XtraCAD Technical Glossary Version 1.0
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Term Definition
abutment An intersection between a roof and a wall.
alkathene Polythene
ampere hour (A·h or amp hr ) A commercial unit of electric charge often used to state the capacity of a battery. One ampere hour is the charge accumulated by a steady flow of one ampere for one hour. This is equivalent to exactly 3600 coulombs.
angle closer A brick cut specially to complete, i.e. close, the bond at the corner of a wall.
annular bit [carp.] A hole saw
APPINFO [CAD-Duct Solids command] Informs the user about the current loaded Cad-Duct version.
ASHRAE The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is an international organisation with chapters throughout the world. The Society is organised for the sole purpose of advancing the arts and sciences of heating, ventilation, air conditioning and refrigeration for the public's benefit through research, standards writing, continuing education and publications.
atmosphere A unit of pressure designed to equal the average pressure of the Earth's atmosphere at sea level. In other pressure units, one atmosphere equals exactly 1013.25 millibars (mb), 101.325 kilopascals (kPa), approximately 29.92 inches of mercury (in Hg), 760.0 millimeters of mercury (mm Hg), or 14.6959 pounds of force per square inch (lb/in2). This is the standard atmosphere; it equals 1.0332 technical atmosphere.
autoclave A pressure vessel in which (for example) calcium silicate bricks are cured at high temperature and pressure in steam
balanced flue A horizontal gas flue that has concentric tubes, i.e. one inside the other, arranged in this way so that one tube carries out the exhaust fumes and the other brings in the air for combustion. The combustion chamber is thus room-sealed and safe.
bar A metric unit of atmospheric pressure, equal to one million dynes per square centimeter, 100 kilopascals, 750.062 torr, 1.019 72 kilograms of force per square centimeter (kgf/cm2), or about 14.503 78 pounds per square inch (lbf/in2). The word comes from the Greek baros, "weighty." We see the same root in our word, barometer, for an instrument measuring atmospheric pressure. One bar is just a bit less than the average pressure of the Earth's atmosphere, which is 1.013 25 bar. In practice, meteorologists generally record atmospheric pressure in millibars (mb). In English-speaking countries, barometric pressure is also expressed as the height, in inches, of a column of mercury supported by the pressure of the atmosphere. In this unit, one bar equals 29.53 inches of mercury (in Hg).
blackheart malleable iron Usually annealed in an inert atmosphere (protective gas or vacuum) and has a uniform structure. The higher carbon content is evenly distributed throughout the structure.
BSF British Standard Fine. A thread form based upon the British Standard Whitworth form but with a finer thread (more threads per inch for a given diameter). This thread form was first introduced in 1908, the thread form is specified in BS 84: 1956.
BSI - British Standards Institution BSI is the independant national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter.
BSW British Standard Whitworth. A thread form developed by Sir Joseph Whitworth in 1841. The thread form has rounded roots and crests, the thread form is specified in BS 84: 1956. This thread form was superceded by first the Unified thread in 1948 and then the metric thread form.
castellated beam Castellated beams are made from standard hot-rolled I, H or U-sections. The web of the beam is split lengthwise in a rack-shaped pattern. The halves so obtained are shifted a half-pitch in relation to one another and then welded together at the tops of the teeth. The result is a beam with a row of hexagonal holes in the body. The beam is much deeper than the original profile it is made from, while its weight is almost the same. It is also possible to weld square or rectangular plates between the cut halves, giving an even deeper castellated beam, now with octagonal holes in its body. Due to their greater depth, castellated beams allow greater bending moments than the rolled beams from which they are made. In other words, they have considerably greater bending stiffness than the profile before cutting. The admissable transverse force is smaller. For this reason, castellated beams are particularly suitable for large spans with small(er) loads. To prevent buckling of the open-work web, infill plates can easily be welded in (if and where necessary).
CHECK [CAD-Duct Solids command] Collision detection on whole drawing. Item collisions are marked on drawing as green circles at item intersections. Type CHECK again after items have been adjusted to remove the green circles.
