58 CONSTRUCTION AND MANAGEMENT OF SMALL GASWORK 



the governor outlet. We know that a flat-flame requires 

 8-tenths, a bunsen burner a minimum of i2-tenths, and 

 incandescent burners about i5-tenths, to ensure satisfactory 

 results. If the consumer gets this pressure, and not less, 

 at all times, he says the gas is good. If he does not, he 

 pronounces the gas to be " bad " ; and also expresses con- 

 siderable doubts as to the ability of the gasworks manager. 

 (a) and (b) will vary according to the rate of consumption 

 and the size of the pipes. The initial or governor pressure will 

 always be equal to a + b + c. Matters can and should be so 

 arranged that b does not exceed 5-tenths, including the 

 pressure required to work the meter. 



The tendency has been, and still is, towards an increase 

 on all these items. The district tends to expand, and the 

 area of supply is increased, while new consumers and 

 additional lights for existing ones are continually coming in. 

 Added to this, the consumer will not be satisfied with less 

 than 2o-tenths at the inlet of the meter. Fifty years ago 

 he would be satisfied with i3-tenths. As the result of 

 increasing c, the other factors are reduced. If the initial 

 pressure is 2 5-tenths, and b + c=i$ there is a margin of 

 i2-tenths left for a. But we have se.n that under 

 present conditions b + c=*2O. a will, therefore, be reduced 

 to 5-tenths, which is not a safe margin for contingencies. 

 For this reason, it is rarely practicable to work satisfactorily 

 with an initial pressure of less than 3o-tenths. There is 

 here an additional reason for seeing that the mains and 

 services are well and soundly laid. 



The relation between the sizes of main pipes and satis- 

 factory conditions of supply can be illustrated by selecting 

 any fixed quantity and distance, and noting the pressure 

 required (a) for various sizes of pipe. Suppose we take 

 1,000 cubic feet of gas per hour to be conveyed a distance 



