Heat exchanger maintenance guide
Read this guide on heat exchanger maintenance. It includes the procedures and activities involved in maintaining or repairing a heat exchanger. It also mentions when and why it’s needed.
A good heat exchanger maintenance procedure is vital
In an ideal world, all of our essential machinery would continue operating indefinitely with no need for repair or replacement. However, in reality, all machinery has a finite lifespan. This is where heat exchanger maintenance activities are vital.
Some types of heat exchangers last longer than others. It depends on the design, the application, and the materials involved. However, every heat exchanger will wear out eventually, and maintenance, repair or replacement will be required.
This article explains the degradation of a heat exchanger and tells you when and how you should maintain them to avoid the need for serious repair. We’ll also look at whether a heat exchanger can be repaired, outlining a repair process for heat exchangers that have already failed.
Causes of wear
We’ll start with the causes of heat exchanger wear. The main culprits are fouling, erosion and corrosion.
What is fouling, erosion and corrosion in a heat exchanger?
Fouling is a build-up of unwanted materials on a heat exchanging surface. The sediment or incrustation insulates critical surfaces, reducing the rate at which heat can be transferred through them. Therefore, it reduces the efficiency of the process.
Some environments can cause heat exchangers to get dirty faster. For example, applications that involve exhaust gases, such as in marine charger coolers. An environment with lots of dust also leads to a build-up of dirt.
Erosion is where the flow of the fluid passing wears away the surface of the tube through it. . This effect can be exacerbated by the presence of particles such as sand or silt in the fluid, which can remove material much faster. This leads to tube wall thinning and ultimately leaks.
Corrosion can also be an issue. Coolants and other mediums can corrode the metals in a heat exchanger, damaging them over time and leading to residues that clog the heat pipes. Coolants can also wear down the surface of the heat exchanger tubes and pipes, thinning the material over time.
How to tell if a heat exchanger needs repairing
There are two common, early signs of an issue:
- reduced performance
Both fouling and corrosion can lead to reduced performance. Whether due to dirt or by-products of corrosion, the internal or external surfaces can become clogged up, leading to overheating. It can also insulate the tubes, reducing the effectiveness of heat conduction.
Leaks occur for a similar reason. The tubes are subject to erosion or corrosion from the coolant moving through the pipe, making them one of the parts more at risk of failing. The first sign of this is a leak.
If your heat exchanger shows reduced performance or has developed a leak, it is best to have it inspected by an expert to avoid more significant issues down the line.
Preventing heat exchanger damage
Companies can mitigate wear-and-tear and reduce the need for costly repairs, by undertaking heat exchanger maintenance activities according to a schedule.
Maintenance is essential in specific industries. For example, if the heat exchanger stops functioning in power plants and oil rigs, the entire process comes to a halt. This can be a disastrous outcome for the company’s productivity.
Many coolers can go a number of years between cleaning and inspection. For instance, hydrogen coolers in power stations may only need to be checked once every four years. However, it does depend on the environment. Where dust is a factor, a cooler might need cleaning as often as every 6 months.
When Sterling TT undertakes scheduled maintenance, there are a number of standard maintenance activities we carry out. For example, we check that the filtration system is working, not blocked, and there’s no risk of foreign objects getting inside.
One way we check for issues involves taking the internal measurements of tubes using eddy current test probes. These tell you how thick the tube is and whether there is any wear on the inside. Using this data over a period of time, we can show at what rate the tube wall is thinning.
Ultimately, failing to keep up with proper maintenance of your heat exchanger might lead to more consequential failures such as a crack.
Can a cracked industrial heat exchanger be repaired?
Yes, but it’s not always the most cost-effective solution. Weld repair can be effective, but it depends on the heat exchanger and the damaged part. It is easier to fix a crack on a larger shell and tube heat exchanger than a smaller one. For example, with a smaller, cheaper aluminium heat exchanger, it is often more cost-effective to replace it than to repair.
How long does maintenance or repair on a heat exchanger take?
Standard heat exchanger maintenance or repair activities usually take a week or two. However, larger installations or more complex fixes take longer.
For example, a large heat exchanger in a power station might take six weeks because there are more steps to take before it can be completed (for instance, inspectors must make their report before contractors can be brought in).
The maintenance and repair process
When Sterling Thermal Technology is contacted to take on a maintenance/repair job, we have a set of heat exchanger maintenance procedures that we carry out as standard:
- We undertake an external visual check for any damage.
- We carry out pressure tests to check for leaks. If there are leaks, we determine how many and their placement etc
- We then take the cooler apart (some can be taken apart to a greater degree than others) to look inside and carry out internal visual checks. We are looking for any wear and tear, signs of erosion or corrosion, and other issues.
- Then we produce a report on our findings.
Our report incorporates photos and a description of the issues. If known, we will also include some history on the unit. We then report on the condition of the equipment. Finally, our report includes our recommendations (including recommendations for further, advanced testing if necessary).
Can all heat exchangers be repaired?
Unfortunately, not all heat exchangers can be repaired. There are a few instances where replacement might be more suitable than repair:
- Some are not designed to have parts replaced
- The corrosion and rust are too extensive.
- Even when a repair is possible, it might not be cost-effective. Sometimes it’s cheaper to replace the heat exchanger with a new one, especially if it is an older model.
- As technology improves, a similar heat exchanger could be made quicker (and therefore at a lower price) than the unit when it was originally manufactured offsetting some of the replacement costs.
Upgrading & improving efficiency
Maintenance or repair is also an opportunity to change the design or make another type of upgrade. As well as making the heat exchanger more efficient, we might be able to upgrade it so that it lasts longer next time.
This is especially worth considering if the process the heat exchanger was installed for has changed over the years. In these cases, it can be very beneficial to alter the heat exchanger to better suit the new process.