Session: OAC-07-01 OAC Ageing and Plant Life Management

Paper Number: 123067

123067 - Failure Analysis and Materials Degradation Properties Assessments in an Aged Hydroprocessing 347h Austenitic Stainless Piping 

During start-up of a hydrocracker unit with one train and both reactors trains online, a leak occurred on the suction piping of a pump connected to one of the two reactors.  Operations initiated shutdown activities and emergency response. After initial inspection, a crack was discovered in a weld on the suction piping to the pump.

Destructive testing revealed a crack in a weld in the pump suction piping.  This weld had recently undergone Non-Destructive Evaluation (NDE).  The results showed that the weld was in acceptable condition, showing no signs of a crack. The NDE phased array method using shear waves is an industry standard, and was believed to be very accurate.  The crack was undetectable with standard NDE due to a combination of the thickness of the pipe, weld root geometry, and the weld metal properties. These features caused sound waves to reflect in a way that prevented distinction of waves reflected from a defect.

The crack in the pump suction line of the reactor had initiated at a stress riser on the surface geometry of the weld. The weld also had impact testing results in the range of 13-31 ft-lbs. and elongation in the range of 15-16% at ambient conditions, suggesting some embrittlement have taken place. For new 347H stainless steel pipe and welds, approximately 80-100 ft-lbs. would be the expected impact test range and >30% elongation. The toughness and elongation had been reduced by the precipitation of brittle phases over the service life of the weld at about 800•F. The reduced toughness/elongation made the weld susceptible to cracking from high strain rate loading. 

Keywords: 347H, aging, failure, hydrocracker

Presenting Author: Jorge Penso Shell Projects and Technology

Presenting Author Biography: Senior Materials and Corrosion Engineer

Authors:

Jorge Penso Shell Projects and Technology
Jorge Hau Shell Global Solutions (US) Inc.
Eric Caldwell Shell Global Solutions (US) Inc.
Kevin Batts Shell Geismar Plant
Mitul Dalal Shell Global Solutions (US) Inc.