Anti-Thixotropic Analysis of Pipeline Metal Losses in Welded Locations due to Particulate Wear

Abstract

This paper examines the causes of metal loss induced by cutting wear within the internal walls of pipelines which could lead to unpredicted and unexpected pipeline failure and the attendant oil spillage in Nigeria. To determine the rate of wear, the flow properties were determined. Flow was found to be turbulent containing sand particles with an average size of 3.8.μm. These particles in their agglomerated form possess a drag coefficient of 8.75x10^-5 when they interact with the internal walls of the pipe, moving with a mass flow rate of 47.06 kg/m.s. Eventually the calculated erosion wear rate was 4.94x10^-4mm/g. This wear rate suggests an immediate replacement of the pipe before a catastrophic occurrence. This investigation was verified by measuring the metal losses using the Ultrasonic Thickness Measurement Gauge. The Ultrasonic Thickness Measurement Gauge was used to measure pipe wall thicknesses at the wellhead 0.05m and 0.10m spool piece at 3, 6, 9, and 12 O’clock positions. The nominal thicknesses of the pipes are 5.5mm and 6.0mm, however, the variance between the measured thickness values and the nominal thickness value was very high. The pipe wear was found to be caused by the presence of large slurry of aggregates of sand stones in the pipelines. Particle size distribution analysis was done and the effective size of the sandstone was found to be 3.8μm. This investigation showed that the sand trap built insitu to sieve the sand and stones from the oil reservoir had failed.

Keywords: erosion wear rate, metal losses, sand particles, pipeline, UTM

Journal of the Nigerian Association of Mathematical Physics, Volume 20 (March, 2012), pp 423 – 428