Choosing a Raman system for a hazardous zone can be difficult. What are the risk factors? What regulations are in effect? How can safety be balanced against measurement quality? In this blog post, we provide you with an insight into how Raman analyzers can be adapted to a hazardous zone.
Flammable vapors and gases are an unavoidable aspect of many manufacturing processes. Petrochemical refining, chemical production, and some types of pharmaceutical manufacturing are just a few of the situations where there is the potential (if not the certainty) of potentially explosive gas species being present. As ignition sources, dust and particulates pose serious risk for creating catastrophic explosions or fires. As such, the IEC, the International Electrotechnical Commission, created a comprehensive set of standards for minimizing risk. The “IECEx” standards (where “Ex” refers to explosive atmospheres) laid out in their 60079 series of documents explain how to avoid creating an ignition source in many different industrial scenarios.
One key concept from this standards framework is the concept of zones. Zones are identified by various regulations in different regions. In Europe, the ATEX directives apply with their various zone designations and serve as a good example for this narrative. Zone 0 is the most hazardous because explosive or flammable gas is always or usually present. In Zone 1, these gases or vapors are likely to occur under normal operating conditions. In Zone 2, the safest of the three hazardous zones, ignitable concentrations of flammable gases or vapors are not likely to occur under normal operating conditions and may only be present for a short period of time. And then in a “safe zone”, there is never any hazardous atmosphere – this would be your control room or a separate building.
One of the great things about Raman technology is that most of the hardware, like the main analyzer unit and control computer, can reside in a safe zone, and the excitation laser light and scattered Raman signal can be conveyed in and out of the hazardous zone by optical fibers.
If you want to make Raman measurements of your process, whether it’s quality control on raw materials, or reaction monitoring, or quantitative evaluation of the final chemical product, you have to be aware of the zone rating of the measurement point(s). Appropriate steps are required to ensure that your measurement equipment in the hazardous zone adheres to the IECEx standards and associated international regulations such as the European ATEX directives.
The biggest risk with doing Raman analysis in a potentially flammable or explosive atmosphere is that the concentrated laser beam may cause heating of a particle or surface and serve as an unintended ignition source. The IEC-60079 standards define three ways to prevent optical radiation (in this case, your Raman excitation laser) from triggering a fire or explosion.
The IEC designation <op sh> refers to having some sort of sensor that will shut off the laser if explosive gases are near the Raman probe focal point. This could be an optical fiber break detection circuit for the case where the cable carrying the laser light is severed. Or, consider a situation where the Raman probe is measuring a liquid in a pipe or vessel. As long as the laser focal point is submersed in liquid and away from oxygen, combustion cannot take place. But a signal from a level sensor would be required to kill power to the laser if the liquid level falls too low and risks exposing the focal point to explosive vapor.
The <op pr> designation provides for a small region around the measurement point where active purging with inert gas or some other protective method will prevent explosive gases from leaking in.
At Tornado Spectral Systems, we have designed our ATEX-safe Raman solution around <op is>, where the “is” stands for “inherently safe”. The standards specify that by limiting the laser power coming into the hazardous zone to a certain level – either 15 mW, 35 mW, or 150 mW, depending on the specific types of gases present – then there is no risk of that laser light triggering an ignition, no matter how tightly focused the beam might get.
Two other important concerns are that an electrical signal going into a hazardous zone, such as a limit switch circuit or a laser safety indicator light, might create a spark, or that the materials that the Raman probe is made of could create a spark, such as from electrostatic discharge or metal surfaces banging together if the probe is dropped against a pipe, for instance. These factors also need to be considered in determining if a Raman system is safe for an IECEx/ATEX deployment.
The Tornado Solution
Our product offering for Raman measurements in hazardous zones combines our revolutionary HyperFlux PRO Plus Raman analyzer with a custom-designed laser subsystem called the OPIS 35 which produces an inherently safe level of laser power. With regulatory certifications proving its compliance with IECEx and ATEX, the OPIS 35 device enables straightforward installation for use with most Zone 0, Zone 1, or Zone 2 locations without the complexity and risk of level sensors or purging. Because of the unbeatable sensitivity of the PRO Plus spectrometer, Tornado Raman measurements at the inherently safe laser power level are equivalent to (if not better than) a conventional Raman system running at full (unsafe) power. For more information about the OPIS 35 solution, please visit: https://tornado-spectral.com/solutions/hyperflux/hyperflux-pro-plus/opis-35/
A complete solution for process analytics requires much more than a great analytical instrument. At Tornado, we have also put a great deal of effort into developing powerful but easy-to-use instrument control software, offering flexible sample interfaces like different types of probes (immersion, flow cells, and non-contact), increasing capabilities for integration into industrial distributed control systems, and safety measures that are equal to the capabilities of our core instrument. All of these factors are critical for providing a comprehensive and fully deployable product for our customer base.
For more information about our ATEX-compliant Raman measurement solutions, please contact us at email@example.com