1. Government Engineering College Bharuch(014)

2. Sub: Instrumentation And Process Control. Topic: Displacement float,Pneumatic balance and Magnetic level indicator. Group Members: 13014015021-Panchal Priyansh 130140105035-Patel Smit 130140105046-Parsana Sanket

3. Displacement Float Liquid level Gauge This type of liquid level indicator can be used in both pressure vessels as well as open vessels. Their range is usually from about 14 to 180 inches change in level & capable of indicating liquid level up to 600 psi vessel pressure. As we can see in figure, a long float of constant cross-sectional area is suspended in the liquid which level is to be measured. The weight of liquid displaced causes an upward force on float, which is counterbalanced by the force exerted by the spring.

4. The movement of the float is carried by the shaft to an indicating pointer & the shaft should be sealed & with bearing to transmit the movement of the float to the pointer. The displacement float gauge usually employs a torque tube in stead of shaft & spring mechanism in order to eliminate the necessity for sealed shafts & bearings.

5. Pneumatic balance Displacement Float liquid level Indicator In this type of liquid level indicator, the force exerts on float due to rising liquid level is balanced by the pneumatic system. As the level of liquid increases, the float moves upwards & the shaft moves in opposite direction. At the same time through pneumatic system, an equivalent amount of air is supplied through the compressor which will balance the shaft through balancing bellows. A pressure gauge is connected with the mechanism which shows the pressure in terms of the head of the liquid in the vessel.

6. The range of this type of liquid level indicator may be as low as 2 inches & as high as the length of the float permits e.g., liquid head up to 60 feet has been measured in this manner The accuracy of the displacement float gauge is better than that of any other method as long as the specific gravity of the liquid is not low. The deposition of solids on the float is a source of error.

7. Magnetic Level Gauge A magnetic level gauge includes a “floatable” device that can float both in high and low density fluids. Magnetic level gauges may also be designed to accommodate severe environmental conditions up to 210 bars at 370 °C. Magnetic float level sensors involve the use of a permanent magnet sealed inside a float whose rise and fall causes the opening or closing of a mechanical switch, either through direct contact or in proximity.

8. Magnetic Level Gauge Magnetic level indicators are low-maintenance alternatives to sight glasses and other level indicators. Low cost solution for measuring highly corrosive liquid Easy to install, no extra piping required in most applications No process liquid in contact with indicator glass Ideal for high-temperature, high-pressure and corrosive applications Magnetic level indicators are quickly replacing outdated level technology Safe, easy to use and reliable

9. How it Works Magnetic level indicators consist of a chamber, a magnet equipped float which rises and lowers with the fluid level, and an indicator which is mounted to the chamber. The indicator houses a column of small flags which indicate the level of the fluid in the chamber, based on the position of the float.

10. How it Works As the fluid level rises and lowers, the float rises and lowers as well, and the flags are tripped from one orientation to the other; typically the red side indicates the liquid level and the silver side indicates the vapor space. As the float rises and falls with the process level, tripping the flags, it also stimulates any attached transmitters and switches, providing a signal back to the control system

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