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Liquid Level Measurement By Indirect Method

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Jaydeep Vakil
Jaydeep Vakil

This ppt contains Differential Method for measuring of liquid level of storage tanks and vessels. Differential method is one of the indirect method for liquid level measurement..

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INSTRUMENTATION & PROCESS CONTROL TOPIC: LIQUID LEVEL MEASUREMENT
LEVEL MEASURING METHODS Direct method:- In this method level of liquid is directly measured on the scale. Direct methods use varying liquid level as the means of level measurement. Indirect Method:- In this type of method level is measured in terms of the variables which changes with change in level of liquid. Such variables are hydrostatic pressure, attenuation of radioactive energy, electrical properties.
LEVEL MEASURING METHODS A)Direct Methods:- a) Based on direct visual observation: 1) Gauge Stick 2) Hook Gauge 3) Gauge Glass b) Buoyancy Methods: 1) Float Gauges 2) Displacer Gauges
LEVEL MEASURING METHODS B)Indirect Methods:- a) Based on HYDROSTATIC HEAD developed by the liquid: 1) Pressure Gauge Method 2) Air Trap Method 3) Diaphragm Box Method 4) Air Purge OR Bubbler Method 5) Differential Pressure Method b) Electrical Capacitance method: c) Radiation method:
Indirect Methods Hydrostatic Methods:- Principle: When the liquid is steady in the tank it exerts pressure on the wall of the tank. Such a pressure due to height of liquid present above a certain reference is called as HYDROSTATIC PRESSURE. P = gh Types of Hydrostatic Method:- 1) Pressure Gauge Method 2) Air Trap Method 3) Diaphragm Box Method 4) Air Purge OR Bubbler Method 5) Differential Pressure Method
Hydrostatic Methods Differential Pressure Method:- All the other hydrostatic level measuring techniques can be used only when the vessel containing liquid is exposed to atmosphere. But in case of liquid in a pressure vessel like Boiler Drum, the bottom pressure corresponds to Hydrostatic Pressure + External Pressure. Hence bottom level cant represent liquid level unless external pressure is balanced. This balancing is achieved by connecting Enlarged Leg Manometer to the pressure vessel as shown in the figure. The manometer reading corresponds to the hydrostatic pressure only hence manometer itself can be calibrated in terms of liquid level.
Differential Pressure Method:- Figure:-
Liquid Level Measurement By Indirect Method

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Liquid Level Measurement By Indirect Method

  • 1. INSTRUMENTATION & PROCESS CONTROL TOPIC: LIQUID LEVEL MEASUREMENT
  • 2. LEVEL MEASURING METHODS Direct method:- In this method level of liquid is directly measured on the scale. Direct methods use varying liquid level as the means of level measurement. Indirect Method:- In this type of method level is measured in terms of the variables which changes with change in level of liquid. Such variables are hydrostatic pressure, attenuation of radioactive energy, electrical properties.
  • 3. LEVEL MEASURING METHODS A)Direct Methods:- a) Based on direct visual observation: 1) Gauge Stick 2) Hook Gauge 3) Gauge Glass b) Buoyancy Methods: 1) Float Gauges 2) Displacer Gauges
  • 4. LEVEL MEASURING METHODS B)Indirect Methods:- a) Based on HYDROSTATIC HEAD developed by the liquid: 1) Pressure Gauge Method 2) Air Trap Method 3) Diaphragm Box Method 4) Air Purge OR Bubbler Method 5) Differential Pressure Method b) Electrical Capacitance method: c) Radiation method:
  • 5. Indirect Methods Hydrostatic Methods:- Principle: When the liquid is steady in the tank it exerts pressure on the wall of the tank. Such a pressure due to height of liquid present above a certain reference is called as HYDROSTATIC PRESSURE. P = gh Types of Hydrostatic Method:- 1) Pressure Gauge Method 2) Air Trap Method 3) Diaphragm Box Method 4) Air Purge OR Bubbler Method 5) Differential Pressure Method
  • 6. Hydrostatic Methods Differential Pressure Method:- All the other hydrostatic level measuring techniques can be used only when the vessel containing liquid is exposed to atmosphere. But in case of liquid in a pressure vessel like Boiler Drum, the bottom pressure corresponds to Hydrostatic Pressure + External Pressure. Hence bottom level cant represent liquid level unless external pressure is balanced. This balancing is achieved by connecting Enlarged Leg Manometer to the pressure vessel as shown in the figure. The manometer reading corresponds to the hydrostatic pressure only hence manometer itself can be calibrated in terms of liquid level.