Maintaining your shell and tube heat exchanger

Most municipal water is safe for heat exchangers as long as it has a neutral pH balance and is free of contaminates.

Most municipal water is safe for heat exchangers as long as it has a neutral pH balance and is free of contaminates.

Your shell and tube heat exchanger could be one of the most important pieces of equipment in your business. In the food, beverage and dairy industries, a heat exchanger will protect customers from contaminated products. The pharmaceutical industry relies on heat exchangers to ensure medicines are top quality.

If a heat exchanger fails, product is contaminated and lost. This could decrease productivity, and in some cases, could result in a reputation-damaging recall. To prevent failure, it is critical that the heat exchanger is reviewed and serviced regularly. Chemical Engineering Magazine explained that, without proper maintenance, heat exchangers are prone to corrosion and fouling, which could lead to leaks. This will cause the product to mix with the cooling or heating fluid and ruin the batch. Corrosion and other deposits collecting on the floor of the exchanger will decrease the efficiency of the exchanger. This could prevent the liquid from reaching the desired temperature.

"If a heat exchanger fails, product is lost or contaminated."

Corrosion leads to bigger problems
A shell and tube heat exchanger is a machine that is expected to have to be repaired or replaced eventually. The nature of its use will wear on it and eventually, corrosion will occur. The goal is to keep the exchanger in operation as long as possible. According to MTS Systems Corporation, a heat exchanger could last up to 20 years with the right maintenance. This includes careful, regular inspections of the machine and all its parts.

MTS said it is important to make sure the heat exchanger is sanitary from the beginning of its life to the end. Before the first use, be sure to look it over thoroughly to make sure everything is secured properly and the tubes and shell have not been contaminated by dirt, dust or other foreign substances.

Corrosion is a process that occurs over time regardless of proper maintenance schedules. It is the result of chemical reactions in or around the heat exchanger. Different metals will react with different substances differently. Stainless steel is a good material to use in exchangers when the substances used within could be harmful to other metals, such as copper alloys. According to the Stainless Steel Information Center, the material can resist corrosion from most acidic, alkaline and chlorinated substances when it is a high-alloy grade. However, the British Stainless Steel Corporation explained that while the metal is highly resistant to corrosion, it will begin to wear over time.

"Stainless steel is resistant to corrosion from many substances."

Water monitoring
MTS explained the best way to prevent corrosion is to make sure only the best substances for the exchanger's material makeup enter the machine. Using the correct chemicals to treat and clean the tubes is essential. This information should be obtained before you begin using your heat exchanger to ensure you are prepared for its maintenance from the get-go.

Many heat exchangers use water as the heat transfer liquid. Tap water is generally of an acceptable quality to use in the machine. However, it is important to double check the water before putting it into the exchanger. The pH should be neutral and the water shouldn't be polluted or have any bacteria or other contaminates in it. If the water comes from a natural source, is should be treated before entering the tubes.

If the water isn't treated or inspected before entering the exchanger, debris could enter the machine and block the chambers. To prevent this from happening, screens or filters can be installed to keep particles out. If they do enter, they will wear against the tubes and cause corrosion.

Monitoring the health of your heat exchanger will help to identify early signs of failure before fouling or contamination become a larger issue. MTS explained that checking on the water quality is a good way to see if failure is a risk or is already happening. Cloudy water indicates the fluid is no longer pure. Taking notes on temperature and pressure changes will reveal problems beginning to form. Reduced efficiency could be a sign of scaling, a solid precipitate resulting from chemical reactions. Scale build-up will lead to fouling and corrosion over time. Checking other aspects of the exchanger, such as tube thickness, will also give indications of emerging problems.

Posted in Shell and Tube Heat Exchanger Solutions

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