Type of Liquid Level Control Systems with Working Principle

Liquid level control systems monitor and control the level of liquids in various tanks. These systems can be used in a wide variety of industries including food, beverage, oil and gas production, and chemical production. 

There are many types of liquid-level control systems available in the market, each with its own unique features and benefits. 

1. Bubbler System or (Air Purge System)

This liquid level is known by indirect method bubbler system or air purge system is a simple measuring instrument of commonly used hydrostatic pressure types and it is suitable for all liquids. The air purge system is shown in the picture below.

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The air purge system connects an empty hose to a water tank or other liquid. In this, two pairs are made from a hall groove, one for air control and the other for a pressure gauge. In which the level of the liquid can be measured, a bubbler is connected to the air source, which controls the flow of air. A level recorder can also be connected to the pitch meter. In which we keep a regular record of liquid level.

Working Principle

When there is no liquid inside the tank, the level of the liquid will be below the bottom of the bubbler tube and the pressure gauge will show zero, in other words, there is no reaction pressure as the air escapes into the atmosphere.

As the level of the liquid rises, the flow of air stops at the bottom and the pressure of the air appears against the top of the liquid as the reactant moves the pressure indicator so that we can measure the pressure of the liquid.

2. Float Type Liquid Level Indicators 

3. Electrical Contact Type Liquid 

In this system, the tank is made of iron, and electrodes are suspended in it at different heights. Each electrode has an indicator bulb connected to each battery. Sometimes the indicator bulb is replaced by a bell, in case the operator is away from the tank.

Working Principle

When the tank is completely empty, no bulb lights up. But as the liquid level increases, it comes in contact with the electrode, due to which the contact of the bulb with that electrode is done by the circuit and it starts measuring. In this way, we measure the liquid level by observing the position of the bulb. 

4. Diaphragm Box Level System 

In this a diaphragm box is filled with liquid, this box is connected by a pressure re-circular. The diaphragm is a very thin flexible and loose diaphragm box made of iron or bronze and is related to a pressure receiver.

Working Principle 

When the diaphragm box is suspended by a chain, the back pressure of the liquid di-phases the diaphragm box, which compresses the medium between the pressure received and the box and the pressure is read per pressure gauge scale. The entire system must be airtight.

Advantages

i. Pressure gauge instrument can be used about 500 feet above or below.

ii. By this we can measure the bottom of the tank from 20 inches to 250 feet.

5. Air Trap System or Air Bellows

The air trap system is very similar to the diaphragm box, the only difference is that it has an air box instead of a diaphragm box. The air bellows are connected to the pressure indicator through a tube. Slateel air is filled between the air below and the pressure indicator.

Working Principle

When the tank is empty, the air filled in the tube becomes uncompressed. Due to this, the pressure indicates as the liquid on a level in the tank rises up, then the compression of the air filled in the tube transits the indicator which is calibrated in the positions of the liquid level. 

> Working Principle and Advantages & Disadvantages of Float Type Liquid Level Indicators