The
C6000 series pump is part of the family of TRIRO positive displacement
rotary screw type pumps from Plenty Mirrlees Pumps. This
design incorporates just three moving parts - a power rotor
and two idlers. The three rotors have accurately machined
precisely intermeshing threads, which form sealed closures
inside the pump casing to enclose the fluid being pumped.
The
power rotor is connected directly to the prime mover, and as
it rotates, the idler rotors turn due tot he action of the
pumped liquid. This action is in effect, that of a piston
moving continuously in one direction, providing a smooth uniform
low shear flow without pulsations.
The
idler rotors perform no work so no gears are required to transmit
power between the screws. Radial forces on the idler
rotors are taken up by creating a hydrodynamic bearing surface
between the idler rotors and the surrounding cylindrical surfaces,
so no other bearings are required. Axial forces on the
screwset, caused by the pressure differential between inlet
and outlet, are balanced hydraulically within the pump.
The
chamber formed between two adjacent threads and the bore is
known as a closure that contains the liquid as it moves through
the pump. As the screwset rotates, the unfolding closures
in the suction chamber create low-pressure area and the absolute
pressure on the liquid at the pump inlet. At the discharge
end, the folding closures force the liquid into the discharge
pipe against the natural resistance (known as discharge pressure)
created by the static head and discharge pipe system frictional
losses.
The
discharge, or backpressure, forces a certain portion of liquid
to pass back along the internal clearances from discharge to
suction. This is a characteristic of all rotary positive
displacement pumps. The very fine working clearances
of a TRIRO pump reduce this leadage or slip to a minimum thus
maximizing the volumetric efficiency.
Discharge
Pressure
Being
a positive displacement pump the TRIRO pump does not create
a discharge pressure by its own action. Positive displacement
pumps provide a flow of fluid to the system, which will consist
of piping, and fittings etc that will cause a resistance to
the flow. This is reflected at the pump as discharge
pressure. A positive displacement pump is capable of
working at pressures that far exceed the rating of its own
components and those of the system. The only thing that
can limit the pressure developed by a positive displacement
pump is a safety relief valve fitted either to the pump
or in the system.
