GAS METER. The quantity of gas which flows through a pipe is measured either by a dry or a wet meter, the latter being used to a far less degree than the former, although for big station meters the wet system is employed.
Briefly, a wet meter has a revolving drum divided into com partments, more than half the drum being submerged in water. The compartments are alternately filled with gas and then emp tied during the revolution, and by knowing the cubical capacity of the compartments, the amount of gas passed during a revolution is also known, and can be read by a suitable registering apparatus.
The dry meter is a more convenient type registering apparatus for long periods. The principle is derived from the original type of Thomas Glover & Co. Ltd., Edmonton, London, and com prises an arrangement of double bellows, made of Persian sheep skins. These are attached to disks in such a manner, and so con nected to valves, that alternate filling and exhausting of the bel lows occurs, and the pulsations are transmitted by a train of gearing to the index dials. The simple adjustment of a pin en ables the meter to be set to compare accurately with a standard meter.
Another type is the rotary meter which is utilized for sta tion registration. The stream of gas passes through a fan wheel, the revolutions of which are communicated to the gearing of the recording mechanism. Special kinds of small meters are con structed also for testing purposes.
On the ordinary meter index there are four dials, a top one showing when a small quantity has passed—say aft. or 5ft., and three others as illustrated, from which the reading is taken. The hands of the outer dials move in the direction of the hands of a clock, that of the centre one in the opposite way. In reading, the figure behind each hand is noted, and two ciphers added to the three numbers; thus 8, 7, 4, indicates 87,400 cubic feet.
Prepayment meters are of two classes. In one the prepayment is made to an inspector, who then sets the meter to pass the cor responding value in gas. The other has a coin attachment, the in sertion of the coin giving a certain amount of gas, changes in the price of gas being met by an adjustment device on the attachment, or by giving a discount at the time of clearing. (F. H.) In the natural gas industry, where high pressures as well as large volumes must be measured, the orifice meter is used. This is essentially a plate, the orifice of which slows up the gas flow. Readings of the resulting pressures on the two sides of the orifice are taken by automatic recording devices and the differentials con verted by means of tables into cubic feet of gas.
