Centrifugal Pumps |
These types of pumps are used extensively in the HVAC Refrigeration industry for all types of applications. They can be defined by the type of:
Impeller: Single or double suction (single most common)
#of Impellers:
-Single stage = 1 Impeller
-Multi-stage = 2 Impellers)
Type of Casing:
-Valute Discharge (Perpendicular to shaft)
-Diffuser Discharge (Parallel to shaft)
Method of connection to driver:
-Close Coupled – Impeller mounts directly on external motor shaft
-Flexible Coupled – Impeller connected to motor shaft with flex coupling
Mounting position in relation to driver
-Horizontal
-Vertical
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Pump Construction
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Material Used:
-Bronze fitted (Impeller/ shaft/ sleeve/ wear ring)
-All bronze
-Iron fitted
Stuffing Box:
-Portion of the pump where the rotating shaft enters the pump casing (A mechanical seal or packing gland is used to) prevent leakage
-*Note: Packing glands are used when abrasive or corrosive liquids are used. Leakage is required to cool + lubricate the area between the packing material and the shaft.
Shaft Sleeves:
-Used to protect motor + pump shafts from excessive wear.
Pump rotation:
-Indicated by arrow. Rotation may be checked by first energizing motor.
-*Note: Never run pump equipment with a mechanically dry seal
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Pump Terminology
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Friction head:
-When pump puts water in motion the water will meet resistance caused by valves, fittings, and piping. Friction head is the resistance the pump must overcome.
Velocity Head:
-The force required to put water in motion.
Pressure Head:
-When pump discharges into vessel under pressure more force is required from the pump.
Dynamic Head:
-Is the term used to express the sum of friction, velocity, and press head.
-Formula: Dynamic Head = Friction + Velocity + Press Head
Total Head:
- The total head required to move the water from the source of supply to the point of discharge
-Formula: Total Head = Total Static Head + Dynamic Head
Static Discharge Head:
-The vertical distance in feet from the center line of the pump to free surface discharge or surface of discharge.
Static Suction Head:
-Is the Vertical distance in feet from the surface of the source of supply to the point of free discharge
-Formula: TSH = SDH – SSH
Static Suction Lift:
-Is the vertical distance in feet from the surface of the source of supply to the center line of the pump. (Source below pump)
-Formula: TSH = SDH – SSL
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