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O

OBSTRUCTION LIGHTS (Natural Draft Tower) Warning lights required by FAA regulations, placed on the outside of the hyperbolic shell.

OCCLUSION An absorption process by which one solid material adheres strongly to another, sometimes occurring by co-precipitation.

ODP Open drip-proof description of a motor enclosure usually used indoors in a fairly clean location.

OFF CYCLE That part of a refrigeration cycle when the system is not operating.

OIL SEPARATOR A device for separating oil and oil vapor from the refrigerant, usually installed in the compressor discharge line.

OIL, REFRIGERATION Specially prepared oil used in refrigerator mechanism circulates to some extent with refrigerant. The oil must be dry (entirely free of moisture), otherwise, moisture will condense out and freeze in the refrigerant control and may cause refrigerant mechanism to fail. An oil classified as a refrigerant oil must be free of moisture and other contaminants.

OLFACTORY Relating to the sense of smell. The olfactory organ in the nose is the sensing element that detects odors and transmit information to the brain through the olfactory nerves.

ONCE-THROUGH COOLING SYSTEM A system that uses water flow to cool a process or equipment and then discharges that water to a receiving stream.

ONCE-THROUGH SYSTEM A system through which water passes only once and is discharged. There is no evaporation.

OPACITY The percentage of light transmission through a plume.

OPEN DISPLAY CASE Commercial refrigerator designed to maintain its contents at refrigerating temperatures even though the contents are in an open case.

OPEN RECIRCULATING COOLING SYSTEM A cooling system that uses water flow to remove waste heat from a process or equipment. The waste heat is rejected to the atmosphere by evaporation and sensible heat exchange through direct contact with air and is then recirculated through the system.

OPERATING BELOW CAPACITY Plant equipment is performing below its rated operational level.

ORAL Used in or taken into the body through the mouth.

ORAL TOXICITY Adverse effects resulting from taking a substance into the body via mouth. Ordinarily used to denote effects in experimental animals.

ORE A mineral containing useful substances which can be extracted.

ORGANIC Generally refereed to cooling water treatments such as tannins, lignins, or any organic material having a useful function in water treating.

ORGANIC CONTENT Synonymous with volatile solids except for small traces of some inorganic materials such as calcium carbonate which will lose weight at temperatures used in determining volatile solids.

ORGANIC DETRITUS The particulate remains of disintegrated plants and animals.

ORGANIC MATTER The waste from homes or industry of plant or animal origin. Organisms of relatively small size, mostly microscopic, that have either relatively small powers of locomotion or that drift in that water with waves, currents, and other water motion.

ORIFICE An opening through which a fluid can pass; a restriction placed in a pipe to provide a means of measuring flow.

ORIFICE An opening through which a fluid can pass; a restriction placed in a pipe to provide a means to measure flow.

ORTHOPHOSPHATE A stable oxide of phosphorous which forms a trivalent negative radical. Combines with calcium to form insoluble calcium phosphate which is useful in boiler treatment practice but which is generally avoided in cooling systems.

ORTHOTOLIDINE A reagent used to determine chlorine concentration in water.

OSHA Occupational Safety and Health Administration of the U.S. Department of Labor; federal agency with safety and health regulatory and enforcement authorities for most U.S. industry and business. Also see "MSHA."

OSMOSIS The passage of water through a permeable membrane separating two solutions of different concentrations; the water passes into the more concentrated solution.

OVERALL TOWER DIMENSIONS (a) width: overall dimensions perpendicular to the tower’s longitudinal axis; (b) length: overall dimension parallel to the air inlet louvers and the longitudinal axis; (c) total height: distance from basin curb to top of fan stack. Dimensions measured in feet.

OVERHEATING (Boiler Metal) Permanent changes in microstructure caused by excessive temperatures, usually weakening the metal.

OVERLOAD Load greater than load for which system or mechanism was intended.

