Water supply equipment for boilers
Equipment for supplying water to the boiler can be:
– Centrifugal or reciprocating pumps with electric or mechanical drive.
– Injector Pump
– Means with a pressure higher than the pressure in the boiler and capable of bringing the feed water into the boiler.
Each boiler – boiler must be equipped with at least 2 water supply devices. It is allowed to place 1 water supply device for boilers with small steam output 150kg/h, pressure less than 4kg/cm2. The capacity of the water supply equipment should be at least 0% greater than the rated power of the boiler.
The boiler feed water pump is a pressure pump that satisfies the following conditions: the pump’s head must be greater than the steam pressure, and the pump flow must be larger than the furnace’s capacity.
– The pump commonly used for industrial boilers is the stage vane pump, which is a vertical or horizontal multistage centrifugal pump. The pump consists of several impellers mounted on the same shaft located in the pump housing. Pump housings are made into separate blocks for each impeller stage, which are linked together by bolts or pins. Water moves from one impeller to the next by means of guide grooves.
Boiler–boiler water level sensor
The application of a water level sensor is to control and alarm the water level in the boiler according to the requirements of the designer, to ensure that the amount of water supplied to the boiler at certain times must be appropriate. Boiler water level sensor includes: float control type and electrically controlled type.
This type has a float made of stainless alloy attached to a permanent magnet through the connecting rod mechanism, when this ball changes position according to the water level, the bar magnet also changes and changes. status of the contacts. It is these contacts that send signals to control the pump motors and alarm or stop the boiler
– Transmission rods
– Water pipes
On the junction box of the sensor, the main ends are the contacts, when looking at the catalog we will see more clearly how to connect.
Automatic water supply for boiler – boiler
Through practical studies, most boiler systems on ships today use a water supply controller in the form of a sensor bar through the water supply control circuit and alarm via PLC. Some ships use a differential water level sensor to convert the level into pressure and then convert the voltage – electricity to the PLC. The boiler control PLC will process this signal to control the pump to operate in automatic mode and alarm at different high and low water levels. A disadvantage of this integrated water supply system is that the automatic water supply process must depend on the PLC system, so when the PLC control program fails, the water supply process is also stopped by hand. But when the PLC fails, the process of fixing it is difficult for the operator because then it needs to be reprogrammed.
On old ships, the equipment has been installed for a long time, so over the time of operation, the equipment is damaged, so it needs to be replaced, but most of these equipment are imported from abroad.
Most boilers on ships are auxiliary boilers – exhaust gas, so during running, the boiler does not need to be burned, but the heat of the main engine and the lamp is enough to maintain the steam pressure for the boiler a little bit. Therefore, in the process of running at sea, the functions of automatic burning, automatic heating of oil, etc. do not need to be operated, so these functions can be cut off the automatic water supply functions, but still need to operate continuously. continuously to supply enough water for the boiler to operate .
It is for this reason that an independent automatic water supply controller is essential. If there is an error in the PLC control program, the water supply process also works independently to provide sufficient water for the boiler to operate, or when there is a problem with the water level, the operator can be alarmed. If the independent automatic water supply system has a problem, it is much easier to fix the problem than the water supply system controlled by PLC.
Water control systems for furnaces with large capacity and pressure use differential pressure water level gauges. Using this differential pressure in combination with the level indicator, we will have a continuous indicator level indicator. The differential pressure of this level gauge is usually chosen to be equal to the height of the glass to see the water directly. For example: 500mm. From the differential pressure gauge, the electrical signal is sent to the PID controller to adjust the automatic valve of the furnace water supply. Thus, we have a 1-element water level controller. If we take the feed water flow signal and the steam flow signal to bring to the controller, we have a 3-element water level control system. Of course 3 elements will give a more stable boiler water level.
For boilers – small capacity boilers can use electrode-type level gauges to design an automatic furnace water supply system. Four electrodes can be used:
+ Level 1: 0% symbol LL (out of water): emergency shutdown action.
+ Level 2: 30% of the L symbol (low water level): the impact of running the supply water pump.
+ Level 3: 60% symbol H (high water level): Stop water pump.
+ Level 4: 100% symbol HH (furnace is full of water): emergency furnace stop .
– Floats are often used to protect the furnace water. Sometimes also used to indicate levels. The electrode type level measurement is only for intermittent water level with a number of display points depending on the number of electrodes. Sometimes there is a design to automatically control the water level by means of an electrode probe.
KS – Boiler specializes in manufacturing, installing and maintaining industrial boilers:
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