This section is from the book "The Building Trades Pocketbook", by International Correspondence Schools. Also available from Amazon: Building Trades Pocketbook: a Handy Manual of reference on Building Construction.
For ordinary purposes, the volume of gas passing through a pipe is measured by an apparatus called a gas meter. A gas meter measures the volume only, and its indications are not affected by any change that may occur in the pressure of the gas. The difficulty thus encountered in correctly measuring the volume of gas actually delivered under varying pressures, is overcome by using a governor between the meter and the street main, or service pipe. The governor is a species of reducing valve which will receive gas at any pressure, whether steady or variable, and will discharge it at a steady low pressure.
Fig. 18 shows a meter of the ordinary type. To read such a meter, note the lesser of the two figures between which each hand points, or the figure to which it points, beginning at the left-hand dial; then add two ciphers to the right of the three figures, and the number so obtained will be the amount of gas in cubic feet which the meter has measured. Thus the pointers in the diagram indicate that 14,200 cu. ft. of gas have passed through the meter.
The dial marked two feet may be used to ascertain the quantity of gas consumed per hour by a burner, by noting the time required for the pointer to make a revolution. Thus, the hand will make 2 1/2 revolutions per hour if 5 cu. ft. pass through the meter in that time. This dial may also be used in testing for leaks.
The objects sought in the use of pressure regulators or governors are economy in the consumption of gas, steadiness of the lights, and most effective operation of the burners. It is of great importance that both volume and pressure at the burners should be closely regulated. The amount of gas wasted by over pressure is much greater than is generally believed. A good new lava-tip burner consuming 5 cu. ft. per hour at .5 in. pressure, will consume about .5 of a cu. ft. more for each increase of .1 in. in the pressure. Thus an over pressure of .1 in. will increase the gas bill about 10 per cent. The variation. in even the best regulated systems, is usually much greater than one-tenth inch, and is frequently ten-tenths or more.
The two systems of regulation in use are the pressure and the volumetric regulation. In the first system, a governor is attached to the service pipe at the meter, and the house dis-tributing pipes are maintained at constant pressure; in the second system, each burner is supplied with a governor, the pressure in the pipes not being controlled.
The proper place for a pressure regulator. If used, is between the meter and the main. The meter should then be adjusted to suit the house pressure instead of the street pressure.
The pressure required at the burners, to secure the best results, varies greatly in different forms of apparatus. The following are the pressures generally used:
.2 in. of water
Common batswing burners............................
.5 in. of water
Wellsbach incandescent burners...................
.5 or more.
Wenham and Lebrun lamps ..........................
.5 to 1 or more.
1.0 or more.