A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Acceleration
The time rate change of velocity, typically expressed in units of inches per second per second (in/sec squared), or g's (percentage of acceleration due to earth's gravity, 386.4 in/sec squared). In seismic applications, multiply this value by a unit's mass (or weight, when using g's), to obtain an applied force.
Active Fault
Faults that are constantly moving, producing stresses that can give rise to earthquakes.
Aerosol
An assemblage of small particles, solid or liquid, suspended in air. The diameter of the particles may vary from 100 microns down to 0.01 micron or less, e.g., dust, fog, smoke.
Air Cleaner
A device designed for the purpose of removing atmospheric airborne impurities such as dusts, gases, mists, vapors, fumes, and smoke. (Air cleaners include air washers, air filters, electrostatic precipitators, and charcoal filters.)
Air Filter
An air cleaning device to remove light particulate loadings from normal atmospheric air before introduction into the building. Usual range: loadings up to 3 grains per thousand cubic feet (0.003 grains per cubic foot). Note: Atmospheric air in heavy industrial areas and in-plant air in many industries have higher loadings than this, and dust collectors are then indicated for proper air handling.
Air Horsepower
The theoretical horsepower required to drive a fan if there were no losses in the fan; that is, if its efficiency were 100 percent.
AISC
American Institute of Steel Construction, Inc. Publishers of the Manual of Steel Construction.
Allowable Force or Load
The working or required load of a material or component with built-in safety factors dependent upon the material or component application.
Allowable Stress Design (ASD)
Design practice within a defined allowable or working stress. For steel, this would be an appropriate factor of the yield stress.
Amplification
The increase of an output amplitude proportional to the input amplitude. Amplitude is typically acceleration, velocity, force, or displacement in a dynamic mechanical system. Also characterized by a transmissibility greater than 1.0 and associated with a resonance condition.
Aspect Ratio of an Elbow
The width (W) along the axis of the bed divided by the depth (D) in the plane of the bend; AR = W/D
Attenuation
The decrease of an output amplitude proportional to the input amplitude. Also characterized by a transmissibility less than 1.0. Sometimes referred to as isolation.
Axial Fan
Fans that have blades that force air to move parallel to the shaft about which the blades rotate. This type of fan is used in a wide variety of applications, ranging from small cooling fans for electronics to the giant fans used in wind tunnels.
Baffle Chamber
This filtration chamber, often used as a prefilter system, directs the air or gas flow with a sudden change in direction that large particles are not able to follow. Instead large particles filter out to a dead space and settle.
Bending Moment
The result of a load applied on an axis parallel to and in the center of a support member.
Blow (Throw)
In air distribution, the distance an air stream travels from an outlet to a position at which air motion along the axis reduces to a velocity of 50 fpm. For unit heaters, the distance an air stream travels from a heater without a perceptible rise due to temperature difference and loss of velocity.
Bounding Spectrum
The maximum response that can be accepted by a piece of equipment as a result of an applied shock without loss of operation.
Brake Horsepower
The horsepower actually required to drive a fan. This includes the energy losses in the fan and can be determined only by actual test of the fan. (This does not include the drive losses between motor and fan).
Cable Brace
A steel cable designed for tension loads for use as a seismic sway brace for suspended equipment, piping, or ductwork.
Capture Velocity
The air velocity at any point in front of the hood or at the hood opening necessary to overcome opposing air currents and capture the contaminated air at that point by causing it to flow into the hood.
Cast-In-Place Anchor
A headed steel bolt or equal deformation set within a concrete form before pouring is completed for use of anchoring equipment or anchor plates.
Center of Gravity
The point of support at which a body would be in balance. Also known as center of mass and inertial center.
Center of Gravity
The point within a piece of equipment or component about which it will balance.
Centrifugal Collector
These collectors use cyclonic action to filter contaminants from a gas stream. In a common cyclonic collector, gas enters and is spun rapidly in a circular motion. This rapid cyclonic action typically throws any contaminants to the walls of the cyclone, which then fall to a collection bin located underneath.
Centrifugal Fan
A fan that has a moving component (called an impeller) that consists of a central shaft about which a set of blades, or ribs, are positioned. These fans blow air at right angles to the intake of the fan, and spin the air outwards to the outlet (by deflection and centrifugal force). The impeller rotates, causing air to enter the fan near the shaft and move perpendicularly from the shaft to the opening in the scroll-shaped fan casing. These fans traditionally produce more pressure for given air volume, and are used where this is desirable. They are typically noisier than comparable axial fans.
