On the level: hidden process parameters revealed
20 Jun 2016
Level and pressure measurement devices are playing an increasingly important role in the quest to improve plant productivity, writes Louisa Hearn.
Careful management of vital but often hidden parameters such as level and pressure are critical to many of today’s process operating environments.
But while their importance in preventing runaway events such as the UK’s Buncefield disaster are widely documented, they are also finding application within plant automation systems.
“Over time and tide we are seeing more and more plants looking to automate and optimise because they need to improve productivity,” says Doug Anderson, Vega marketing manager.
“That is a common theme across a range of industries as regards to level measurement.”
Over time and tide we are seeing more and more plants looking to automate and optimise because they need to improve productivity
Doug Anderson, Vega marketing manager
Vega supplies level measurement solutions for bulk and liquid level monitoring, and according to Anderson, commercial pressures mean companies are seeking new ways to automate their inventory systems and buying procedures.
“If you can measure the contents of the tank and send that to the supplier, they will know when to replenish it,” he says.
But as technology solutions evolve, Anderson explains that increasingly complicated devices must become easier to setup and use.
This is partly because there are fewer engineers on the ground, says Anderson, along with a growing reluctance to send staff to dangerous locations or to work at height.
The company anticipated this need back in 2002 when it rolled out a modular product design for its instruments to reduce build time and simplify maintenance.
And because of its modular design, all of its devices dating back to 2002 can now be equipped with Bluetooth, says Anderson.
Got to hand it to them
This allows operators to programme units remotely from any handheld device using the company’s Vega Tools smartphone app.
“This means you can basically use your smartphone for any Vega instrument,” says Anderson.
Honeywell is also seeing a shift to intelligent device management among its user base in chemicals, oil & gas refining, pulp & paper and power industries, says Mike Cushing, product manager at Honeywell Process Solutions.
The growth of wireless applications has added to the number of measurements available from instruments in the plant, and with more data coming in, companies want to do more advanced analytics, he says.
This not only opens remote access to instruments, but allows users to monitor inventory and automatically schedule refills because they are getting data accurately and reliably.
“Moving to cloud computing applications means the cost of data modelling analysis is also coming down,” he says. “So where once you might only have instrumented critical items of machinery, now you can instrument much smaller devices.”
Where once you might only have instrumented critical items of machinery, now you can instrument much smaller devices
Mike Cushing, product manager at Honeywell Process Solutions
Honeywell supplies a range of pressure and guided wave radar level measurement instruments, providing a toolbox for users to choose from, depending on their process.
Multivariable transmitters – which enable users to measure pressure, level and temperature in a single device – are also growing in popularity for specific applications such as monitoring evaporation, says Cushing.
A new cross-industry field device integration (FDI) effort is also underway to boost device integration for process automation and analytics, he adds.
FDI promises a common set of development tools and a single path to managing the flood of information from intelligent devices across different networks to the applications and analytics software making use of the information.
Problem solving
According to Peter Gardner, managing director of Turck Banner, the compatibility of component parts in a system can be crucial to eliminate potential problems such as the remote IO not talking to the PLC.
“We have seen may people buy products from [one place] and cabling from somewhere else, and suffer these silly little problems that can stop the plant running.” 
He says Turck Banner offers a wide range of level and pressure instruments for process monitoring as well as the necessary cabling and connectors to create very complete solutions that can closely match solutions to customers’ actual needs.
“More and more flexibility is being demanded of manufacturers, so they increasingly want things to be universal to allow them to change their process or mixture without having to change their equipment,” says Gardner.
Foaming factors
How do you measure the level of foaming fluid? This is a problem arising more often as demand for water-based products increases, says Darren Pratt, industrial instrumentation product manager at SICK.
“In some industries there are moves away from oil-based fluids to water- based fluids,” Pratt explains.
An example of this is paint, where water-based products can now boast real improvements in their surface finish.
These also have a greater tendency to foam when processed.
Guided wave radar (GWR) is the technology behind SICK’s solutions for foaming fluids.
As a radar-based technology, it can also prove effective against other process effects such as build up and coating, where most traditional float systems begin to struggle, says Pratt.
“Imagine an application where you are measuring the level of liquid chocolate, which tends to stick to things and creates a buildup on any contact level measuring technology that you put in there.”
This is where the selection of technology becomes important. For instance, in a dairy application, bottles of milk are filled on rotary filling machines.
“Obviously the dairy wants the fastest throughput they can achieve, but that often means having to move fluid more quickly and that means bigger potential for generation of foam,” he says.
One of the technologies that tended to be used was capacitive level measuring technology, says Pratt. “But as it sped up, it would end up measuring the foam, and as the filling process continued, bottles were coming out half empty.”
The shift away from full fat milk to skimmed milk has exacerbated the likelihood of foam developing in the process.
“If you have under filled cartons, they have to be captured, and either thrown out or the milk has to be put right back into the beginning of process,” he says.
Cottage cheese is another problematic product to measure, says Pratt, with any contact-based probe needing frequent cleaning.
“It costs a lot to send a service engineer to rectify this relatively simple problem.”
Once reserved for high-end applications, Pratt says SICK has been working on its GWR technology to lower the adoption threshold. Companies are also increasingly willing to stand a little more in their initial spend to increase the reliability of their products in the field, he says.
Especially as these devices are also able to generate their own reliability information to provide operators with more “tangible information on how the sensor is working in the application”.
