Working principles of servo gauge

The principle of servo gauge measurement is based on Archimedes law, which states “any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.”

Typical servo gauges consist of three compartments: drum compartment, drive compartment, and power supply compartment. The drum compartment contains a precise machined drum on which the measuring wire is wound. The displacer is suspended by this wire into the tank. The drive compartment contains the drive train (servo gauge motor and electronics) and the measurement electronics.

A magnet coupling is used to convey torque between the drive train and the drum and forms the isolation between the process and the electronics and environment. The displacer is moved by a stepper motor in the drive compartment.

As soon as the displacer reaches the surface of the liquid in a tank, buoyancy reduces the apparent weight of the displacer. This is measured by the servo gauge electronics using the force transducer. By also keeping track of the exact position of drum and number of revolutions, the length of the expanded wire can be measured. In combination with the known position of the servo gauge (gauge reference height, GRH), the exact product level can be calculated. This level is then corrected for several typical tank uncertainties, such as product temperature, tank shell effects, changes in GRH due to hydrostatic tank bulging, etc.

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Different types of level gauges

Slight glass level gauge

A glass of sight or a water gage is a transparent tube through which a tank or boiler operator can observe the level gauge of liquid contained in it.

It is positioned parallel to the vessel along the elevation over which the level gauge is to be indicated and mounted with appropriate fittings for retaining the pressure and sealing the ends of the sight tube.

However, this building is not well adapted for use with hazardous process liquids.

Reflex Level Gauges

A reflex gage is more complicated than a slight glass, but it can make a better difference between air (steam) and fluid (water).

The gage comprises a vertically oriented slotted steel frame with a powerful glass tray installed on the open end of the cabinet facing the user, rather than holding the documents in a glass box.

Most of the light is transferred from the bottom of one drawer to the next and back to the user in the area that is contact with the water, appearing creamy white. In the area in touch with the fluid, most of the light is refracted into the fluid, which causes this area to look nearly black to the user.

Bi-Color Level Gauges

For caustic media, a bi-colour gage is usually chosen to provide protection for the crystal. The gage comprises of a vertically oriented, slotted steel frame with a powerful simple front and back glass.

The front and rear surfaces of the body are in vertical planes that are not parallel. Behind the reference body are light sources, typically red and green, with two quite distinct colors. The fluid area looks blue to the viewer due to the distinct refraction of blue and blue light, while the gas area looks purple

Magnetic Level Gauges

The magnetic value gage does not take an immediate view of the point (i.e., glass is not needed), the test room can be transparent and the building of welded steel is usually used.

This significantly improves the variety of working temperatures and reduces the roughness relative to test glass rooms. The broad temperature spectrum is feasible because the chamber of measurement can have about the same heat growth ratio as the ship, and there is no plastic to interact with the chamber of steel.

This article comes from automationforum edit released

Technology Selection for Automatic Tank Gauge

Complete, and Completely Flexible

All of the options you need, and none of the complexity you don’t: That’s what the automatic tank gauge and Environmental solution delivers.

Complete, and Completely Flexible

We deliver a complete, integrated automatic tank gauge and forecourt solution that’s also completely flexible. It offers a variety of hardware and software options that can be included from the start, or retrofitted remotely to meet changing needs. It’s also designed to integrate seamlessly with the forecourt system for full visibility into all aspects of operations. Adding capabilities and expanding to more sites is as easy as adding modules.

A streamlined automatic tank gauge platform with a multitude of flexible options

All of the options you need, and none of the complexity you don’t: That’s what the automatic tank gauge delivers. The automatic tank gauge platform requires no automatic tank gauge specific console, minimizing the basic number of components required and lowering the initial system investment.

This article comes from wayne edit released

Measurement Technologies of Level Gauge

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.

This article comes from globalspec edit released

Servo gauge – the advanced gauging tool

Outstanding Accuracy

Servo gauges series ATG and XTG are miscroprocessor controlled tank level gauges. The measuring accuracy is superior to what has been available up to now.

Weights & Measures

Servo gauges meet the international requirements for custody transfer, confirmed by certification from Custody & Excise and official Weights & Measures authorities.

Increased Safety

Servo gauges are approved for use in hazardous areas. The gauges are also provided with a unique lightning protection system to avoid damage by thunderstorms.

This article comes from aguamarket edit released

Comparison of Servo Gauge with Level Gauge

There are four basic types of servo gauge:

First, is the low-accuracy pulse radar units, such as those made by Endress+Hauser, Siemens/Milltronics, and Ohmart/Vega. Now these are only “low accuracy” when compared to units designed for tank farm gauging. These are excellent general purpose radar units, but they are limited in use to materials with dielectric coefficients greater than about 8 or so. It generally rules them out for low viscosity hydrocarbons.

Second is the various radar-by-wire designs, such as Alliant(Bindicator-Celtek) and Magnetrol, etc. These are mostly used for solids, but could be used in hydrocarbons. They are also relatively

Next are the FMCW units, these are moderately high accuracy, and can be used in gauging fluids with a dielectric of 3-5 or so. The compromises made in the designs of these units in order to make them look through small (4″<100 mm> to 6″ <150 mm>) vessel ports reduces the accuracy and the ability of these units to see lower dielectric constants. These are designed as
process servo gauges, not tank farm designs.

The highest level of accuracy are the units designed specifically for Tank Farm Gauging, they were designed to compete specifically with servo gauges and with hydrostatic level gauge and are designed to be used specifically for tank farms. These servo gauges consistently outperform their competition but are very expensive.

This article comes from control edit released

Nuclear Level Gauge Measurement

Nuclear or nucleonic level gauge measurement devices can be employed in both point and continuous level gauge detection applications. They are usually applied in fields where all other level gauge measurement techniques fail to work owing to their capability of working with hazardous situations. In this method, energy needed for level gauge measurement is emitted arbitrarily by radio isotopes in the form of bursts.

The major source utilized in nucleonic level gauge controls includes gamma radiations. These are electromagnetic radiations which exhibit almost identical behavior to that of microwaves and light waves. However, they have comparatively higher energy and shorter wavelength owing to which these radiations are competent enough to break through the walls of process vessel and material.

The field strength of these gamma radiations is determined by a sensor mounted on the other end of the vessel, which ultimately detects the level gauge of process material in the vessel. “Different radioisotopes are used, based on the penetrating power needed to “see” the process within the vessel. With single point gauges the radiation provides a simple on/off switching function, whereas with continuous level gauge measurement the percentage of transmission decreases as the level increases.”

This article comes from chipkin edit released