. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . anical Engineer for Messrs. Manning^ Maxwell & Moore, Inc. (Extracts from paper, A. S. M. E., Feb.) The functions of a safety valve are toprevent the pressure in the boiler to whichit is applied from rising above a definitepoint, and to do this automatically andunder the more severe conditions whichcan arise in service. For this, the valvemust have a relieving capacity at leastequal to the boiler evaporation underthese conditions. If it has not this ca-[lacity, the toiler pressure will contin
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . anical Engineer for Messrs. Manning^ Maxwell & Moore, Inc. (Extracts from paper, A. S. M. E., Feb.) The functions of a safety valve are toprevent the pressure in the boiler to whichit is applied from rising above a definitepoint, and to do this automatically andunder the more severe conditions whichcan arise in service. For this, the valvemust have a relieving capacity at leastequal to the boiler evaporation underthese conditions. If it has not this ca-[lacity, the toiler pressure will continue torise, although the valve may be with the exception of a requisitemechanical reliability, the factor insafety-valve construction which bears themost vital relation to its real safety, isits capacity. Two factors in a safety valve geomet-rically determine the area of discharge,and hence the relieving capacity. Theseare the diameter of the opening at theseat, and the valve-lift. The former is thenominal valve size, the latter is the amountthe valve disc lifts vertically from the. K STREET SIGNAL TOWER AND ELECTRIC PLANT. D. D. Carothcrs. chief engineer of the seat when in action. In calculating the Baltimore & Ohio Railroad, and Mr. A. size of valves to be placed on boilers, C. Shand, chief engineer of the P. R. R., rules which do not include a term for this Mr. W. F. Strouse being the engineer in valve-lift, or an equivalent, such as a term 144 KAILUAV ANU LOCOMOTIVE April, 1909. for the effective area of discharge, assume,in their derivation, a lift for each size ofvalve. Nearly all existing rules andformulas are of this kind which rate allvalves of a given nominal size as of thesame capacity. To find what amount of lift standardmakes of valves actually have in practiceand thus test the truth or error of thisassumptioa that they are same for the same size of valve, anapparatus has been devised and carefultests have been made upon
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