The traditional approach to level measurement in a pressurised vessel, such as a boiler, has been to use a conventional differential pressure (DP) transmitter with external water-filled ‘wet’ legs connecting both the high and low pressure sides of the transmitter to the drum. The use of DP transmitters for drum level is ideal because of their low cost, ease of installation and high reliability. However, the output of a conventional DP transmitter in this application will have inaccuracies caused by changes in static pressure, the densities of the water in each leg, and the densities of the steam and water in the drum.
The Foxboro solution
The Foxboro IMV31 density-compensated level transmitter provides a new approach to drum level measurement. While maintaining all the advantages of DP transmitters, it uses multiple measurements and on-board level calculations to provide a more accurate measurement. This eliminates the need to make similar level calculations in the control system.
The new instrument is based on Foxboro’s proven multivariable transmitter technology, which was originally developed for flow measurement. The heart of the device is its ability to conduct on-board level calculations based on multiple measurements and fluid density calculations. The transmitter has a pressure sensor and a differential pressure sensor, as well as two internal temperature sensors. It also has the ability to power and monitor an external RTD temperature sensor.
The transmitter continuously calculates the unique fluid densities, based on measured pressures and temperatures, and uses this information along with the DP measurement to calculate an accurate density-compensated liquid level. The densities of both the water and steam are calculated separately, based on the pressure measurement and vessel temperature. The transmitter has an RTD input and can also use the saturation stream table’s temperature corresponding to the measured vessel pressure in calculating water and steam densities.
Results
Regardless of the size of the drum and the saturation pressure, the IMV31 significantly improves the accuracy of drum level measurement over conventional DP transmitters and automatically provides dynamic compensation for varying pressures and temperatures.
A fresh approach to dairy processing VEGA Controls SA
Level Measurement & Control
Ensuring the quality and safety of milk throughout the production process is of the utmost importance in the dairy industry. The VEGABAR pressure transmitters are suitable for hygienic applications. They are an asset in the dairy industry and have been used with success for measuring the milk level and the process pressure in storage tanks.
Read more...Simple and efficient level measurement in the mining, minerals and metals industries Endress+Hauser South Africa
Editor's Choice Level Measurement & Control
Measuring devices in the mining, minerals and metals industries face the challenge of varying material states and long distances in measurement height. Endress+Hauser’s answer to these challenges is the new Micropilot family.
Read more...Level measurement of an acid dosing tank at a WWTP
Level Measurement & Control
Ferric chloride and other acids are essential chemical substances in water and wastewater treatment. To control the dosing of acid solutions, an Australian wastewater treatment plant uses a special container to store, mix and add these chemicals. The company opted in favour of KROHNE’s OPTIWAVE 1540 radar level transmitter
Read more...Powering sub-Saharan Africa’s energy future VEGA Controls SA
Level Measurement & Control
Crude oil storage plays an important role in the energy infrastructure of sub-Saharan Africa. The management of crude oil storage in comes with numerous challenges, including safety concerns, environmental conditions and infrastructural limitations.
Read more...Level measurement of leachate from sewage sludge humification
Level Measurement & Control
A municipal utility in eastern Germany operates a state-of-the-art wastewater treatment plant with sustainable sludge treatment. The ultrasonic signal was being partially deflected by the wind, leading to frequent false measurements and inefficient process workflows. The problem was solved by replaced the ultrasonic level sensor with KROHNE’s OPTIWAVE 1540 non-contact radar.
Read more...Groundbreaking measurement system Mecosa
Level Measurement & Control
Berthold Technologies has launched the LoopSeries LB 430, an innovative, industry-leading measurement system designed to enhance operational efficiency with advanced level, density, and level switch capabilities.
Read more...Level measurement of a water sump at a sewage treatment plant
Level Measurement & Control
A major city council in South East Queensland, Australia maintains and operates a wastewater treatment plant (WWTP) for municipal, industrial and agricultural wastewater. Due to the risk of flooding, the water sump must be continuously monitored. The solution is KROHNE’s OPTIWAVE 1540 radar level transmitter.
Read more...Simplicity in measurement Endress+Hauser South Africa
Level Measurement & Control
Endress+Hauser’s new 80 GHz compact radar range is designed to help customers reach their compliance targets through simple yet efficient measurement solutions.
Read more...Case History 196: Unstable condensate level control. Michael Brown Control Engineering
Editor's Choice Level Measurement & Control
The operators in a petrochemical refinery were having great trouble in trying to stabilise the condensate level in a vessel, and this was adversely affecting other loops downstream. Several unsuccessful attempts had been made to retune the controller.
printer friendly version