channels in the disc. These discs are then placed in the grooves in the casing at regular intervals, and in the spaces between them are the running wheels.

The casing is divided into an upper and lower half. The running wheels are built with a cast steel hub having a steel disc riveted on to each side, thus forming a circumferential ring space into which the running vanes are riveted. A thin steel band or rim is tied on the outer edge of the vanes, thus forming an outer wall to the steam channels and confining the steam within the vanes. These vanes are also milled on both edges, on the influx and efflux side of the wheel, thus forming them to the shape corresponding to the theoretical diagram.

The running vanes conform in section somewhat to the Parsons type, but the action of the steam upon them and also within the stationary vanes is different. The expansion of the steam and consequent development of velocity takes place entirely within the stationary vanes, which also change the direction of flow of the steam and distribute it in the proper manner to the vanes of the running wheels, which, according to the claims of the makers, the steam enters and leaves at the same pressure, thus allowing the wheel to revolve in a uniform pressure.

Fig. 141 shows a general view of the HamiltonHolzwarth turbine, and the action of the steam within the machine may be described as follows: After leaving the steam separator that is located beneath the bed plate, the steam passes through the inlet or throttle valve, the stem of which extends up through the floor near the high pressure casing and is protected by a floor stand and equipped with a hand wheel, shown in Fig. 141. The steam now passes through the regulat

ing valve, which will be described later on. From this valve it is led through a curved pipe to the front head

FIGURE 141.

.

of the high pressure casing or cylinder. In this head is a ring channel. into which the steam enters, and from whence it flows through the first set of stationary vanes. In these vanes the first stage of expansion occurs, the velocity of the flow is accelerated, and the direction of flow is changed by the curve of the vanes in such manner that the steam impinges the vanes of the first running wheel at the proper angle and in a full cylindrical belt, imparting by impulse a portion of its energy to the wheel. Passing through the vanes of this wheel, the steam immediately enters the vanes of the second stationary disc, which are larger in area than those of the first, and here occurs the second stage

of expansion, another acceleration of velocity, and also the proper change in direction, and the steam leaves this distributer and impinges the vanes of the second

running wheel. This cycle is repeated throughout the several stages of the turbine, a certain percentage of the heat energy in the steam being imparted by impulse to each wheel and thence to the turbine shaft. From the last running wheel the steam is led through receiver pipes to the front head of the low-pressure cylinder, or, if there is but one cylinder, directly to the condenser or the atmosphere.

In the low-pressure casing, which is larger in diameter than the high-pressure the steam is distributed in the same manner as it is in the high-pressure casing. There is, however, in the front head of the low-pressure casing an additional nozzle through which live steam may be admitted in case of overload. The design of this nozzle is such that the live steam entering and passing through it and controlled by the governor exerts no back pressure on the steam coming from the receiver, but, on the contrary, its action is similar to the action of an injector, that is, it tends to suck the low-pressure steam through the first set of stationary vanes of the low-pressure turbine.

The first stationary disc of the low-pressure turbine has guide vanes all around its circumference, so that the steam enters the turbine in a full cylindrical belt, interrupted only by the guide vanes. To provide for the increasing volume as the steam expands in its course through the turbine, the areas of the passages through the distributers and running vanes must be progressively enlarged. The gradual increase in the dimensions of the stationary vanes permits the steam. to expand within them, thus tending to maintain its velocity, while at the same time the vanes guide the steam under such a small angle that the force with which it impinges the vanes of the next running wheel

is as effective as possible. The curvature of the vanes is such that the steam while passing through them will increase its velocity in a ratio corresponding to its operation.

The purpose of the stationary discs is, as has been stated, to distribute the steam to the running wheels. They also take the back pressure of the steam as it impinges the vanes of the running wheels, thus in a sense acting as balancing pistons.

In all steam turbines one of the main requisites for a quiet-running machine is that the revolving element or rotor shall be perfectly balanced. The rotary body of the Hamilton-Holzwarth turbine consists of a plurality of running wheels, each one of which is balanced by itself before being placed upon the shaft. All the bearings are lubricated in a thorough manner by oil forced up into the bottom bushing or shell under slight pressure. Flexible couplings are used between the high and low-pressure shafts, and for connecting the turbine shaft to the generator shaft or other shaft to be driven. By means of the thrust ball-bearing on the exhaust end of the turbine the shaft may be adjusted in an axial direction in such manner as to accurately preserve the desired position of the running wheels with relation to the stationary discs.

The governor is of the spring and weight type, adapted to high speed, and is designed especially for turbine governing. It is directly driven by the turbine shaft, revolving with the same angular velocity. Its action is as follows: Two discs keyed to the shaft drive, by means of rollers, two weights sliding along a cross bar placed at right angles through the shaft and compressing two springs against two nuts on the cross bar. Every movement of the weights, caused by

increasing or decreasing the angular velocity of the turbine shaft, is transmitted by means of levers to a sleeve which actuates the regulating mechanism. These levers are balanced so that no back pressure is exerted upon the weights. The whole governor is closed in by the discs, one on each side, and a steel ring secured by concentric recesses to the discs. In order to decrease the friction within the governor and regulating mechanism, thrust ball-bearings and frictionless roller-bearings are used.

As previously stated, the regulating valve is located beneath the bed plate. One side of it is connected by a curved pipe with the front head of the high-pressure cylinder and the other side is connected with the inlet valve. The regulating valve is of the double-seated poppet valve type. Valves and valve seats are made of tough cast steel, to avoid corrosion as much as possible, and the valve body is made of cast iron.

Immediately below the regulating valve and forming a part of it in one steam chamber is located the bypass regulating valve. Thus the use of a second stuffing box for the stem of this valve is avoided., The function of this valve is to control the volume of the live steam supply that flows directly to the by-pass nozzles in the front head of the low-pressure casing. This valve is also a double-seated poppet valve.

The main regulating valve is not actuated directly by the governor, but by means of the regulating mechanism. The construction and operation of this regulating mechanism is as follows: The stem of the regulating valve is driven by means of bevel gears by a shaft that is supported in frictionless roller-bearings. On this shaft there is a friction wheel that the governor can slide across the face of a continuously revolving