U.K. Grant Targets Sensors for Corrosion Protection in Heating, Cooling Units

Steve Munn, managing director of Hevasure, looks over data captured by the company’s sensor system for corrosion monitoring. Photo courtesy of Hevasure.

A new grant from Innovate UK—the government-funded innovation arm of the United Kingdom—is aimed at helping clean technology company Hevasure (Derbyshire, United Kingdom) further develop remote corrosion monitoring solutions for heating, ventilation, and air conditioning systems.

The company is a unique spinoff from Midland Corrosion Services (Derbyshire, United Kingdom), which has carried out investigations into over 300 failures in heating/cooling and drinking water systems over the past 17 years. As part of the Innovate UK project, it will collaborate with The University of Derby (Derby, United Kingdom) on the technical development of a new generation of sensors to monitor corrosion, reduce risks, and improve efficiency in water-based heating and cooling systems.

“We have the technology to capture and display the data,” Managing Director Steve Munn says of his company’s monitoring system, which uses up to eight sensors in a typical installation. The sensors meaure dissolved oxygen, pressure, temperature, flow rate, conductivity, pH, galvanic currents, and crevice corrosion, with data transmitted to the cloud via cellular networks.

“We can now develop our ideas for further cost-effective sensors that can track the corrosion rate for a wide range of metals,” Munn says. “Derby has considerable expertise in sensor development. By working together, we can get sensors that will give us even more accurate corrosion and pitting rates and facilitate predictive maintenance for heating and cooling systems. We have experience they don’t have, and they have knowledge we don’t have.”

Corrosion rates on carbon steel (CS), stainless steel (SS), copper, aluminum, and others can be monitored through the system. Data are relayed over a mobile phone network to a central database and web server, and can be viewed in real time on a dashboard. “The secret is to be able to rectify any fault before significant corrosion occurs,” Munn says.

Benefits of Continuous Monitoring

According to Munn, one of the main problems encountered in monitoring these systems is the reliance of traditional maintenance and facilities management companies on outdated periodic water sampling methods to check on the health of the systems.

“This old approach gives only a partial picture, because water composition is only one aspect that needs to be considered, and it is only a snapshot view,” Munn explains. “It can miss events that are happening, and it’s open to misinterpretation. It gives no information on why corrosion is occurring.”

“The industry is now waking up to the opportunity that continuous monitoring presents; namely, measuring and recording all of the key parameters that influence corrosion,” he adds.

Recent developments in sensors, data loggers, and communication technology are making it possible to monitor many parameters remotely and continuously, while providing electronic alerts if critical levels are exceeded, he explains.

“Having a monitoring system gives you a much better picture,” Munn says. “Real-time monitoring can capture planned and unplanned events so that we have a complete record of everything that has happened in the lifecycle.” He notes that in the event of potential litigation, the real-time monitoring system can also provide much needed hard data.

System Parameters Monitored

In developing the monitoring system, Munn says his company has already introduced sensors to track parameters that give rise to both galvanic and crevice corrosion. The galvanic corrosion sensors monitor the currents that occur between different metals in the system.

“In plain water, galvanic currents increase in proportion to dissolved oxygen [DO],” Munn explains. “However, inhibitors at the correct strength passivate metal surfaces and suppress galvanic currents. By using this sensor, we can check that the inhibitor is doing its job effectively, even when there is some oxygen in the system. Our sensors look not only at the corrosion, but also at the cause.” In localized regions of these units, such as near weld seams and underneath debris, crevice corrosion is particularly concerning. In these places, rapid pitting and pinholes can occur, leading to potentially catastrophic failure of the system, he explains.

“The biggest cause of corrosion is usually a systemic problem,” Munn says of potential causes.

To check for such scenarios, a wide range of parameters are evaluated, starting with DO. Munn says it is essential that DO remain low in a closed system—ideally less than 0.2 mg/L.

“Dissolved oxygen provides the main cathodic reaction, which drives metal corrosion,” Munn says. “By measuring DO, we can ensure the system is airtight and that any oxygen introduced by fresh aerated water is quickly consumed.”

Corrosion data from the sensor monitoring system can be examined remotely via smartphones or tablets. Photo courtesy of Hevasure.A related variable is pressure, since a closed system must maintain a positive relative pressure at all times to avoid sucking air into the system. “We monitor this at the highest point in the building using a small satellite monitoring system,” Munn explains.

For these water-based systems, he says, it is also important to measure characteristics of the water—namely, its conductivity, pH, and risk of biofilms.

“For inhibited systems, measuring conductivity (and compensating for temperature) tells us the concentration of the water treatment products,” Munn says. “We are able to tell if a system is being overdosed or under-dosed with inhibitor.”

For systems containing aluminum, the system checks to ensure the pH does not exceed 8.5. “Otherwise, the passive films break down, and aluminum components such as heat exchangers can start to corrode,” he explains.

A final consideration is the potential formation of biofilms, which can lead to oxygen concentration cells on pipework and promote the growth of sulfate-reducing bacteria and microbiologically influenced corrosion (MIC). “When biofilms form, MIC often occurs, and this can lead to wall thinning and pinholing in metal pipes,” Munn says. “We are trialing a sensor that will enable us to monitor the risk of biofilm formation.”

Based on corrosion concerns, Munn says some industry companies are shifting away from CS and toward more expensive SS and aluminum solutions, which have problems that also can benefit from remote monitoring. However, he believes CS remains viable, if monitored.

“Carbon steel is a very good product, [less expensive] to put in, and easy to install,” Munn says. “You just have to make sure the system is monitored.”

Future Collaborative Steps

The collaboration between the company and university aims to improve both the technology of the sensors and their economics. 

“Right now, there are a lot of corrosion sensors on the market that are good devices, but they’re too expensive,” Munn explains. “For just one [component], you’ll pay something like $4,000 or $5,000 for one sensor. That’s not commercially viable for monitoring the sorts of systems that we’re trying to monitor here. So I applied for the Innovate UK grant with some ideas on how we could develop lower-cost sensors for a range of metals, which we could then integrate with our system.”

Going forward, the company plans to work with the school’s laboratory technicians to ensure the sensor system’s accuracy. “They’ve got a great engineering department,” Munn says of the school. “We’re going to put in some prototypes to ensure that everything works. We’ll compare what the sensors tell us with metal coupons to make sure that we have accurate measurements of the corrosion rates.” 

The Derby consultancy team is led by Ahmad Kharaz, a specialist in sensor technology, of the school’s engineering and technology department. The project is scheduled to be completed by October 2018.

Besides the academic collaboration, the technology company is also looking to industry partnerships as the technical refinement of the sensors continues and commercial exploitation accelerates.

“We’re very much looking at partnerships,” Munn says. “We are a small pioneering technology company. What we’re doing is investing time and effort to develop intellectual property and partnerships with companies in the United Kingdom and elsewhere who can use our technology.”

Source: Hevasure Ltd., www.hevasure.com. Contact Steve Munn, Hevasure—email: smunn@hevasure.com.

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