In order to find a
solution to the problem of the huge amount of water recovered together with the
spilled hydrocarbons we need to know how these are pumped from the skimmers,
because their knowledge will help us to find the best way to integrate the
industrial separation methods presented in the previous post.
Once recovered the
spilled oil using the different types of existing skimmer we need to pump it to
the temporary storage tanks.
Sometimes the
skimmer's workplace and the location of the operator advise the use of a
suction pump or on the contrary a delivery pump.
When access to the
spill zone is complicated it may be more interesting to use lightweight
skimmers by working with a self-priming pump located in the proximity but on
the ground or on the deck of the response vessel. This configuration has an
important limitation, the pump maximum suction head. A self-priming pump will
never be able to suck from a height greater than 9.8 meters, a height that is
reduced as the viscosity of the product to be pumped increases.
To avoid this handicap
skimmers can be equipped with transfer pumps. In this way the limitation of
height becomes a minor problem. A logistical problem arises; however, to move
and raise these skimmers it is necessary to use cranes.
Among the first
type of pumps, the most used are lobes pumps, peristaltic pumps and membrane
pumps. All are self-priming positive displacement pumps capable of working with
high viscosities fluids even in the presence of solids. The differences between
them focus on the necessary maintenance, diameter of solids, ability to work
dry and price. In any case, they are bulky and heavy pumps, characteristics
that hinder, but not prevent, their use as a transfer pump in skimmers.
Usually skimmers
equipped with pumps use the following types:
- Lobe pumps: their weight does not make them the best solution
- Open impeller axial centrifugal pumps: emulsify the water-hydrocarbon mixture and work especially poorly with viscous hydrocarbons.
- Sealing disc Archimedes
Screw Pumps: the most widely used and best-performing pumps to be uses with
water-hydrocarbon mixtures and viscous hydrocarbons.