OVERLOAD PROTECTOR A device, either temperature, pressure, or current operated, which will stop operation of unit if dangerous conditions arise.

OVERRUNNING A condition when service

OXIDATION A chemical process that involves a loss of electrons.

OXIDATION POND A man-made lake or body of water in which wastes are consumed by bacteria. It is used most frequently with other waste treatment processes. An oxidation pond is basically the same as a sewage lagoon.

OXIDATION REDUCTION POTENTIAL (ORP) CONTROLLER An instrument that measures the concentration of an oxidizing agent in solution. The readings and results are provided in millivolts (mv).

OXIDATIVE PHOSPHORYLATION The conversion of adenosine diphosphate to adenosine triphosphate in the process of respiration.

OXIDE Reaction product of oxygen with a metal.

OXIDE FILM A thin film formed by the reaction product of oxygen with a metal and deposited on the metal surface.

OXIDIZER A chemical substance or mixture that initiates or promotes combustion in other materials, thereby causing fire either of itself or through the release of oxygen or other gases.

OXIDIZING AGENT A chemical or substance which brings about an oxidation reaction. The agent may provide the oxygen to the substance being oxidized in which case the agent has oxygen or contains oxygen), or it may receive electrons being transferred from the substance undergoing oxidation (chlorine is a good oxidizing agent for electron-transfer purposes, even though it contains no oxygen).

OXIDIZING BIOCIDE A biocide that is able to accept electrons from other chemical compounds.

OXYGEN A gaseous material that is very reactive with most common metals when dissolved in water contacting these metals. In cooling waters, air is the source of the dissolved oxygen.

P

PACKAGED BOILER A boiler designed, manufactured, assembled and tested prior to shipment.

PACKING The structural system that keeps the water evenly distributed as it falls through he tower.

PACKING -Numerous small, irregular shaped objects packed in a degasifier vessel that serve to break up the incoming water into a thin film, increasing the surface area for maximum efficiency. (Also see Filling)

PART PER BILLION (ppb) A measure of proportion by weight, equivalent to a unit weight of solute per billion (10⁹) unit weights of solution. Note: A part per billion is generally considered equivalent to one millionth of a gram per liter, but this is not precise. A part per billion is equivalent to a milligram of solute per one thousand kilograms of solution.

PART PER MILLION (ppm)) A measure of proportion by weight and equivalent to a unit weight of solute per million unit weights of solution. Note: A part per million is generally considered equivalent to a milligram per liter, but this is not precise. A part per million is equivalent to a milligram of solute per kilogram of solution.

PARTICULATE MATTER That matter, exclusive of gases, existing in the nonliquid state which is dispersed in water to give a heterogeneous mixture

PARTITION Am interior wall subdividing the tower into cells or into separate fan plenum areas.

PARTS PER MILLION (ppm) A measure of proportion by weight of a compound or ions to the weight of solution. An expression of concentration.

PASSIVATION Corrosive action considered relative to the thickness or wall of a metal surface in contact with a solution. Attack in-depth.

PASTURIZE A heating process that destroys bacteria in a liquid, not to be confused with sterilization or disinfection.

PASTEURIZATION A process for killing pathogenic organisms by heat applied for a critical period of time.

PATHOGENS Disease-producing microbes.

PE Polyethylene plastics, usually semi-opaque and resistant to most water treatment chemicals. Low Density Polyethylene is most flexible and generally used as chemical pump tubing. High Density Polyethylene has higher structural strength and is the choice for totes and bulk tanks.

PEARLITE Grain of alternating platelets of ferrite and cementite that appears as the darker area in a normal, etched, low carbon steel microstructure. This is the normal carbide microstructure that imparts strength to most mild steel.

PEDESTALS (Natural Draft Tower) Used as a transition from the cross struts to the foundation.

PEL Permissible Exposure Limit (established by OSHA). The concentration of a chemical in the breathing air that it is believed nearly all workers may be exposed to repeatedly, day after day, without adverse effect.

