JPH06229508A - Feed water system for combined multiboilers - Google Patents

Abstract

PURPOSE:To provide a feed water system which is efficient and achieves long durability of a feed water pump by putting a pressure relief valve into a circulation passage so that the revolution of the feed water pump is controlled to maintain always a set feed water pressure thereby feeding water to a boiler by opening and closing a feed water control valve. CONSTITUTION:A feed water pressure measuring device 4 and a branch point for a circulation passage 6 are provided downstream of a feed water pump 3 and a pipe line branched from the branch point is connected to the suction side of the feed water pump through a pressure relief valve 5 to form the circulation passage 6. A motor-driven open/closure valve 8 is provided in each of the feed water pipe line branched to each boiler, wherein the valve 8 is controlled by a feed water controller 7 of each boiler. A feed water control device 10 connected to the pump 3 is connected to a feed water pressure measuring device 4 to control the revolution of the pump 3 so that the feed water pressure thereof becomes a pressure having been set beforehand. As a result, frequent starting and stopping of the pump can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water supply system for supplying water to a multi-can installed boiler.

[0002]

2. Description of the Related Art Since a multi-tube once-through boiler has a small amount of water, a severe water supply control is required. For the water supply to the boiler, the water supply pump is operated when the water level falls below the water supply start level from the boiler water level detection device, and the water supply pump is stopped when the water level rises to the water supply start level. Since the water level difference between the water supply start level and the water supply stop level is small, the number of times the water supply pump is started and stopped is large and the service life of the water supply pump is short.

Due to the advantages of the high efficiency and short rise time of the multi-tube type once-through boiler, the installation of multiple cans with a plurality of boilers has become popular. As a control method for multi-can installation, a method of detecting the supply steam pressure and controlling the number of operating boilers and the combustion state is adopted, and the control of water supply is controlled by signals from the water level detection device in the boiler. It was done by turning on and off the connected water supply pump.

[0004]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to provide a water supply system which is efficient and extends the life of a water supply pump when a multi-tube once-through boiler is installed in multiple cans.

[0005]

[Means for Solving the Problems] In the water supply route of a boiler with multiple cans, one or more water supply pumps are connected to the collective water supply pipe section before branching to each boiler to detect the pressure in the water supply pipe. A water supply pressure detecting device for controlling the water supply pressure, a pressure relief valve for opening and closing the valve when the pressure increases, and a circulation flow path for circulating from the discharge side of the water supply pump to the suction side. The water supply pipe after branching from the collective water supply pipe to each boiler is provided with a water supply control valve whose opening and closing is controlled by the water supply control unit of each boiler. For the steam pressure detection device provided in the steam collecting pipe, the water supply pressure detection device, and the water supply pump control device connected to the water supply pump, different water supply pressure ranges are set depending on the steam pressure, and the applicable pressure range is set. Change the rotation speed and the number of operating water supply pumps. If the water supply pressure rises and reaches the upper limit pressure even at the minimum speed,
The pressure relief valve is opened, water is circulated to the suction side of the water supply pump, and when the pressure drops, the pressure relief valve is closed.

[0006]

[Function] By integrating the water supply pumps in one place, the water supply pumps that were individually installed are no longer necessary, and by controlling the rotation speed of the water supply pumps so that the water supply pressure becomes the set pressure,
Stable water supply can be obtained and start / stop of the water supply pump can be suppressed. Furthermore, by providing a circulation flow path connecting the front and rear of the water supply pump and circulating the water from the downstream side to the upstream side of the water supply pump when the water supply pressure rises, it is possible to prevent the water supply pump from being stopped while the boiler is operating. When supplying water to a boiler, there is a pressure fluctuation at the water supply destination, and if the pressure inside the can is low even at the same water supply pressure, the amount of water supply increases and the water supply speed increases, and if the pressure inside the can is high, the amount of water supply decreases and the water supply speed decreases. The pressure in the can is obtained by using the value obtained from the steam pressure detection device provided to determine the number of boilers burned. If the steam pressure is high, the feed water pressure is high, and if the steam pressure is low, the feed water pressure is high. By changing the pressure to be low, it is possible to efficiently control the water supply pump without taking too much time to supply the water and causing an abnormal water level, and without unnecessarily increasing the water supply pressure.

