Evaporator Condenser Passivation

If you have ever been involved in buying or installing a new evaporatively cooled condenser, then you’ve probably heard about evaporative condenser passivation. You probably heard it is important and a process you should strive to complete. But if you are like many owners, operators, or heck even refrigeration engineers, that’s probably where your knowledge gets a little fuzzy. Condenser passivation is often overlooked as a nuisance that most people are content to saddle their water treatment vendor with and move on. In many cases it’s hard to blame equipment owners for that mentality, so rarely is there time for a true downtime passivation. Let’s take a deeper look into passivation and see what the ramifications of that decision are.

Passivation is, as the name suggests, making the material more passive, and therefore less reactive. When we discuss passivation of evaporative condensers, we typically mean passivating galvanized steel against the formation of destructive white rust. This is done by using water treatment with specific chemical compositions ensuring the formation of a zinc carbonate layer on the exterior of the metal. Completion of passivation process will reduce corrosion of the steel components and will increase equipment life dramatically versus poorly or non-passivated galvanized components.

So what’s the catch? A proper passivation, according to Evapco and other evaporative ammonia condenser manufacturers, is supposed to take place without heat, aka refrigeration load. Secondly, it takes on average 1-3 months. Rarely do customers have that long to have an installed condenser running with water that can stay idle. Many condenser replacements use existing support structures, are like for like replacements, or are emergency swaps that don’t have an extra 3 months to wait.

So what do we do about it? Carlson and Stewart Refrigeration (CSR) can’t give you a perfect answer, as every facility has different needs and capabilities. If a construction schedule can allow for it, consider completing the condenser and water systems early in new projects to allow passivation time. Evapco offers a Pass Protect process which boasts superior passivation as an option on new condensers. If downtime is not an option or water chemistry is questionable, consider a stainless-steel evaporative condenser which doesn’t require this passivation process. Some water treatment companies will feel confident they can achieve a good passivation process on a loaded condenser. The most important thing you can do is to make sure you have the conversation with your water treatment team and form an effective treatment plan with a high degree of monitoring during the first few months of condenser operation. Water chemistry is extremely important during this initial period and supply water composition is unique to each location, so have a plan ready before commissioning. Be certain to ask Evapco, BAC, SPX, or whoever your desired condenser manufacturer is for their passivation recommendations for their materials of construction.

As always, Carlson and Stewart Refrigeration’s team of engineers would be happy to discuss options with you on your next ammonia refrigeration project.

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