PENETRANT Chemicals used to reduce the surface tension of water, allowing the water to penetrate previously impervious deposits.

PENETRATION Corrosive action considered relative to the thickness or wall of a metal surface in contact with a solution. Attack in depth.

PERCENT CONCENTRATION BY WEIGHT The weight of a solute as a percentage of the total weight of the solution.

PERCENT Units of hazardous ingredient per 100 units of product, expressed in weight on MSDS’s

PERCENT VOLATILE Percent volatile by volume; the percent of a liquid or solid (by volume) that will evaporate at an ambient temperature of 70° F (21° C). (Unless some other temperature is stated.) Examples: butane, gasoline, and paint thinner (mineral spirits) are 100 percent volatile; their individual evaporation rates vary, but over a period of time each will evaporate completely.

PERFORATION Corrosive action that is completed through the thickness dimension or wall of a metal surface.

PERFORMANCE CHARACTERISTIC, KAV/L Relative efficiency factor for a given L/G ratio, volume, and cross section of a cooling tower, related to the design heat transfer capability of the fill, expressed by the formula KAV/L where "K" equals the coefficient of mass transfer in pounds per hour per square foot which is a unit of humidity potential. "A" equals total interfaced area per unit packed volume of tower in foot squared per foot cubed. "V" equals packed tower volume foot cubed per foot squared. "L" equals mass velocity of liquid in pounds per hour per foot squared of tower cross section. Liquid/Gas ratio relationship of water to air volume and water volume. This is a valuable tool to rate the performance of a tower for heat transfer characteristics of a specific type of fill referred to as L/G or L over G.

PERFORMANCE CURVES Performance of a cooling tower is rated in terms of water temperatures, approach, wet bulb temperature, range static pressure, and air movement. The ratio of a cooling tower is established by developing a series of charts that relate to these variables.

PERIODIC CHART An arrangement of the elements in order of increasing atomic numbers, in a way to illustrate the repetition (or periodicity) of key characteristics.

PERMANENT HARDNESS Permanent hardness is caused by neutral salts of calcium and magnesium that include chlorides, sulfates, nitrates and fluorides. Permanent hardness is also known as non-carbonate or non-alkaline hardness.

PERMEABILITY The ability of a body to pass a fluid under pressure.

PETRI DISH A round glass or plastic dish with cover, 3.5" in diameter and 0.5" in depth, used to grow cultures of bacteria. Proper nutrients are placed in the dish and incubated for a specific time period under specific temperature, pressure, gas and light conditions to promote growth of target organism.

pH The pH value indicates the relative intensity of acidity or alkalinity of water, with the neutral point at 7.0. Values lower than 7.0 indicate the presence of acids; above 7.0 the presence of alkalies.

pH of Saturation The pH at which a water will be saturated with precipitable material under certain controlling responsible conditions. Useful in predicting scaling potential of a water.

pH OF WATER The measure of purity, acidity, or alkalinity of water. 7.0 is arbitrarily selected as the neutral area where both the hydrogen and hydroxyl ions are present in exactly the same proportions so that the water is neutral. Lower than 7.0 is acid, higher is alkaline on a scale of 0 to 14.

pH VALUE A number of denoting the alkaline or acid nature of water. A number below 7.0 indicates acidity. Numbers above 7.0 indicates alkalinity. The pH scale runs from 0 to 40, 7.0 being the neutral point.

PHAGOCYTE See White Blood Cell.

PHASE physically homogeneous portion of a material system.

PHASE DIAGRAM Graphical representation of the equilibrium temperature and the composition limits of phase fields and phase reactions in an alloy system.

PHENOLPHTHALEIN A titrimetric indicator used in the determination of carbonate and hydrate forms of alkalinity. Color change occurs at pH 8.3 to red when alkaline.

PHOSPHONATE An organic phosphorus compound.

PHOTOMETRIC Refers to a method for determining concentration of certain materials in water by measuring the intensity of light or degree of light absorption of a beam passed through a prepared sample.

