. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . of se-curities made by them. 320 RAILWAY AND LOCOMOTIVE ENGINEERING October, 1917. Construction and Operation ol Locomotive Safety Valves Variations and Improvements in Designs—Methods of Repair and Adjustment In common with many of the devicesused on the mudern locomotive, the safetyvalve may properly be said to havereached a degree of perfection in con-struction and operation that little furtherimprovement may be expected. To theinexperienced it might seem a simpleproblem to fit a movable p
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . of se-curities made by them. 320 RAILWAY AND LOCOMOTIVE ENGINEERING October, 1917. Construction and Operation ol Locomotive Safety Valves Variations and Improvements in Designs—Methods of Repair and Adjustment In common with many of the devicesused on the mudern locomotive, the safetyvalve may properly be said to havereached a degree of perfection in con-struction and operation that little furtherimprovement may be expected. To theinexperienced it might seem a simpleproblem to fit a movable plug in an oriliceto be held in place by a spring adjustedto a desired pressure, and easy, and tosome extent ciTective as this is, it hasits mechanical draw-backs, particularly inthe vibration or chattering at the open-ing and closing of the plug or valve, withthe effect of damaging the valve andvalve seat, not to speak of the disagree-able succession of noises incident to thechattering referred to. Not only so, butit was soon discovered that the lift ofthe valve did not increase sufticiently to. FIG. 1. THE CROSBY ORIGINAL ENCXSEDLOCOMOTIVE POP SAFETY VALVE. relieve the boiler under all circumstances,but that the pressure might continue toincrease while the valve is in operation,and would also continue to blow after thepressure of the steam had fallen below thepoint of opening. This is largely owingto the unavoidable friction of its the importance of improving. thedevice. With the advent of high-powered loco-motives it became necessary to effect im-jirovements on the safety valve. .-Vmongthe earlier improvements the Crosby lo-comotive pop safety valve, Fig. 1 showsthe original design of this device. Thevalve proper rests upon two flat annularseats VV and WW on the same plane,and is held down by the steel spiralspring S. The tension of the spring is obtained by screwing down the threadedbolt L. The area contained between theseats W and V is what the steam pressurea
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