Use Frequency Conversion Technology to Adjust Boiler Water Supply System

April 29, 2021

As the brain of the boiler system, electric control controls all the operation of the boiler. The role of electronic control is self-evident. It can not only monitor the real-time working status of the boiler in real time, but also control all the operation of the boiler system. So how does the electric control control the boiler feed water?

At present, there are two main ways of boiler water supply: 1. Position water supply 2. Continuous water supply

Different water supply methods use different working principles. In order to facilitate customers to choose more clearly, EPCB analyzes the boiler water supply mode according to customer needs, and elaborates how to use frequency conversion technology to realize boiler continuous water supply technology.

Comparation of position water supply and continuous water supply

Working principle of position water supply:

When the water level gauge detects that the water level reaches the low point, the point with the low water level is connected in parallel with the electric start button to start the water pump and start adding water. When the water level is high, the level gauge contact is disconnected (this contact is connected in series with the stop button), and the pump Stop functioning.

Most of the water supply methods of small steam boilers use electric contact liquid level control. The system uses the state of the electric contact on the steam drum to sense the water level of the boiler and control the start and stop of the water pump.

Advantages:

The principle is simple, and it can be realized by ordinary electric control system, so the price is cheap.

Disadvantages:

1. The water pump starts frequently, and it is easy to cause damage to the water pump and motor, and at the same time increase the pressure of the pipeline and waste energy.

2. When the water level reaches a low point, the pressure in the boiler changes, and at this time, the water pump injects cold water, which will damage the boiler steam and affect the steam quality.

Working principle of continuous water supply:

The continuous water supply is to use the frequency conversion technology to adjust the boiler water supply, which requires the use of a differential pressure transmitter, a three-valve group and a double-chamber balance vessel to measure the boiler liquid level and realize the frequency conversion control of the water supply.

The boiler electric control system needs to install a frequency converter and a set of electrode type liquid level controller. When the differential pressure transmitter senses the pressure change in the boiler, this pressure change can be more accurately simulated to the water level difference in the boiler. This signal is transmitted to the electric control, and the electric control controls the water pump to achieve continuous water supply.

Advantage:

1. This method of continuous water supply can reduce the start-up of the water pump and reduce the pressure shock of the pipeline.

2. Continuous water supply will not cause the internal pressure difference and temperature difference of the boiler, and can ensure the steam quality.

3. It can be realized by adopting a simple PLC system, and the price is not expensive.

Disadvantages:

In summary, the realization of variable frequency continuous water supply is of great significance for protecting the pump and improving steam quality. So how to install boiler accessories to achieve continuous boiler water supply?

Installation diagram:

Note:

There are obvious high-pressure and low-pressure port marks on the double-chamber balance vessel and differential pressure transmitter, which are "L" and "H" respectively. Do not connect them wrongly. Connect the "L" of the balance vessel to the "L" of the differential pressure transmitter. "H" is the same.

变频给水

Installation Method:

1. The opening sequence of the three-valve group is to open the high-pressure valve first, close the balance valve, and finally open the low-pressure valve. The closing sequence of the three-valve group is to close the low-pressure valve first, then open the balance valve, and finally close the high-pressure valve.

2. The operating procedure when the differential pressure transmitter is put into operation: First, open the two drain valves on the differential pressure transmitter, then open the balance valve, and then slowly open the two shut-off valves to remove the air or dirt in the pressure guiding tube. Remove the waste, close the two drain valves, then close the balance valve, the transmitter can be put into operation.

Conclusion:

The use of frequency conversion technology to adjust boiler feed water can extend the service life of the water pump, thereby protecting the boiler system, and ensuring the steam quality to achieve the maximum utilization of boiler efficiency. Therefore, when equipped with a boiler system, you can actively choose electronic control equipment with this frequency conversion technology, which is inexpensive and has many benefits. If you have other suggestions about the use of the boiler, please contact EPCB.