Page 279 - Pipeline Rules of Thumb Handbook

266 Pipeline Rules of Thumb Handbook

diversity factor the ratio of the sum of the non-coincident liquefied petroleum gas (LPG) any hydrocarbon mixture,
maximum demands of two or more loads to their coinci- in either the liquid or gaseous state, the chief components
dent maximum demand for the same period. of which consist of propane, propylene, butane, iso-butane,
dyne the standard centimeter-gram-second unit of force, butylene or mixtures thereof in any ratio.
equal to the force that produces an acceleration on one load curve a graph in which the send-out of a gas system,
centimeter per second on a mass of one gram. or segment of a system, is plotted against intervals of
erg the centimeter-gram-second unit of work or energy, equal time.
to the work done by a force of one dyne when its point of load density the concentration of gas load for a given area,
application moves through a distance of one centimeter in expressed as gas volume per unit of time and per unit of
the direction of the force. area.
flat rate schedule a rate schedule that provides for a speci- load duration curve a curve of loads, plotted in descending
fied charge irrespective of the quantity of gas used or the order of magnitude, against time intervals for a specified
demand. period. The coordinates may be absolute quantities or
gauge pressure the pressure generally shown by measuring percentages.
devices. This is the pressure in excess of that exerted by the load factor the ratio of the average load over a designated
atmosphere (see absolute pressure). period to the peak load occurring in that period. Usually
gross calorific (heating) value the gross calorific value at expressed as a percentage.
constant pressure of a gaseous fuel is the number of heat low pressure gas distribution system a gas distribution
units produced when unit volume of the fuel, measured system, or the mains of a segment of a distribution system,
under standard conditions, is burned in excess air in such operated at low pressures of less than 15 inches water
a way that the materials after combustion consist of the column.
gases carbon dioxide, sulfur dioxide, oxygen and nitrogen, LPG-air mixtures mixtures of liquefied petroleum gas and
water vapor equal in quantity to that in the gaseous fuel air to obtain a desired heating value and capable of being
and the air before combustion, and liquid water equal in distributed through a distribution system also used for
quantity to that produced during combustion, and that the stand-by and peak-shaving purposes by gas utilities.
pressure and temperature of the gaseous fuel, the air, and manufactured gas combustible gases derived from primary
the materials after combustion are one standard atmo- energy sources by processes involving chemical reaction.
sphere and 25°C. For instance, gas produced from coal, coke or liquid
inch of mercury a unit of pressure (equivalent to 0.491154 hydrocarbons (see also town gas).
2
2
lbf/in. ) by which one lb/in. equals 2.036009in. of mercury meter (gas) a mechanical device for automatically measur-
column at 0°C. ing quantities of gas. Some of the more important types are:
inch of water a unit of pressure (equivalent to 0.03606 Diaphragm Meter a gas meter in which the passage of
2
2
lbf/in. ) by which one lb/in. equals 27.68049in. of water gas through two or more chambers moves diaphragms
column at 4°C. which are geared to a volume-indicating dial. Sizes up to
2
interruptible gas gas made available under agreements 20,000 cubic ft per hour and 1,000lbf/in. working pressure
which permit curtailment or cessation of delivery by the are available.
supplier. Mass Flowmeter a type of meter in which the gas flow is
joule the work done when the point of application of a force measured in terms of mass by utilizing the velocity and
of one newton is displaced through a distance of one meter density of the gas stream to calculate the mass of a gas
7
in the direction of the force. It is equal to 10 ergs, and in flowing in unit time.
electrical units is the energy dissipated by one watt in a Orifice Meter meter for measuring the flow of fluid
second. through a pipe or duct by measurement of the pressure dif-
kilocalorie one thousand calories. ferential across a plate having a precision machined hole in
kilowatt-hour a unit of energy equivalent to the energy its center. Ratings up to very high throughputs and pres-
transferred or expanded in one hour by one kilowatt of sures are available.
power. Rotary Displacement Meter the positive-pressure
line pack a method of peak-shaving by withdrawing gas blower principle in reverse is used in this meter in which
from a section of a pipeline system in excess of the input gas pressure turns twin matching impellers and the quan-
into that section, i.e., normally the difference between the tity of gas passing through is proportional to the number of
actual volume of gas in the pipeline at low flow (increased revolutions. These meters are made in the range of 3,000
pressure) and that at normal flow. to 1,000,000 cubic ft per hour and for pressures up to 1,200
liquefied natural gas (LNG) natural gas that has been lbf/in. 2
liquefied by cooling to minus 258°F (-161°C) at atmo- Turbine Flowmeter a type of meter in which there is a
spheric pressure. turbine wheel or rotor made to rotate by the flowing gas.