aftermarket engineer removing header at Sterling TT's factory

Heat exchanger servicing: expert insights and tips

“A lot of the time, we will be asked to manufacture to a design life of, say, 10 years. That design life can be extended by regular cleaning, regular inspection, and maintenance,” said Alan.

Alan Taylor, Head of Aftermarket at Sterling Thermal Technology
Alan Taylor, Head of Aftermarket at Sterling Thermal Technology

Heat exchangers are indispensable components in various industries, playing a crucial role in heat transfer and fluid handling processes. Like any mechanical equipment, they must be looked after to perform their best.

To understand the complexity of maintaining these systems, we spoke to Sterling Thermal Technology engineer Alan, a seasoned professional who heads up our Aftermarket Department.

We discussed everything from when to get a heat exchanger serviced, how customers can prevent issues, and what cases cause particular challenges. This blog summarises what we learned.

When a service occurs

We started by asking Alan about the process customers follow to service their heat exchangers. Alan explained that Sterling TT proactively assists customers who have had a new heat exchanger installed.

“To new customers, after initial installation & commissioning, we will follow up a year to months down the line to check if they are having issues.”

However, most service work is unscheduled maintenance because the customer identified an issue. Alan explained that customers often monitor their heat exchangers’ temperatures, pressures, and flow rates. If they notice a decrease in flow rates or an increase in temperatures, they may consider scheduling a service.

Some issues are more urgent than others, especially where there is a leak or failure, but thankfully, they are less common.

When asked about recommended maintenance intervals, Alan highlighted the variability due to the uniqueness of each heat exchanger. He mentioned that customers often assess their units by themselves, checking for blockages and leaks. Depending on the industry and process, maintenance cycles can range from annual checks to four or five years – it really depends on the complexity and criticality of the system.

“It’s very dependent on who the client is, what industry it’s in, and what the process parameters are.”

What happens at a service

“A heat exchanger service is a bit like an MOT on a car.”

Now that we understand when a service should occur, we asked Alan what work is carried out.

Information gathering

Alan explained that they start the process with a discussion with a customer. This critical step gives them a chance to outline issues they might have experienced and whether they are aware of any problems that Sterling TT can help identify and rectify.

Not all heat exchangers that Alan’s team works on are designed by Sterling TT. In this case, it would be extremely helpful if the client could provide documentation, drawings, or data sheets about the heat exchanger.


Aftersales service on heat exchanger performed by Sterling Thermal Technology in its UK factory

From there, the process starts with a testing inspection of the heat exchanger. Depending on the unit type, an air or hydro test is needed to check for leaks.

In some instances, the tests might involve a third-party inspection that employs a probe that goes into each heat exchanger tube to measure the remaining thickness. This measurement can be compared to the original tube thickness at the time of manufacture, from the original drawings or data sheets. This tells the team how much thinning has occurred over time.

There may also be a requirement for any existing welds to be inspected by Non-Destructive Testing (NDT)

These tests form part of the final inspection report.


The cleaning process typically involves steam cleaning or a high-pressure water jet, depending on the unit’s processes and contamination levels. Chemical treatment might be necessary for more intensive cleaning,  which is outsourced due to specific material considerations.


It’s then time to produce an inspection report with photos, 3rd party reports (NDT, tube bore inspection, etc.) repair recommendations, and a detailed quotation to bring the exchanger back into service.

Below are some examples of recommendations.

  • Clean, re-test, certify & re-use the exchanger with new gaskets & bolting.
  • Re-tube of the exchanger.
  • Replace damaged/failed components while re-using existing parts that pass inspection.
  • Replacement of the complete exchanger

Repairs or replacement

Customers choose repairs or replacement depending on the heat exchanger’s damage, importance and required timelines.

Following any repairs, Sterling TT conducts another hydro test and provides certification for it. NDT, complete with reports, will be carried out where required. We’ll also provide a material certification for any replacement components.

Common issues and causes

damaged shell and tube that leaks
Damaged shell & tube

Alan emphasised that the most frequent issues are blockages, corroded tubes, and leaks. In these cases, customers will contact Sterling Thermal Technology to investigate.

He highlighted the impact of harsh environments, both external (e.g., seawater exposure) and internal (e.g., corrosive processes). These environments can accelerate wear and necessitate more frequent servicing. Offshore environments, in particular, present challenges due to limited access and withdrawal space.

Tips for reducing the need for maintenance

Alan mentioned several tips for customers to extend the lifespan of their heat exchangers and save money on servicing and repairs.

