The working principle of the water level gauge is that when it is put into a certain depth in the liquid to be measured, the pressure on the sensor’s front surface is converted into the liquid level height.
The calculation formula is Ρ=ρ.g.H+Po, in the formula P is the pressure on the liquid surface of the sensor, ρ is the density of the liquid to be measured, g is the local acceleration of gravity, Po is the atmospheric pressure on the liquid surface, and H is the depth at which the sensor drops into the liquid.
The level gauge is a device designed to monitor and measure liquid (and sometimes solid) levels. When the liquid level is detected, the sensor converts the sensed data into an electrical signal. Level gauge are mainly used for monitoring reservoirs, oil tanks or rivers.
There are various methods to measure the liquid level and other liquid characteristics. The technique of measurement relies on the type of tank gauging system, the liquid type and how the tank gauging system is used.
Modern tank measuring devices digitize tank measurements and communicate tank information digitally to a control room where liquid volume and mass information are distributed to inventory data consumers.
Usually storage tanks come in four basic designs: Cylindrical fixed roof tanks, cylindrical floating roof tanks and either spherical or horizontal cylinder design pressurized tanks. For all these kinds of tanks, tank gauging system are accessible.
Having an accurate density meter that produces reliable results is only part of the equation. Your instrumentation also needs to be simple to use, easy to clean and offer superior traceability.
Density Meters use proven touchscreen interface. The graphic user interface (GUI) has been enabling users of touchscreen RFM refractometers and ADP polarimeters to quickly and easily take measurements, calibrate, and analyse data for many years. Users new to the system will appreciate the intuitive layout, and quick access to regularly used controls including “READ” and “METHODS”. To learn more about the benefits of touchscreen technology check out our blog here.
Density Meters not only sport a great touchscreen (usable with PPE gloves), but also fast networking abilities, USB functionality for optional mouse/keyboard support and exporting of data (via PDF/.CSV) to USB drives. Large capacity memory means room for over 100,000 readings without the need to purchase costly storage.
To facilitate measurement, Density Meters utilise the oscillating u-tube principle. Using a secondary oscillator allows the instrument to monitor and adapt to long-term instrument drifts and environmental influences, meaning calibration can hold and be relevant for a long time. Results are displayed in less than 15 seconds, depending on the mode selected, whilst smart temperature stabilisation helps provide the most accurate results in super-fast time.
Density Meters have been designed with a variety of industries in mind. From edible oils and soft drinks in food & beverage, to raw materials testing in pharmaceutical.
We developed an innovative tank gauging system that is designed to simultaneously measure and display liquid level and volume in horizontal and vertical cylindrical tanks. Do you really know what your liquid levels are! With the tank gauging system, you will have no doubt, even in cylindrical tanks.
The tank gauging system combines unparalleled accuracy with convenient versatility. The system includes a level sensor and monitor. The monitor can be programmed to handle a variety of tank geometries and values can be displayed in any engineering unit. The display hardware is mounted in a weatherproof NEMA4X enclosure and is visible through a window in the door showing level (feet) and volume (gallons) on a back lighted LCD screen.
The system also includes a fused power supply, a surge suppressor and a built-in thermostatically controlled enclosure heater. This all adds up to the most dependable, easy-to-use tank gauging system available today.
This paper presents an outline of the most commonly adopted servo tank gauge and level measurement systems used in the gasoline storage industry.
It highlights the advantages and disadvantages of the named systems and gives a brief explanation of how the systems work. The outcome of discussion held with professionals and manufacturers in the industry and their view on how level measurement technology is evolving and improving is then summarized showing how more accurate and operationally reliable level measurements should be possible in the future.
It is intended that this review will present information to help reduce the risk of such an equipment failure contributing to a servo tank gauge overfill event in the future, by highlighting appropriate and established level measurement systems for gasoline storage facilities.
Primary hybrid tank gauging system solution consists of a level instrument (tank gauge), a temperature sensor and HART® pressure sensor(s) integrated into the 4590 TSM. The level gauge selected depends on the product application at hand.
In the case of light distillates, we would recommend a servo or radar gauge, combined with a 4532 ATC (or 4539 ATC) based on the requirement for inventory management (or custody transfer, NMi approved) applications. The 4590 TSM is able to provide hybrid calculations at the tank side and transfer of data to the control room.
Alternatively, FuelsManager can replace the tank side device to perform hybrid calculations. In this solution, either a servo gauging system or a radar tank gauging system and pressure device can be used to supply the required measurement data.
Level gauges, consist of a chamber, a magnetic float and a flipper type indicator scale mounted to the side of the chamber. Understanding the operation of the level gauge is quite simple. The fluid in the tank seeks its own level inside the chamber. The magnetic float in the chamber rises and falls with the fluid level. As the Magnetic float rises and falls, it changes the orientation of the flippers on the scale providing a visual level gauge. In addition, as the magnetic float rises and falls, it actuates any transmitter or alarm switches that are attached to the side of the gauge.
Level gauges are custom made based on your requirements. The float construction is determined by the process fluid, pressure, temperature and specific gravity of the fluid. Level gauges are generally made of 316SS, but can be made from a variety of other materials including CPVC, Kynar, Hastelloy, Monel or other exotic metals. A variety of mounting style options and process connections are available to meet your needs.
Additionally, MLS Series magnetic alarm switches can be added, external to the float chamber, for alarm or control functions. These switches can easily be moved up or down the float chamber without shutting down or disturbing the process.
Measuring the density and specific gravity at a given temperature, density meters are especially useful when working with viscous liquids or difficult gases.
Portable or benchtop densitometers have high storage potentials for easy comparisons of collected data.
Used in various research or product-developing industries to check batch consistencies, the digital devices guarantee quality control. The flexible density meters will accommodate common cuvette and tube sizes for highly accurate readings.
Two types of measurement methods are used for tank gauge LTD (Level-Temperature- Density) mass custody transfer: volume or mass based. In a volume based system, level is measured. In a mass based system, the measurement of the hydrostatic pressure of the liquid column is used. The users choice should, therefore, be based on how product inventory is calculated and accounted via volume or weight.
Both methods provide a direct measurement of one factor in the inventory equation, level or pressure. However, bulk storage tanks tend to have large diameters, store products with varying densities that can stratify, and require consideration for high tank levels and overfill protection. A small change in level can make a big difference in accountable volumes (level x diameter), while stratification can lead to level changes that are undetectable by mass based systems. Varec, therefore, recommends level (volume) based measurement systems.
Float and Tape Tank Gauge LTD (Level-Temperature- Density) Mass Custody Transfer
These instruments have been the liquid level measurement technique of the petroleum tank gauging market for over 90 years due to their simplicity, reliability and cost.
Float and tape tank gauge LTD (Level-Temperature- Density) mass custody transfer solution consists of a ATG selected for the appropriate tank type. The instrument provides a measurement to +/- 4 mm accuracy and tank side display that is suitable for inventory management to API specifications. If control room integration and volumetric calculations are required, a tank gauge LTD mass custody transfer transmitter is recommended with a STS for spot temperature measurement. The selection of the transmitter often depends on the required or existing field communications and protocols.
The servo gauge system uses the small displacer. The displacer has buoyancy, but on the liquid it does not float. The displacer must be held on top of the tank by a thin wire linked to the servo gauge.
A servo weighing system senses the tension in the wire, signals from the weighing mechanism control an electrical motor in the servo unit and the displacer follows the liquid level movements.
An electronic transmitter sends the field bus level data to the control room reader. A still pipe is needed wherever a servo gauge is installed to prevent the displacer from drifting in the tank. In fixed roof tanks, this is also required.