Chemical Anchor
An anchor designed to bond directly to concrete within a predrilled hole using a chemical compound.
Coefficient of Entry
The actual rate of flow caused by a given hood static pressure compared to the theoretical flow which would result if the static pressure could be converted to velocity pressure with 100 percent efficiency. It is the ratio of actual to theoretical flow.
Comfort Zone (Average)
The range of effective temperatures over which the majority (50% or more) of adults feel comfortable.
Compression
The act of applying a load to an object to shorten its length. Conversely, a compression load.
Compressive Force or Load
An axial force that produces a uniform compression of a material perpendicular to its cross section.
Convection
The motion resulting in a fluid from the differences in density and the action of gravity. In heat transmission this meaning has been extended to include both forced and natural motion or circulation.
Cubic Feet Per Minute (CFM)
A non-SI unit of measurement of the flow of a gas or liquid that indicates how much volume in cubic feet pass by a stationary point in one minute. The higher the CFM, the better the suction.
Density
The ratio of the mass of a specimen of a substance to the volume of the specimen. The mass of a unit volume of a substance. When weight can be used without confusion, as synonymous with mass, density is the weight of a unit volume of a substance.
Density Factor
The ratio of actual air density to density of standard air. The product of the density factor and the density of standard air (0.3075 lb/ft^3) will give the actual air density in the pounds per cubic food; Density = df X 0.075lb/ft^3 (the density of standard air).
Design Strength
A material’s ultimate loading capability with appropriate reduction factors for specific applications (e.g. earthquake loads, gravity loads, live loads, etc.)
DSA
Department of the State Architect in California. Reviews all public schools in California for compliance with state adopted codes.
Ductile Connection
A connection point between two ductile materials that behaves similarly to a ductile material.
Ductile Material
A material that will undergo large deflections under load before failure.
Dust
Small solid particles created by the breaking up of larger particles by processes, i.e., crushing, grinding, drilling, explosions, etc. Dust particles already in existence in a mixture of materials may escape into the air through such operations as shoveling, conveying, screening, sweeping, etc.
Dust Collector
An air cleaning device to remove heavy particulate loadings from exhaust systems. Usual range of particulate loading: 0.003 grains per cubic foot or higher. These systems consists of blowers, dust filters, a filter cleaning system, and a dust deposit or removal system.
Five Basic Types Are:
- Inertial Separators
- Fabric Filters
- Wet Scrubbers
- Electrostatic Precipitators
- Unit Collectors
Elastomeric
A material with flexibility in all directions that will recover to its original form if removed from its environment when deformed due to its environment.
Expansion Anchor
A post-installed concrete anchor that uses some form of expansion of a wedge or its shell against the drilled hole in the concrete. Tensile forces are resisted by friction. This is not true in the case of an undercut anchor where tensile forces are resisted by mechanical means of a flared bottom.
Flexible Connector
A connector designed with an appropriate amount of flexibility between a piece of equipment, component, or system and another system to achieve the desired amount of separation.
Flexible Equipment
A piece of equipment constructed so that it deforms more under load than that to which it is attached.
Flexibly Mounted Equipment
A piece of equipment supported on or from a vibration isolator.
Focus
Location deep inside the earth along the fault where the slip occurs and out of which the P and S waves emanate.
Fragility
The maximum shock in Gs that a piece of equipment can take without suffering sufficient damage to render it inoperable.
Gases
Formless fluids which tend to occupy an entire space uniformly at ordinary temperatures and pressures.
Gravity Load
The vertical load due to a component’s or system’s weight due to gravity.
Groove-Fitted Joint
A mechanical connection between two pipe sections using a tongue-and-groove concept.
Hood
A shaped inlet designed to capture contaminated air and conduct it into the exhaust duct system.
Housekeeping Pads
Concrete pad that is used under equipment to raise it off the structural slab. Also called plinths, or plinths, in many countries.
Humidity, Absolute
The weight of water vapor per unit volume, pounds per cubic food or grams per cubic centimeter.
Humidity, Relative
The ratio of the actual partial pressure of the water vapor in a space to the saturation pressure of pure water at the same temperature.
IBC
The International Building Code due to be published in the year 2000, representing the three model building codes in the United States-The building Officials Code Administration (BOCA), the Southern Building Code Congress International (SBCCI), and the Uniform Building Code (UBC).
ICBO
The International Conference of Building Officials, publishers of the Uniform Building Code and the ICBOES Evaluation Service, evaluation reports for building materials.
Inch of Water
A unit of pressure equal to the pressure exerted by a column of liquid water one inch high at a standard temperature.
