On the level: A guide to level measurement

ABB offers an extensive range of level measurement instrumentation. Les Slocombe explains about the recent developments in technology and what the future holds for level measurement applications.

What are the key recent developments in level measurement?

Being able to transmit level data via 4-20 mA, HART, Foundation Fieldbus and the other commonly used communication methods is a key advance in level measurement. An example is our magnetostrictive level transmitters, which come ready to support communication protocols, allowing transport of level measurement information.

How has this changed the way level measurements are performed?

In the past, level measurement meant an operator going round to check the level at the vessels. Today’s level transmitters can relay this information to the control system so it appears on screen in an easily readable format.

What benefits have these developments brought?

As well as being far more convenient, it can also be much safer, keeping personnel away from potentially hazardous materials.

As well as the convenience of easy communication, many of today’s level measurement systems are also easier to install, configure and maintain. Previous generations of level technology often required a fair amount of technical knowledge to install and configure properly, today’s software rich level measurement systems allow just about anybody to commission the device.

There has also been a significant increase in the accuracy of interface measurement. The latest magnetostrictive technology is capable of accuracies 0.010 per cent to 0.25 per cent. This compares extremely well with older methods like hydrostatic tank gauging, which could only offer accuracies ranging from 1 per cent to 25 per cent.

How should level measurement solutions be chosen?

One of the most important considerations, particularly when specifying magnetic level gauge technology, in is in the manufacture of the float. A magnetic level gauge relies on a float to give a level measurement, which must be designed specifically to suit the process medium being measured. A magnetic level gauge can give 30 to 40 years of reliable service, but a poor choice of float construction could cause performance and reliability to suffer.

Avoid the temptation to go for level measurement systems that can do everything. Concentrate on the core goals of the application and keep in mind that the product itself is less important than the solution you’re trying to achieve.

To guide your selection, keep some essential question in mind:

• What kind of accuracy does the application require?
• What is the temperature, pressure, media type?
• What is the temperature range of the application?
• What is the budget?

Overall, keep three key factors in mind when evaluating your level measurement systems:

• Safety
• Efficiency & reliability
• Environmental

What should I look for in a level measurement vendor?

Look for a supplier with a broad range of level measurement solutions, as they will be able to identify the appropriate solution for your application. They might also offer online tools to make commissioning, installing and troubleshooting the level measurement system easier and more convenient.

Also, keep in mind that a low cost product may not offer the performance and safety levels provided by current generation level measurement solutions.

Talk to the manufacturer and give them as much application information as possible. For example, if the application involves a dirty fluid with the possibility of build-up, then a float-based approach will require special considerations. Again, if the application is susceptible to a high vibration levels, a reed switch technology would probably not be ideal.

What does the future hold for level measurement?

There will be more support for protocols in level measurement systems, including 4-20 mA, HART and Foundation Fieldbus, together with more emphasis on functional safety with products certified to standards such as SIL2.

The future is sure to see level instruments incorporating more digital features, as well as using wireless in creative ways to provide application visibility and flexibility for level measurements.

ABB now offers an extensive range of level measurement products across a variety of applications in pulp and paper processing; mining and construction; food and beverage manufacturing; oil and gas production; and chemical processing. For more detailed information on ABB’s level measurement offering please phone 0870 600 6122 re: ‘level measurement’ or email moreinstrumentation@gb.abb.com.

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