Non-Contact Level and Mass Flow Measurement and Control with Microwave and Radiometric based Instruments in Solids Handling – PART 1
Mr. Doug Anderson, Mr. Graeme Cross, Mr. Gary Baker
Abstract
Solids handling offers many challenges for measurement and control. The product properties are the most major – dust abrasion, impacts, bulk density, material flow and movement. These all have an impact on the type of handling equipment, as well as the measurement and control systems that say “when” and “how much”, no matter what parameter is being measured. Many measurement systems incorporate mechanical parts or movements, which require contact with the product or process. By using non-contact devices, the ease of implementation, and improvement to lifespan and reliability can outweigh any price difference, should there be one.
Introduction
This paper looks at 2 areas in particular, level and mass flow measurement, to explore the options for some applications, particularly for difficult to handle product or difficult to measure situations. These are not definitive for all applications, but some alternative ideas, with application examples, to show other ways these have been solved, to increase reliability and productivity, saving space and downtime for some difficult to measure areas.
Factors to consider for level measurement of solids
The product to be measured and the accuracy required, are the first considerations for a system.
A silo weighing system may be more suitable for the application, whenever it is practicable and affordable to use one, especially on a new installation, they are normally the first choice.
However this is not always suitable, and some of these considerations will also help decide. The elements to factor in for a measurement application is the type of vessel, what the surface area and profile is likely to be like for a representative level measurement, what the vessel is manufactured from, and the top and bottom forms, outlet and roof structures etc. These will have an affect on the performance of a measurement system.
Process conditions for measurement
If a vessel is to be measured, the filling stream and type has to be taken into account. Dust, air conveying, filling noise and turbulence will all play a role.
When the vessel is emptying, will there be bridging or rat-holing? If the vessel is ‘zeroed’ or ‘tared’ on a weigh cell system, because there is ‘nothing coming out’, what are the consequences if there are still tons of material inside? Temperature of the incoming product and pressure inside the vessel, particularly if it is high, also play a part.
Mechanical, product and safety
Mechanical forces exerted by the product, for example if a cable based level device is used and it is a mass flow silo, will there be a significant loading on the roof of the vessel, or will corrosion/abrasion cause wear to any devices in contact with the process. Could the product build-up significantly on the vessel or on the measurement probe. Finally there are the safety considerations, is ATEX for combustible dust and ignitable gases etc. required and what are the consequences should the vessel overfill?
PART 2 coming soon….
If you would like more information on the above blog please contact us on the details below.
Factors to consider for level measurement of solids
Related posts:
- Dirty Business for Solids Radar
- Innovation Award for microwave barrier VEGAMIP
- Drilling Mud pipe flow sensor using non contact radar
- Basics of level measurement
- VEGA @ Bulk Solids Europe in Glasgow
