Keeping track of liquid, solid and gas quantities in a busy manufacturing environment is not easy, says Greg Pitcher, but technology is evolving to help.
With all the wizardry and complexity of the modern manufacturing process, the task of measuring raw materials could be regarded as at the mundane end of the technological scale.
Far from it – in fact methods continue to evolve to bring ever greater value to plant managers through cutting edge level measurement.
“Automation technology is rapidly replacing mechanical devices and manual level measurements, helping to provide far greater reliability and accuracy,” says Ingemar Serneby, senior application specialist at Emerson Automation Solutions.
Plant managers are looking for level measurement solutions offering high levels of reliability, minimal maintenance requirements and diagnostics that identify when a device is not performing correctly
Ingemar Serneby, senior application specialist, Emerson Automation Solutions
Knowing how much of a solid, liquid or gas you have in a tank or silo is not a standalone admin issue for production firms, but goes to the heart of business models. It impacts on accounting accuracy, production output, safety and customer relations – meaning it has an important role in the success or failure of an enterprise.
“Every plant’s business goals depend on the performance and reliability of its critical production assets, including its level measurement technology,” says Serneby.
“Plant managers are looking for level measurement solutions offering high levels of reliability, minimal maintenance requirements and diagnostics that identify when a device is not performing correctly.”
He says that while reliability is still the priority, the marketplace has come so far that new horizons are coming into view.
“The challenge now is to make level measurement technology easier to install, operate and maintain, while also helping to improve plant and worker safety.”
Well-established level measurement technologies include the use of ultrasonic, differential pressure transmitters, vibrating forks, guided wave radar, non-contacting radar and acoustic devices.
Each have pros and cons according to the conditions and requirements of their use, and consultants and suppliers can help guide process managers through the procurement process.
“It is critical to select the correct technology for your specific application,” says Serneby. “Factors such as the dialectic value of the material being measured; disturbance caused by filling; presence of foam or interface; changes to density; type and size of vessel; and required speed and accuracy of measurement must all be carefully considered.”
Ever changing
The different technologies are all evolving, meaning previously discarded options can be revisited from time to time.
“Non-contacting radars using high frequency technology have been introduced, complementing the low and mid frequency instruments already providing reliable level measurements,” comments Serneby.
“Another advancement is the availability of two-wire non-contacting radar transmitters that use the frequency-modulated continuous-wave (FMCW) technique to perform measurements.”
He says that, although FMCW technology can provide accuracy and sensitivity, it has previously been mainly used within four-wire devices due to its power requirements.
“That can necessitate additional cable infrastructure, which is costly and time-consuming.”
Vega marketing manager Doug Anderson says 80 GHz radar – with its high frequency, intense focus and small antenna – has expanded into new sectors this year.
Ability to work in challenging conditions is a key selling point of the technology. “The 80 GHz radar has grown phenomenally,” he says. “It can work in really poor installation positions, in vessels with old nozzles that would cause all sorts of problems for old technology.
“And where a signal is sometimes lost due to foam or condensation from the process, we are taking off old products and putting on 80 Ghz radar.”
Some sectors have their own particular requirements of level measurement tools. “We are making headway with contactless measurements of liquid gases,” says Anderson. “When you measure liquid gas in giant spheres you want the process instrumentation to be fully isolatable and removable.”
This often leads to a double isolatable valve system where a small amount of gas is isolated between the two and removed to protect the main body of gas within the vessel if a measurement tool has to be removed.
This means a radar instrument can be mounted on a vessel to measure what’s inside.
“In the past we have had to use 30 metre-long distilling tubes down the middle of the vessel, but imagine the engineering – you need a crane to install it – and the risk of blockages.”
While level measurement technology is evolving rapidly, ensuring users have the right systems to read and analyse the data produced is critical to maximising the benefits.
“We are getting more and more into digital considerations,” says Anderson. “You need to make sure your control system and transmission is at a high enough level.
“If I’m measuring in millimetres over 30 metres then I have 30,000 measurement points. Old analogue systems often don’t have that level of resolution, they might have 10,000 bit resolution, so it can be like using an HD camera to film on to a VHS cassette.”
A lot of industries need serious investment. We still see sites where someone is tasked with climbing up all the silos. Is that the best use of their time, and is it the most accurate?
Doug Anderson, marketing manager, Vega
Handheld devices are increasingly offering alternatives to traditional control systems. “We offer customers the opportunity to look at individual centres on their phones, using Bluetooth communication kit inside a plug-in programmer, to check readings, diagnostics or commission,” says Anderson.
“Any continuous measurement instruments bought from Vega since 2002 can be made into a Bluetooth device to communicate with a tablet, iPhone or PC.”
This brings its own challenges, including cyber security considerations. “You have to be within a range of about 25 metres to read the data,” says Anderson, “there is 64 bit encryption and pin code protection.
“We talk to people about how to look after and protect their instruments.” This starts with the most basic measures, such as switching Bluetooth off when it’s not required.
“All our Bluetooth comms units have a physical switch on them. You might just use it during the set-up phase and switch it off and even remove the plug-in module so it becomes a discrete unit again. The ultimate cyber security is breaking the link to stop people getting in.”
Risks remain low when using Bluetooth to read measurements, Anderson stresses. “To connect to one of our devices you would have to be able to identify it, know which app to use it, and then know the code to talk to it. A good hacker could potentially work it out – but they can get into anything.”
Switching gear
It seems the future will only see more evolution of level measurement in process plants, although not all owners are switched on to the benefits.
“A lot of industries need serious investment,” says Anderson. “We still see sites where someone is tasked with climbing up all the silos. Is that the best use of their time, and is it the most accurate?”
He says multi-parameter measurement is likely to evolve. “You will see pressure transmitters that also measure temperature and so on. We already have level sensors that measure moisture.”
Using the data correctly will be critical as ever. “You have to have the back-end systems,” says Anderson. “There is no point having the information shown on the side of the tank, it has to be distributed among all the people who need to see it.”