PHOTOMICROGRAPH Photographic reproduction of an object magnified more than ten times.

PHOTOSYNTHESIS The process of converting carbon dioxide and water to carbohydrates, activated by sunlight in the presence of chlorophyll, liberating oxygen.

PHYLUM A main category of taxonomic classification into which the plant and animal kingdoms are divided.

PHYSICAL HAZARD A chemical is considered to present a physical hazard if it falls within the OSHA guidelines of what constitutes a physical hazard.

PHYSICAL STABILITY The quality which an ion exchange resin must possess to resist changes that might be caused by attrition, high temperatures, and other physical conditions.

PICKLE LIQUOR Acid used in treating steel for removal of oxide scale.

PIER In a wood tower an interior column support used to elevate column footings above the basic floor or foundation grade. Also known as Internal Pier.

PILASTER An exterior column support, usually an integral part of the basin wall. Also known as Internal Pier.

PISTON PUMP A reciprocating type, positive displacement pump using check valves and a sealed plunger to draw in and expel liquids. Used to meter chemical solutions against high pressures.

PITCH ANGLE Fan blade angle measured between the horizontal and upper side of the fan blade from leading edge to trailing edge. (discharge side)

PITCHING FAN BLADES Angle of attack on fan blades of most modern cooling towers is adjustable. A bubble is initially set at the manufacturers recommended pitch angle at a designated place on each blade; the blade is turned to the angle and locked in place. This is done for all blades and the fan is rotated while the amperage is checked. Additional air volume or less air volume may be generated by the fans depending upon the pitch of the blade. It is important to know that the amperage of the system should remain approximately 10% below the motor plate.

PITOT TUBE An instrument that operates on the principle of differential pressures. The primary use on cooling towers is the measurement of circulating water rate.

PITS Corrosion of a metal surface confined to a point or a very small area. Attack progresses in-depth rather than laterally.

PITTING Corrosive action that produces pits

pK An expression of the extent of dissociation of an electrolyte; the negative logarithm of the ionization constant of a compound.

PLAN AREA The cross section of the working area of the tower, measured in feet of length and width.

PLANKTON Small organisms with limited powers of locomotion, carried by water currents from place to place.

PLANCTONIC Free swimming mircobials, much like plankton in the sea.

PLASTIC DEFORMATION Permanent distortion of a material due to imparted stress.

PLC Programmable Logic Controller.

PLENUM The enclosed space between the drift eliminators and the fan stack in induced draft towers, or the enclosed space between the fan and the fill in forced draft towers.

PLUME The cloud formed over a cooling tower as a result of the atmospheric condensation of evaporated water in the warm exhaust air as it contacts cooler, ambient air.

PMCC Pensky-Martens Closed Cup; a flash point test method.

Pneumonia An illness caused by S. pneumococcus, a common parasite of the human respiratory system and an opportunistic pathogen, striking when conditions are favorable.

pOH An expression of the alkalinity of a solution; the negative logarithm of the hydroxyl ion concentration.

POISON A chemical substance or mixture that causes a high level of acute toxicity. Legally, a chemical with an oral LD₅₀ of 50 mg/kg or less.

POLARIZATION The action of a counter-emf produced by products or concentrations resulting from a passage of a current between the electrodes of an electrolytic cell.

POLARIZE In corrosion, to develop a barrier on the anodic or cathodic surface, disrupting the corrosion process.

POLISHING Final treatment stage before discharge of effluent to a water course, carried out in a shallow, aerobic lagoon or pond, mainly to remove fine suspended solids that settle very slowly. Some aerobic microbiological activity also occurs.

POLLUTANT A contaminant at a concentration high enough to endanger the aquatic environment or the public health.

POLYACRYLAMIDES Synthetic organic polymers used in boilers for sludge conditioning.

POLYELECTROLYTE A polymeric material having ion exchange sites on its skeleton.

