Heat Exchanger Tube Leak Testing: Pinpointing the Leaking Tube
Heat exchanger tube leak testing by helium mass spectrometry, tracer gas, acoustic and pressure decay methods, pinpointing individual tubes for repair.
A leaking exchanger tube contaminates one side of the process with the other, and the difficulty is rarely detecting that a leak exists: it is identifying which tube, out of hundreds, is responsible. itmad applies the method best suited to the exchanger, the fluids and the time available, and pinpoints individual tubes so that repair or plugging is targeted and not speculative. itmad operates across the Middle East, Asia and Europe.
Methods
Helium mass spectrometry is the most sensitive option, detecting leak rates far below what pressure testing can resolve, and it is used where the consequence of a small leak is severe or where other means have not found the leak. Tracer gas detection introduces hydrogen or nitrogen mixtures on one side and detects them on the other. It is fast across a full bundle and effective for locating the leaking tube and not only confirming that one exists.
Acoustic and ultrasonic detection picks up the signature of gas escaping through a defect, and can be applied with the exchanger under pressure and without flooding, so no drying is needed before return to service. Pressure and vacuum decay measure loss over a controlled hold period to confirm overall integrity, and are used to establish whether a leak is present before committing to tube-by-tube location.
Why these methods rather than a hydrotest
Their sensitivity is well beyond hydrostatic testing, so they detect leaks that only appear in service. Dry techniques are available, so water-sensitive processes need no drying before restart, and there is no chemical contamination of the process side. They also find leaks that partially reseal when the exchanger cools and the metal contracts, which is a common reason a leak disappears during offline testing. Preparation is minimal, often no more than opening inspection hatches, and turnaround is faster, so the exchanger returns to line sooner.
Method selection
The choice depends on the fluids, the sensitivity that the process demands, whether the unit can be flooded, and how quickly it must return to service. Where the tube population needs condition assessment and not leak detection alone, eddy current testing examines wall loss, pitting and cracking before failure occurs, whereas leak testing finds tubes that have already failed. itmad advises which of the two answers the client's question.
Applications
Shell and tube exchangers in process and refinery service; surface condensers and steam plant; air-to-air and air-to-water heating and cooling systems; coolers, chillers and HVAC plant; post-repair verification after tube plugging or replacement; and investigation of process contamination of unknown origin. Testing is carried out on site, typically during shutdowns and turnarounds.
What the client receives
A report that identifies the exchanger, the method applied and the test parameters, with each leaking tube identified by row and column position on the tubesheet. The leak rate is given where the method provides a quantitative result, a tubesheet map marks the affected tubes for the repair team, and the result is stated as pass or fail against the client's acceptance criteria.
Frequently asked questions
How is a leaking tube found among hundreds?
By matching the method to the exchanger and fluids: helium mass spectrometry for the most sensitive detection, tracer gas for fast location across a full bundle, or acoustic detection under pressure. Each leaking tube is identified by row and column position on the tubesheet.
Why not just use a hydrotest?
A hydrotest is far less sensitive and can miss leaks that only appear in service. It also leaves the exchanger wet, whereas dry techniques need no drying before restart and do not contaminate the process side.
Why does a leak sometimes disappear during offline testing?
Some leaks partially reseal when the exchanger cools and the metal contracts. More sensitive methods such as helium and tracer gas still find them.
What is the difference between leak testing and eddy current testing of tubes?
Leak testing finds tubes that have already failed, while eddy current testing examines wall loss, pitting and cracking before failure occurs. itmad advises which answers the question being asked.
What equipment can be tested?
Shell and tube exchangers, surface condensers, air-to-air and air-to-water systems, coolers, chillers and HVAC plant. Testing also verifies repairs after tube plugging or replacement and investigates process contamination of unknown origin.
What does the report contain?
The exchanger, method and test parameters, the leaking tubes by row and column position, the leak rate where quantitative, and a tubesheet map for the repair team. It states pass or fail against the acceptance criteria.