Service Life Of Pipes Research Articles

Possibilistic approach for consideration of uncertainties to estimate structural capacity of ageing cast iron water mains

Drinking water distribution networks form essential components of all urban centres. Water mains buried in the soil-backfill are exposed to different deleterious reactions, with the result being that the design factor of safety may significantly degrade, leading to structural failure. In particular, metallic distribution and trunk mains are subject to corrosion. Proactive pipeline management, which entails timely maintenance, repair, and renovation, can increase the service life of pipes. Several nondestructive evaluation techniques have recently become available to measure the remaining wall thickness of metallic pipes. In this paper, a previously developed analytical model based on Winkler-type pipe–soil interaction (WPSI) is cast in a "possibilistic" framework to translate the remaining pipe wall thickness to current structural factor of safety. The WPSI model takes into consideration external (traffic, frost, etc.) and internal (operating and surge pressures) loads, temperature changes, and loss of bedding support and the reduction of pipe structural capacity in the presence of corrosion pits. Uncertainties associated with the input data–parameters are handled using fuzzy arithmetic operations and interpreted through possibility theory. A Monte Carlo type random sampling method is carried out for performing sensitivity analyses to identify the critical data-parameters that merit further investigation.Key words: water mains, pipe–soil interaction, uncertainty analysis, fuzzy arithmetic, possibility theory.

Fatigue failure analysis of copper pressure conduit

The analysis of initiation and propagation of a fatigue crack in a copper pressure conduit is presented. The pipe, made of high-purity copper in soft temper, was a part of the pneumatic-hydraulic drive system of a circuit breaker used in a power plant control system. Failure analysis was performed on the grounds of metallographic examination using light microscopy, SEM and evaluation of service loads that resulted in damage during the pipe service life. It was found that the crack initiated at the flange root of one pipe end, along a deep groove embossed by the sharp edge of the flanging device as a result of bending stresses, caused by repeated straightening of the pipe in each pressure-rise cycle. In this paper, beside the detailed fracture and material analysis to explain the reason for the failure, discussion of the ways to avoid such failures is also presented.

A method for the prediction of the service life of high-strength drill pipes based on the criteria of corrosion fatigue

We present the results of the investigation of the growth of corrosion fatigue cracks in TBVK 140×11L drill pipes, determine quantitative characteristics of fatigue cracks in the pipes under stresses of different types as functions of the elapsed part of the entire service life, perform their statistical analysis, and propose a method for the prediction of the residual service life of these pipes.

Control of Corrosion by Inhibitors in Drilling Muds Containing High Concentration of H2S

Abstract Corrosion and its control of mild steel in drilling muds containing 3.2 g/L H2S have been studied with the wheel test method to increase drill pipe service life. The high corrosion rate is...

Service Life of Pipe Exposed to Domestic Waters

Service Life of Pipe Exposed to Domestic Waters