POLYMER A chain of organic molecules produced by the joining of primary units called monomers.

POLYMER DISPERSANT Polyelectrolytes having molecular weights ranging from 1,000 or 10,000. Low molecular weights make them incapable of flocculation, but do allow for impartation of ionic charges making them effective as dispersing or fluidizing agents for boiler or cooling water suspended solids.

POLYMER DOSAGE The amount of polymer used in a given water treatment.

POLYMER FLOCCULANT Long-chain polymeric electrolytes having molecular weights typically greater than 1 million. High molecular weights make them particularly effective in flocculation of coagulated particles by forming molecular bridges.

POLYMERIZATION Process whereby single polymer units bond together into a chain or repeating units.

POLYPHOSPHATE Molecularly dehydrated forms of phosphate.

POLYSACCHARIDE EXOPOLYMER Gelatinous polymeric material secreted by bacteria as a protective mechanism.

POND In a cooling pond heat is dissipated from the surface of a body of water by evaporation, radiation and convection. A spray pond was the original heat transfer cooling device. An improvement was the addition of an aeration spray extending the water surface by bringing it in contact with the air. The weaknesses of the cooling ponds are their dependence on the unpredictable prevailing winds, and excessive area of real estate required.

PONDING A waste treatment technique involving the actual holdup of all wastewaters in a confined space with evaporation and percolation the primary mechanisms operating to dispose of the water.

PONTIAC FEVER A mild, non-pneumonic, non-fatal illness, from which most people recover in two to three days. It is thought to be a Legionella-related illness.

POROSITY An expression of the degree of permeability in ion exchange resins to liquids and large organic molecules. Gel resins, even when referred to a highly porous, have a negligible porosity in comparison to the macropores inherent in the macroreticular resins.

POROSITY Voids in cast metals or welds resulting in unsoundnesss.

PORT A connection between a computer data bus and a peripheral device or communications line.

POSITIVE CHARGE The electrical potential acquired by an atom which has lost one or more electrons, a characteristic of a cation.

POSITIVE DISPLACEMENT PUMP The pumping action displaces a specific volume of liquid with each revolution or stroke, thus providing a constant feed rate.

POTABLE WATER Water that is suitable for drinking by humans.

POTENTIAL The electromotive force developed between a metal in an electrodes of an electrochemical cell.

POTENTIAL DIFFERENCE Difference in electromotive force between electrodes of an electrochemical cell.

POUNDS PER SQUARE INCH ABSOLUTE (PSIA) Absolute pressure in the gauge pressure (psig) plus 14.7 (atmospheric pressure).

POUND/net A net laid perpendicularly out from the shoreline with a circular impoundment at the seaward end.

POWER Time rate at which work is done or energy emitted; source or means of supplying energy.

POWER FACTOR The power factor is a measure of the inefficiency of running an induction electric motor.

POWER ELEMENT Sensitive element of a temperature operated control.

PP Polypropylene plastic. Resistant to most water treatment chemicals.

PPB Parts per Billion. In reference of PEL to TLV, this represents the parts of vapor or gas present in each billion parts of air by volume. 1 ppb is equivalent to 2 seconds in an average lifetime, or 15 inches on the way to the moon (approximately 250,000 miles from earth).

PPM Parts per million, also referred to as milligrams per liter (mg/1). This is a unit for expressing the concentration of any substance by weight, usually as grams of substance per million grams of solution. Since a liter of water weights one kilogram at a specific gravity of 1.0, one part per million is equivalent to one milligram per liter.

PRECIPITATE An insoluble reaction product of an aqueous chemical reaction, usually a crystalline compound that grows in size to become settleable.

PRECIPITATION The act of formation of insoluble salts from a solution.

PREDICTIVE INDICATIONS Chemical dosages determined by raw water analysis.

PRESSURE The normal force exerted by a homogeneous liquid or gas, per unit of area, on the wall of its container.

