A heat exchanger only tells part of the story during a single inspection. To properly assess why performance is changing, how quickly fouling is developing or why certain damage keeps recurring, its history is just as important.
That is why it is advisable to keep not only drawings and nameplate data throughout the service life of a heat exchanger, but also operating data, inspection results, maintenance reports, photos, test results and records of changes to the installation.
You do not need to store every possible measurement for years. The key is to retain the information that allows you to compare the current situation with what was previously considered normal.
Why is a heat exchanger maintenance history important?
Suppose a cooler appears to be delivering less capacity. On its own, that observation tells you very little.
It becomes far more useful if you know that, under the same operating conditions, the outlet temperature has gradually increased, the pressure drop has risen and the heat exchanger has shown progressively heavier fouling during the last two maintenance intervals. That is when a trend starts to emerge.
A good maintenance history therefore does more than help you look back. The information can also be used to identify changes earlier and to plan future inspections and maintenance more effectively.
Inspection remains essential. Historical data can support a diagnosis, but on its own it does not prove the cause of a problem.
1. Keep the basic technical information
It starts with identifying the heat exchanger. Especially with equipment that remains in service for decades, drawings, manuals and other documents can gradually become difficult to trace.
As a minimum, try to keep the following information in one central location:
- Manufacturer
- Type and model
- Serial number
- Year of manufacture, if known
- Nameplate data
- Drawings and datasheets
- Design pressure and design temperature
- Original capacity
- Fluids used
- Materials used
- Dimensions and connections
- Part and article numbers
- Relevant certificates
It is also a good idea to take a clear photo of the nameplate and keep it with the equipment records. This makes details such as the manufacturer, type, model and serial number easy to retrieve and forward when maintenance, spare parts or an overhaul are required. The correct type or model number alone can help identify the exact version more quickly and determine which parts belong to it.
Depending on the type of heat exchanger, additional information may be important. For a plate heat exchanger, for example, the plate material, plate type and gasket type are useful to record. For a shell-and-tube heat exchanger, you will want to know, among other things, which materials were used for the tubes and tube sheet.
This information becomes particularly important when spare parts need to be ordered, materials need to be assessed or the heat exchanger needs to be overhauled.
What if the original drawing is missing?
A missing drawing does not automatically mean that maintenance or an overhaul is no longer possible.
With older installations, documentation is often incomplete. Depending on the type of heat exchanger, the nameplate, existing components, dimensions, materials and current construction can then be used as a starting point.
The better the original information is known, however, the easier it is to compare the current condition with the conditions for which the heat exchanger was originally designed.
2. Keep track of operating data and performance
A heat exchanger is designed to transfer heat under specific conditions. If its performance changes, operating data is important for understanding what has changed.
Relevant information may include:
- Inlet temperatures
- Outlet temperatures
- Flow or flow rate
- Pressure
- Pressure drop across the heat exchanger
- Load
- Fluids used
- Operating hours
- Relevant process conditions
A single measurement is usually less useful than the way a value develops over a longer period.
A higher pressure drop, for example, can be consistent with fouling or a partial blockage, but it can also be related to a change in flow rate or other operating conditions. Likewise, a higher outlet temperature does not automatically mean that the heat exchanger is fouled.
Where possible, compare the same parameters under comparable operating conditions. The trend is often more valuable than a single reading.
3. Record every cleaning and maintenance intervention
A maintenance report should say more than simply that the heat exchanger “was cleaned”.
As a minimum, record:
- Date of maintenance
- Reason for maintenance
- Work carried out
- Cleaning method used
- Fouling found
- Parts replaced
- Repairs carried out
- Gaskets replaced
- Observations during disassembly or reassembly
- Checks and tests performed
This information is what makes meaningful comparison possible.
If three consecutive maintenance interventions show that the same side of a heat exchanger is fouling more quickly each time, for example, that is a different situation from finding only light fouling after several years of operation.
In the first case, it may be worth looking beyond the heat exchanger itself and considering factors such as the fluid, water quality, flow rate, operating conditions or a change elsewhere in the system.
4. Keep photos and inspection results
Photos are particularly useful for tracking the condition of a heat exchanger, provided it is clear what they show.
Where possible, keep photos of:
- Fouling before cleaning
- The surface after cleaning
- Corrosion
- Erosion
- Damaged plates
- Damaged tubes
- Gaskets and sealing surfaces
- Leaks
- Cracks or deformation
- Repaired areas
Also record when the photo was taken and which component or location it shows.
“Corrosion on the heat exchanger” is not very useful at the next maintenance interval.
“Localised attack around the tube inlet, identified during the 2026 overhaul” provides much more useful information and allows the same location to be checked specifically during the next inspection.
The same applies to measurements such as wall thickness readings. A single value is only a snapshot. Repeated measurements at the same location can show whether material loss is developing and how quickly it is progressing.
5. What information should a service report contain?
A good service report makes the condition before, during and after the work clear.
Depending on the type of work, the report may include:
- Condition on arrival or before disassembly
- Damage and fouling identified
- Photos
- Cleaning carried out
- Parts replaced or rejected
- Repairs carried out
- Relevant measurement data
- Pressure or leak tests
- Results of the final inspection
- Points to note for the next inspection
During an overhaul, it is particularly important not only to record that the heat exchanger was overhauled.
Which plates were replaced? Were any tubes rejected? Had the gaskets hardened? Was localised corrosion visible? Was the unit tested after reassembly?
That is the information that will be useful at the next overhaul.
