heat exchanger tube failure - materials processing institute · section of heat exchanger with...

Address: Materials Processing Institute Eston Road Middlesbrough TS6 6US United Kingdom Contact Details: t: +44 (0)1642 382000 enquiries@mpiuk.com www.mpiuk.com Copyright © Materials Processing Institute UK CS/002/ME/2015 THE PROJECT The Institute was requested to carry out an investigation into a recurring problem with water leaks on a heat exchanger associated with the steel production process route. The request was to identify the root cause of the problem and to suggest remedial action. The heat exchanger was designed for an operational life of 15 months, but due to increasing numbers of leaks it was taken out of service after 12 months. Reduced lifespan of the heat exchangers was noted on successive occasions. Water leaks led to downtime for weld repairs and excessive water leakage at this location was a safety concern. On-site inspections were carried out followed by sampling. From optical and electron microscopy analysis it was found that the whole of the heat exchanger tube work was suﬀering from severe cracking. THE OUTCOME It was determined that the leaks were occurring by corrosion fatigue cracking. The mechanism was symptomatic of the plant operating method and necessitated a redesign to give future viability to the operations. This was done and in the three years of operation water leaks have not been a problem. Section of heat exchanger with multiple weld repairs on some tubes Sample of tube with surface cracks plus cross sectional microstructure Heat Exchanger Tube Failure Outer Face (Hot Face) Outer Face (Hot Face) Inner Face (Water Side) Tube Wall Outer Face (Hot Face) CASE STUDY

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Page 1: Heat Exchanger Tube Failure - Materials Processing Institute · Section of heat exchanger with multiple weld repairs on some tubes Sample of tube with surface cracks plus cross sectional

Address: Materials Processing InstituteEston RoadMiddlesbroughTS6 6USUnited Kingdom

Contact Details: t: +44 (0)1642 [email protected]

THE PROJECTThe Institute was requested to carry out aninvestigation into a recurring problem withwater leaks on a heat exchanger associatedwith the steel production process route. Therequest was to identify the root cause of theproblem and to suggest remedial action.

The heat exchanger was designed for anoperational life of 15 months, but due toincreasing numbers of leaks it was taken outof service after 12 months. Reduced lifespanof the heat exchangers was noted onsuccessive occasions. Water leaks led todowntime for weld repairs and excessivewater leakage at this location was a safetyconcern.

On-site inspections were carried out followedby sampling. From optical and electronmicroscopy analysis it was found that thewhole of the heat exchanger tube work wassuffering from severe cracking.

THE OUTCOMEIt was determined that the leaks wereoccurring by corrosion fatigue cracking. The mechanism was symptomatic of theplant operating method and necessitateda redesign to give future viability to theoperations. This was done and in the threeyears of operation water leaks have notbeen a problem.

Section of heat exchanger with multiple weld repairs on some tubes

Sample of tube with surface cracks plus cross sectional microstructure

Heat Exchanger Tube Failure

Outer Face(Hot Face)

Outer Face (Hot Face)

Inner Face(Water Side)

Tube Wall

Out

er F

ace

(Hot

Fac