CHSPEC [CAD-Duct Solids command] Select item on the drawing and right-click to change the specification. The dialogue box displayed is similar to the Set Specifications Icon dialogue box, but the specification can be changed for the selected item type only.
CIBSE The Chartered Institute of Building Services Engineers is an international body, with a membership of 15,000 (one fifth of which is overseas), which represents and provides services to the building services profession. The Institution has two main functions: it confers an internationally recognised badge of quality and it undertakes a wide range of learned society activities.
cleaning eye An access eye or rodding eye
cleanout [USA] An access eye, soot door, etc.
close-coupling A flow measurement device directly coupled to the upstream (inlet) side of a double regulating valve to form a one piece measurement, regulation and isolation commissioning set.
condenser The outside unit in an air-conditioning system that disperses the waste heat and condenses the gas back to a liquid.
CONNFLAG [CAD-Duct Solids command] Sets the option flags for CONNMATCH (below).
CONNMATCH [CAD-Duct Solids command] Changes connector pair at user pick point.
dB A symbol indicating that a measurement is made using a logarithmic scale similar to that of the decibel (see below) in that a difference of 10 dB- corresponds to a factor of 10. In each case, the actual measurement a is compared to a fixed reference level r and the "decibel" value is defined to be 10 log10(a/r).
dB A, dB C Units of sound intensity, exactly like the decibel except that before the measurement is made sounds of high and low frequencies, heard poorly or not at all by the human ear, have been filtered out. The letters A and C refer to two filtering methods.
deadlight, fixed sash, fast sheet, stand sheet A window in which the glass is fixed directly to the surround, i.e. that does not open.
decibel (dB) A customary logarithmic measure most commonly used (in various ways) for measuring sound. The human ear is capable of detecting an enormous range of sound intensities. Furthermore, our perception is not linear. Experiment shows that when humans perceive one sound to be twice as loud as another, in fact the louder sound is about ten times as intense as the fainter one. For this reason, sound is measured on logarithmic scales. Informally, if one sound is 1 bel (10 decibels) "louder" than another, this means the louder sound is 10 times louder than the fainter one. A difference of 20 decibels corresponds to an increase of 10 x 10 or 100 times in intensity. The beginning of the scale, 0 decibels, can be set in different ways, depending on exactly which aspect of sound is being measured. For sound intensity (the power of the sound waves per unit of area) 0 decibels is equal 1 picowatt per square metre; this corresponds approximately to the faintest sound that can be detected by a person who has good hearing. A quiet room has a normal sound intensity of around 40 decibels, ten thousand times louder than the faintest perceptible sound, and a thunderclap may have an intensity of 120 decibels, a trillion times louder than the faintest sound. For sound pressure (the pressure exerted by the sound waves) 0 decibels equals 20 micropascals (µPa) RMS, and for sound power 0 decibels sometimes equals 1 picowatt. In all cases, one decibel equals about 0.115 129 neper and d decibels equal d(ln 10)/20 nepers. See also dB- (above).
DIN Deutsche Industrie Norm (German industry standard).
DN A symbol for "nominal diameter", a size measure for piping, valves, fittings, etc. Nominal diameter is essentially the inside diameter of the piping in millimeters. Industrial standards organizations, such as the American National Standards Institute (ANSI), set standards for pipes and fittings based on DN ratings; these standards specify in detail the size, composition, and strength of each component.
dry riser A vertical pipe in a tall building, with inlet connections at the fire brigade's access point, through which water can be pumped in by the fire brigade for them to fight the fire from any point upstairs where fire hydrants are located on it.
dyne (dyn) The CGS unit of force. One dyne is the force that accelerates a mass of one gram at the rate of one centimeter per second per second. Expressed in SI units, the dyne equals 10-5 newton. This is quite a small force: it equals about 2.248 x 10-6 pound of force (lbf) in the traditional English system. The word dyne comes from the Greek dynamis, power.
electric horsepower A unit of power, equal to exactly 746 watts (550.221 foot pounds per second), used in the electric industry. This is slightly larger than the ordinary or mechanical horsepower of exactly 550 foot pounds per second.
