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Economizer Tube Failure Analysis


A petrochemical plant has experienced several failures in the past few years in the tubes of a recycle gas cracking furnace. A root cause failure analysis shows the failures are likely caused by vaporization in the coils causing thermal fatigue cracking. KHE was asked to determine possible solutions to prevent future failures.


Auger Shaft Metallurgical Analysis


An auger that has run normally for 17 years suddenly fails. Visual inspection showed that the shaft used to mix additives into polypropylene powder has fractured into two halves with a secondary partial fracture. KHE was asked to conduct metallurgical failure analysis to determine the cause of the failure.


Boiler Tube Damage Assessment

A company experienced multiple boiler tube failures at their facility. They have since experienced several tube leaks which they believe were caused by this incident. They hired KHE to perform a damage assessment of the tubes and determine the exact causes of the leaks.

Visual inspection revealed uneven thickness of the tube and metal loss due to pitting on the inner diameter. SEM analysis contributes the metal loss to oxidation. This analysis also suggested that the microstructure and hardness of the tube has not been damaged by the incident but further suggests that the metal loss could be due to the chemistry of the boiler water.

The client implemented measures to more closely monitor it’s boiler feed water chemistry to avoid similar problems in the future.

Furnace Tube Failure Analysis

A major chemical company experienced a failure due to a crack in a tube in the convection section of a furnace. This furnace is set to operate at 47 psi and 1200°F and has been operating for 13 years. The company contracted KHE to conduct a metallurgical failure analysis of the tube.

From initial visual inspection, wall thinning and corrosion is observed on the ID of the tube. Further material testing and SEM-EDS analysis revealed that the main cause of this failure was due to overheating and excessive localized oxidation. The materials testing determined this oxidation to be due to iron oxide scale which likely formed when the tube was heated over 1058°F forming Wüstite. The oxidation then led to wall thinning and eventual cracking.

The client took measures to prevent the unit from experiencing temperature excursions beyond its design limits. This will protect the equipment from similar damage and allow the unit to operate for longer periods without and outage.


KnightHawk Engineering is a specialty engineering company that can address all the physics of a problem in a short time. Knighthawk is the name industries depend on when the most critical failures happen. At Knighthawk, we know that a solution too late, is no solution at all.

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KnightHawk Engineering, Inc.
17625 El Camino Real, Suite 412
Houston, TX 77058

(281) 282-9200 telephone
(281) 282-9333 fax

General Information: hawkwork@knighthawk.com

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Customer Support: Chris Creech

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