Investigating Sold Particle Erosion of Pipeline Material

In the oil and gas industry, the integrity of pipelines is paramount, owing to the consequences which arise from the failure of these assets. Reduced production, loss of assets, increased maintenance cost, fatalities and loss of product through spillage, coupled with the far reaching environmental effects, are all by-products of the failure of pipelines. One of the major contributing factors impacting the integrity of these assets is that of the localised degradation of the pipeline material due to solid particle impingement. As a result, it is crucial to understand and quantify the manner in which a material responds to a myriad of erosive conditions. The occurrence of erosion on a material surface is influenced by a considerable number of factors. Research has found that the impact of each contributing parameter varies based on the conditions. As such the field of erosion studies has been heavily reliant on establishing empirical relationships.

The work presented in this thesis is backed by an established experimental approach to solid particle erosion, replicating practical engineering problems found in oil conveying pipelines with entrained solid particles. The first aspect of the work conducted focuses on the evaluation of erosion through experimentation, using a slurry erosion test pot. For this study, olivine, which is a naturally occurring mineral has been used as the erodent, with mild carbon steel representing the target material. A qualitative assessment was conducted on the friability of olivine under the operating conditions, giving an insight into how the recirculating nature of the test pot affects the initial particle parameters, principally the size and angularity. Both qualitative and quantitative analysis have been carried out on the impact of flow velocity, time and three distinct size ranges of multi-sized particle slurries on the material loss of the target material. The relationship of velocity has been found to be consistent with that found in literature, while the effect of increasing the diameter of the multi-sized particles produces a different response from that found in literature for equi-sized particles. Time has been found to have no noticeable effect on the erosion rate under the conditions evaluated in this study. Moreover, a novel erosion rate prediction model has been developed based on the Zhang/Tulsa model, which now encompasses the influence of the weighted mass particle size for multi-sized slurries.

The second aspect of this study assesses the nature in which the surface texture of the material changes as the erosive conditions change. Using a non-contact surface measurement method, the change in the material surface roughness is assessed as a function of exposure time, impact angle, velocity and weighted mass particle size. This work presents the first in-depth assessment of the change in developed interfacial area ratio as a result of slurry erosion. A qualitative and quantitative investigation was carried out on the results obtained, from which the impact of each parameter evaluated has been presented, showing that each parameter has an impact on the change in developed interfacial area ratio. Additionally, a comparison is presented between the developed interfacial area ratio and the arithmetical mean height. This highlighted the influence of the measurement parameter on the results being processed.