Fig. 656. Operating Costs, Fixed Charges and Total Costs per Kilowatt Hour for All Types of Units at Various Load Factors. LOAD IN KILOWATTS Fig. 657. casings which are not affected in this way. In the larger size units, where the casings are large and heavy, we accomplish the same results by lining the runner chamber with bronze. As the runners and sleeves on the shaft are of bronze, this recent change has entirely overcome the trouble which sometimes occurred with this type of gland. Oil Baffles "To prevent oil vapor from finding its way along the generator shaft from the intermediate and outboard pedestals it is now our custom to furnish oil baffles containing two felt washers fitting closely around the generator shaft. These felt washers, together with suitably located oil slings on the shaft, provide an efficient means for preventing vapor from escaping from the pedestals and finding its way on to the collector rings and into the generator. "The above are the more recent improvements in the details of our small steam turbines. Naturally the proportioning of the blading to obtain best efficiency has received careful consideration. The progress made in this direction is clearly illustrated in Fig. 658, which is a summary of official test results obtained from a 1000 kw. 3600 r.p.m. Allis-Chalmers steam turbine installed for the city of Grand Rapids. These tests indicate the high efficiency now possible on units of small size and will no doubt be of interest to the members of your association. Combined Speed and Pressure Regulator 200 400 GENERATOR OUTPUT K.W.HR. Fig. 658. 1000!? 1200 in Fig. 659 is designed for use on a non-condensing steam turbine operating in parallel with condensing units. The mechanism can be so regulated that the exhaust steam from the non-condensing unit can be limited to the exact requirements for low pressure steam, and, as these requirements vary, the load on the non-condensing unit is automatically transferred to or from the condensing units with which it is working in parallel. "The operation of the regulator is as follows: "'A' is the stem from the centrifugal governor extending through the governor casing. This stem connects to bell crank 'B' and through link 'C,' and Tee lever 'D' operates a relay valve 'E,' which in turn controls the oil relay piston 'O.' This oil relay piston 'O' E -CONNECTION TO TURBINE EXHAUST NOZZLE. "In addition to the recent improvements enumerated above, we wish to draw your attention to the combined speed and pressure regulator recently introduced by this Company. This regulator is for use in plants where there is a demand for low pressure steam for Fig. 659. Combined Speed and Pressure Regulator, Allisany purpose whatever. The apparatus which is shown Chalmers. 20 19 Fig. 660. Typical Allis-Chalmers Non-Condensing Steam Turbine. Sizes 125 K.W. to 1250 K.W. is in turn connected and operates directly inlet valve 'P.' The turbine unit is controlled by this governor entirely when the unit is not operating in parallel with other units. Under these conditions it will be readily seen that any movement in the governor is immediately transferred to the steam inlet valve. "The pressure operation of this valve gear is based on the fact that an increased demand for low pressure steam will reduce the pressure in the system, and when the requirement decreases the pressure in the system will increase. From the bottom of pressure cylinder 'F' a connection is made to the exhaust of the noncondensing turbine. Any fluctuations, therefore, in the exhaust pressure is immediately felt under pressure piston 'G.' This pressure piston 'G' is connected to Tee lever 'H' and through links 'K' to the lower arm of the previously mentioned Tee lever 'D.' Should the pressure in the exhaust, and consequently pressure cylinder 'F,' fall due to an increased demand for low pressure steam, the spring will force piston 'G' downward and, through the lever connections mentioned above, will operate the relay valve 'E,' opening the inlet valve sufficient to correspond to the increased requirements for low pressure steam. The reverse of the above will take place if the steam requirements in the low pressure system should decrease, as the pressure in the system will then increase a small amount. During the former operation it is obvious that the non-condensing unit will carry a greater load, whereas in the latter case the load on the non-condensing unit will decrease, transferring part of its load to the other units. "In order to adjust the apparatus, and also for varying the pressure in the exhaust of the turbine, an adjusting screw 'M' is provided to vary the compression of the spring 'L.' The dashpot 'N' serves as a 4 |