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Absolute Pressure - A quantity of pressure with respect to
total vacuum. Equal to the sum of a pressure gauge reading and atmospheric pressure (14.69 psia at sealevel).
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Absorption - The "soaking up" of gas, liquids
or dissolved substances into a solid material.
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| Air - The mixture of gases that surrounds the earth. The composition
of air is 78.08% nitrogen, 20.95% oxygen,0.03 carbon dioxide and 0.93% argon.
Standard air has a density of 0.075 lb/ft3 measured dry at 70 °F (21.1 °C)
and 760 mm Hg, M.W. 28.3. |
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Anhydrous - A descriptive term meaning without water.
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Back Pressure Regulator - Used for controlling inlet pressure (upstream
pressure) rather than reducing. Normally used for pressure relief applications.
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Balance Gas - A gas used to "top off" a gas
mixture after individual component gases at specified concentrations are
added.
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Calibration Gas - A gas of accurately known concentration
that is used as a comparative standard in analytical instrumentation.
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Carrier Gas - Pure gases or gas mixtures used to move
a sample to be analyzed through the gas analysis system at an even rate
and provide a zero reference (baseline) when a sample is not being detected.
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CGA/DIN Fittings - CGA is the abbreviation for Compressed
Gas Association, which is the group that established the standards used
in the gas industry for fittings that attach to gas cylinders. The DIN
system was established by the Germans and is used in Europe.
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Compressed Gas - Any material or mixture having in the
ontainer either an absolute pressure exceeding 40 psia at 0 °F or an absolute
pressure exceeding 104 psia at 130 °F.
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Corrosive - Gases that corrode material or tissue with hich they
come in contact, or do so in the presence of ater, are classified as corrosive.
It is essential that quipment used for handling corrosive gases be onstructed
of proper materials. Proper protective lothing and equipment must be used
to minimize exposure to corrosive materials.
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Creep - This is an increase in outlet pressure occurring after
lockup. Creep normally appears as a gradual rise in outlet pressure over
a period of time. The usual cause of creep is contamination in the regulator
seat causing the regulator to remain slightly open, henceforth additional
outlet pressure.
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Critical Flow - This is sometimes referred to as sonic
flow and is the maximum flow that can pass through a regulator or an orifice.
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Cv (Flow Coefficient) - This is a flow expression whose number
is a measure of the gallons per minute of water that will pass through
a stated flow restriction based on a pressure drop of one psi.
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Cylinder - A pressure vessel designed for pressure higher than
40 psia and having a circular cross-section.
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Droop - This is the amount of outlet pressure decrease with
respect to increasing flow demand on a pressure-reducing regulator. It
can be expressed in percentage change of the set point or can be shown
as pounds per square inch change with respect to flow increases.
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Explosion Proof - An enclosure for an electrical apparatus
so designed that an explosion of flammable gas or vapor inside the enclosure
will not ignite flammable gas or vapor outside.
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FID Fuels - Hydrogen-nitrogen and hydrogen-helium mixtures burned
as a source of heat and power in FIDs.
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Flammable - A substance that will ignite easily and burn rapidly
in the presence of an oxidizer.
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Flashback - The phenomenon characterized by vapor ignition and flame
travelback to the vapor source.
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Flow Rate - A quantity of liquid passing through a controlled orifice
during a specific time period. Units of measure include: SCFM (Standard
Cubit Feet per Minute) and SCFH (Standard Cubic Feet per Hour).
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GC - Gas chromatograph.
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| DID (Discharge
Ionization Detector) Atmospheric contaminants in
the helium carrier gas can cause baseline noise
and reduced detector sensitivity |
| ECD (Electron
Capture Detector) Oxygen and water can reduce detector
response, and halocarbons can give rise to baseline
noise and negative peaks. |
| FID (Flame Ionization
Detector) Hydrocarbons in carrier and fuel gases
can cause baseline noise and reduced detector sensitivity.
Oxygen and water can cause column deterioration.
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| FPD (Flame Photometric
Detector) Carbon dioxide can suppress detector response,
and organics can yield baseline noise. |
| FTIR (Fourier
Transform Infrared) Any impurity coinciding with
quantitated peaks can cause analytical inaccuracies.
Water interferes with infrared spectra, and oxygen
can oxidize the sample during Matrix Isolation.
