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F.P.M. (fpm.): Feet per minute. When used in the context of seals it is measured at the center of the seal face.

Face combination: The materials chosen for the lapped seal faces. Usually a grade of carbon graphite running on a hard face material.

Face flatness: Measured by an optical flat and a monochromatic light. The measurement is read in helium light bands (.0000116 inches or 0,3 microns).

Face lubrication: The fluid or vapor that sometimes exists between lapped mechanical seal faces.

Face Piping: The piping with all valves and fittings which is used to connect the filter system together as a unit. This includes all valves and piping necessary for the filter plant to perform the functions of filtering or backwashing, either by the plant as a whole or any unit operating singly.

Face pressure: The sum of all the loads on the seal face including the spring load, hydraulic load and shaft axial thrust, divided by the area of the seal face. This face load is reduced by friction between the sliding elastomer and the shaft or sleeve.

Face to face seals: Two seals running against a common seal face. The barrier fluid pressure is always lower than stuffing box pressure.

Factor of safety: The ultimate load divided by the safe load or the ultimate strength divided by the allowable stress.

Fast Charging: A term used to describe charging a battery at a rate of 0.5C or higher — i.e., in less than 2 hours.

Feed Water: Water under pressure entering a purification system or an individual piece of purification equipment, such as an ultra filter, distiller or reverse osmosis system.

Feet of head: A basis for indicating the resistance in a hydraulic system, equivalent to the height of a column of water that would cause the same resistance (100 feet of head equals 43 pounds per square inch). The total head is the sum of all resistances in a complete operating system. The principal factors affecting a head are vertical distances and the resistance caused by friction between the fluid and pipe walls.

Ferric Iron: Small solid iron particles containing trivalent iron, usually as gelatinous ferric hydroxide or ferric oxide, which are suspended in water and visible as "rusty water". Ferric iron can normally be removed by filtration. Also called "precipitated iron".

Ferrous Iron: A divalent iron ion, usually as ferrous bicarbonate which, when dissolved in water, produces a clear solution. It is usually removed by cation exchange water softening. Also called "clear water" iron.

Fibrewound Tank: A tank body made from polyethylene plastic fibers wound around a mandrel.

Fill Water: Used in filling or adding to the water level. Whether from the hose or from a well, your fill water brings its own chemical make up and water balance (or lack thereof).

Filled carbon: Contains organic or inorganic materials that might be sensitive to temperature, or be attacked by the fluid you are sealing. Usually a low cost carbon.

Fill-Trol Expansion Tank: An extrol expansion tank that features an integrated and specially designed automatic fill valve.

Film-X: A compound of citric acid used in cleaning plaster and other pool areas. Safe replacement for muriatic acid.

Filter Agitation: The mechanical or manual movement to dislodge the filter aid and dirt from the filter element.

Filter Aid: A type of finely divided media used to coat a septum type filter, usually diatomaceous earth or volcanic ash. (NOTE: Alum, as used on the bed of a sand filter, is also referred to as a filter aid).

Filter Cartridge: A filter which operates through a disposable cartridge. These are of two general types: The surface or area type where the suspended matter is removed at the surface, and the depth type in which the interstices vary from large to small in depth.

Filter Cycle: The operating time between cleaning or backwash cycles.

Filter Diatomite: One designed to filter water through a thin layer of filter aid such as diatomaceous earth or volcanic ash. Diatomite filters may be of the Pressure, Gravity, Suction or Vacuum type.

Filter Element: A device within a filter tank designed to entrap solids and conduct water to a manifold, collection header, pipe or similar conduit. A filter element usually consists of a septum and septum support.

Filter Media: The finely graded material which entraps suspended particles (sand, anthracite, diatomaceous earth, etc.).

Filter Medium: A finely graded material such as sand, diatomaceous earth, polyester fabric, or anthracite coal that removes suspended particles from water passing through it.

Filter Pump: The device that pulls water from the pool and pushes it through the filter on its way back to the pool.

Filter Rock: Graded, rounded rock and/or gravel used to support filter media.

Filter Septum: That part of the filter element consisting of cloth, wire screen or other porous material on which the filter cake is deposited.

Filter, Gravity - Sand: A filter with a layer of filter media (usually silica sand) supported on graded gravel through which water flows by gravity.

Filter, Pressure - Sand: A sand filter enclosed in a tank to operate under pressure.

Filter, Sand: A type of filter media composed of hard sharp silica, quartz, or similar particles with proper grading for size and uniformity.

Filter, Vacuum (Suction): A filter which operates under a vacuum or from the suction side of a pump.

