September 2018 - Belzona Blog

In terms of HVAC maintenance, corrosion is a major issue for building owners and managers. If corrosion is left untreated, the overall efficiency and longevity of the equipment can be affected, leading to an increase in operating costs and expensive replacement in the event of equipment failure. Repair and, most importantly, prevention of corrosion problems is critical to avoid premature replacement.In this article we will:Look at the HVAC maintenance problems within industrial and commercial unitsReview alternative repair optionsLook at methods of how these solutions can be appliedSee some case studiesIf you have any further questions about HVAC maintenance once you reach the end of the article, you are welcome to submit them as comments and an engineer will respond shortly.WEBINAR RECORDINGCORROSION AND EROSION WITHIN AN HVAC UNITWhat are some of the most common HVAC maintenance problems? First we will look at condenser water systems, then chilled water systems and, finally, review problem areas within air handling units and ductwork. HVAC almost always is a closed loop process, so the whole system needs to be functioning in order for any output to be achieved.To form a corrosion cell, we need 3 things. An anode, a cathode and an electrolyte. Unfortunately, all of this is usually present within an HVAC systems. Tube sheet heat exchangers are a classic example of this. Large surface areas of metal in contact with a large volume of liquid makes them susceptible to corrosion. Not only standard corrosion, but bi-metallic (or galvanic) too!If not properly treated, metals gradually self-destruct when exposed to air and water, especially where dissimilar metals are in close contact. The wet and warm conditions inside HVAC systems, combined with cleaning agents and process chemicals, accelerate corrosion.Usually in a tube sheet heat exchanger, the tubes are made from copper, whilst the face is mild steel. As copper is a more noble material, the steel will begin to corrode preferentially, causing rapid loss of material.New tube sheetHVAC MAINTENANCE SOLUTIONSIn a lot of cases, replacement is the first choice. This brings you back to your starting point, with a brand new piece of equipment.However, this will not last. You need to ask – “have we found and fixed the root cause of the issue?”. If the answer is no, then you can expect history to repeat itself. Patch repairs and weld overlay are, to put it simply, adding more metal to the surface. With these, you encounter a few issues.1) You’re not fixing the issue permanently2) Over time, you will need to complete multiple repairs to the same equipmentYou could perhaps choose to use a type of paint (limited service life) or sacrificial anodes (require replacement), but these would need routine HVAC maintenance in order to be effective.Cooling TowersCompleted ApplicationLive Leak SealedCOOLING WATER PIPE LEAKS SEALEDMore info on this applicationFAN BLADE EROSION REPAIRIn order to allow some of the warm air to vent out of the commercial systems, a fan is used. On first glance, a fan rotating and forcing air out of a system doesn’t seem like it would cause that much damage. However, much like their bigger turbine counterparts, the small amounts of moisture in the air can cause severe erosion damage to the leading edge. These blades are designed to a very tight specification, and so any deviation in this design causes issues. The repair method is relatively straightforward:Surface preparation and rebuilding using a paste gradeCeramic coatings for leading edge protectionGeneral polymeric coatings for protection from corrosion and chemical attackCASE STUDY: REPAIR OF SEVERELY ERODED FAN BLADESBelow, you can see a clear picture of exactly what happens when this issue goes unnoticed for a long time. Severe erosion on the FRP fan blade is evident. The worn edge of the blade has been rebuilt with a ceramic epoxy, which adheres very well to FRP. Combined with the Reinforcement Tape, it will prevent blade disintegration and strengthen its structure.This is a great alternative to replacement and jobs like this can even be carried out insitu.Edge rebuiltBlade protectedMore info on this applicationCASE STUDY: WEAR ON FAN BLADES LEADING EDGESThis system was beginning to see a loss of efficiency due to erosion of the blades. Engineers were finding that they needed to replace blades every 5-7 years, and with 12 towers this was becoming too costly.With the use of 4 different products, including Belzona 1111 (Super Metal) and ceramic coatings, the blades were rebuilt to match their original specification. The customer noted after that they had saved as much as 80% on their replacement costs – due to the minimal amount of material/equipment required. The overall cost of buying new blades was very high in comparison.This system was beginning to see a loss of efficiency due to erosion of the blades. Engineers were finding that they needed to replace blades every 5-7 years, and with 12 towers this was becoming too costly.With the use of 4 different products, including Belzona 1111 (Super Metal) and ceramic coatings, the blades were rebuilt to match their original specification. The customer noted after that they had saved as much as 80% on their replacement costs – due to the minimal amount of material/equipment required. The overall cost of buying new blades was very high in comparison.Repaired fan bladeCorroded tube sheetClose up of damageGeneral viewShell faired backDeteriorated jointJoints sealedDegraded insulationRecoated and protected

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