Solving The Biggest Issues with Air-Cooled Heat Exchangers
Heat exchangers are important for many industrial applications, but like any equipment, they’re not without their challenges. Air-cooled heat exchangers, in particular, can present issues such as vibration, noise, fouling,, and leaking. Let’s explore these common problems and offer practical solutions to keep your air-cooled heat exchanger operating.
Structural or mechanical vibration in an air-cooler can be the result of damage, misalignment, or improper parts and assembly. Check the condition of all belts and bearings, and replace if suspect. Ensure all fasteners are tight and secured. Inspect for bent or damaged rotating components, especially fan blades, shafts and sheaves. Ensure all bracing, guards, and structural components are properly installed and secured. If vibration is being measured, ensure the measuring device is at a suitable location.
Air-cooled exchanger noise is generally the result of considerations and trade-offs made during the design stage. Noise is typically measured 1m (3 ft) from the fan blade tip. Air-cooler noise can be reduced by changing the type, brand, or model of fan used, reducing fan speeds, adding inlet bells, or even changing the type of drive belt. Unusual noises are likely to indicate bearing, vibration, or mechanical damage and should be investigated immediately.
Fouling – Internal (Tube ID)
Fouling is the accumulation of unwanted material on the heat exchanger surfaces, reducing efficiency. This is a common problem in air-cooled heat exchangers, but it can be resolved through regular maintenance and cleaning. Chemical cleaning can be used to remove fouling, but make sure they are compatible with your system’s process and metallurgy to avoid bigger issues. Altex has specialized grit-blasting equipment to clean heavily fouled surfaces.
Fouling – External (Tube OD and Fins)
Fouling on the air-side of the cooler occurs on the fins and tube-OD. The most common type of external fouling in Canada is poplar fluff, specifically, the oil in the seeds. Popular fluff is easily sucked-in by the fans and blown into the tube bundle. We recommend mesh ‘bug’ screens on air-cooled heat exchangers where poplar fluff could be a concern.
Another type of external fouling on air-cooled exchangers is deposits from water minerals. Some sites rely on external water sprayers to emit a mist over the bundle surface and create evaporative heat transfer, which enhances the heat rejection possible during the hottest summer days. The advantages of evaporative cooling do not last, as fouling and damage caused by the water deposits quickly outweigh the benefits. Embedded and L-Fin (overlap) fin-tubes are prone to becoming damaged, with L-Fin tubes especially susceptible to fouling between the fin and tube, greatly reducing their effectiveness. It is ideal to avoid evaporative cooling on air-coolers that were not designed for it. Design considerations would be extruded-fin tubes and using demineralized water, but ultimately it may be more economical and practical to design the air-cooler to a higher ambient temperature with more surface area.
Air-cooled heat exchangers typically leak at the tube-to-tubesheet joint, and at the header-plug. Tubesheet joint leaks can be repaired via re-rolling, welding, or plugging. Header-plug leaks are best solved with new header plugs and gaskets with freshly tapped threads. On occasion, the header plug gasket seating surface may need machining, or the threads may need to be re-tapped to the next available plug size.
Contact Altex Industries for Air-Cooled Heat Exchanger Maintenance Services
Maintaining an air-cooled heat exchanger can be challenging, but professional help is available. Altex Industries has specialized maintenance services to diagnose and address a variety of common issues, and even the uncommon ones! With expert assistance, you can make sure your heat exchanger remains efficient and operational for years to come. Contact us to learn more about our maintenance services for air-cooled heat exchangers.