EUROVENT EUROVENT is an omnibus word standing for the European Committee of the Construction of Air Handling Equipment. The committee was formed in 1959, and in 1977 its constituent members were the relevant national associations in Austria, Belgium, Denmark, Finland, France, German Federal Republic, Italy, Netherlands, Norway, Sweden, Switzerland and the United Kingdom.
face mark, X-mark [carp.] A mark pencilled on the face to show that other surfaces are to be trued from it. One of the two corners of the face is also trued to form a straight line from which the setting out begins.
flash point The lowest temperature at which a substance momentarily ignites when a flame is put to it. See fire point
gig stick [plas.] A radius rod
GMT Abbreviation for Greenwich Mean Time, the standard time of longitude 0°. This meridian of longitude, called the prime meridian, was fixed as the longitude of the Royal Greenwich Observatory in London by the International Meridian Conference of 1884. The abbreviation UT (Universal Time) has largely replaced GMT.
headloss The drop in pressure which results from the inclusion in a system of a valve or measurement device.
high strength friction grip bolts Sometimes abbreviated to HSFG bolts. Bolts which are of high tensile strength used in conjunction with high strength nuts and hardened steel washers in structural steelwork. The bolts are tightened to a specified minimum shank tension so that transverse loads are transferred across the joint by friction between the plates rather than by shear across the bolt shank.
inch of water column (in WC) A traditional unit of pressure, used in plumbing to describe both water and gas pressures. The conventional equivalent of one inch of water is 249.0889 pascals, which is 2.490 889 millibars, about 0.036 127 pounds per square inch (psi) or about 0.073 556 inches (1.868 32 millimeters) of mercury.
inch of water gauge (in wg or "wg) Another common name for the inch of water column. The word "gauge" (or "gage")after a pressure reading indicates that the pressure stated is actually the difference between the absolute, or total, pressure and the air pressure at the time of the reading.
jamb The vertical flank of a wall opening, to the full thickness of the wall, often also the joinery covering the flank. Compare with reveal.
joule (J) The SI unit of work or energy, defined to be the work done by a force of one newton acting to move an object through a distance of one meter in the direction in which the force is applied. Equivalently, since kinetic energy is one half the mass times the square of the velocity, one joule is the kinetic energy of a mass of two kilograms moving at a velocity of 1 m/sec. This is the same as 107 ergs in the CGS system, or approximately 0.737 562 foot-pound in the traditional English system. In other energy units, one joule equals about 9.478 170 x 10-4 Btu, 0.238 846 (small) calories, or 2.777 778 x 10-4 watt hour. The joule is named after the British physicist James Prescott Joule (1818-1889), who demonstrated the equivalence of mechanical and thermal energy in a famous experiment in 1843.
kBtu A symbol for 1000 British thermal units. This unit of energy equals about 1.055 megajoules (MJ) or 0.2931 kilowatt hour (kWh).
kelvin The SI base unit of temperature, previously called the degree Kelvin (°K). One kelvin represents the same temperature difference as one degree Celsius. In 1967 the General Conference on Weights and Measures defined the temperature of the triple point of water (the temperature at which water exists simultaneously in the gaseous, liquid, and solid states) to be exactly 273.16 kelvins. Since this temperature is also equal to 0.01 °C, the temperature in kelvins is always equal to 273.15 plus the temperature in degrees Celsius. The kelvin equals exactly 1.8 degrees Fahrenheit. The unit is named for the British mathematician and physicist William Thomson (1824-1907), later known as Lord Kelvin after he was named Baron Kelvin of Largs. He is best remembered for his pioneering work on the physics of heat, but he was also a strong advocate of the metric system; his support helped establish the now-familiar electrical units such as the ohm, volt, and farad.
kilopond Another name for the kilogram of force (kgf).
KV The factor which together with the flow can be used to calculate the headloss caused by any particular device or combination of devices.
KVs The factor which together with the signal pressure drop can be used to calculate the flow through any particular device.
