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Everywhere. Reliable. Purge Solutions from Pepperl+Fuchs

17 March 2023

When it comes to using electrical equipment to control or monitor systems in hazardous areas, a close inspection quickly reveals how well enclosure solutions with purge and pressurization from Pepperl+Fuchs are suited for this.

Ex p protection is effective and enables the use of standard equipment, such as PLCs, frequency inverters, and IPCs. Power dissipation can be installed more cost effectively than other types of protection. Systems can be installed and serviced very easily. With more than 20 years of experience designing and constructing these solutions, Pepperl+Fuchs is a real specialist in this field. In addition to global support, the company also offers international approvals according to NEC, ATEX, and IECEx, which are suitable for both conventional and future industries.

How does purge and pressurization work?

Electrical equipment can be protected in different ways when used in hazardous areas. In process automation, methods such as Ex d (flameproof enclosure) and Ex e (increased safety) are the most common versions. Another interesting type of protection is the technology of purge and pressurization. The concept is to design and construct an enclosure solution — for example, for a control system—in such a way that the electrical equipment installed in it is separated from the explosive atmosphere.

This type of protection, abbreviated to Ex p, is suitable for use in environments with combustible gases and dust. To ensure safe operation, the enclosure is "cleaned" before commissioning. The enclosure is cleaned by pressurizing the explosive gas with either clean air or inert gas. Dust is wiped off the inside of the enclosure before it is sealed. The control is set so that the pressure inside the enclosure is always a few millibars higher than the hazardous ambient atmosphere. The compact control unit mounted on the outside of the cabinet and the associated equipment, such as valve and enclosure protection vent, monitor that no ignitable atmosphere enters the enclosure. This ensures that equipment can be operated as intended inside the control cabinet without individual approval for hazardous areas.

Another great advantage of purge and pressurization is that the system does not simply send a message in the event of technical faults, it safely shuts down the system in an emergency. If a pressure drop occurs in the cabinet, due to defective seals or cable glands, a warning signal is output by the control unit (controller). This warning signal is either visual, acoustic, or a combination of the two. If the pressure drop is not too high, leakage compensation temporarily compensates for the pressure loss and the fault can be corrected during operation. However, if the pressure drop exceeds a preset limit value, the purge system will automatically shut down.

Standardized and Fully Certified Solutions for Rapid Commissioning

However, the occurrence of leaks can be limited very effectively by careful planning and selecting an enclosure with long-lasting cabinet seals. The enclosure must withstand a defined internal pressure. Minimal adjustments to the enclosure are often sufficient to significantly improve the robustness. It is possible to reinforce enclosure walls, doors, hinges, and use special seals. The need for such measures may cause customer uncertainty, but companies such as Pepperl+Fuchs with years of experience provide customers with very intensive support and will design the entire solution if necessary.

To minimize the costs for customers in terms of approval, selecting the right enclosure, and a purge and pressurization system, Pepperl+Fuchs also offers "package solutions" that offer far-reaching advantages. The pre-designed and standardized enclosures allow customers to easily set up a standard-compliant purge and pressurization system for Zones 1/21 or 2/22. The package solutions are available in several sizes for Zones 1/21 and 2/22, already contain all required components, and can be ordered directly based on a fixed price structure. These solutions are also available with additional power contactor and Vortex cooler, if this option is necessary from a technical point of view. Full certification is also offered, including installed cable glands, lamps, buttons, and operating elements. This covers almost all eventualities, allowing customers to use the pressurized cabinets for a wide range of applications in hazardous atmospheres. 

Predefined enclosure solutions with purge and pressurization are also developed for specific applications. Pepperl+Fuchs offers customers ATEX- and IECEx-certified stainless-steel enclosures for installing printers that enable label printing applications in hazardous areas. Frequently used in cleanrooms in the pharmaceutical industry. The concept is not rigid, because despite a certain degree of standardization, it is possible to use different printer models, interfaces, windows, and operating elements. Purge and pressurization offers a great advantage with such solutions because the possibility of using standard equipment also allows solutions to be quickly and easily customized according to customer specifications.

Customized Solutions for Individual Applications

However, other solutions must be found for applications that are individually configured. Standards usually do not help in this case. For more complex projects or special requirements, Pepperl+Fuchs supports its customers from the design phase. From time to time, specifications are so complex and extensive that several of these pressurized cabinets are required, such as the solution from a German manufacturer of tunnel boring machines, commissioned by the city of Los Angeles for the construction of a sea outfall tunnel. These tunnels are designed to discharge wastewater from sewage treatment plants into the sea over several miles. To bring wastewater back into circulation without additional chemicals, a tunnel of approx. 12.5 km in length was drilled. A controller consisting of several pressurized cabinets up to 9 m long had to be integrated into the associated drilling machine. These have been certified for use in the USA according to UL, Class I, Division 1, and Class I, Division 2. Design, construction, and certification were carried out under the responsibility of Pepperl+Fuchs.

Solutions in purge and pressurization enclosures are also suitable for future technologies. The use of green hydrogen is one of these technologies. In India, the first hydrogen filling station was recently built as a clean fuel initiative. This plant sells green hydrogen to customers who already use cars and small trucks with this technology. The term green hydrogen is used to refer to hydrogen produced by electrolysis with energy from renewable sources. Pepperl+Fuchs was part of this project as a recognized expert and supplier of purge and pressurization systems. The 5500 series purge and pressurization system was a critical part of certifying the analysis panel integrated into the dispenser for use in Zone 2. The analysis panel has the critical task of monitoring whether the hydrogen provided meets the quality requirements.

Top-Level Service—Available Globally

Pressurized enclosure solutions from Pepperl+Fuchs are based on the company's special service concept. The entire project processing is carried out by our engineers in close coordination with customers. Change and adaptation requests are discussed quickly and are incorporated according to customer specifications—from design to joint acceptance. Product specialists are located in Solution Engineering Centers (SECs) around the world and support the field service, which also has a global presence. In the end, the customer always receives the best custom solution from Pepperl+Fuchs.

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