[0007]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 relates to claim 1, in which two water supply pumps (3) are installed in parallel in a collective water supply pipe (2) through which boiler water sent from a water supply tank (not shown) is passed. A water supply pressure measuring device (4) and a branch point for a circulation flow path are provided on the downstream side, and a pipe branched from the branch point is a relief valve (5).
And is connected to the suction side of the water supply pump via to form a circulation flow path. A water supply pipe branched to each boiler (1) is provided with an electric opening / closing valve (8) controlled by a water supply control unit (7) of each boiler. The steam generated in the boiler passes through the collective steam pipe (9) and is supplied to the steam using equipment. The water supply pump control device (10) connected to the water supply pump is connected to the water supply pressure detection device, and controls the rotation speed of the water supply pump so that the water supply pressure is set in advance.

During operation of the boiler, the water supply control device controls the water supply pump so that the water supply pressure becomes a set value, that is, when the water supply pressure is low, the number of revolutions is large, and when the water supply pressure is high, the number of revolutions is small. . The water supply control of each boiler is performed by the water supply control unit of each boiler detecting the water level in the can and opening and closing the electric on-off valve. When the amount of water supplied to the boiler decreases and the water supply pressure rises due to the steam usage status, the relief valve opens when the upper limit pressure is reached and circulation is performed to prevent the water supply pump from being burdened.

FIG. 2 relates to claim 2. Two water supply pumps (3) are installed in parallel in a collective water supply pipe (2) for passing boiler water sent from a water supply tank (not shown), and a water supply pressure measuring device (4) is provided downstream of the water supply pump.
A branch point for the circulation flow path is provided, and the pipe branched from the branch point is connected to the suction side of the water supply pump via the relief valve (5) to form the circulation flow path. A water supply pipe branched to each boiler (1) is provided with an electric opening / closing valve (8) controlled by a water supply control unit (7) of each boiler. The steam generated in the boiler passes through the collective steam pipe (9) and is supplied to the steam using equipment, and the collective steam pipe has a steam pressure detecting device (1) for detecting the steam pressure.
1) is provided. The water supply pump control device (10) connected to the water supply pump is connected to the water supply pressure detection device and the steam pressure detection device.

Different water supply pressures are set to the water supply pump control device so that the water supply pressure is low when the steam pressure is low, and the water supply pressure is high when the steam pressure is high. The water supply pump control device determines the water supply pressure based on the value from the steam pressure measuring device, and controls the number of rotations and the number of operating water supply pumps so that the water supply pressure becomes that pressure.

[0011]

EFFECTS OF THE INVENTION By properly controlling the water supply pressure with respect to the steam pressure, it is possible to supply water properly without excessively taking time to supply water and without raising the water supply pressure unnecessarily, and installing it in each boiler. By integrating the water supply pumps that were used in one place, the number of water supply pumps can be reduced and the installation space can be reduced. In addition, water supply efficiency was improved by suppressing frequent start and stop of the water supply pump, and the service life of the water supply pump was improved.

[Brief description of drawings]

FIG. 1 is a flow sheet according to claim 1.

FIG. 2 is a flow sheet of claim 2.

FIG. 3 is a flow sheet of a conventional method

[Explanation of symbols]

 1 Boiler 2 Collecting water supply pipe 3 Water supply pump 4 Water supply pressure measuring device 5 Relief valve 6 Circulating flow furnace 7 Water supply control unit 8 Electric on-off valve 9 Steam collecting pipe 10 Water supply pump control device 11 Steam pressure detecting device

Claims (2)

[Claims] 1. In a multi-can installation system in which a plurality of multi-pipe type once-through boilers are installed to perform centralized control, one or more water supply pumps are installed in the collective water supply pipe, and the water supply pump is downstream of the collective water supply pipe. A supply water pressure detection device and a branch point for circulation are installed on the side, and a circulation pipe that returns from the branch point to the suction side of the water supply pump via a pressure relief valve is connected to each boiler in the pipe after branching to each boiler. Is equipped with a water supply control valve electrically connected to the water supply control unit, and controls the rotation speed and the number of operating water supply pumps by a signal from the water supply pressure detection device, and controls the water supply by opening and closing the water supply control valve. A water supply system for a multi-can installed boiler. 2. The water supply system for a multi-can installed boiler according to claim 1, further comprising a steam pressure detecting device for detecting the pressure of the collective steam taken out from the boiler, and the water supply pressure is determined by a signal from the steam pressure detecting device. , A water supply system for a multi-can installed boiler, characterized in that the number of rotations and the number of operating water supply pumps are controlled so that the determined water supply pressure is achieved.