LDIM [CAD-Duct Solids command] Displays the length dimension of selected item(s).
malleable cast iron The traditional material for manufacturing pipe fittings whose characteristics make it an ideal choice. It is an iron-carbon alloy which combines the outstanding properties of cast iron and steel to produce a material which can still be cast but has improved strength and ductility. It also allows the production of complex shapes combined with a thin wall section.
MASKVIEW [CAD-Duct Solids command] Hides all drawing except selected item(s). Restore the rest of the drawing by typing SHOWALL.
nano- (n-) a metric prefix meaning 10-9, or one billionth. The prefix comes from the Greek word nanos, dwarf.
newton (N) the SI unit of force. A force of one newton will accelerate a mass of one kilogram at the rate of one meter per second per second. The corresponding unit in the CGS system is the dyne; there are 105 dynes in one newton. In traditional English terms, one newton is about 0.224 809 pounds of force (lbf) or 7.233 01 poundals. The newton is also equal to about 0.101 972 kilograms of force (kgf) or kiloponds (kp). The newton is named after Isaac Newton (1642-1727), the British mathematician, physicist, and natural philosopher. He was the first person to understand clearly the relationship between force (F), mass (m), and acceleration (a) expressed by the formula F = ma.
nox a unit of (low) illumination equal to 0.001 lux. This unit was used in Germany during World War II to describe permitted levels of lighting during air raids. "Nox" is the Latin word for "night."
nut dilation Under load, the wedging action of the threads causes dilation of the nut resulting in an increase in the minor diameter of the nut and reducing the effective shear areas of both the external and internal threads.
opening light [carp.] A window which opens, not a deadlight.
pascal (Pa) The SI unit of pressure. The pascal is the standard pressure unit in the MKS metric system, equal to one newton per square meter or one "kilogram per meter per second per second". In traditional English terms a pascal is only 0.000 145 pounds per square inch (0.020 885 lbf/ft2 or 0.007 50 mmHg). Thus pressure is more commonly measured in kilopascals (kPa), with 1 kPa = 0.145 lbf/in2. Air pressure is measured in hectopascals (hPa), with 1 hPa = 1 millibar. The unit is named after Blaise Pascal (1623-1662), French philosopher and mathematician, who was the first person to use a barometer to measure differences in altitude.
patina A thin, stable, protective film of oxide which forms on metals exposed to air, particularly the green coating on copper or its alloys (verdigris) which usually takes many years to form, but can now be made artificially by chemical means in much less time.
PN A symbol for "nominal pressure," a measure used for rating piping, valves, fittings, etc. Nominal pressure is essentially the pressure rating of the piping system, measured in megapascals at a temperature of 20 °C (68 °F). (One megapascal equals approximately 145.038 pounds per square inch in traditional English units.) Industrial standards organizations, such as the American National Standards Institute (ANSI), set standards for pipes and fittings based on PN ratings; these standards specify in detail the size, composition, and strength of each component.
pressured system A hot water and radiator system that has a sealed pressure vessel to deal with expansion and a safety valve to prevent damage. The advantage is that higher temperatures can be reached, a header tank does not limit the height of radiators and the system can be compact for flats. The system does need special approval from the local council building control.
principal post [carp.] A door post in a framed partition.
psi, psia, psid, psig Traditional symbols for pressure units used in hydraulics and plumbing. psi is a symbol for pound per square inch. psig is a symbol for pound per square inch gauge; this means that the pressure has been read from a gauge which actually measures the difference between the pressure of the fluid and the pressure of the atmosphere. psia means pound per square inch absolute, which is the total pressure including the pressure of the atmosphere. psid, pound per square inch differential, is a symbol for a difference between two pressures, neither of which is atmospheric pressure. Corresponding symbols for pound per square foot (psf, etc.) are also used.
PURGEDB [CAD-Duct Solids command] Same as shift right-click Cadduct Solids - Purge Database. Removes items added to the database from drawings or .ITM files opened that contain information that did not exist in the database.
