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Dubai
Dubai
Abu dhabi
+971 4 883 0233 Sun - Thu 08:00 - 5:30 MB06, RA08, Jebel Ali Free Zone, Dubai , UAE
+971 2 6765979 Sun - Thu 08:00 - 5:30 P.O. Box : 33719, Abu Dhabi, UAE
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Level Measurement Techniques

Every industry needs to have the most appropriate and trusted level measurement system to provide the best solutions. There are various level measurement systems and Emphor IAD, leading industrial automation provider explains them in this article.

In industrial automation, level measurement is critical and most needed. There are different kinds of level measurement. Emphor IAD, a leading industrial automation service provider explains the different methods of level measurement. Level measurement can be simple to complex depending upon the subject of measurement. This article explains different kinds of level measurements currently used in industries. Level measurement can be broadly classified into two, direct and indirect level measurement methods.

Direct Method

The direct method is often simple and economical. A direct measurement from the datum line is used as a primary indication. The method isn’t digitalized and therefore remote control and the indication isn’t possible with the direct method.

  1. Dipstick and Lead lines
    Mostly used in the marine industry, the dipstick method uses flexible lines fitted with end weights called chains to gauge the depth of water under the ship. Steel tape having plump bob – like weights, and stored conveniently in a reel are still used extensively for measuring level in fuel oil bunkers and petroleum storage tanks. This method is accurate to 0.1% with range up to 20 feet. Even though this method is simple, reliable and dependable, the process isn’t efficient when it comes to continuous representation and is unable to measure levels in pressurized vessels.
  2. Sight Glass
    The method is as simple as the dipstick method. Both the levels in the vessel and the glass needs to be correlated to each other. It provides a continuous visual indication of liquid level in a tank and is more convenient than dipstick, dip rod and manual gauging tapes. There are two types of sight glass, low-pressure sight glass and high-pressure sight glass.

A low-pressure sight glass is suitable for open tanks. A metal ball is used as a regulator to control the overflow. Tubular glass is available up to 70 inches in length and pressures up to 600 psi. A high-pressure sight glass is used for the pressurized and atmospheric process. It is therefore used in boiler drums, evaporators, condensers, still tanks, distillation columns and other applications. The length of reflex glass gauges ranges from few inches to eight feet, but gauges can be put together for any lengths.

Due to the simplicity and reliability of such gauges, these can be used for local indication. When there is an issue with level transmitters, manual means can be used for measurement purposes.

  1. Chain or float gauge

    Float and Chain gauges are used in a similar position as earlier ones. Float gauges use the principle of buoyancy to float on the surface of the liquid and change the position as the liquid level vary. The float is connected to a pulley with the help of chain which is connected to an indicating device. As the float moves upwards, counterweight cable is fastened and the indicator moves along the circular state. There are different kinds of float gauges used in the industry right now. Many methods have been used to give an indication of level from a float position with the most common being afloat and cable arrangement.

Indirect Method

The indirect method is done using a material that has a physical property, which can be measured and related to level. The physical and electrical property of the material is used for the purpose. The method is suitable for remote indication and transmission. The method employs the latest technology in measurement. Emphor IAD list down various indirect methods used in industrial automation.

  1. Buoyancy: Force produced by a submerged body that is equal to the weight of the fluid displaced.
  2. Hydrostatic Head: Force or weight produced by the height of the liquid.
  3. Sonar: High frequency sound is used to locate a specific object and calculate its distance.
  4. Microwave: Similar to sonar, but the medium used is microwave.
  5. Conductance: the material to be measured conducts (or ceases to conduct) electricity between two fixed probe locations or between a probe and vessel wall.
  6. Capacitance: A dielectric material is used between two fixed capacitor plates. The method uses two substances, which form dielectric, the material whose measurement is desired and the vapour space above. The total dielectric value change as the number of one material increases while the other decreases.
  7. Radiation: In the capacitance method, vapour space above the measured material has an absorbing character, in radiation method; the material absorbs radiated energy to provide a more accurate result.
  8. Weight: Force due to weight can be related very closely to level when its density is constant. Variable concentrations components or temperature variations may vary according to measuring conditions.
  9. Resistance: Applied pressure on a material squeezes separated conductors together, reducing overall circuit resistance in a proportional level.
  10. Micro-Impulse: Electrical pulses launch and travel back in frequency directly proportional to the level of the liquid.

Emphor IAD is a trusted dealer in the level measurement systems. They have expert engineers and scientists who can help clients in choosing the most apt level measuring system suitable for their purpose.