6. Record failures as specifically as possible
A failure that is recorded only as a “leak” is difficult to analyse later.
Where possible, record:
- When the problem occurred
- What the complaint or symptom was
- The operating conditions at the time
- Where the problem was located
- Which symptoms were visible
- Which temporary measure was taken
- Which root cause was ultimately identified
- How the problem was permanently repaired
There is a major technical difference between an externally leaking gasket and internal leakage caused by a damaged plate. Yet both can easily end up being recorded simply as “heat exchanger leakage” in a basic maintenance log.
The more specific the record, the easier it is to recognise recurring problems later.
7. Do not forget changes to the installation
A heat exchanger can operate reliably for years and later develop problems even though the heat exchanger itself has not changed.
The conditions around it, however, may have changed.
Record important changes such as:
- A different fluid
- A change in fluid composition
- Higher or lower operating temperatures
- A change in pressure
- Higher load
- A different flow rate
- Modifications to pumps or piping
- A change in water quality
- Longer operating hours
- Changes to the process
This is important when interpreting historical data.
If the pressure drop is suddenly higher than it was three years ago, but the flow rate has also been increased significantly in the meantime, the two situations cannot be compared directly.
What information should you keep as a minimum for a heat exchanger?
Not every installation needs an extensive digital monitoring system. A practical equipment record can already provide a great deal of useful information.
Level | What should you keep? |
Minimum | Nameplate data, manufacturer/model, drawings if available, materials, fluids and maintenance/overhaul dates |
Valuable | Additionally: service reports, photos, fouling and damage found, replaced components and test results |
Ideal | Additionally: historical temperature, pressure, flow-rate and pressure-drop data, allowing trends to be tracked over several years |
The most important thing is to store the information consistently.
A simple record that is updated after every maintenance intervention is often more valuable than a large dataset where, years later, no one knows which measurements can actually be compared.
What if hardly any historical information is available?
Especially with older heat exchangers, a complete file is often the exception rather than the rule. An installation may have changed ownership, a vessel may have been acquired second-hand or drawings may have been lost over the course of decades.
In that case, you can establish a new baseline.
Start, for example, by:
- Identifying the manufacturer and model
- Recording the nameplate data
- Documenting the current construction and dimensions
- Identifying the available material information
- Inspecting plates, tubes, gaskets and other components
- Recording current operating data
- Taking photos of the initial condition
- Keeping inspection and test results
From that point onwards, you have a new reference point.
At the next maintenance interval, you will be able to make a meaningful comparison for the first time.
From maintenance data to a maintenance strategy
Collecting data is not a goal in itself. Its value comes from comparing different maintenance intervals with one another.
At the next assessment, ask questions such as:
- Is the interval between necessary cleanings becoming shorter?
- Is the pressure drop increasing more quickly than before?
- Does damage keep recurring in the same location?
- Are more components being rejected during each overhaul?
- Is the amount or type of fouling changing?
- Is heat-transfer performance after cleaning still comparable with previous years?
- Have the operating conditions changed in the meantime?
These comparisons help determine whether cleaning alone is sufficient or whether repair or overhaul is required.
Eventually, replacement may also need to be considered. However, the age of a heat exchanger is not a decisive criterion on its own. Technical condition, performance, reliability, spare-part availability, maintenance history and cost all need to be considered together.
An older heat exchanger in good technical condition may remain serviceable for many years. A newer heat exchanger operating under severe conditions, on the other hand, may require attention much sooner.
As a minimum, keep the manufacturer, type, serial number, materials, fluids, design data and available drawings. Add maintenance reports, photos, repairs carried out, replaced components and test results throughout the service life. Operating data such as temperature, flow rate and pressure drop also makes it possible to compare performance over time.
Temperatures, flow rate and pressure drop can provide useful indications, particularly when the data is compared over time under similar operating conditions. Photos and information on fouling found during previous cleaning work are also useful. No single measurement, however, proves that fouling is the cause.
There is no universal interval. The appropriate inspection frequency depends on factors including the type of heat exchanger, fluid, load, operating conditions, fouling rate, criticality of the installation and previous maintenance findings. Historical data helps determine a suitable interval for a specific installation.
A single temperature, pressure or pressure-drop reading says little without a reference point. By tracking the same data over time under comparable conditions, changes become visible. This can show, for example, that pressure drop is gradually increasing or that heat-transfer performance is declining more quickly between maintenance intervals.
For technical purposes, it is valuable to keep the maintenance history available throughout the full service life of the heat exchanger. Older reports can show how fouling, wear or performance develops over time. Any formal retention periods may also depend on the sector, installation, class requirements or company requirements.
That does not necessarily make maintenance or overhaul impossible. Depending on the type of heat exchanger, nameplate data, existing components, dimensions and material information can be used to establish a new set of basic technical information. A new maintenance record can then be built up from the next inspection onwards.
That depends on the technical condition, extent of the damage, availability of spare parts, required reliability and cost. Age alone is not enough to make this decision. An older heat exchanger may still be perfectly suitable for overhaul, while replacement may be more logical in cases of severe or recurring damage.
Need help with your heat exchanger?
At Blue Orange, we look beyond the current condition of a heat exchanger during maintenance, cleaning and overhaul. Where available, we also take previous service reports, operating data and maintenance history into account. This context helps to identify what has changed, where possible causes may lie and which next step makes the most technical sense.
Would you like to have a heat exchanger inspected, cleaned or overhauled, or discuss the maintenance data you already have? Get in touch with us! We are happy to help assess the condition of your equipment and determine the next step.