Q unit A unit of heat energy equal to one quintillion (1018) Btu, 1000 quads, or about 1.055 zettajoules (ZJ).
radian A unit of angle measure widely used in mathematics and science. One radian is the angle subtended by an arc length equal to the radius of the circle. Since the circumference equals 2 pi times the radius, one radian equals 360°/(2 pi), or approximately 57.295 779°. Using radians to measure angles seems unnatural at first. However, when angles are stated in radians the constant pi tends to disappear from the equations, and this greatly simplifies calculation. For example, the length of an arc is simply its radius multiplied by its angular measure in radians, and the area of a sector of a circle is simply its angular measure in radians multiplied by half the square of the radius. The radian was defined and named by James Thomson in 1873. Thomson was a mathematics professor at Queens College, Belfast, Northern Ireland, and the brother of the famous physicist William Thomson, Lord Kelvin.
raked joint A mortar joint which has been cleaned of mortar for about 2cm back from the face before pointing or plastering.
rat-trap bond, all-rowlock wall A brick bond in which the bricks are laid on edge in courses 11.5cm deep to build a 23cm thick wall.It consists of two leaves 7.6cm thick in which headers and stretchers alternate. A cavity, 23 x 7.6cm in plan, is left opposite each stretcher. The wall is cheap and fairly strong.
rebar sizes Numerical size designations for steel reinforcing bars ("rebars") used to strengthen concrete. The size number is the diameter of the rod in 8ths of an inch (1/8 inch = 3.175 millimeters); thus a rod 1 inch in diameter is a #8 rebar.
REPORTS [CAD-Duct Solids command] Report Builder dialogue box displayed. Printed reports can be built, saved and customised to individual requirements. Can also be accessed from shift right-click menu Cam/Print - Print Layout.
reveal The visible part of a jamb in a door or window opening, not covered by the frame.
Rockwell hardness (RH-) A measure of the hardness of a metal introduced by Rockwell in 1922. In a Rockwell hardness test, a penetrator makes an indentation in the metal under two constant loads, a "minor" load (generally 10 kilograms) and then a "major" load. The difference in penetration depth between the two loads provides the measure of the hardness, usually read from a gauge on the testing machine. There are several Rockwell scales for different ranges of hardness. The most common are the B scale (RHB), for which a steel ball is used as the penetrator, and the C scale (RHC), for which a cone-shaped diamond is used. The B scale is appropriate for soft metals, the C scale for hard metals. Rockwell hardness numbers are not proportional to Brinell or Vickers hardness readings.
ROTATEATEND [CAD-Duct Solids command] Rotates the drawing item (and attach arrow) positioned at current active end by number of degrees specified.
rowlock, rolock A brick on edge course. See rat-trap bond
SHOWBYNAME [CAD-Duct Solids command] Hides all items on a drawing except for those with the specified name. Restore the rest of the drawing by typing SHOWALL.
SI French Systeme International (d'Unites), international metric system of units of measurement.
siemens (S) The SI unit of electric conductance. The most important property of a conductor is the amount of current it will carry when a voltage is applied. A conductor has a conductance of one siemens if it carries one ampere of current per volt of potential. Conductance is the inverse of resistance, and the siemens is the reciprocal of the ohm. In other words, the conductance, in siemens, is simply 1 divided by the resistance, in ohms. The unit is named after the German electrical engineer Werner von Siemens (1816-1892).
signal pressure drop The pressure differential measured between the upstream and downstream pressure test valves of a flow measurement device using a manometer.
sound transmission class (STC) A rating of the ability of building materials to stop the transmission of unwanted sounds. The rating is designed so that it expresses, as best one can with a single figure, the sound transmission loss in decibels when sound passes through the material. To determine the STC rating, test sounds of 16 different frequencies are transmitted through the barrier. The data is then smoothed to a standard contour using an established protocol, and the STC rating is the "smoothed" sound transmisson loss at a frequency of 500 hertz. Ordinary conversation can be understood through a window pane rated STC 25; a wall rated STC 50 stops all but the loudest shouting.
