10) Fixed orifice (11) Flow meter (12), (13) Monitor switch (14) Interlock circuit (15) Overheat prevention valve (on / off valve) (16) Circulation flow control valve (17) Function generator

Claims (2)

[Claims] 1. A deaerator, a water supply tank connected to the deaerator through a water supply line, a water supply pump provided on the water supply line, and a water supply line downstream of the water supply pump. And a water level controller that sends an opening signal to the water control valve according to the deaerator water level in order to maintain the water level of the deaerator at a specified value, and the water supply pump of the water supply line. In a water supply system of a deaerator having a water supply circulation line branching from the middle of the water supply control valve to reach the water supply tank, a circulation flow rate control valve provided in the water supply circulation line is provided with the water supply controller from the water level controller. A deaerator feed water pump overheat prevention control method, characterized in that control is performed based on an opening signal sent to a control valve. 2. A deaerator, a water supply tank connected to the deaerator via a water supply line, a water supply pump provided on the water supply line, and a water supply line downstream of the water supply pump of the water supply line. And a water level controller that sends an opening signal to the water control valve according to the deaerator water level in order to maintain the water level of the deaerator at a specified value, and the water supply pump of the water supply line. In a water supply system of a deaerator having a water supply circulation line branching from the middle of the water supply control valve to reach the water supply tank, a circulation flow rate control valve provided in the water supply circulation line and the water supply from the water level controller After the opening signal sent to the control valve reaches the minimum flow rate necessary to prevent overheating of the water supply pump, the total flow rate passing through the water supply control valve and the circulation flow rate control valve is equal to or more than the minimum flow rate. The opening signal A deaerator water supply pump overheat prevention control device, comprising a function generator for sending to a circulation flow rate control valve.