Filter: A device that separates solid particles from water by recirculating the water through a porous substance (a filter medium element). Permanent Medium Filter: A filter that utilizes a medium that under normal use will not have to be replaced. Diatomaceous Earth Filter: A filter that utilizes a thin layer of diatomaceous earth as its filter medium that periodically must be replaced. Cartridge Filter: A filter that utilizes a porous cartridge as its filter medium.

Filter-1-: A device to clean pool water by filtering out dirt, oils, etc. Filters may use diatomaceous earth (DE), cartridges with a fine-mesh element, or a sand bed as the filtering agent.

Filter-2-: A devise used to remove solid particles from liquid. It removes smaller particles than a strainer.

Filtrate: The portion of the feed stream that has passed through the membrane or filtering media.

Filtration Flow: The rate of flow in volume per time (gallons per minute, gallons per hour), through the filter system installed per manufacturer’s instructions with a new, clean filter medium.

Filtration Rate: The rate of filtration of water through a filter during the filter cycle expressed in US gallons per minute per square foot of effective filter area.

Filtration Rate-1-: The rate of water pumped through a filter, in gallons per minute (gpm).

Final Dispersal: The movement of effluent water to the ground for absorption and filtration.

Finished Water: Water that has been treated and is ready to be delivered to customers.

Finite element analysis: A computer generated method of predicting seal face distortion.

First Affinity Law: With the same impeller, if you double the diameter, the flow doubles.

Fitting: As opposed to a threaded fitting, rings projecting outward around fitting designed to grip hose. Usually measured in O.D. (outside diameter) , as opposed to hose measured in I.D. (inside diameter).

Fixture count: A method of establishing the required number of gallons per minute to satisfy water needs by counting the number of water-fixtures in a home, where one fixture equals 1 GPM.

Fixture Unit Value: An assigned value for flow created by plumbing fixtures. The value assumes the likelihood of any given plumbing fixture operating at the same time and the amount of wastewater it may create.

Flange or Face: Specially machined drive end bearing housing with flat surface and bolt holes to provide easy mounting to driven equipment. Used extensively on pumps and gear reducers, NEMA flanges are designated by C, D or P and the letter will appear on the nameplate in the frame space, i.e. 256TC, etc.

Flange: A device used to couple to a pipe on the suction or discharge of a 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.

Flashing: A rapid change in liquid state from a liquid to a gas.

Flat curve: Head decreases very slowly as flow increases.

Flatness: Measured by Helium light bands (0.0000116" or 0,3 microns) as opposed to surface finish that is measured by R.M.S. or C.L.A.

Flexibility factor: Same as L3/D4 used to predict shaft-bending problems.

Flexible member: The portion of the seal containing the springs or bellows.

Flexible shaft: A shaft with an operating speed higher than its first critical speed.

Float Charging: A term used to describe charging a battery at a rate only sufficient to neutralize its self-discharge — i.e., maintain it at full capacity.

Float Switch: A device used to start and stop a pump based on preset water levels.

Flocculating Agent: A compound, such as one of the alums, which forms minute flakes in water which attract or enmesh small suspended particles.

Flocculent: Chemical which, when added to water, causes particles to coagulate into larger groupings that settle out easier. Aluminum compounds are common catalysts in this process.

Flocculent-1-: Essentially the same as a coagulant, this chemical (such as alum) is used to combined suspended alkaline material and/or algae into a heavy gel, which sinks to the bottom for vacuuming to waste.

Flood plain: A strip of relatively flat and normally dry land alongside a stream, river, or lake that is covered by water during a flood.

Flood stage: The elevation at which overflow of the natural banks of a stream or body of water begins in the reach or area in which the elevation is measured.

Flood, 100-year: A 100-year flood does not refer to a flood that occurs once every 100 years, but to a flood level with a 1 percent chance of being equaled or exceeded in any given year.

Flood: An overflow of water onto lands that are used or usable by man and not normally covered by water. Floods have two essential characteristics: The inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river, stream, lake, or ocean.

Flooded cell: A type of wet cell where the active electrodes are submerged in liquid electrolyte. The common car or truck battery uses this type of cell.

Flooded Suction/Gravity Fed: Liquid source is higher than the pump, and liquid flows to pump by gravity. Flooded suctions are recommended for centrifugal pump pond installations.

Flooded Suction: The condition where the water supply is above the pump.

Flooded suction-1-: When the liquid source is higher than the pump, and the liquid flows to the pump by gravity. Preferable for centrifugal pump installations.

Flood-way: The channel of a river or stream and the parts of the floodplain adjoining the channel that are reasonably required to efficiently carry and discharge the flood water or flood flow of a river or stream.

Floor Heating: Radiant Heating Floor System

Floor Slope: The slope in the pool floor, usually expressed in feet (or inches) of vertical rise in feet (or inches) of horizontal distance.

