Sensors that keep up with the volatility


We hear from Michael Matheson, electrical and instrument engineer for explosives at Orica Yarwun, and Graeme Corder, Brisbane area manager for VEGA Australia, about how the “VEGAPULS 64” non-contact radar level transmitter has been instrumental in maintaining operations at Orica. 

One of the biggest issues that Michael Matheson comes across in his line of work with volatile liquids at Orica Yarwun is obsolete equipment. 

As plants start to age, a lot of equipment will start to have experience failures that are random and unpredictable. 

“There’s some instrumentation out there, where there’s no amount of condition monitoring that can tell you it’s going to fail,” he said.  

The plant deals with a lot of hazardous substances, such as ammonia and nitric acid. Without the right equipment, it is a serious challenge for the business.  

“A lot of our horns use nucleonic measurement techniques to give level measurement. And, of course, they all have a recommended working life,” Matheson said. “They are expensive – and not just the initial purchase, but ongoing costs in the upkeep and maintenance of nucleonic equipment.” 

“I’ve got a responsibility to try and reduce industrial gauge inventory at every opportunity, so when these gauges were due for replacement, I went looking for alternative level measuring technology.”  

Enter, the VEGAPULS 66. 

The VEGAPULS 64 radar has been a key part of maintenance operations at Orica Yarwun.

“The VEGAPULS 66 radars were available, so we went with those, which were 6.3 GHz operating frequency. They worked admirably across the whole business,” Matheson said.  

However, Matheson faced a new problem in two “Reactor Product Tanks”, which held an 88 per cent ammonium nitrate solution in the midst of ongoing chemical reactions. 

“There’s an ammonia sparging ring in the bottom of each tank that injects ammonia – so you’ve got a solution that is reacting, foaming, there’s vapour and steam,” Matheson said. 

While this is an ideal situation for nucleonics or non-contact radar, the horn radar did not suit these two particular tanks. 

“The risks we needed to eliminate were nuisance trips and restarting plants,” he said. “We found that about every three to four weeks, we’d have a nuisance trip or a level control problem. 

The technicians would need to stop the process, put on their PPE, and isolate all the processes and equipment to remove the horn and give it a clean. The volatility of the solution would periodically splash the horn and trigger false signals.”  

This built up to the point where the business could no longer tolerate the trips and associated risks of process disruption. On evaluating the issue, Corder saw what was needed to overcome Orica’s problem.  

Enter, the VEGAPULS 64 80 GHz Non-contact radar level transmitter. 

“What the VEGAPULS 64 does best is penetrate foam. It has a feature where it ignores anything on the antenna of the radar,” Corder said. 

“Couple that with the PTFE antennae, it is a success. It has a very narrow beam angle of three degrees. Where the older radars were, they were seeing the wall and that was also giving issues due to the lower frequency have a much larger beam angle. We don’t have that problem, with the VEGAPULS 64’s narrow beam angle. So, we’ve gone from a large beam angle to a much smaller beam angle, basically looking straight down at the medium.” 

The VEGAPULS 64 is also more cost efficient. 

“Typically, a VEGAPULS 64 is a probably a quarter the cost of a nuclear system, with no ongoing maintenance costs,” Matheson said.   

“Plus, because the medium is highly aggressive, we were able modify the radar or customise the radar to suit aggressive mediums. 

The new product had a domed PTFE antenna, among other specifications, which Matheson deemed the ideal instrument for this application. 

“I went through our change management process and managed to get sign off from all the key stakeholders, installed two VEGAPULS 64’s and have not looked back,” Matheson said. 

“It’s getting splashed and it’s getting a build-up, but it just doesn’t care. Any build-up that should get big enough just falls off under its own weight anyway, because it’s a PTFE dome that is immune to build up. 

This means that the VEGAPULS 64 has revolutionised the way these two tanks function, providing stable and reliable level measurement, and eliminating the process interruptions, risks, and on-going costs associated with the previous equipment.”

“It’s been set and forget. That process the guys had of periodically removing and cleaning those tanks is long gone, it’s never been done since,” Matheson said. 

“Eventually we included in the modification proposal to progressively change all the VEGAPULS 66’s to VEGAPULS 64’s, knowing that if it works in these tanks it can work anywhere – that’s a fact.” 

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