When a shell and tube heat exchanger reaches the end of its serviceable life, sourcing a direct replacement is not always straightforward. The original manufacturer may no longer support the equipment, drawings may be incomplete, and the identification plate may be damaged or missing.
That does not necessarily mean the entire system needs to be redesigned. With the right information, an existing unit can be assessed and a replacement developed around the required duty, physical arrangement and site connections.
Why shell and tube heat exchangers become difficult to replace
Shell and tube heat exchangers are often kept in service for many years. During that time, manufacturers can change, product ranges can be discontinued and original records can be lost. Previous repairs or system modifications may also mean that the installed unit no longer matches its original specification exactly.
Common challenges include:
- An obsolete or unsupported original unit
- A missing or unreadable nameplate
- Incomplete drawings or operating records
- Limited space around the installation
- Existing pipework that must be retained
- A change in process conditions since the unit was installed
Each of these issues needs to be understood before a suitable replacement can be proposed.
Start with the information that is available
A complete original drawing is helpful, but it is not the only place to begin. Useful information can often be gathered from the existing heat exchanger and the surrounding system.
This may include:
- Clear photographs of the complete unit and its nameplate
- Overall dimensions and available installation space
- Connection sizes, types, positions and orientations
- Shell, tube and header construction details
- Process fluids on both sides of the exchanger
- Inlet and outlet temperatures
- Flow rates and allowable pressure drop
- Design and operating pressures
- Material requirements and known corrosion concerns
Where records are limited, the existing unit may provide further information through inspection and measurement.
Matching more than the external dimensions
A replacement heat exchanger must do more than fit into the available space. Its thermal performance, pressure capability, materials and internal configuration all need to suit the application.
Simply reproducing the outside dimensions without reviewing the operating duty can create problems. A unit may physically fit but deliver insufficient heat transfer, excessive pressure loss or unsuitable fluid velocities. Equally, a replacement based only on historic duty information may be impractical if it does not align with the existing supports and connections.
The most effective replacement process considers both sides of the requirement: what the system needs thermally and what the installation needs mechanically.
Consider what has changed
Replacement also creates an opportunity to check whether the original specification is still appropriate. Flow rates, temperatures, operating hours or fluid composition may have changed over the life of the equipment. Recurring fouling, corrosion or leakage may indicate that the original arrangement or material selection should be reviewed.
Any known operating problems should therefore be included in the enquiry. Repeated tube failures, restricted cleaning access or difficulty obtaining replacement parts can all influence the most appropriate solution.
Plan for installation and future maintenance
The practical details around the exchanger are important. Available withdrawal space, lifting access, mounting points and pipework alignment can affect the replacement design and installation plan.
Future maintenance should also be considered. Access for inspection and cleaning, replaceable components and the availability of accurate documentation can make the equipment easier to support throughout its working life.
Support from AMI Exchangers
AMI Exchangers supports customers with replacement shell and tube heat exchangers for marine and industrial applications. Depending on the information available, our team can review drawings, photographs, nameplate details, measurements and operating data to help assess the requirement.
If an existing shell and tube heat exchanger is obsolete, leaking, repeatedly failing or becoming increasingly difficult to maintain, send us the details you have. We can help review the available information and discuss the next steps.
Speak to AMI Exchangers about your shell and tube heat exchanger requirements.
