With recent technology advances, intrinsic safety now offers the safest, most cost effective and easiest way to deploy solutions that safeguard process operations.
In every industry, exploding equipment is a bad thing. In process industry settings, however, the risk of explosions is very real. And the stakes — from impacts on revenue and the environment to loss of life — are far too great to ignore.
Engineers designing electrical equipment and processes for use in hazardous areas are offered many different methods of explosion protection. These range from exclusion methods, such as oil immersion or purge and pressurization, to containment in the use of explosion-proof or flame-proof enclosures, as well as energy limiting technologies such as non-incendive, increased safety or intrinsic safety. These principles and techniques have some inherent advantages and disadvantages. There also are some ideal applications, such as protecting an entire control room using pressurization.
In the correct situation, however, intrinsic safety stands out as the safest, least expensive and easiest to deploy. Here are three reasons why.
1. Intrinsic safety is the safest
Intrinsic safety is the only method of explosion protection approved for Zone 0. This is the most hazardous area recognized by ATEX, IECEx and NFPA 70-2020: National Electrical Code (NEC), Article 505 and is considered hazardous “continuously.” This is because intrinsic safety is required to withstand two electrical faults and remain safe. It is also immune to some of the issues arising from mechanical explosion-proof installations such as improperly sealed conduits and damaged or improperly secured enclosures. Intrinsic safety also is inherently safer for personnel as its energy limiting principle typically allows only up to 30 V or 100 mA into the hazardous area.
2. Intrinsic safety is the least expensive
In many cases, nonhazardous-rated equipment can be used in an intrinsically safe circuit if it meets certain criteria. These devices are considered “simple apparatuses,” which means they are not capable of generating more than 1.5 V, 100 mA or 1.5 W, or they dissipate no more than 2.5 W. These devices include thermocouples, switches, RTDs and LEDs and are typically less expensive and more readily available than hazardous area approved devices.
Another area in which intrinsic safety is less costly than other forms of explosion protection is the ongoing maintenance of the process or machine. Since they use energy limitation as an explosion protection concept, the devices in the hazardous area can be worked on without removing power. Additionally, maintenance time and effort can be significantly reduced because no gas clearance is required, and additional time is no longer needed to access electronics inside explosion-proof enclosures.
3. Intrinsic safety is the easiest
One of the biggest deployment advantages to intrinsic safety is the ability to use mostly safe area wiring practices. Of course, there are some wiring rules to follow, i.e., intrinsically safe and non-intrinsically safe wiring must be separated by 50 mm, and intrinsically safe wiring must be identified by a label or light blue cable jacket. However, all other aspects of wiring — when to use cable tray, types of glands, etc. — are similar to safe area wiring practices. This is in comparison to the many rules regarding explosion-proof wiring installations such as how and where conduit must be sealed as well as the type of cables and fittings required by the electrical codes. Intrinsic safety is also much easier to deploy than purge or pressurization systems as there is no need for an inert gas supply to pressurize the enclosure nor the tubing and fittings associated with this gas supply.
Exciting technological advances in intrinsic safety technology are making these deployments even simpler. An example is the integrated intrinsic safety in new EtherCAT input/output (I/O) terminals (see Figure 1). These components combine explosion protection with a standard, DIN-rail-mounted I/O terminal (see Figure 2). Other vendors offer some sort of integrated approach to explosion protection, but many result in different form factors than their non-ex counterparts and they cannot be integrated directly into the same I/O node with non-ex terminals.
The integrated approach provides many other benefits. For starters, it eliminates the need for a third-party intrinsic safety barrier. This not only greatly reduces the size of the enclosure that houses the control system, but it also cuts the number of time-consuming wiring terminations in half. This also eliminates the need to add another vendor to the bill of materials. Another noteworthy benefit of these integrated technologies is that engineers can take advantages of the benefits of EtherCAT technology, including:
- Real-time communication speeds at 100 Mbit/s and the EtherCAT G/G10 Gigabit expansions that will soon offer even greater bandwidth for demanding applications.
- Free selection of topology without impact on performance,
- Practically no network size limitations, with up to 65,535 nodes on a single EtherCAT network.
- High synchronization due to the principle of distributed clocks.
In terms of safety, cost and ease of deployment, the benefits of intrinsic safety are clear. Engineers should evaluate whether this method fits their application and implement it as appropriate. It’s also important to work with technology partners that take the risks just as seriously as you do and provide solutions to help keep your team, company and equipment safe.
Jesse Hill is the process industry manager at Beckhoff Automation.
