Leveltroll is a combination of torque chamber, torque arm, torque tube, displacer and with this mechanism we can measure the level.A Leveltroll in and instrument used for measuring the liquid level between two known points. The Leveltroll works on the buoyancy principal. Leveltroll has a float, which submerses proportionately with liquid level raise in the float chamber. The amount of submersion of the displacer depends on the liquid density, which produces a torque. The amount of torque produced in measured in terms of % of level.
In most of the cases the leveltroll is calibrates in the field due to its complex structure as you can see in the pictures.
Parts of Leveltroll:
Float chamber, Float, Torque lever, Knife edge, Feedback Bellows, Air Relay, Restriction, Flapper, Nozzle, Feedback link, Density range, Action change lever, HP and LP flange.
Equipments need for leveltroll calibration:
Multimeter, leveltroll, transparent tube
- Close the both primary isolation valves
- Drain the liquid in the displacer chamber through the drain valves
- Now there is no liquid in the chamber so it means 0%, so adjust the zero pot in the transmitter and check the value in multimeter and correct to 4ma.
- Now open 1st primary isolation valve and fill the liquid to the center of the top flange(if the liquid is water, otherwise calculate the length of full level of the liquid by taking product of specific gravity of liquid and height of the displacer)
- Adjust the span pot in the transmitter and adjust 20ma in multimeter.
- Repeat the process.