Flow Inducer Sleeve: A sleeve attached to a submersible pump to force water to pass around it and enter the pump's suction intake from below the motor for cooling purposes.

Flow Rate or Capacity: The volume of liquid that passes a given point in a specified unit of time.

Flow rate: How many gallons per minute (GPM) of pump flow are required. Flow can also be expressed in gallons per hour (GPH) and in million gallons per day (MGD).

Flow Rate-1-: The quantity of water flowing past a specific point in a specified time (e.g. the number of liters flowing through the filter in 1 hour).

Flow Rate-2-: The volume of liquid that passes a given point in a specified unit of time. Capacity is also commonly used to designate Flow Rate when working with pumps. Example - GPM (Gallons per minute), GPH (Gallons pre Hour), or GPD (Gallons per day)

Flow Restrictors: Valves or bends in a pipe system that restricts the flow of liquid.

Flow splitter: See suction flow splitter.

Flow Velocity: A quantitative expression of the rate of linear motion at which water passes through a pipe or conduit.

Flow:  The measure of the liquid volume capacity of a pump. Given in Gallons Per Hour (GPH) or Gallons Per Minute (GPM) as well as Liters Per Minutes (LPM), and milliliters per minute (ml/m).

Flowing well/spring: A well or spring that taps ground water under pressure so that water rises without pumping. If the water rises above the surface, it is known as a flowing well.

Fluid  Type: Whether the fluid being pumped is clean or dirty, contains any solids or abrasives, or is a hazardous material.

Fluid: The material assumes the shape of its container. It could be either a liquid or a gas.

Fluidization: A process by which particles are suspended by an upward flow of liquid, such as may occur during back washing of ion exchange resin or carbon media.

Fluids:  Include liquids, gases, and mixtures of liquids, solids, and gases. In this catalog, the terms fluid and liquid are both used to mean a pure liquid or a liquid mixed with gases or solids that acts essentially like a liquid in pumping applications.

Fluoride: A salt of hydrofluoric acid which may occur naturally in water supplies or be added by municipal processes for the prevention of dental caries. Fluoride is considered toxic in most medical settings and has been implicated with a wide range of physiological disorders including renal bone disease.

FLUOROCARBON (FKM) (VITON®) (FLUOREL®):  Fluorocarbon elastomers are inherently compatible with a broad spectrum of chemicals. Because of this extensive chemical compatibility, which spans considerable concentration and temperature ranges, fluorocarbon elastomers have gained wide acceptance as a material of construction for butterfly valve o-rings and seats. Fluorocarbon elastomers can be used in most applications involving mineral acids, salt solutions, chlorinated hydrocarbons, and petroleum oils. They are particularly good in hydrocarbon service. Fluorocarbon elastomers have one of the broadest temperature ranges of any of the elastomers, -20°F to 300°F; however, they are not suited for steam service. FLUOREL is a registered trademark of the 3M Company.  VITON is a registered trademark of the DuPont Company.

Fluorocarbon-1-:  Genetic term for the elastomer called Viton? Viton is a Dupont Dow elastomer product.

Flush: Putting an outside liquid into the stuffing box of the pump at a pressure higher than stuffing box pressure. All of this liquid mixes with and dilutes the pumped fluid.

Flux/Flux Rate: The rate per unit of area at which water passes through a semi-permeable membrane, such as those used for ultrafiltration or reverse osmosis.

Flyweight: A weight mounted on the side of a rotor designed to snap outward as the motor reaches a critical speed.

FNPT: This refers to the female pipe thread, in which the threads are on the inner side on the connection fitting.

Foaming: A term used to describe surface foam on your water, esp. in spas/hot tubs. Foaming is caused by high TDS levels working in combination with soft water and oils. Certain low grade algaecides can foam when added to pool or spa. Use enzymes for foam control.

Foot or Check Valve: A device that keeps water/liquid flowing one way through a pump or piping system; A foot valve is a modified check valve that has a screen on the suction end to prevent debris from entering the pump or pipe.

Foot  Valve:  A type of check valve with a built-in strainer. Used at point of liquid intake to retain liquid in the system, preventing loss of prime when liquid source is lower than pump.

Foot valve-1-: A screened check valve used at the end of the suction pipe to prevent dirt and debris from clogging the pump and maintain prime.

Foot valve-2-:  A check valve that is put on the end of the pump suction pipe, often accompanied with an integrated strainer.

Force: An applied effort that tends to attempts to move something.

Force: Created whenever pressure works on an area. The units are pounds. (F = P x A).

