The frequency with which the exchangers need to be cleaned depends entirely on the process it is used for. “If you are using chilled water, you probably only need to clean it once a year, or every other year. If we are talking about a boiler, you need to clean it every year to remove any deposits that have built up. An automotive radiator, however does not need to be cleaned very often as it is a closed system, and not much dirt will get into it,” Schweighardt continued. “Now, if you drive in Texas and the front of your radiator is full of bugs, that is when you will have to wash it so you can still get airflow.”
Although there are a number of chemicals that can be used to clean a heat exchanger, one of the most common things that we use is nitrogen. “We make thousands of tons of nitrogen every day. It is inert at the temperatures and pressures we are using. For us, it is relatively inexpensive, so that is what we use to blow through the pipes and Balanced Heat Exchanger (BHX),” he said. Nitrogen will blow through the pipes of the plant during a turnaround period and will sweep away any potential bits of moisture or other particles that made it into the heat exchanger.
This process is called derime. Schweighardt continued, “If moisture somehow got into the heat exchanger and, over the years, has built up and freezes during operation, the derime process will melt it all and sweep it out so that you are able to start fresh with your heat exchanger.”
Heat exchanger challenges
Although the most common challenge for heat exchangers is the cleaning and maintenance, choosing the heat exchanger best suited to the required application can be a tricky task. “There are many different designs within each major category of heat exchanger, and each design has a number of variations,” explained Schweighardt. “First, you need to look at flow rate and ambient conditions. You need to make sure it can reach the right temperatures for the specific fluid or gas that will be passing through it. The last thing you want is your heat exchanger turning into a freezer and being covered in ice,” he continued. “Ice is a really good insulator, and it will ultimately stop the heat transfer. Heat exchangers that run into that problem may not have been chosen properly for the project.”
Operating with new materials
Even though heat exchanger technology and the use of industrial devices to perform heat exchanging tasks have been around for several hundred years, there are always variations that can be made to improve the equipment. “A lot of the time, the modifications made to improve the heat exchange process focus on the materials that are being used. The abundance of developed materials that are able to withstand corrosive fluid can make the process much more effective and efficient. There are new metals, polymers and resins that can do the job properly,” Schweighardt expressed.
In Schweighardt’s opinion, as long as you take care of your heat exchanger, it will last until it is no longer economical to run. “The technology used in heat exchangers is a testament to how long something can last without needing major upgrades. If you take good care and make sure that nothing gets into the heat exchanger that is not supposed to be there, it will last you forever.”
*Portions of this article were previously featured in other KCI publications.