Robert Kuipers, product manager at Pentair Thermal Management, discusses the different control and monitoring solutions available for industrial heat tracing systems, and explains how local control and central monitoring can help plant owners to comply with ATEX regulations and optimise efficiencies

The combination of fewer on site maintenance personnel and strict regulations surrounding industrial environments has increased the need for instant access to information about industrial heat tracing systems. In addition to safety considerations and peace of mind for plant owners, choosing the right control and monitoring system can be cost effective, saving on both cabling and maintenance costs. As budgets continue to be squeezed, installing the best solution has never been so important. 

Control and monitoring is particularly critical for oil and gas refineries and petrochemical plants, where an uncontrolled increase in temperature could lead to an increased chance of explosion. In the European market, any control and monitoring products used in these areas must comply with stringent ATEX regulations.

Controlling a heat tracing circuit can be as simple as a mechanical thermostat. However, in larger, more complex environments such as refineries or chemical plants, more sophisticated control and monitoring requirements are necessary. With a variety of options available, plant owners need to know that they are selecting the most appropriate system for their application. This is where complete heat management solutions providers can add real value – by partnering with a heat tracing specialist at the beginning of the specification and design process, plant owners can be sure  they are getting the best system and configuration.

Further to a simple thermostat, there are three advanced control options that plant owners can choose from. The first combines local control with local monitoring, with both of these elements located in the field. This is suitable for smaller applications where maintenance professionals are able to get to the site quickly and easily.

The second option combines central control with central monitoring which addresses the problem of sending maintenance operatives to the field, as everything is controlled from a central location. This is convenient, but can be costly as each heat tracing circuit has to have its own power and temperature sensor cable connecting it back to the substation.

The third approach combines local control with central monitoring. A ‘best of both worlds’ solution, this enables areas with small temperature changes to be controlled locally, with all of the source site data sent to a central location away from the field. A cost efficient option, it incorporates ‘daisy chain’ power distribution wiring, wherein the local controllers can be connected to each other, optimising the power cabling infrastructure.

Once a plant owner has decided on the system most suitable for his site, he needs to ensure that it is approved for use in hazardous areas, which means it must comply with ATEX regulations. There are two ATEX directives   the ATEX 95 equipment directive 94/9/EC covers equipment and protective systems intended for use in potentially explosive atmospheres, whereas the ATEX 137 workplace directive dictates the minimum requirements for improving the health and safety of workers potentially at risk from explosive atmospheres.

So, how can control and monitoring systems help plant owners comply with ATEX regulations? With a local control and central monitoring system, most of the maintenance can be carried out from a central location, so maintenance personnel do not have to go into the field as frequently. If a heat tracing circuit is likely to exceed the specific temperature class (T class) in Zone 1, a Safety Temperature Limiter is required. The DigiTrace NGC 20 is a controller, which combines local control with central monitoring and contains a Safety Temperature Limiter (Pentair Thermal Management’s DigiTrace NGC 20) when required. The limiter is defined as a SIL 2 device under the International Electrotechnical Commission’s (IEC 61508) standard.

Pentair Thermal Management