SAFETY VALVE.
Safety Valves, or pop valves, as they are sometimes termed, are made in many different kinds and styles, but the one most commonly used on a farm engine is constructed with a coil spring, which is adjustable, to allow the valve to pop off at a certain pressure. When the pressure exceeds this amount, it raises the valve from its seat and allows the surplus steam to escape. It should be set with the steam gauge, to allow a little margin of steam pressure over that which is necessary to drive the load, and should be compared with the steam gauge frequently to see that it works accurately. It is furnished with a lever for raising the valve, which should be raised occasionally to see that it operates freely.
Kunkle Safety Valve.
Kunkle Safety Valve,
Sectional.
The safety valve being set with steam gauge, the gauge should be watched when safety valve blows off. If it indicates more or less than the gauge something is wrong, the valve marked incorrectly or the steam gauge is out of order. In case the safety valve and steam gauge do not register alike, the valve should be examined to see that the valve is not stuck in its seat, and should be thoroughly cleaned of all sediment; then put back in place again and compared with the steam gauge as before. If they do not register alike, the gauge should be examined.
Q. Is not a safety valve attached to a boiler to prevent explosion and loss of life?
A. The Safety Valve is only intended to prevent an explosion from excessive steam pressure, and should never be set to hold more than the required pressure to give the rated power for which the engine is designed.