. Railway master mechanic [microform] . e. The principal defect of these rules in the light of the pre-ceding tests is that they assume that valves of the samenominal size have the same capacity, and they rate themthe same without distinction, in spite of the fact that inactual practice some have but one-third of the capacity ofothers. There are other defects, as have been shown, suchas varying the assumed lift as the valve diameter, while inreality with a given design the lifts are more nearly thesame in the different sizes, not varying nearly as rapidly asthe diameters. And further than this
. Railway master mechanic [microform] . e. The principal defect of these rules in the light of the pre-ceding tests is that they assume that valves of the samenominal size have the same capacity, and they rate themthe same without distinction, in spite of the fact that inactual practice some have but one-third of the capacity ofothers. There are other defects, as have been shown, suchas varying the assumed lift as the valve diameter, while inreality with a given design the lifts are more nearly thesame in the different sizes, not varying nearly as rapidly asthe diameters. And further than this, the actual lifts as-sumed for the larger valves are nearly double the actualaverage obtained in practice. The direct conclusion is this, that existing rules andstatutes are not safe to follow. Some of these rules in usewere formulated before, and have not been modified since,spring safety valves were invented, and at a time when 120lbs. was considered high pressure. None of these rules take« RAILWAY MASTER MECHANIC April. Lift Apparatus at the Plant of the Consolidated Safety Valve Co. account of the different lifts which exist in the differentmakes of valves of the same nominal size, and they thusrate exactly alike valves which actually vary in lift and re-lieving capacity over 300 per cent. It would therefore seemthe duty of all who are responsible for steam installation andoperation to no longer leave the determination of safetyvalve size and selection to such statutes as may happen toexist in their territory, but to investigate for themselves. The uncertainity of the co-efficient of flow, that is, of theconstant to be used in Napiers formula when applied to theirregular steam discharge passages of safety valves, has prob-ably been largely responsible for the fact that this method ofobtaining valve capacities has not been more generally determine what this constant or coefficient of flow is, andhow it is affected by variations in valve design and adjus
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