International Pipeline Conference & Expo

Dates:  September 26 -30, 2022 (conference)   |  September 27 -29, 2022 (expo)       

Booth #:  616  

Location: Telus Convention Centre | Calgary, Alberta


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Presentations and Papers

Fatigue Analysis of Pipe Hammering During Construction

by Roger Chen, Kenny Farrow, Joseph Anthony

Pneumatic hammering may be used to assist with pipe installation and/or removal of stuck pipe during horizontal directional drilling and straight bore crossing operations. Pipe stresses induced during hammering are often poorly understood or undocumented.

To gain a better understanding of the induced stresses, elastic wave analyses were performed to simulate stress waves which travel from the struck end of the pipe and back via reflection from the other end. Due to the nature of the reflections, even compressive hammering (e.g., for pullback assist) results in tensile stress waves (and potential fatigue damage), which sometimes goes unrecognized.

To predict the damage accumulation at planar circumferential flaws (e.g., girth weld defects) from repeated hammering, flaw growth analyses were performed via Paris Law fracture mechanics formulations. An initial flaw based on NDE detection limits was grown to the maximum permitted by API 1104 weld quality requirements. This assumes that the hammered pipe will be used within the pipeline construction assembly and must therefore meet initial inspection requirements for screening of in-situ welds.

For this study, different combinations of pipe diameter, wall thickness, pneumatic hammer model, input energy and soil type were investigated to discover trends and determine limits on hammering force and hammering hours. Allowable hours for a particular set of parameters are provided, along with recommendations concerning monitoring of hammering operations, constructability considerations, and future work to refine the methodology presented herein.

Analytical and Experimental Assessment of Short Bolted Flange Nuts Subjected to Tensile Loads for Development of Mitigation Strategy

by Jonathan Brewer and Colton Sheets

Analytical and experimental methods were used to develop a strategy for assessing short bolted threaded connections (studs and nuts) under tensile loading. Short bolting occurs when a threaded connection has some number of threads that remain unengaged. This unthreaded length is called shortfall. Analytical efforts primarily focused on predicting the failure loads and failure modes associated with various levels of shortfall. An analytical methodology for assessing short bolting is important as it allows an end user to develop a threat prioritization or integrity management program based on a desired level of risk tolerance. A risk averse, conservative approach could require that all nuts have sufficient engagement length to produce a tensile overload failure of the stud. A risk tolerant approach might utilize predicted failure load as an integrity criterion instead of predicted failure mode.

Development of the analytical models, including a review of existing literature, is described within this paper. The primary output of the analytical models includes the expected failure load as a function of the threaded connection engagement length and the critical “transition engagement length” at which the failure mode changes from thread shear to stud tension. Above this engagement length, the threaded connection is expected to fail due to tensile overload of the stud and is “full strength”. Below this engagement length, the threaded connection is expected to fail by thread shearing, at a load lower than the tensile strength of the stud.


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