Author: joyo

Throughout this article we assume the density of the vapor in the headspace (typically air) to be negligible compared with that of the process fluid. We will assume also that there is only one, uniform, process fluid in the tank. Some of these technologies can be used for multilevel applications where two or more immiscible fluids share a vessel.

1. Glass Level Gauge. Available in a variety of designs, both armored and unprotected, glass gauges have been used for over 200 years as a simple method to measure liquid level gauge. The benefit of this design is the ability to the see the true level gauge through the clear glass. The down side is the possibility of glass breakage resulting in spills or safety to personnel.

2. Floats. Floats work on simple principle of placing a buoyant object with a specific gravity intermediate between those of the process fluid and the headspace vapor into the tank, then attaching a mechanical device to read out its position. The float sinks to the bottom of the headspace vapor and floats on top of the process fluid. While the float itself is a basic solution to the problem of locating a liquid’s surface, reading a floats position (i.e., making an actual level measurement) is still problematic. Early float systems used mechanical components such as cables, tapes, pulleys and gears to communicate level. Magnet-equipped floats are popular today.

Early float level gauge transmitters provided a simulated analog or discrete level gauge measurement using a network of resistors and multiple reed switches, meaning that the transmitter’s output changes in discrete steps. Unlike continuous level gauge-measuring devices, they cannot discriminate level values between steps.

Reflex level indicators are for applications that involve high temperature, high pressure and use of corrosive fluids. The colorless fluid used in this apparatus gives better clarity to level indication.

Reflex glass level gauges working principle is based on the light refraction and reflection laws.

Reflex glass level gauges use glasses having the face fitted towards the chamber shaped to have prismatic grooves with section angle of 90°.

When in operation, the chamber is filled with liquid in the lower zone and gases or vapors in the upper zone; the liquid level is distinguished by different brightness of the glass in the liquid and in the gas/vapor zone.

The reflex level gauges do not need a specific illumination: the day environmental light is enough. Only during the night an artificial light must be provided.

The benefits of using microwave-based technology for level gauge measurement

Level gauge measurement has always played a key role in the quarrying industry and today it has even more significance with demands for de-manning, automation, and inventory control, as well as for safety and environmental reasons. The challenges for a reliable solution are numerous. For solids these include: dust, product build-up, abrasive products, and uneven surface levels. In general, liquids are easier to deal with, although bitumen requires particular solutions, however it is also important to avoid spillage and contamination by liquids. The working environment for all devices is harsh as vibration, noise, weather and impacts from falling materials are common.

To meet many of these needs, microwave-based technology has now become firmly established in a broad range of quarrying applications. With reducing costs, higher performance and special variants, could it be a question of when, not if, it can replace ultrasonic transmitters for the majority of applications?

The benefits of using microwaves for level gauge measurement are clear. Practically uninfluenced by process variables such as temperature, pressure, vapours, dust or gas composition in the vessel air space, they are suitable for a wide range of applications. The development of new radar and guided-microwave (or TDR) sensors, optimized for applications in bulk materials, brings the goal of a ‘universally applicable’ sensor a step closer. The use of microwaves, however, offers a ‘universal technology’ now.