We are manufacturer and supplier of Air Operated Double Diaphragm Pump (AODD Pump), Diaphragm Pump, Rubber and Industrial Products. http://antliaworks.com/

1. Useful information on positive
displacement pumps

2. • What is a positive displacement pump?
A positive displacement pump moves a fluid by repeatedly
enclosing a fixed volume & moving it mechanically through
the system. The pumping action is cyclic & can be driven by
pistons, screws, gears, rollers, diaphragms or vanes.
• How does a positive displacement pump works?
Although there are a wide variety of pump designs, the
majority can be placed into two different
categories: reciprocating & rotary.

3. • Reciprocating positive displacement pumps
A Reciprocating Positive Displacement pump works by the repeated back &
forth movement of a piston, plunger or diaphragm. These cycles are as also
called as reciprocation. In a piston pump, the first stroke of the piston
creates a vacuum, opens an inlet valve, closes the outlet valve & draws fluid
into the piston chamber (the suction phase). As the motion of the piston
reverses, the inlet valve, now under pressure, is closed & the outlet valve
opens allowing the fluid contained in the piston chamber to be discharged
(the compression phase). The bicycle pump is simple example. Piston pumps
can also be double acting with inlet & outlet valves on both sides of the
piston. While the piston is in suction on one of the side, it is in compression
on the other. More complex, radial versions are often used in industries.
Click here to know more about air operated double diaphragm pump.
Plunger pumps operate in a same way. The volume of fluid moved by a
piston pump depends on the volume of cylinder; in a plunger pump it
depends upon the plunger size. The seal around the piston or plunger is
important to maintain the pumping action & to avoid leaks. In general, a
plunger pump seal is easy to maintain since it is stationary at the top of the
pump cylinder whereas the seal around a piston is repeatedly moving up &
down inside the pump chamber.

4. • Rotary positive displacement pumps
Rotary positive displacement pumps use the actions of rotating cogs
or gears to transfer fluids, rather than the backwards & forwards
motion of reciprocating pumps. The rotating element develops a
liquid seal with the pump casing & creates suction at the pump inlet.
Fluid, drawn into the pump, is enclosed within the teeth of its rotating
cogs/gears & transferred to the discharge. This is the simplest
example of a rotary positive displacement pump is the gear pump.
There are two basic designs of gear pump: external & internal. Get
here the latest information about diaphragm pump.
An external gear pump consists of two interlocking gears which is
supported by separate shafts (one or both of these shafts may be
driven). Rotation of the gears traps the fluid between the teethes
moving it from the inlet, to the discharge, around the casing. Fluid is
not transferred back through the centre, between the gears, because
they are interlocked. Close tolerances between the gears & the casing
allow the pump to develop suction at the inlet & prevent fluid from
leaking back from the discharge side.

5. • What are the main features & benefits of a positive displacement
pump?
There are two main families of pumps: positive displacement &
centrifugal. Centrifugal pumps are capable of higher flows & can work
with lower viscosity liquids. In some chemical plants, 90% of the
pumps in used is centrifugal pumps. However, there are numbers of
applications for which positive displacement pumps are preferred. For
example, they can h &le higher viscosity fluids & can operate at high
pressures & relatively low flows more efficiently. They are also more
accurate when metering is a very important consideration. Buy AODD
Pump online at Antlia Engineering Works.
• What are the main applications for positive displacement pumps?
Positive Displacement pumps are commonly used for pumping high
viscosity fluids such as oil, paints, resins and foodstuffs. This pump is
preferred in any application where accurate dosing or high pressure
output is required. Unlike centrifugal pumps, the output of a positive
displacement pump is not affected by pressure so they also tend to
be preferred in any situation where the supply is not regular.

6. • Summary
A positive displacement pump moves a fluid by repeatedly enclosing
a fixed volume, with the aid of seals or valves, & moving it
mechanically through the system. The pumping action is cyclic &
can be driven by pistons, screws, gears, lobes, diaphragms or vanes.
There are two main types: reciprocating & rotary. To know more
about double diaphragm pump contact Antlia Engineering Works.

7. Thank you