Level best

The 2005 Buncefield incident shone a spotlight on the level measurement industry, in particular to devices and methods deployed to prevent ‘overfill’.

The final report on the incident, published in 2008, included a mandatory requirement that overfill be prevented by “independent and automatic means” that did not rely on human intervention.

“Certainly the level device failed on that [Buncefield] tank,” says Honeywell Field Solutions EMEA sales director Richard Thompson.

All of the contact level measurement devices we sell must now include software to ensure they remain in place on the level

Honeywell sales director Richard Thompson

“It was a contact measuring device that was meant to sit on the surface of the liquid but somehow it got stuck and was showing a static level when in fact the tank was filling up.”

Since then, there have also been new recommendations made by the American Petroleum Institute (API) in regard to overfill practices, says Thompson.

“All of the contact level measurement devices we sell must now include software to ensure they remain in place on the level,” he says.

Another outcome of the Buncefield incident is the trend to deploy independent high-level alarms, which trigger when stored material reaches a certain level.

“That might be another radar, a servo gauge, or a switch that responds when the level touches it by simply shutting down a pump that feeds the tank,” says Thompson.

“Buncefield has really pushed that approach to a much wider implementation.”

Because most of its business is in the transport, storage and distribution of feedstock coming in and out of a refinery, Honeywell Field Solutions supplies mainly ultra-high precision level measurement devices based on radar technology.

“Our level devices will get down to less than 1/2mm accuracy on a storage tank up to 40m high,” says Thompson.

On top of the safety considerations, the high commercial value of the commodity being tracked means that temperature, pressure, level and flow rate must all be carefully monitored to ensure there is no opportunity for product to go missing, he says.

“Customs and Excise want to know exactly what is coming in and out and you also need to ensure nothing is leaking so you don’t have an overfill situation.”

Another of the key impacts of Buncefield has been to create a preference for non-contact radar level measuring devices, he says.

When it comes to navigating the myriad safety standards associated with storage and movement of hazardous substances, Thompson says he spends “a lot of time in a consulting role”.

“We invest a lot of our time listening to our customers and getting out and about with operators loading up tanker trucks, or seeing how a train unloads its cargo,” he says.

“We’re trying to break down any barriers where the technology is too complex. We want to ensure that the younger population can come in and get trained very quickly. To reduce the chances of misuse we try to make our technology easier to use with big icons, and touchscreens where appropriate.”

The new generation of engineers don’t want to spend lots of time configuring a level transmitter, says Christoffer Widahl, a senior product manager at Emerson Process Management.

“They just want it to work. There is the same expectation for the use of this type of technology as the devices they use privately.”

According to Widahl, the most popular level measurement product line among oil and gas, refining and petrochemicals customers is guided wave radar (GWR).

“It is well suited for most applications, including where temperatures and pressures are high,” he says.

“Process companies need accurate and reliable level measurement, and they don’t want anything that could shut down the process, as that would cost tons of money.”

Although GWR technology was launched at end of 1990s, Widahl says it is still considered quite new.

“The technology did struggle for a couple of years, but it is getting more mature and people are starting to trust the products and find them a very reliable method of level measurement,” he says.

“We have had a huge success in upstream oil and gas in the north American market, and that is one of the contributing factors to our success with guided wave radar.”

However, no single technology can be used to measure every level and for this reason the company supplies a wide portfolio of devices.

“Every plant has one or a few applications where nothing has been proven to work when it comes to measuring level,” says Widahl.

“Typically this is where you have lots of turbulence or foam in a process fluid, or in tall vessels requiring long measurement ranges. One way in [to a new site] is to try and see if you can solve this.”

“We are coming to a point where the next challenge is to get more than just a measurement out of a measurement device, says Andreas Hessel, marketing manager at Emerson Process Management.

This means greater automation and diagnostics.

“Up until now the differentiation between devices has been between accuracy, sensitivity and range,” he says.

“But now most vendors are focusing on building more functionality and ease of use in transmitters. So instead of just an error code, you’d get a clear text message asking for maintenance or communicating a problem with the process.

There are applications out there where radar or hydrostatic technology wasn’t considered because the technology wasn’t there

Impress Sensors & Systems’ Sam Drury

“So we’re building more and more smart transmitters with more and more diagnostics offering advice to the user rather than them having to troubleshoot on their own.”

Wireless capabilities are also proving increasingly popular in remote locations or where there is no existing infrastructure.

“We recently launched the world’s first wireless GWR, which offers good performance and a nine-year battery life,” says Widahl.

When it comes to level measurement for environmental, sewage and wastewater applications, hydrostatic devices have an edge over other devices says Sam Drury, sales and marketing director at Impress Sensors and Systems.

“Hydrostatic devices … are unaffected by foam and offer a good compromise of cost and performance.”

Another key feature, says Drury, is that hydrostatic devices have a flush diaphragm on the sensor so there is no possibility of blocking or clogging, hence they are often favoured in a sludgy environment.

For this reason, key applications include fresh water, wastewater, sewage treatment plants through to transportation of liquids and chemicals in tanks.

However, there are still many legacy devices in place based on what people have always used, says Drury.

“There are applications out there where radar or hydrostatic technology wasn’t considered because the technology wasn’t there,” he says.

“When people are used to using non-contact solutions they need to be convinced that a contact solution is as good.”