Designing Commercial and Industrial Coils for Extreme Conditions

In demanding applications, standard heating and cooling coils simply can’t survive the extreme conditions. That’s why you want a custom manufacturer like Marlo when you need commercial or industrial coils that perform – and continue to perform – in very harsh environments.

Our expertise in engineered-to-order coils means we’ll design your coils to stand up to your specific environment – including choosing robust materials and coatings to match your needs. At Marlo, our extensive experience in a wide range of industries assures that we can design and build custom coils that will handle the most challenging applications.

Understanding Extreme Environments

There are various harsh conditions that coils can be exposed to, which can be referred to as extreme. Each of these environments stresses coils in unique ways, and each requires careful engineering to ensure durability and performance. Examples include:

• High temperatures: From rooftop units in desert climates to high-temp industrial process heating applications.
• Freezing environments: Heating coils in air handlers or makeup air units in sub-freezing (even sub-zero) conditions.
• Corrosive conditions: In chemical and other industrial plants, or in coastal areas or marine applications with high salt exposure.
• High-pressure systems: Various industrial processes with elevated fluid pressure, as well as cooling applications with high-pressure refrigerants.

Materials Make the Difference

The first line of defense against harsh conditions is material selection for all coil components, in order to ensure they won’t degrade prematurely. Of course, most coil manufacturers are familiar with standard materials such as copper tubes and aluminum fins. But at Marlo, we have expertise in a wide range of metals, including the following:

• Copper-nickel (or cupro-nickel) tubes: A combination of these two metals – with the percentage of each varying depending on the specific application – is ideal for corrosive environments, including marine applications.
• Stainless steel tubes and casings: Stainless offers excellent resistance to moisture, corrosion, and harsh chemicals. In addition, stainless steel tubes provide the needed strength for high temperature and high-pressure applications.
• Copper and stainless fins: These alternatives to the standard aluminum fins are required for corrosive environments, including those with high salt content, and are also chosen for their antimicrobial qualities in clean environments.
• Headers and fittings in stainless steel, black iron and red brass: We offer a variety of metals to assure the necessary strength are durability.

Design Considerations for Reliability

For coils operating in extreme conditions, the mechanical design is just as important as the materials. So each coil must be custom engineered with its exact application in mind. Design features to be considered include:

• Wall thickness: Heavier tube walls and reinforced headers can withstand higher pressures and thermal stress, and increase the life of a coil.
• Fin spacing and geometry: Adjusted to minimize frost accumulation in cold conditions or to promote heat transfer at high air velocities.
• Circuiting and flow design: Optimized to maintain uniform refrigerant or fluid distribution, such as choosing a distributing steam coil design to avoid freezing in cold climates, or to optimize the performance of chilled and hot water coils.
• Proper drainage: Especially critical in freezing or humid environments to prevent water retention and ice buildup.

Protective Coatings

Even when extra durable materials are selected for a coil, additional coatings are sometimes needed to extend coil life in extreme environments. Particularly when coils will be subjected to corrosive materials, protective coatings can help maintain coil performance over years of chemical, salt or other corrosive exposure.

At Marlo, we use two types of coatings: Heresite P-413, a baked-on phenolic epoxy coating, and ElecroFin E-Coat, an electro-deposited epoxy. Both offer excellent corrosion resistance and are ideal for salt-laden air applications, as well as environments where the coil is exposed to corrosive chemical fumes and condensate. The two types employ different methods of achieving uniform coverage of the coating – including the fins, tube exteriors and casings – which is essential to provide maximum protection. Our engineers can help determine the best coating for your particular application.

Airtight Coil Housings

In many extreme applications, especially those involving process air isolation – such as pharmaceutical, clean rooms, semiconductor manufacturing, chemical processing and others – it’s not enough for the coil to be built to withstand the environment. In these situations, the coil housing itself must be airtight.

The most common use of airtight coil housings is to prevent cross-contamination of airstreams. In clean rooms, labs or pharma plants, the airtight housings keep unfiltered air from entering the manufacturing area. In other industrial processes, toxic or specialized gases must be isolated to ensure safety or product quality. Another use of airtight coil housings is in wash-down applications, when cleaning or sterilization – often using caustic chemicals and/or high-pressure cleaning – can damage interior components of the coil if the housing is not airtight.

Real-World Applications

At Marlo, we regularly design and manufacture heating and cooling coils to provide long-lasting reliable performance under extreme conditions. Just a few examples include:

• Chemical Manufacturing: Coils built with stainless-steel (tubes, fins, casings) to resist highly caustic atmospheres and elevated temperatures. Airtight coil housings are often needed when ambient air must be isolated from the plant air-stream.
• Maritime Environments: Shipboard coils, including those for the U.S. Navy, that must resist salt corrosion, high vibration, and tilting/sea-motion. These often require durable materials like copper-nickel, as well as salt-protective coatings.
• Semiconductor and Pharmaceutical Manufacturing: Applications requiring ultra-tight tolerances for temperature and humidity, plus airtight housings to prevent cross-contamination of airstreams and to withstand washdown conditions.
• Food Processing: Food manufacturing plants, breweries and dairies are ultra-clean environments that require metals like copper and stainless steel that are not only antimicrobial, but also can withstand caustic cleaners and chemicals.

These are just a few of the many industries we serve. See more examples industries we serve.

The Marlo Difference

For more than 100 years, Marlo has specialized in custom-engineered coils for a wide range of applications, including those with very challenging environments. So whether you need a standard heating or cooling coil – or one designed and built for a unique and demanding application, rest assured that Marlo can get the job done.