Pump

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Pumps

• Pump What is a Pump?
• A device that moves liquids or gasses by
  mechanical action
• How pumps work
• Operate by some mechanism (Reciprocating, Rotary)
• Perform mechanical work moving the fluid
• Consume energy to perform the work
• Types of Pumps
• Positive Displacement
• Velocity
• Gravity
• Steam

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Pumps

• Positive Displacement Pumps
• How do they work?
• They make fluid move by trapping a fixed amount
  and forcing (displacing) that trapped volume into
  the discharge pipe.
• Theoretically can produce the same flow at a
  given speed (RPM) no matter what the discharge
  pressure.
• Called constant flow machines

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Pumps

• Must not operate against a closed valve on the
  discharge side of the pump, it has no shutoff
  head like centrifugal pumps
• When operating against a closed discharge valve
  it continues to produce flow and the pressure in
  the discharge line increases until the line
  bursts, the pump is severely damaged, or both.
• A relief valve on the discharge side of the
  positive displacement pump is therefore necessary

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Pumps

• Types of Positive Displacement Pumps
• Classified according to the mechanism used to
  move the fluid
• Rotary-type
• Internal gear, screw, vane
• Reciprocating-type
• Piston or diaphragm pumps
• Linear-type positive displacement
• Rope pumps and chain pumps

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Pumps

• Positive Displacement Rotary Pump
• How do they work?
• Move fluid using a rotating mechanism that
  creates a vacuum that captures and draws in the
  liquid.
• Advantages
• Very efficient because they naturally remove air
  from the lines, eliminating the need to bleed the
  air from the lines manually.
• Disadvantages
• Pump has very close clearances between the
  rotating pump and the outer edge, making it
  rotate at a slow, steady speed. If operated at
  high speeds, the fluids cause erosion, which
  eventually causes enlarged clearances that liquid
  can pass through, which reduces efficiency.

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Pumps

• Types of Rotary Positive Displacement Pumps
• Gear
• A simple type of rotary pump where the liquid is
  pushed between two gears.

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Pumps

• Screw Pumps
• The shape of the internals is two screws turning
  against each other pump the liquid.
• One or several screws to move fluids or solids
  along the screw(s) axis
• The pumped fluid is moving axially without
  turbulence.
• Eliminates foaming that would otherwise occur in
  viscous fluids.
• Pump fluids of higher viscosity without losing
  flow rate.

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Pumps

• Rotary vane
• Cylindrical rotor encased in a similarly shaped
  housing.
• As the rotor orbits, the vanes trap fluid between
  the rotor and the casing, drawing the fluid
  through the pump.

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Pumps

• Common Uses of Rotary Vane
• High pressure hydraulic pumps and automotive uses
  including, supercharging, power steering and
  automatic transmission pumps.
• Advantages
• Vane extension makes up for wear
• Can be used with various materials and
  viscosities
• Can run dry for a little while.
• Disadvantages
• Very close tolerances are required between the
  case and the rotating pump.
• Cannot operate at too high a speed. Erosion in
  the pump, causing inefficiency.
• Cannot tolerate debris.

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Pumps

• Reciprocating Positive Displacement Pumps
• How do they work?
• Move the fluid using one or more oscillating
  pistons, plungers, or membranes (diaphragms),
  while valves restrict fluid motion to the desired
  direction.
• Expanding cavity on the suction side and a
  decreasing cavity on the discharge side.
• Liquid flows into the pumps as the cavity on the
  suction side expands and the liquid flows out of
  the discharge as the cavity collapses. The volume
  is constant given each cycle of operation.

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Pumps

• Types of Reciprocating Positive Displacement
  Pumps
• Plunger - a reciprocating plunger pushes the
  fluid through one or two open valves, closed by
  suction on the way back.
• Piston - The high-pressure seal reciprocates with
  the piston. Piston pumps can be used to move
  liquids or compress gases. Also simple devices
  for pumping small amounts of liquid
• or gel manually.

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Pumps

• When the Piston is actuated up,
• Liquid and or air is sucked in
• from the inlet port.
• When the Piston is actuated
• down all the pressure and
• liquid is released through
• the outlet port
• Diaphragm - the plunger pressurizes hydraulic oil
  which is used to flex a diaphragm
• in the pumping cylinder.
• Diaphragm valves are
• used to pump hazardous
• and toxic fluids.

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Pumps

• Advantages of Positive Displacement Reciprocating
  Pumps
• Long life, reliable service
• Low pressure applications
• Can be made of multiple materials
• Self priming. No need to fill the cylinders

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Pumps

• Disadvantages of Positive Displacement
  Reciprocating Pumps
• Pulsating flow.
• The suction stroke is difficult when pumping
  thick liquids.
• Severe wear when handling fluids with suspended
  solids.
• Low volume rates of compared to other types of
  pump.

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Pumps

• Rope Pump
• Loose hanging rope is lowered down into a well
• Drawn up through a long pipe with the bottom
  immersed in water.
• Round disks or knots matching the diameter of the
  pipe are attached and pull water to the surface.

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Pumps

• Velocity Pumps
• How do they work?
• Kinetic Energy is added to the fluid by
  increasing the flow velocity.
• What is Kinetic Energy? energy an object
  possesses due to its motion.
• Work needed to accelerate a body
• of a given mass from rest to its
• stated velocity.
• Having gained this energy during
• its acceleration, the body maintains
• this kinetic energy unless its speed
• changes.

The cars of a roller coaster reach their maximum
kinetic energy when at the bottom of their path.
Other examples, Billiards
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Pumps

• Most common Velocity Pump to move fluid through
  piping (water, petroleum, chemicals)
• Centrifugal Pump (also called Radial-Flow Pump)
• What is radial flow?
• Having the working fluid flowing mainly along the
  radii of rotation

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Pumps

• Rotating impeller to increase the pressure and
  flow rate of a fluid
• The fluid enters the pump impeller
• along or near to the rotating axis.
• Accelerated by the impeller
• Flows radially outward into a
• diffuser or volute chamber
• Exits in the downstream
• piping system.

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Pumps

• Potential Issues with Centrifugal Pumps
• Not good with solids
• Causes impeller wear
• Overheating due to low flow
• Cavitation due to low suction
• Mechanical seal leaks
• Lack of prime
• Must be filled with water to operate

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Pumps

• Gravity Pumps
• Most Common Siphon
• Steam Pumps
• Any type pump driven by steam
• Been around long time
• Used in remote areas without power source
• Railroad Engines

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Homework

• What are the 4 types of pumps?
• Explain how a positive displacement pump works.
• What are the types of positive displacement
  pumps?
• Explain how a rotary positive displacement pump
  works.
• What type of Positive displacement pump is good
  for high viscous fluids?
• What are the disadvantages of a Rotary Vane Pump?
  

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Homework

• Name the types of Reciprocating Positive
  Displacement pumps.
• Define Kinetic Energy.
• Why is a Centrifugal pump alse called a
  Radial-flow pump?
• What is Radial Flow?