SPECSIN [CAD-Duct Solids command] Imports Specifications - can also be accessed from shift right-click menu Import - Specifications.
SPECSOUT [CAD-Duct Solids command] Exports Specifications - can also be accessed from shift right-click menu Export - Specifications.
split system A term used to describe comfort cooling, commonly termed 'air-conditioning', where the room evaporator and the outside condenser are split and not within a combined unit.
standing leaf [carp.] A leaf of a folding door which is bolted in a closed position, as opposed to the opening leaf.
SWG Abbreviation for Standard Wire Gauge.
TBAR [CAD-Duct Solids command] Regenerates CAD-Duct Solids toolbar.
tinning Coating steel, copper, or other metal with a film of tin or tin alloy to reduce corrosion.
tommy bar A loose bar inserted into a hole in a box spanner to provide the leverage for turning it.
UNCATALOGUE [CAD-Duct Solids command] Turns selected catalogue item on drawing into editable item.
veneered stock [carp.] An early name for plywood.
vermiculite A highly insulating, lightweight material made by heating a mica found in USA and South Africa. It is used in floor and roof screeds for its insulation and fire resistance.
voussoir An arch-stone in a stone arch or an arch-brick in a brick arch.
wall plate A horizontal timber along the top of a wall at eaves level. It carries the rafters or joists.
watt The SI unit of power. Power is the rate at which work is done, or (equivalently) the rate at which energy is expended. One watt is equal to a power rate of one joule of work per second of time. This unit is used both in mechanics and in electricity, so it links the mechanical and electrical units to one another. In mechanical terms, one watt equals about 0.001 341 02 horsepower (hp) or 0.737 562 foot-pound per second (lbf/s). In electrical terms, one watt is the power produced by a current of one ampere flowing through an electric potential of one volt. The name of the unit honours James Watt (1736-1819), the British engineer who built the first practical steam engines.
watt hour (W·h) A common metric unit of work or energy, representing the energy delivered at a rate of one watt for a period of one hour. This is equivalent to exactly 3.6 kilojoules (kJ) of energy, or about 3.412 141 Btu, 0.859 846 (kilogram) Calories, or about 2655 foot pounds.
wave or wavelength A unit of relative distance equal to the length of a wave: this could be a light wave, a radio wave, or even an ordinary water wave. In communications engineering, the length of an antenna is often stated in waves. In optics, the surfaces of lenses and mirrors are required to be precisely polished to within a very small fraction of a wavelength of green light (546 nanometers).
whiteheart malleable iron Produced by annealing in an oxidising atmosphere. The result is a lower carbon content, particularly in the surface zone of the material.
X-mark [carp.] See face mark.
xylol [pai.] A solvent for synthetic resins and gums, distilled from coal tar.
yocto- (y-) A metric prefix denoting 10-24 (one septillionth). Adopted by the CGPM in 1990, the prefix is derived from the Latin octo and Greek okto, meaning 8, because this is the eighth prefix (n = 8 in 10-3n) in the SI system of metric prefixes. The y was added arbitrarily to provide a non-confusing letter for abbreviations.
yotta- (Y-) A metric prefix denoting 1024 (one septillion). The prefix was coined to parallel the prefix yocto-.
zinc electroplating Zinc electroplating is a common way to protect threaded fasteners from the effects of corrosion. Zinc electroplating can be completed in acid chloride, alkaline or cyanide baths. Supplemental coatings are frequently applied to zinc electroplating. These coatings, such as zinc phosphate or chromate conversion, provide a protective passivation layer on the zinc which assists in reducing the corrosion rate.
zinc phosphate conversion coating A zinc phosphate conversion coating is frequently added to zinc electroplated parts, such as bolt threads, to improve corrosion resistance. This type of chemical conversion coating provides a protective passivation layer on the zinc improving its corrosion resistance.
zinc/cobalt alloy electroplating This coating is similar to zinc electroplating completed in an acid chloride bath - a small amount of cobalt (typically about 1%) is added to increase the plating speed.



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