23-02-2013, 03:57 PM
Level Measurement
Level Measurement.ppt (Size: 647.5 KB / Downloads: 187)
Level Measurement
Inventory:
a constant supply or storage of material
Control:
continuous, batch, blending, and mixing control
stabilize flow to the next process
Alarming:
hi/lo limits, safety shut down
Data Logging:
material quantities for inventory and billing purposes and where regulatory requirements are necessary
What is measured?
The measured medium can be liquid, gas or solid and stored in vessels (open/closed tanks), silos, bins and hoppers.
Units of level can be expressed in:
feet (meters)
gallons (liters)
pounds (kilograms)
cubic volume (ft3, m3)
Direct Methods
Direct methods sense the surface or interface of the liquid and is not affected by changes in material density (Specific Gravity)
Examples:
Dip Stick
Resistance Tapes
Sight Glass
Floats
Ultrasonic
Selection Criteria
Open tank or closed tank?
Can the level sensor be inserted into the tank or should it be completely external? Contact or non-contact?
Continuous measurement or point measurement?
Direct or Indirect measurement?
What type of material is being measured? Liquid or Solid? Clean or Slurry?