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| Hall® (lectrolytic
Conductivity Detector) To minimize baseline noise
and analytical inaccuracies, Hall® Grade gases
are specifically manufactured for use with the Tracor
Hall; Electrolytic Conductivity Detector. |
| HID (Helium Ionization
Detector) Atmospheric contaminants in the helium
carrier gas can cause baseline noise, signal polarity
and reduced detector sensitivity and stability.
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| MS (Mass Spectrometer
) Any impurity coinciding with quantitated peaks
can cause analytical inaccuracies. |
| PID (Photoionization
Detector) Oxygen can cause suppressed detector response,
and hydrocarbons yield baseline noise. |
| TCD (Thermal Conductivity
Detector) Atmospheric contaminants can oxidize the
detector filament and give rise to reduced sensitivity
and negative peaks. |
| USD (Ultrasonic
Detector Atmospheric contaminants in the carrier
gas may cause baseline noise and loss of sensitivity.
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| |
| Impurity - Amount of foreign material
or contaminants found in a pure material. |
| Purity Contamination |
99.9999% 1 ppm
99.999% 10 ppm
99.99% 100 ppm
99.9% 1000 ppm |
| Inert - Gases that do not react with other
materials under normal temperature and pressure.
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| Inboard Leakage - This refers to leakage
of the atmosphere or the environment surrounding
the regulator while it is in service at operating
pressure. The test for this is usually done with
a mass spectrometer leak detector, which is sensitive
to helium and for practical purposes, a vacuum is
pulled on the internal of the regulator and helium
surrounding the regulator. For this reason, the
leak rate is usually expressed in standard cc per
second of helium, and the numbers are usually small,
such as 1 x 10-8 cc/sec helium. |
| Inlet Pressure - This is always the pressure
at the inlet of the regulator from the cylinder.
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| Lockup - This is the amount of outlet
pressure increased beyond the set pressure with
respect to decreasing flow demand on a pressure-reducing
regulator. |
| Molecular Weight - The sum of the atomic
weights of all the constituent atoms in a molecule.
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| Off-gassing - The removal of gas, liquids
or dissolved substances from the surface of solids.
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| Outboard Leakage - This refers to leakage
of the regulator from the internal area to the atmosphere
while at operating pressures. |
| Outlet Pressure - This is always the pressure
at the outlet of the regulator. |
| Oxidant - A gas that does not burn but
will support combustion. |
| PPM - Parts Per Million. |
| PPB - Parts Per Billion. |
| PPT - Parts Per Trillion. |
| Process Analyzer - A general class of
instrumentation, which is used to analyze conditions
in process streams on a continuous basis. |
| Pyrophoric - Materials that spontaneously
ignite on contact with air at normal conditions.
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| Setability - This is a term used to describe
the ability to adjust a hand loaded pressure regulator
to a specific set point. This involves the number
of turns of rotation on the adjusting knob to reach
the set point. This is sometimes referred to as
resolution. |
| Set Point - This is the control point
desired for operation of a regulator. |
| Single Stage Pressure Reducing Regulator -
A regulator that reduces high pressure to low pressure
and controls the low or outlet pressure with one
stage of pressure reduction. |
| SLPM - Standard Liters per Minute, SCC/MIN
-Standard Cubic Centimeters per Minute. Standard
condition for all of the above is 60 °F and
14.7 psia. |
| Specific Gravity - The ratio of the weight
of any volume to the weight of an equal volume of
another substance taken as a standard. For solids
or liquids, the standard is usually water and for
gases, the standard is air. |
| Specific Volume - The volume of a unit
weight of a substance at a given temperature. |
| TLV - Threshold Limit Value: The time-weighted
average concentration of an airborne substance that
represents the condition under which it is believed
nearly all workers may be exposed in a normal eight-hour
day, five-day work week without suffering adverse
effect. |
| Toxic Gas - Gases that may chemically
produce injuries or lethal effects to humans. |
| Two Stage Pressure Reducing Regulator -
A regulator that reduces high pressure to low pressure
and controls the low or outlet pressure with two
stages of pressure reduction. Used when more stability
of operation is required. |
| Vapor Pressure - The pressure exerted
when a solid or a liquid is in equilibrium with
its own vapor at a particular temperature. |
| Wetted Parts - This term refers to the
area of the device that comes in contact with the
flow stream. This does not normally include the
cap, range spring knob, etc. |
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