PRESSURE DROP Static pressure or amount of resistance of air movement through the tower caused by obstructions such as air louver inlets, fill configuration, tower supports, spray system piping, drift eliminators, static and mechanical equipment components, fan cylinder resistance and construction.

PRESSURE DROP The pressure difference at two ends of a circuit, the two sides of a filter, or the pressure difference between the high side and the low side in a refrigerator mechanism.

PRESSURE FILTRATION A mechanical process in which solid wastes are forced from a sludge by mechanical pressure.

PRESSURE REGULATOR, EVAPORATOR An automatic pressure regulating valve. Mounted in suction line between evaporator outlet and compressor inlet, its purpose is to maintain a predetermined pressure and temperature in the evaporator.

PRESSURE STAGING The process of limiting steam pressure drop at a single set of nozzles.

PRESSURE, ABSOLUTE Pressure referred to that of a perfect vacuum. It is the sum of gauge pressure and atmospheric pressure.

PRESSURE, ATMOSPHERIC The pressure due to the weight of the atmosphere. It is pressure indicated by a barometer. Standard Atmospheric Pressure or Standard Atmosphere is the pressure of 76 cm of mercury having a density of 13.5951 grams per cu cm, under standard gravity of 980.665 cm per (sec) (sec). It is equivalent to 14.696 psi or 29.921 in. of mercury at 32F.

PRESSURE, DISCHARGE (Head) Operating pressure measured in the discharge line at a compressor outlet.

PRESSURE, OPERATING The pressure that would be indicated by a gauge in the part of the system involved when the system is in normal operation.

PRESSURE, SAFE WORKING The maximum allowable working pressure for which a specific part of a system is designed.

PRESSURE, SATURATION The saturation pressure for a pure substance for any given temperature is that pressure which vapor and liquid, or vapor and solid, can coexist in stable equilibrium.

PRESSURE, STATIC The normal force per unit area that would be exerted by a moving fluid on a small body immersed in it if the body were carried along with the fluid. Practically, it is the normal force per unit area at a small hole in a wall of the duct through which the fluid flows (pieometer) or on the surface of a stationary tube at a point where the disturbances, created by inserting the tube, cancel. It is supposed that the thermodynamic properties of a moving fluid depend on static pressure in exactly the same manner as those of the same fluid at rest depend upon its uniform hydrostatic pressure.

PRESSURE, SUCTION (Back) Operating pressure measured in the suction line at a compressor inlet.

PRESSURE, TOTAL In the theory of the flow of fluids, the sum of the static pressure and the velocity pressure at the point of measurement. Also called dynamic pressure.

PRESSURE, VAPOR The pressure exerted by a vapor. If a vapor is kept in confinement over its liquid so that the vapor can accumulate above the liquid, the temperature being held constant, the vapor pressure approaches a fixed limit called the maximum, or saturated, vapor pressure, dependent only on the temperature and the liquid. The term vapor pressure is sometimes used as synonymous with saturated vapor pressure.

PRESSURE-LIMITING DEVICE A pressure-responsive mechanism designed to stop automatically the operation of the pressure imposing element at a predetermined pressure.

PRETREATMENT Term applied to define mechanical or chemical treatment of water prior to its end use.

PRIMARY AIR In boilers, the air used to provide oxygen for the initial combustion.

PRIMARY COAGULANT A chemical used to neutralize the charge of suspended particles and cause them to coagulate into microfloc.

PRIMARY SLUDGE A sludge containing large, coarse solids that dewater well.

PRIMARY TREATMENT Removes the material that floats or will settle in sewage. It is accomplished by using screens to catch the floating objects and tanks for the heavy matter to settle in.
Process of heating and cooling (usually prolonged mild overheating) that produces a rounded or globular form of carbide in steel. During boiler tube overheating, this process weakens tube, causing failure.

PRIMARY WATER QUALITY STANDARDS Specific finished-water requirements for a given clarifier operation.