Fouling: The deposition of insoluble materials, such as bacteria, colloids, oxides and water-borne debris, onto the surface of a media such as water softening resins, reverse osmosis or ultrafiltration membrane. Fouling is associated with decreased flux rates and may also reduce the rejection rates of reverse osmosis membranes.

Four-Pole Motor: Motors with two pairs of running windings that usually run at 1750 rpm.

Fourth Float: Used in a duplex system, when called for in specifications, to activate the alarm. In this case the Lag Float only activates the lag pump.

Frame or Frame Size: Generally refers to the NEMA Standardized dimensioning system. Also used to refer to the yoke or supporting structure for the stator parts.

Frame: A wraparound tubular frame provides protection for the casing and engine. These frames can simplify storage (stacking) and lifting.

Frame-1-: The dimensional standard or physical set of members that are used on a motor.

Francis vane impeller: The most popular impeller shape with a specific speed between 1500 and 4000.

Free length: The uncompressed axial length of a seal.

Freeboard: The clear vertical distance between the top of the filter medium and the lowest outlet of the upper distribution system in a permanent medium filter.

Frequency - Hertz (HZ): Frequency in cycles per second of AC power; usually 60 Hz in U.S. and 50 Hz is common overseas.

Freshwater: water that contains less than 1,000 milligrams per liter (mg/L) of dissolved solids; generally, more than 500 mg/L of dissolved solids is undesirable for drinking and many industrial uses.

Fret or fretting: Damage or grooving caused by the removal of the protective oxide that is formed on most corrosion resistant metals. It happens when a softer material (rubber) rubs against a hard shaft or sleeve. A common problem with low cost OEM mechanical seals and bearing grease or lip seals.

Friction (pipe): The force produced as reaction to movement. All fluids are subject to friction when they are in motion. The higher the fluid viscosity, the higher the friction force for the same flow rate. Friction is produced internally as one layer of fluid moves with respect to another and also at the fluid wall interface. Rough pipes will also produce high friction.

Friction factor f (pipe): The friction factor f is required for the calculation of the friction head loss. It is given by the Moody diagram, or the Colebrook equation or the Swamee-Jain equation. The value of the friction factor will depend on whether the fluid flow is laminar or turbulent. These flow regimes can be determined by the value of the Reynolds number.

Friction Head Difference: The difference in head required to move a mass of fluid from one position to another at a certain flow rate.

Friction head loss (pipe): The friction head loss is given by the Darcy-Weisbach equation and in many tables such as provided by the Cameron Hydraulic data book. It is normally given in feet of fluid per 100 feet of pipe.

Friction Head: The pressure expressed in lbs./sq. in. or feet of liquid needed to overcome the resistance to the flow in the pipe and fittings.

Friction Loss (or Head Loss): The Dynamic Suction Head plus the Dynamic Discharge Head. Also referred to as Total Dynamic Head (TDH).

Friction Loss Calculation: Based on the type of pipe to be used, the size of the pipe, the average flow rate, and the length of the pipe.

Friction Loss Charts: A table showing resistance to water movement within various types of piping material. All charts are not the same - Pentair uses the Williams and Hazen chart.

Friction Loss: Reductions in flow due to turbulence as water passes through hoses, pipes, valves, and fittings. This includes both suction and discharge friction losses.

Friction Loss-1-: 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.

Friction loss-2-: The loss of pressure expressed in feet (head) caused by the turbulence created in water while traveling through the pipe. To express pressure in feet, multiply by 2.31.

Friction Loss-3-: The loss of pressure or head due to the resistance to flow in the pipe and fittings. Friction loss is influenced by pipe size and fluid velocity, and is usually expressed in feet of head; a form of energy, which is another name for head.

Friction: the force produced as reaction to movement. All fluids produce friction when they are in motion. The higher the fluid viscosity, the higher the friction force for the same flow rate. Friction is produced internally as one layer of fluid moves with respect to another and also at the fluid/wall interface.

Friction-1-: The resistance to motion of two objects or surfaces that touch.

Front cover: See end-suction pump.

Front plate: See end-suction pump.

Full Load Amps (F.L.A): Rating on the motor nameplate. The FLA is the amperage rating at the motor nameplate horsepower rating and at its rated (nominal) voltage. This is usually the point of maximum efficiency and maximum power factor for the motor. This is where the motor prefers to run.

Full-Load Amps (F.L.A.)-1-: Current (Amps) drawn by motor operating at rated horsepower and voltage. Important for wire and control selection and is on the motor nameplate.

Fulvic Acids: Acidic substances which are found in humic (organic) soils and which may become suspended in water. A component in the production of chloramines.

Fungus: A parasitic plant which produces no chlorophyll and is dependent on other life forms for its existence.