Once flow has been observed the extreme viscosities may prevent acceleration so that the column can only be slowly displaced. However, for many fluids, even with slight shear, the degradation of gel structure can be high leading to significant lowering of viscosity and thus rapid acceleration and displacement of the cold fluid.
KAT can determine flow development following the restart in both the model pipeline test and by using controlled stress rheometry.
As with the pour points, above, restart determinations made with stabilised crude samples are usually considered sufficient. However, KAT has developed the bespoke test equipment and methodology for studying the restart of pressurised fluids up to a maximum working pressure of 5,800psi [400barg].