PRIMING A form of chemical carryover where a slug of foam or water enters and deposits in superheaters.

PROCESS THROUGHPUT The rate at which a liquid/solid mixture is processed.

PROCESS VARIABLE CONTROL Chemical feed is based on process instrument readings reaching predetermined endpoints.

PROCESS WATER All water that comes into direct contact with the raw materials, intermediate products, final products, by-products, or contaminated waters and air.

PROGRESSIVE CAVITY PUMP Interaction between a helical rotor and a reverse, double helical stator causes progressive movement of the fluid through the pump.

PROFILING The strategy of testing all compontents of a system in order to determine the condition of that system.

PROPORTIONAL CONTROL Chemical feed pump output is increased or decreased in response to changes in a process variable.

PROPORTIONAL FEED The addition of chemicals to a water system in an amount proportionate to the make-up.

PROPORTIONAL OUTPUT A type of signal output that maintains a ratio or comparative relationship between input and output it is tracking, for example:
1. Flow Proportional - A metering device (contacting head water meter) or paddle wheel flow sensor that paces a pump on a timed or pulse basis.
2. 4-20 mA Output - A modulating milliamp input is followed with a milliamp output. Generally zero (offset) and span (gain) adjustments are desirable.

PROTOCOL A set of specifications which defines the hardware and software interface requirements for a particular type of communications.

PROTOZOA Large, microscopic single-cell organisms higher on the food chain than bacteria, which they consume.

PSI A symbol or initials used to indicate pressure measured in pounds per square inch.

PSIA A symbol or initials used to indicate pressure measured in pounds per square inch absolute. Absolute pressure equals gauge pressure plus atmospheric pressure.

PSIG A symbol or initials used to indicate pressure in pounds per square inch gauge. The "g" indicates that it is gauge pressure and not absolute pressure.

PSYCHROMETER An instrument used primarily to measure the wet bulb temperatures. Either a sling or a mechanically aspirated type of psychrometer is acceptable provided the instrument is properly shielded from radiation and the air across the wick is limited to approximately 1,000 ft./min.

PSYCHROMETRIC CHART A chart that shows relationship between the temperature pressure and moisture content of the air.

PULL DOWN An expression indicating action of removing refrigerant from all or a part of a refrigerating system.

PULP Fibrous matter.

PUMP DOWN The operation by which the refrigerant in a charged system is pumped into the liquid receiver.

PUMPING HEAD Energy required to raise the water to the distribution elevation and overcome friction losses through pipe, valves, fittings and nozzles. It is expressed in feet of liquid the pump must move and equals the totals of friction loss, static head, plus pressure drop through the distribution system.

PUNKY That condition in which the wood retains most of its original shape, but has lost most of its strength. Although the wood is soft and spongy to the touch when wet it may be friable, when dry. Punky wood may result from the action of microorganisms, physical agents (heat), chemical agents and/or any combination of biological, physical and chemical agents.

PURGE Removing the concentrated impurities from evaporation or discharging water from the system to prevent precipitation of solids. (Blowdown).

PURGING The act of blowing out gas from a refrigerant-containing vessel, usually for the purpose of removing noncondensables.

PVC Polyvinyl chloride.

PYROMETER An instrument used for measuring high temperature.

PYROPHORIC MATERIAL A chemical substance that will ignite spontaneously at or below 130° F.

Q

QUATERNARY AMMONIUM A specific basic group (-N(CH₃)₄ ⁺ ) on which depends the exchange activity of certain anion exchange resins.

QUENCH HARDENING Hardening of a ferrous alloy of suitable composition by heating within or above the critical range, and cooling at a rate sufficient to increase the hardness substantially. The process usually involves the formation of martensite.

QUIESCENT FLOW A stilling of the water in the clarifier. This stilling enables the particulate matter to settle.

QWAT A -cide preparation containing quaternary ammonium compounds used to minimize affect of total bacterial population in system on heat exchange efficiency.

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