Water D3 Pumps & Motors

Cavitation

A condition that can occur when pumps are run too fast or water is force to change directions quickly. This can cause pitting of the impeller and reduce pump efficiency.

Critical Speed

Is the Theoretical angular velocity that excites the natural frequency of a rotating object, such as a shaft. First velocity is at least 20% higher or lower than rated velocity of pump to prevent shaft vibrations.

Demand Meters

Used to measure avg power of a load over a specific time interval as well as recording the peak power consumption during the period.

Differential Relay

Often used on large equipment to check whether all the current entering a system comes out of the system. It will shut down a system that is losing current as a safety precaution

Flexible Diaphragm Coupling

Coupling that can compensate for up to 4 degrees of angular movement.

Flexible Disc Coupling

Coupling that can compensate for up to 1/32 of an inch of parallel shaft misalignment.

Frequency Relay

• Used when power is generated locally to respond to changes in the frequency of an AC power Supply.

• Used as well on synchronous motor starters to sense when the motor has reached synchronizing speed.

Friction Head

Is the amount of energy in feet required to overcome resistance to flow in a pipe.

Head

The energy possessed by water in a hydraulic system measured in feet.

Hydraulics

The study of fluids in motion

impeller

A rotating set of vanes that forces water through a pump. Its often called the heart of the pump.

Lantern Ring

• Used to prevent air leakage along the pump shaft when it is operating under suction lift conditions

• Also called a Seal Cage

Mechanical Seal

• A seal placed on a pump shaft to prevent water from leaking out along the shaft. They can also prevent air from entering the pump

• Used in place of packing when the pump suction pressure is under 60 psi.

OHM’s law

An equation expressing the relationship between volts, current and resistance in an electrical system.

• Volts = AMPs x Ohms

Packing

• Rings of graphite impregnated cotton, flax or synthetic materials used to control pump shaft or valve stem leakage.

• Designed to wear out over time during normal use.

Packing Gland

A follower ring that compresses the packing placed in the stuffing box. Either tightened or loosened to control shaft leakage.

Parallel Operation

Two or more pump discharges enter a common pipe to increase the volumetric flow rate. It increases flow rate without increasing head.

Racking

A condition where a pump is subject to frequent on/off cycling due to pressure surges that effect the pump controller.

Radial Load

A load acting at a right angle to the shaft.

• A radial bearing supports a shaft and allows it to rotate freely around its axis, compensating for these angular forces.

Thrust Load

A load that acts parallel to the axis of rotation. Compensates for the axial of a shaft.

Rectifier

A piece of electrical equipment that changes AC to DC by allowing the electric current to flow in one direction but blocking flow in the opposite direction.

Series Operation

One pump discharging into the suction line of another pump to increase the overall discharge head.

Slip

Recirculation within a centrifugal pump casing due to a blockage of the pump discharge.

Stuffing Box

Houses the packing and lantern ring in a centrifugal pump.

Thermal Overload Relay

An overcurrent protection device placed on each phase of a power supply to open up a control circuit and stop a motor, if the current becomes excessive.

Voltage Relay

An electrical device used to detect power loss and initiate an automatic switchover to another power supply.

Wear Ring

Made of brass or bronze placed on the impeller and/or casing of a centrifugal pump to separate the suction side of the pump from the discharge side.

Pump Curves

Is a graph showing the characteristics of a particular pump and are commonly called “pump characteristic curves” theres 4 types.

• Capacity

• Head

• Power

• Efficiency

To properly design a pump station

System head requirements most be known and can be expressed by a system head curve which includes static pressure, system head loss, and possibly an elevation difference. Then the pump or pumps are sized by referring to the pump characteristic curves.

Head Curve

Feet of head for a given flow rate

Efficiency

Pump efficiency for a given flow rate.

BEP - Best Efficicency Point

The flow at which the pump operates at the highest or optimum efficiency for a given impeller diameter.

Break Horsepower

Power required from the motor to drive the pump at a given head to deliver a given volumetric flow rate.