Inertial Separator Dust Collector
These separate dust from gas streams using a combination of forces, such as centrifugal, gravitational, and inertial. These forces move the dust to an area where the forces exerted by the gas stream are minimal. The separated dust is moved by gravity into a hopper, where it is temporarily stored.
Limit Stop
A design feature within a vibration isolator that limits upward motion due to earthquake loads or reduction of gravity loads.
Longitudinal Brace
Brace that restrains pipes or ducts parallel to the longitudinal direction.
Love Wave
Horizontal surface wave that mimics an S wave and moves residential buildings off their foundations.
Lower Explosive Limit
The lower limit of flammability or explosibility of a gas or vapor at ordinary ambient temperatures expressed in percent of the gas or vapor in air by volume. This limit is assumed constant for temperatures up to 250 F. Above these temperatures, it should be decreased by a factor of 0.7 since explosibility increases with higher temperatures.
Manometer
An instrument for measuring pressure; essentially a U-tube partially filled with a liquid, usually water, mercury or a light oil, so constructed that the amount of displacement of the liquid indicates the pressure being exerted on the instrument.
Maximum Unbraced Rod Length
The maximum length a threaded vertical support rod can be and accept a defined compressive force without buckling.
Mechanical Fan
An electrically powered device used to produce airflow for the purpose of creating comfort, ventilation, exhaust, cooling, or any other gaseous movement.
Micron
A unit of length, the thousandth part of 1 mm or the millionth of a meter (approximately 1/25,000 of an inch).
Minimum Design Duct Velocity
Minimum air velocity required to move the particulates in the air stream (fpm).
Mists
Small droplets of materials that are ordinarily liquid at normal temperature and pressure.
Modified Mercalli Intensity Scale
System to determine the strength of an earthquake. Verbal accounts and visual inspection using 12 values for damage.
Moment Magnitude
Based on the geometry of the fault plane after the seismic event; more accurate than the Richter magnitude, but takes weeks if not months to determine.
National Design Specification for Wood Construction
Complete design manual for all types of wood and wood products used in buildings.
No-Hub Pipe
Piping with connections that do not interlock or permanently join, such as shield and clamp assemblies for cast iron drainage pipe.
Normal Fault
Vertical displacement where one side slides down away from the other side.
OSHA
Occupational Safety and Health Administration is an agency of the United States Department of Labor. Their mission is to prevent work-related injuries, illnesses, and deaths. Since the agency was created in 1971, occupational deaths have been cut by 62% and injuries have declined by 42%.
OSHPD
Office of Statewide Health Planning and Development in the state of California; Reviews all hospital projects for compliance with state codes.
P Waves
Moment waves with zones of compression and elongation that emanate from the focus of the earthquake. These waves can be refracted as they encounter different strata. Also known as primary waves.
Pressure, Static
The potential pressure exerted in all directions by a fluid at rest. For a fluid motion, it is measured in a direction normal to the direction of flow. Usually expressed in inches water gauge when dealing with air. (The tendency to either burst or collapse the pipe.)
Pressure, Total
The algebraic sum of the velocity pressure and the static pressure (with due regard to sign).
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, Velocity
The kinetic pressure in the direction of flow necessary to cause a fluid at rest to flow at a given velocity. Usually expressed in inches water gauge.
Prestretched Cables
Cable that has been stretched after manufacturing to reduce the constructional stretch that is inherent from winding and can provide certified modulus of elasticity.
Radiation Thermal (Heat)
The transmission of energy by means of electromagnetic waves of very long wave length. Radiant energy of any wave length may, when absorbed, become thermal energy and result in an increase in the temperature of the absorbing body.
Rayleigh Wave
An elliptically rolling wave in the direction of travel with both horizontal and vertical movement.
Replacement Air
A ventilation term used to indicate the volume of controlled outdoor air supplied to a building to replace air being exhausted.
Response Spectrum
The maximum response (in acceleration, velocity, or displacement) experienced by a single degree-of-freedom system, as a function of its natural frequency, in response to shock.
Restoring Force
A force that can be used in seismic design to restore the loading conditions to their original condition (e.g., gravity loads).
Resultant Force or Load
The addition of all forces in the x, y, and z directions, resulting in one single force in a specific direction.
Richter Magnitude
Based on seismographs, the time delay between the P and S waves is plotted against the maximum amplitude of the S waves and a straight line drawn between them on special graph paper that has the Richter magnitude line also plotted on it. Where it crosses this line is the Richter magnitude. It is available immediately after the seismic event and is, therefore, quoted by the media. It is also used to pinpoint the focus.
