Types of Level Gauges

Level gauges are meters used to determine the level of a liquid in a fixed storage or process tank. The gauge is composed of several parts including head, float, measuring tape, bottom anchored bracket, guide wires, elbows, anchors, coupling, pipe support brackets, and pipework. Liquid level gauge calibration is used to ensure proper readings are obtained when using level gauges.

Level gauges have several advantages including durability for harsh environments, including the ability to withstand high pressure, temperature, and vibrations. They are easy to read from a distance and can be used in addition to a switch or alarm in a system. There is little maintenance required and all repairs can be done without disturbing the system. They can also be customized for extreme applications.

There are several basic types of level gauges.

Fuel level gauges - A fuel level gauge provides a direct fuel level reading for vehicles and equipment. The two main parts of a fuel gauge are the sender and the gauge. The sender measures the fuel level in the tank and the gauge displays the level to the user. The sending unit measures the fuel once the float has dropped below a certain level. When the tank is full, the float is near the top and the wiper rests close to the grounded side. This means that the resistance is small and a relatively large amount of current passes through the sending unit back to the fuel gauge. As the gas level drops, the float also begins to sink and the wiper moves to increase the resistance and cause the amount of current sent back to the gauge to decrease.

Measurement Technologies

Level gauges take level readings using several different techniques. The measurement technology should be chosen based on the user's application. These level sensors also have different display options based on user preference.

Magnetic level gauges - A magnetic level gauge is used to control the level of fluids. The gauges operate under Archimedes Principle, which states that any object submerged in a fluid experiences the same buoyant force as the weight of the liquid displaced. Magnetic level gauges are extremely durable and can be used in applications that would break or destroy glass gauges. They can be used underground with a maximum working temperature and pressure range of 4000C and 220 bar. These gauges are capable of inter-phase level detection, even in highly toxic or corrosive mediums.

Reflex level gauges - A reflex level gauge is used to detect level in a vessel or container. It operates by using the dissimilarity in the index of refraction between fluids and vapors. They are usually made of carbon or stainless steel, which provides the durability needed to work in a temperature and pressure range up to 400°C and 400 bar respectively. If the vessel is filled with vapor, the observer will see a silvery white color because the light radiations running into the grooved surface of the sight glass will be completely reflected. If the vessel is filled with liquid, the observer will see black because the light radiations coming across the liquid region will be completely absorbed. The sight glass is a transparent tube which is clamped to the gauge body.

Transparent level gauge - Transparent level gauges are very similar to reflex level gauges. They consist of two transparent glasses which are integrated with the liquid cavities on both sides. Transparent level gauges work by detecting the dissimilarity in the transparent characteristics of two glasses which are integrated with the liquid cavities on both sides. In an application which uses water and steam, an illuminator is employed to make the liquid level easier to see. The light rays emitted by the illuminator are directed in an upward direction towards the water column causing the surface of the liquid to become illuminated. The light radiations generally fall upon the divided surface between water and steam and then reflect back to the eye of the user.

Bi-color level gauge - Bi-color level gauges are used to measure the media level in a boiler. The gauge uses high quality mica sheets to guard against the wet steam generated in a boiler drum. The level is detected by distinguishing the index of refraction between the steam and water. Bi-color level gauges are a transparent gauge that has a liquid chamber in a wedge shaped section. The rear side of the device has an illuminator which is fitted with two color filters; one red and the other green. When red color light radiations hit the water, they get averted to one side and absorbed. When the same light hits the steam, the light passes through and shows up as a red color. The reverse happens for light passing through green filters. This allows users to tell how much of each media is in the system.