What is level measurement?

Level Measurement

Q. What is level? 

> difference between two height of liquid in tank or vassel. 

UNIT

> Percentage ( o to 100 % ) 

> meter

> Feet

> inch

Q. What are the instruments used for level measurement? 

> types of level measurement

1.Dpt type Lt or Hydrostatic Head type Lt

2.Radar type Lt or Non contact type Lt

3. Level tro Or displacer type Lt

Sight glass method

Dpt level measurement

>Dpt type Lt work on the basic principle of " Pressure produced by the height of liquid which is measured in terms of level. 

> pressure is depends on two factor that is height and specific gravity of liquid, it does not depends on diameter of tank. 

DPT : DIFFERENTIAL PRESSURE TRANSMITTER

There are two types of leg , 

1.Wet leg 

> when process vapor is condensable ( liquid- vapour- liquid) then wet leg is used. 

2.Dry leg

> when process vapour is non condensable ( liquid- vapour×liquid) then dry leg is used. 

Calibration of dpt type level transmitter

> Take  a work permit. 

> Take loop in manual from dcs. 

> isolation dpt from process liquid by using 3 way manifold. Close both isolation valvevand open both drain valve. 

> Connect Hart at supply or connect multimeter at test point. 

> check zero ( 4.00 ma)  , if it is disturbed than adjust it using zero pot or push button and Hart. 

> connect pneumatic pressure source at high side and low side open to atmosphere. 

> Apply pressure at high side according to upper range value. 

>check span ( 20.00 ma) . if it is disturbed then adjt it using span pot or push button or Hart. 

> check linearity( 12.00ma)  by applying 50 ℅ input pressure. 

> Reduce pressure to zero. Remove pressure source. 

> close both drain valve and open both isolation valve. 

> Take loop in auto from dcs. 

Calibration Diagram