Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

491 OF ENGINKEEING FOBMULÆ. Safety-valves. (French Practice.) Two Safety-valves to each Boiler. S = Heating surface of boiler in square metres,, P = Pressure of steam in atmospheres. D = Diameter of each, valve in centimetres. *D = 2'6A/P^4i2- Table of Diametebs of Safety-valves in Millimetres for Diffebent Pbessubes. Heating' Surface 1 Press are of Bteani iu Atmospheres. in square' métres. 2 3 4 5 6 7 8 mil]. mill. mill. mill. mill. & 46 36 31 27 24 22 21 10 65 51 43 38 35 32 30 15 80 62 53 -17 42 38 36 20 92 72 61 54 49 45 42 25 I 103 81 69 60 55 50 47 30 113 88 75 66 60 55 52 40 130 101 86 75 69 64 59 50 145 113 96 84 76 70 61 60 158 121 106 94 «4 18 73 * Equivalent Formula in English Measube. Two Safety-valves. S = Heating surface in square yards. P = Pressure in atmospheres. D = Diameter of each safety-valve in inches. D = -945 S p - 1 + 558 ’