LEVEL MEASUREMENT BY, B.Raveender Singh
Level Measurement • CONTENTS • Classification of level system • Brief introduction to the methods • Level switches • Summary
Level Measurement LEVEL SYSTEMS ELECTRICAL TYPES MECHANICAL METHODS THERMAL TYPES Classification of Level Measurement Systems:
Level Measurement MECHANICAL METHODS HYDROSTATIC TYPE GAUGE/SIGHT GLASS DISPLACER TYPE FLOAT TYPE Classification of Mechanical Level Measurement Systems:
Level Measurement GAUGE GLASS • Simplest of level indication • Direct level indication • For local display • Can also be used for closed/pressurized tanks
Level Measurement Float Type Level Measurement: • Used mainly for open tanks local level indication. • Float and tape method is widely used. • Spherical floats are preferred . • Magnetic bond type ball float .
Level Measurement Displacer Type : Principle of operation : Works on Archimedes Principleof Buoyancy It states that the resultant force of a fluid on a body immersed in it acts vertically upwards,which is equal to the weight of the liquid displaced.
Level Measurement F V Vx Fg Theory Buoyancy Force F = (Vx * Ph*g) + (V-Vx )*PL *g V – Displacer volume Vx – Volume of medium displaced by displacer Ph – Average density of heavier medium. PL -- Average density of lighter medium. Fg-- Displacer body weight.
Level Measurement Displacer Type : • Commercially named as Level Trol. • Torque tube forms the main transducting element. • Torque developed is converted to standard signal and transmitted to control room.
Level Measurement Displacer Type : • Mainly used for remote level indication and control • Simple reliable and accurate. • Can be used for liquids which tends to solidify under atmospheric conditions. • Can be used at very high temperatures and pressures.
Level Measurement Hydrostatic Type : Hydrostatic head is the force due to liquid weight above the reference line .It is exerted equally in all directions and independent of volume or shape of the vessel. Pressure P = p g h P – density h