“…The resistant frictional force resulting in the plastic deformation of the waxes is assumed to be the minimum required force to remove the wax deposits. 37–40 The frictional resistant forces with different wax concentrations and different scraping speeds during the wax oil deposit removal processes are presented in Figures 10, 11, and 12. Figure 10.Frictional resistant force with different scraping speeds.…”
Pigging is the most effective and common way to remove the wax deposits in pipelines. The discs, cups, or brushes of a pig are executing components for waxy oil deposit removal. In this study, a homemade experiment setup was built and employed to conduct the waxy oil deposit removal experiments with various wax concentration at different scraping speeds using polymeric bristled brushes. An explanation model was established to analyze the formation of waxy oil deposit chips. The entire removal processes were captured and the resistant friction forces were measured during the experiments. Our results show that there are three stages in the scraping process: (a) brush deforming; (b) steady scraping; (c) brush leaving; In the scraping stage, the frictional resistant force was found to decrease as the scraping speed increases. The frictional resistant force increases as the wax concentration increases. There is obvious stick-slip phenomenon in the steady scraping process. The wax concentration influences the shape of the chips. The shape of the high wax concentration deposit chips is saw-toothed.
“…The resistant frictional force resulting in the plastic deformation of the waxes is assumed to be the minimum required force to remove the wax deposits. 37–40 The frictional resistant forces with different wax concentrations and different scraping speeds during the wax oil deposit removal processes are presented in Figures 10, 11, and 12. Figure 10.Frictional resistant force with different scraping speeds.…”
Pigging is the most effective and common way to remove the wax deposits in pipelines. The discs, cups, or brushes of a pig are executing components for waxy oil deposit removal. In this study, a homemade experiment setup was built and employed to conduct the waxy oil deposit removal experiments with various wax concentration at different scraping speeds using polymeric bristled brushes. An explanation model was established to analyze the formation of waxy oil deposit chips. The entire removal processes were captured and the resistant friction forces were measured during the experiments. Our results show that there are three stages in the scraping process: (a) brush deforming; (b) steady scraping; (c) brush leaving; In the scraping stage, the frictional resistant force was found to decrease as the scraping speed increases. The frictional resistant force increases as the wax concentration increases. There is obvious stick-slip phenomenon in the steady scraping process. The wax concentration influences the shape of the chips. The shape of the high wax concentration deposit chips is saw-toothed.
“…Through a series of experimental results, Lan et al proposed a physical model to illustrate the friction mechanism at the surfaces of two wax-oil gels, which fits the wax plug transportation process. The extruded oil from wax crystal network plays an important role in the frictional process.…”
Section: Model Developmentmentioning
confidence: 99%
“…In that case, the interfacial shear strength of the unlubricated area is equal to the yield stress of the wax deposit. As for the interfacial shear strength of the lubricated area, it is much lower than the interfacial shear strength of the unlubricated area, because the extruded oil plays a lubricated role in the sliding friction …”
Section: Model Developmentmentioning
confidence: 99%
“…To ensure the measured yield stress reflects the actual yield stress in pigging experiments, the wax samples in the rheometer and pigging experiments experiences an equivalent thermal history, that is, heat to 80 °C and cool to the desired temperature, then hold for 1 h. A logarithmic stress ramp was utilized in this work. 39 The initial stress was 0.1 Pa, and the loading time between two decades of stress was 100 s. 40 proposed a physical model to illustrate the friction mechanism at the surfaces of two wax-oil gels, which fits the wax plug transportation process. The extruded oil from wax crystal network plays an important role in the frictional process.…”
Section: Pigging Facilitymentioning
confidence: 99%
“…As for the interfacial shear strength of the lubricated area, it is much lower than the interfacial shear strength of the unlubricated area, because the extruded oil plays a lubricated role in the sliding friction. 40 Average interfacial shear strength τ is defined to reflect the interfacial adhesion contact in the wax plug transportation. It is given by τ = cτ y , where c is the interfacial lubrication coefficient.…”
Wax plug growth in
pipeline pigging significantly impacts the crude
oil transportation, even resulting in a wax blockage accident of pipeline.
A pigging facility was constructed to conduct the pigging experiments.
A physical model was proposed to illustrate the mechanism of wax plug
transportation. Furthermore, a theoretical model was developed to
estimate the wax plug transportation force per unit contact area.
It is found that the wax plug transportation force per unit contact
area is independent of the wax plug length and radius, while correlated
to the wax yield stress and the interfacial lubrication coefficient.
These predicted correlativities match with the experimental results.
Additionally, the experimental results show that the wax plug transportation
force per unit contact area is independent of the pig geometry and
hardness. With the experimental results, the interfacial lubrication
coefficient for wax sample prepared from crude oil and diesel oil
were calculated to be 0.0749 and 0.0442, respectively. It is indicated
that the extruded diesel oil at the contact surface provides a better
lubrication effect for wax plug transportation than the extruded crude
oil. Experiments with different pig geometries and hardnesses were
performed to verify the modeling results. The cases of two field wax
blockage accidents were used for validation. With the results from
the developed model, an engineering implication was presented accounting
for formation condition of wax blockage and emergency operation scheduling
as well as selection of an appropriate pig diameter.
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