STEAM ACCUMULATORS are devices for equalizing steam flow and steam demand. They are inserted between the source of steam supply and the point where it is used for the pur pose of absorbing steam at times of low demand and releasing it when needed; several types have been developed. One of the earli est was the Rateau accumulator or regenerator. Its primary pur pose was to utilize the intermittent exhaust from prime movers— such as steel rolling-mill engines—for driving low-pressure turbines carrying a fairly constant load; installed in the steam line between these two units, it served to equalize supply and demand, the tur bine governor being designed to admit live steam when necessary. Another type is the Smoot accumulator, designed primarily for use in gas manufacturing plants. It collects, or accumulates, in a steel tank the exhaust from pumps and auxiliaries and from the hot-water drips ; by decreasing the pressure in this tank steam is made available for the intermittent operation of the water-gas apparatus, and deficiency in supply is taken care of by a live steam "make-up" valve. The latest development is known as the Ruths steam accumulator, and while it operates on the same gen eral principle as the others; it has been applied over a wider field of usefulness. Specially designed governor valves make its opera tion entirely automatic up to 200 lb. per sq.in. and through greater pressure ranges (fig. r). The tank A is filled with water to 90% of its capacity, and the regulating valves and V-2 automatically control the charging and discharging of the accurnu lator. The accumulator must be placed between the high and the low pressure steam line, and its pressure varies between these limits; accumulated steam is made available by the regulating valves in such a way as to maintain uniform steam pressures in the low pressure steam lines. Any steam generated by the boilers
and not used by the high pressure consumers overflows through valve into the accumulator. V-2 maintains a uniform pres sure in the line P carrying the low pressure steam, so that if the valve is passing more steam than is required in the low pres sure line, the excess is stored in the accumulator. Charging nozzles G are equipped with circulating pipes H which permit a uniform and noiseless heating of the water. Should a sudden demand for high pressure steam arise the boiler pressure would drop slightly, would close and a certain amount of steam would become available at or near this higher pressure. This diversion to the high pressure line of steam intended for the lower pressures would cause a deficit in the low pressure line. V-2 would then open and the heat energy previously stored in the accumulator would instantly flash into steam to meet this deficit. Should the sudden increase in demand be caused by low pressure consumption and the flow through V-z not sufficient, the accumulator would sup ply it. (R. A. L.) is a box cast on or attached to the side of a steam cylinder, and containing the slide-valve which slides over the steam and exhaust ports, and uncovers these in turn. A stuffing box maintains the valve-rod steam-tight. Some engines have two valves, one sliding upon the top of the other, for the purpose of giving expansive working of the steam. Cylindrical or piston valves are used extensively in marine and locomotive cylinders, as they give a balanced effect all around. In locomotive practice these valves have to be placed above the cylinders in many cases for reasons of design.