Underflow piping

Costs of moving spigots, discharge pipelines, and cyclone underflow pipes... 

The total loss shown above is that which occurs from inlet to (gas) overflow and represents also the loss in static pressme over the cyclone. As a rough estimate, the difference in static pressme between the inlet and the (solids) underflow, under the point at which the vortex ends, is the same as that computed by Eq (6.6.1) but without the core loss contribution. However, if the vortex core happens to extend or dip down to the underflow pipe, the difference in static pressure between inlet and imderflow can equal—or even exceed—the total pressure drop from inlet to overflow. 

Excessive amounts of foam in a vessel can result in a host of operating and production problems, including reduced product throughput, level control problems, excessive liquid entrainment out the vapor outlet piping, excessive vapor out the liquid underflow piping, and underflow pump cavitation problems. If foaming occurs in a compressor knockout drum it can easily flood a mesh pad or vane (chevron) separator. When this occurs, the foam carryover from the drum can severely damage the gas compressor downstream. 

The suspended solids separate from the water and fall to the bottom of the tank, in which they move to the centre because the bottom is in the form of an inverted cone, and the solids shde down the sloping walls of this cone. They are assisted in this movement towards the centre by a set of vanes that turn on a centrally mounted shaft, turning slowly so as not to resuspend the separated solids. The solids flow out of the clarifier as a thick sludge through the underflow pipe, which has an integral flow control device to stop water leaving as well. 

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