  • Consult the maintenance manual provided by the manufacturer.
  • Regularly clean and monitor your heat exchanger’s condition.
  • Communicate openly with experts to identify and address issues promptly.

Detecting issues and preventive measures

“We don’t usually see structural deformation like warping, twisting or welds disintegrating unless the unit’s very old. Most issues tend to be process-driven like pressure drops, increasing temperatures or pressures.” 

Alan stressed the importance of monitoring and trend analysis. Customers with experience can anticipate issues by observing trends, such as rising temperatures or decreasing flow rates.

Additionally, he mentioned that some customers follow a preventative maintenance approach. They replace units before their expected lifespan ends based on historical knowledge and their interaction with the units.

Clients often fall into the trap of reactive maintenance, waiting until a problem escalates before seeking assistance. This approach can lead to temporary fixes that could cause more damage in the long run.

Alan encouraged clients to be proactive, ensuring regular inspections, cleanings, and proper maintenance to extend the lifespan of their heat exchangers. This is similar to servicing a car regularly to prevent more significant issues down the road.

This practice is widespread in the oil and gas industry, where downtime can lead to significant financial losses. We asked Alan to tell us more about special cases like these.

Special circumstances

Offshore Inspections

Heat exchanger servicing is more comprehensive than onshore facilities alone. Sterling TT also conducts inspections offshore.

“You could see sea life in them. You’d be shocked to see how much shellfish and debris we find in seawater cooling systems. There should be in-line filters that customers should ensure they are maintained. But we do still see shell life.”

This type of service requires specific qualifications due to the environmental risks. The Sterling TT engineers who carry out this work hold offshore certifications for the UK North Sea. These certifications, known as BOSET (Basic Offshore Safety Induction and Emergency Training) and MIST (Minimum Industry Safety Training), are essential for engineers working on rigs or FPSOs (Floating Production Storage Offloading vessels) in offshore locations.

Safety precautions and hazardous materials

“These units will be made from corrosion-resistant materials such as titanium. Especially in chemicals and oil and gas plants. If you’re out in the North Sea, they have a harsh seawater environment externally.”

Given that some heat exchangers handle hazardous materials, safety precautions are paramount. Alan explained that their engineers require specific information about the substances that have passed through a unit. This helps them determine the appropriate personal protective equipment (PPE) and safety measures. In some instances, they need to wear breathing apparatus or chemical suits.

Before any Sterling TT intervention, customers are responsible for providing a certificate of cleanliness and material safety data sheets outlining the substances processed. Without this information, work on the unit is delayed until safety is assured.

Tube bundle extraction

Alan also mentioned that some units require extraction due to their size or weight, and specialised equipment is needed.


One key takeaway from the interview was the emphasis on communication and building relationships with your manufacturing partners:

 “One of the engineers will pick the phone up. The aim is to gather information to understand the problem better. Sometimes, it could be an easy fix. We need to know if the customer has done something wrong. Have they over-pressurised the unit? Have they changed the process? Have they reversed the flow? Have they left it full of water when it wasn’t running over winter? It’s about trying to build that relationship where they’ll be honest with us. The more honest they are, the easier we can diagnose and cure the problem .”

The significance of documentation

Maintaining accurate records and documentation emerged as a critical aspect of heat exchanger servicing.

Alan highlighted the importance of a comprehensive service history, which aids in understanding the heat exchanger’s past maintenance, repairs, and processes it has been subjected to.

A lack of proper documentation can complicate matters, especially when units change ownership or key personnel transition to new roles. “We advise customers to keep detailed records and maintain open communication to ensure that servicing can be carried out effectively and safely.”


“Better to get the experts involved rather than guessing what  the issue is … and end up causing bigger problems.”

Maintaining heat exchangers requires a blend of proactive measures and responsive actions, from monitoring trends and conducting regular inspections to collaborating with experts and adhering to manufacturer guidelines. Effective maintenance can extend the life of these critical equipment. By understanding the unique demands of your industry, environment, and process, you can make informed decisions that ensure the optimal performance of your heat exchangers over time.

Alan’s insights shed light on the often-overlooked intricacies of heat exchanger servicing and provide clients with a deeper understanding of the processes involved. As we wrap up this article, we thank Alan, Head of Aftermarket at Sterling TT, for sharing his knowledge and experience with us. His insights will undoubtedly contribute to a more informed and responsible approach to heat exchanger servicing across various industries.

If you’re interested in learning more about Sterling TT heat exchanger servicing, feel free to contact us. We’re here to help you make the most of your heat exchangers and ensure their optimal performance.

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