Air Bound A condition occurring when a centrifugal pump body is filled with air and a vacuum can no longer be formed allowing water to flow into the pump.Atmospheric Losses Engine performance DECREASES with altitude. The higher the altitude, the less air there is available to support combustion. Maximum engine power DECREASES about 3.5% per 1000 feet of altitude.Atmospheric Pressure At sea level, the atmosphere exerts a pressure of 14.7 psi all around us. If one end of a tube is placed in water and a perfect vacuum is applied to the other end, that 14.7 psi could hold a column of water 33.9 feet high. This is only obtainable at sea level and with a perfect vacuum. In reality, ALL centrifugal pumps can lift water no more than 26 feet at sea level. This drops off approximately 2 feet for each 1000 feet of altitude above sea level.Capacity Capacity is the water handling capability of a pump commonly expressed as either gallons per minute (GPM) or gallons per hour (GPH).Cavitation The sudden formation and collapse of low-pressure vapor (bubbles) across the vanes of the impeller. When the surface pressure on a liquid becomes low enough, the liquid will begin to boil (even at room temperature). With centrifugal pumps, cavitation can occur when the suction vacuum becomes to great enough to allow water vapor or bubbles to begin forming at the impeller. When this water vapor travels through the rapid pressure increase across the impeller, a large amount of energy is released which can cause impeller damage. Minimizing suction head and using the largest practical suction hose diameter will reduce the likelihood of cavitation. You should never use a suction hose with a diameter smaller than the pump’s suction port.Centrifugal Force As the engine starts, the impeller turns which forces the water around it out of the pump's discharge port. The partial vacuum created, allows the earth's air pressure to force water up the suction hose and into the suction (inlet) side of the pump to replace the displaced water. When the water hits the rotating impeller, energy of the impeller is transferred to the water, forcing the water out (centrifugal force). The water is displaced outward, and more water can now enter the suction side of the pump to replace the displaced water.Cleanout Covers On trash pumps a removable cover that allows easy access to the interior of the pump casing for removal of any debris.Dewatering The removal of unwanted water (clear or dirty) but free from hazardous materials.Diffuser A staionary housing similar to a volute in which the impeller rotates. Compact in design, it enables the pump to produce higher heads/pressures.Discharge Hose A collapsible hose used to move the water discharged from the pump.Discharge Port Same as the outlet. The point where the discharge hose or pipe is connected to the pump.Drain Plugs Removable plugs used to drain water from the pump during periods of inactivity.Dynamic Discharge Head The static discharge head plus the additional discharge head created by friction or resistance (usually referred to as losses) from the liquid flowing through the hoses, fittings, sprinklers, nozzle, etc.Dynamic Suction Head The static suction head plus the additional suction head created by friction from the liquid flowing through the hoses, fittings, etc. Atmospheric pressure enables pumps to lift water. As a result, an atmospheric pressure of 14.7 psi at sea level limits practical dynamic suction head lift to less than approximately 26 feet for any pump.Flapper Valve Rubber molded around a steel weight that seals off the inlet or outlet preventing water from either entering or exiting the pump at the wrong time of the cycle.Frame A wraparound tubular frame provides protection for the casing and engine. These frames can simplify storage (stacking) and lifting.Friction Loss The additional pressure or head created at the pump due to the friction of the liquid flowing through the hoses, pipes, fittings, etc. Friction losses always occur when a liquid is flowing through pipes and becomes greater as the length of pipe increases and/or the diameter decreases. Friction losses result in reduced pump output and can be minimized by used the largest and shortest hoses possible. Friction losses are included in dynamic suction and dynamic discharge head.Hazardous Material Any volatile, explosive or flammable liquid that requires special handling and should not be used with a dewatering pump.Head Refers to the height of a column of water that can be supported by the pressure or vacuum exerted at the pump.Impeller A disk with multiple vanes. It is attached to the pump engine or motor and is used to create the centrifugal force necessary for moving water through the pump casing.Mechanical Seal This is a spring-loaded device consisting of several parts that seals the rotating impeller in the pump case and prevents water from leaking into and damaging the engine. Mechanical seals are subject to wear when pumping water containing abrasives and will quickly overheat if the pump is run without filling the pump chamber with water before starting the engine or with a closed discharge.Net Positive Suction Head (NPSH) Positive flow of water to the suction port of the pump.Performance Curves Chart water flow by comparing total head to flow rate.Pressure Pressure is force per unit area and is usually listed in psi (pounds per square inch). Pressure is often included in pump performance curves. Pressure and head are directly related when referring to pump performance. The pressure exerted (in psi) at the base of a column of water is 0.433 x Head (in feet). If you attach pressure gauge at the base of a pipe 100 feet tall pipe filled with clear water, you would measure 43.3 psi. Notice how the diameter of the pipe doesn’t affect the pressure value. The maximum pressure (at zero discharge) of any pump can be determined by multiplying the maximum head by 0.433.Prime Most centrifugal pumps require the pump casing to be filled with water before starting.Pump Housing The pump body or casing. Depending on the design may be made of plastic, aluminum, cast-iron or stainless steel.Self Priming Most centrifugal pumps require the pump casing to be filled with water before starting. Self-priming is a term often used to describe pumps that have the ability to purge air from the case and create a partial vacuum, allowing water begin flowing through the suction hose.Shock Mounts Rubber mounts used to dampen vibration from the engine and help prevent the pump from "walking away".Skid Mount Pump and engine mounting mounted on a base.Slow Seepage Water that drains slowly into a trench or work area from the surrouding area. Possibly caused from run off or high water tables.Solids Any particulate that passes through the pump: mud, sand, rock or other debris.Strainer A fitting at the end of the suction hose that prevents solids larger than the pump is capable of passing from entering.Static Discharge Head The vertical distance between the pump’s discharge port and the point of discharge, which is the liquid surface if the hose is submerged or pumping into the bottom of a tank.Static Suction Head The vertical distance between the pump impeller and the surface of the liquid on the suction side of the pump.Suction Hose A reinforced hose through which water flows into the suction end of a pump.Suction Port Same as the inlet. The point where the suction hose or pipe is connected to the pump.Total Dynamic Head The dynamic suction head plus the dynamic discharge head. Also known as Total Head.Total Head The dynamic suction head plus the dynamic discharge head. Also known as Total Dynamic Head (TGH).Volute A stationary housing inside the pump housing in which the impeller rotates. It is used to separate air and water.Water Hammer Water Hammer is energy transmitted back to the pump due to the sudden stoppage of water flowing from the pump. Water hammer is more likely to occur when using a very long discharge hose. If the flow of water at the end of the discharge hose is shut off in less than the "critical time", energy is transmitted back to the pump causing a large pressure spike in the pump housing. Water hammer often results in damage to the pump casing.Wear Plate A replaceable steel insert that fits inside the voluyte or suction cover of a pump. Helps to form a vacuum with the impeller and reduce the cost of replacement parts.
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