Rigid Equipment
A piece of equipment constructed so that it does not deform under load relative to that to which it is attached.
Rigid Mounted Systems
Systems that are either solidly braced or bolted directly to structure without vibration isolators.
S Waves
Vertical and horizontal movement waves that emanate from the focus and can be reflected as they encounter different strata. They do the most damage and are also known as secondary waves.
Seismic Capacity
The rated or allowable load of a prescribed restraint to accept seismic loads. For seismic sway brace systems, this could be in the form of a length of pipe or duct (e.g., the seismic capacity of the sway brace is 50 ft of 8 in. diameter pipe).
Seismic Joint
A section of pipe routed from one building to another and designed to accept a predicted amount of differential motion between the two buildings.
Settling Chamber
This chamber consists of a large box installed throughout ductwork. The sudden expansion of the ductwork allows for the airstream to slow down, which in turn filters out heavier particles.
Shallow Concrete Anchor
From the 1997 Uniform Building Code (UBC) and the 2000 International Building Code (IBC), any cast-in-place, chemical or expansion anchor with an embedment length-to-diameter ratio less than 8.
Smoke
An air suspension (aerosol) of particles, usually but not necessarily solid, often originating in a solid nucleus, formed from combustion or sublimation.
Snubber
A device used to increase the stiffness of an elastic system whenever the displacement exceeds the design value; a seismic restraint used on isolated systems with an air gap and neoprene cushioning.
Solid Brace
A steel angle or strut channel designed for tension and compression loads for use as a seismic sway brace for suspended brace for suspended equipment, piping, or ductwork.
Specific Gravity
The ratio of the mass of a unit volume of a substance to the mass of the same volume of a standard substance at a standard temperature. Water at 39.2 F is the standard substance usually referred to. For gasses, dry air, at the same temperature and pressure as the gas, is often taken as the standard substance.
Standard Air
Dry air at 70 F and 29.92 (in Hg) barometer. This is substantially equivalent to 0.075 lb/ft^3. Specific heat of dry air = 0.24 BTU/lb/F.
Stiffness
The ratio of the change in force to the change in displacement in an elastic element.
Supplemental Support Frame
A separate steel frame to support equipment designed for both gravity and seismic loads.
Sway Bracing
Generic term for systems that seismically restrain mechanical, fire protection, or electrical systems. There are two types of sway bracing: one is solid bracing using steel members such as angles or pipes, and the second is cable bracing using aircraft cable.
Tectonic Earthquake
The most common type of earthquake; caused by the shifting or sliding of tectonic plate edges past each other.
Tectonic Plates
The outermost layer of rock that covers the entire surface of the earth.
Temperature, Effective
An arbitrary index which combines into a single value the effect of temperature, humidity, and air movement on the sensation of warmth or cold felt by the human body. The numerical value is that of the temperature of still, saturated air which would induce an identical sensation.
Temperature, Wet-Bulb
Thermodynamic wet-bulb temperature is the temperature at which liquid or solid water, by evaporating into air, can bring the air to saturation adiabatically at the same temperature. Wet-bulb temperature (without qualification) is the temperature indicated by a wet-bulb psychrometer constructed and used according to specifications.
Tensile Force or Load
An axial force that produces a uniform stretching of a material perpendicular to its cross section.
Threshold Limit Values (TLVs)
The values for airborne toxic materials which are to be used as guides in the control of health hazards and represent time-weighted concentrations to which nearly all workers may be exposed 8 hours per day over extended periods of time without adverse effects.
Transcurrent Fault
Predominately horizontal slippage defined as either left-lateral or right-lateral movement. For example, if you are standing on one side of a fault and the movement on the other side is from the right to left, it is a left-lateral fault. Also known as a strike-slip fault.
Transverse Brace
Brace that restrains pipes or ducts perpendicular to the longitudinal direction.
Turn-Down Ratio
The degree to which the operating performance of a system can be reduced to satisfy part-load conditions. Usually expressed as a ratio; for example, 30:1 means the minimum operation point is 1/30th of full load.
Twisting Moment
The result of a load applied in an axis perpendicular to and off center from a support member.
Vapor
The gaseous form of substances that are normally in the solid or liquid state and that can be changed to those states either by increasing the pressure or decreasing the temperature.
Variable Pitch Fan
Fans that are used where precise control of static pressure within supply ducts is required. The fan wheel will spin at a constant RPM.
Vibration-Isolated Systems
Systems that incorporate resilient mountings between the equipment and the structure; must be seismically restrained.
