June 2022 Blog Post
Author: Erik Hansen
Subject: Stainless Steel Condenser Tubes or Galvanized? That is the question!
NOTE: The posting will dig a little into product selection revolving around evaporative style condenser products and not necessarily air-cooled or adiabatic condensers.
Industrial refrigeration systems in the Midwest often use evaporative type condensers for their refrigeration system. These condensers, as a standard, are equipped with hot-dipped galvanized tube bundles, galvanized sump basins and galvanized cabinets/housings. With any evaporative system, water treatment needs to be a consideration for not only just micro-organism/living things growth, but also making sure the wetted parts stay in good working order. Therein lies the issue…
Galvanized steel needs time to become “passivated” so it can withstand or stave off corrosion. In years past, these galvanized components could be passivated naturally by just sitting outdoors, but with today’s world of needing to ship something right after it gets off the line and it needs to be working within the next couple of days after that, water treatment companies have been tasked to make sure evaporative condenser coils are chemically passivated. This is a very important step and if not done properly will significantly lead to premature failure of the tube bundles or other metal areas that are wetted. Galvanized steel is still the “norm” and the least costly for first purchase. If chemical passivation is not done properly though, it can be the most costly. While Carlson & Stewart Refrigeration does not self-perform water treatment services, we can get your water treatment specialist in touch with manufacturer’s water treatment departments to make sure your assets are being taken care of properly.
Enter Stainless Steel. Does stainless steel need to be passivated? The answer is “no”. Keep in mind that if the sump basin or cabinet are still galvanized, they will still benefit from chemical passivation. Often, when a client is interested in stainless steel condenser coil, Carlson & Stewart Refrigeration at least recommends a stainless steel sump basin as well. Stainless Steel coils still need to be treated regularly (just like a galvanized coil), but the passivation is not required. In general, a stainless steel coil should give the operator a better chance of the equipment living a “full life” before needing replacement.
There is one large penalty to utilizing stainless steel though. That is the thermal performance is worse compared to that of steel. This means that for the same net heat rejection affect, more surface area is needed which means a larger condenser, which means additional upfront cost. Based on recent selections (late May 2022), a stainless steel evaporative condenser comes with an approximately 3% performance penalty, and costs an additional 24.6% compared to that of the standard all galvanized unit.
In summary, stainless steel has some obvious benefit when compared to standard galvanized selections. Its flexibility when it comes to passivation should give the end-user a better chance at a longer-term solution. If a galvanized unit is well taken care of by the water treatment company, the additional upfront cost for a stainless steel unit may unnecessary.
If you need assistance in this decision making process, let Carlson & Stewart Refrigeration be part of the process to get you to YOUR best solution.