Food Plant Pumps - Unit 1

Food Plant Pumps - Unit 1

• The syllabus covers pumping theory, head development, different pump types (centrifugal, reciprocating, rotary gear, vane, diaphragm, peristaltic), pump construction, working principles, and applications.
• Simple problems will be included.

Rotary Gear Pump

• This is a common rotary pump type, comprised of two intermeshing gears inside a casing.
• One gear is driven, the other idles.
• Gears move in the direction of flow when close to the casing, pushing liquid forward between consecutive teeth.
• Liquid is discharged before the teeth mesh.
• In lobe pumps, teeth are replaced with lobes, functioning similarly.
• Gear pumps are self-priming.
• Leakage or slip between gears and casing is present but reduces with fluid viscosity.
• Suitable for viscous liquids, not suspensions.
• High-pressure delivery, mostly constant with pressure.
• Positive displacement pumps, moving a fixed amount of fluid per revolution.
• Some can function as motors or as pumps.

Spur Gear Pump

• A type of external gear pump, using two external spur gears.
• Internal gear pumps use both an inner and outer spur gear.

Working Principle

• Fluid flows into the cavity and is trapped by gear teeth as they rotate.
• Liquid moves along the interior casing in pockets between teeth and casing.
• Gears force the liquid out the outlet port under pressure. This cycle repeats.

External Gear Pumps

• Often used for lubrication, fluid power transfer, and engine oil pumping.
• Larger capacity pumps often use helical or herringbone gears.
• Smaller pumps usually operate between 1750 and 3450 rpm. Larger models go up to 640 rpm.
• Close tolerances and shaft support on both sides are characteristics.
• Used for precise transfer and metering involving polymers, fuels, and chemical additives.

Construction

• Diagram showing suction port, drive gear, case seal, seal, drive shaft, idler gear, mounting flange, and pressure port.

Internal Gear Pumps

• Versatile, usable for thin liquids (solvents, fuel oil) and thick liquids (asphalt, chocolate, adhesives).
• Viscosity range from 1cP to over 1,000,000cP.
• Fluid enters between rotor (large exterior gear) and idler (small interior gear) teeth.
• Travel occurs within the "gear-within-a-gear" between teeth and casing.
• A crescent shape divides liquid and acts as a seal.
• Pump head nearly flooded just prior to forcing liquid out discharge port.
• Intermeshing gears create locked pockets, ensuring volume control.
• Rotor and idler teeth perfectly mesh to form a seal equidistant from the suction and discharge.

Applications for External Gear Pumps

• Fuel oils and lube oils
• Chemical additives and polymer metering
• Chemical mixing and blending (double pump)
• Industrial and mobile hydraulic applications (like 10g splitters, lifts)
• Handling acids and caustic materials (using stainless steel or composite construction)
• Low-volume transfer or applications.

Applications for Internal Gear Pumps

• All varieties of fuel oil and lube oil
• Resins and polymers
• Alcohols and solvents
• Asphalt and bitumen

Vane Pumps

• Consist of slotted rotor attached to drive shaft, rotating within a cam ring.

• Vanes are fitted to rotor slots, matching internal width of cam ring.

• Centrifugal force and system pressure push vanes outwards against cam.

• Vanes touch internal cam surface, defining pumping chamber. Rotor, vanes and 2 side plates form pumping chamber

• Partial vacuum creates at suction side as space between rotor and ring increases.

• Liquid is pushed out of the pump as space decreases.

• Displacement depends on ring and rotor width, and cam "throw".

• Available in designs for low and medium volume range, operating pressures up to 200 atmospheres.

• Reliable, efficient and easy to maintain.

• Offers various control to adjust to different customer needs: pressure controller and horse power controller.

• Cleanliness of pump and appropriate liquid essential for long life.

Vane Types

• Swinging vane
• Sliding vane

Sliding Vane Type

• Blades/vanes fit into slots.
• Grooves admit fluid ahead of slots in rotation direction.
• Fluid moves vanes outward with force or locking pressure that changes with pump pressure.
• Grooves create vacuum on admission side.
• Centrifugal and hydraulic pressure help hold vanes in place.

Vane Pump Types

• Single-stage, double stage
• Combined-stage using two separate vane pumps on a common shaft.

Key Variations

• Balanced vane pump: prevents side loading on shafts and bearings by arranging outlet ports at 180 degrees apart. Discharge is fixed.
• High-low pump: can combine larger high-pressure and smaller lower-pressure pumps
• Variable volume pumps: use pressure compensators to control maximum system pressure.
• Pump displacement can change to supply exact flow rate required.