G'+G= 21 + 2,or23—— = 530.43
G'+G= 21 + 2,
or
23—— = 530.43
feet approximately. Since the static head was 34 feet, the head lost in friction was evidently
53-34 = 19feet, or1900—— = 3653
53-34 = 19
feet, or
1900—— = 3653
per cent., approximately.
In addition to this the supply of cooling water was limited, the vacuum being extremely low at just the time when efficient operation should be had. The natural result occurred, which was this: As the load on the turbine increased, the amount of steam issuing into the condenser increased,beatingthe circulating water to a temperature which the cooling tower (not in the best condition) was unable to decrease to any great extent. The vacuum gradually dropped off, which indicated that the condenser was being filled with vapor, and in a short time the small centrifugaltail-pump lost its prime, becoming "vapor bound," and the vacuum further decreased. The steam which had condensed would not go into the tail-pump because of the tendency of the dry-pump to maintain a vacuum. When a certain point was reached the dry-vacuum pump started to draw water in its cylinder, and the unit had to be shut down immediately.
As the circulating water gradually rose in temperature the circulating pump also became "vapor bound," so that the unit would be tied up for the rest of the night, as this pump could not be made to draw hot water. The reason for this condition may be explained in the following way. When the circulating pump was operating and there was a suction of 2 pounds indicated atG, the water was not flowing to the pump of its own accord, but was being pulled through by force. This water would flow through the pump until a point was reached when the water became hot enough to be converted into vapor, this occurring at a point where the pressure was sufficiently reduced to cause the water to boil. Naturally this point was in the suction pipe and vapor was thus maintained behind the pump as long as it was operating. In this case the pump was merely maintaining a partial vacuum, but not drawing water. After the vacuum was once lost, by reason of the facts given, it could not be regained, as the circulating water, piping and condenser required a considerable period of time in which to cool.
Before any radical changes were made it was decided that a man should crawl in the suction pipeA, and remove such sand, dirt, or any other obstacles as were believed to cause the friction. After this had been done and considerable sand had been removed, tests were resumed with practically the same results as before. The investigation was continued and the dry-vacuum pumps were overhauled, as they had been damaged by water in the cylinders, and furthermore needed re-boring. In short, the auxiliaries were restored to the best condition that could be brought about by the individual improvement of each piece of apparatus. As this was not the seat of the trouble, however, the remedy failed to effect a "cure." It was demonstrated that the steam consumption of the turbines was greatly increased due to priming of the boilers, as well as condensation in the turbine casing; hence, the ills above mentioned were aggravated.
After a great deal of argument from the chief engineer, and the firm which furnished the pump, both making a strong plea for a change in the piping, the company accepted the inevitable, and the dotted portion shows the present layout. The elbowMwas removed, and a tee put in its place to which the pipingDwas connected. The circulating pump was removed to the position shown, and a direct connection substituted for the S-bend. The discharge pipeCwas carried from No. 1 unit separately, as shownin the elevation, and terminated at No. 1 cooling tower instead of No. 2, which shortened the distance about 60 feet, the total length of pipe (one way) from No. 1 unit being originally 250 feet. In this way the condensing equipment was made practically separate for each turbine, as it should have been in the first place.
With the new piping a vacuum of 24 inches on the peak could be reached. While this is far from an efficient value, yet it is better than the former figure. The failure to reach a vacuum of 28 inches or better is due primarily to a lack of cooling water, but an improvement in this regard could be made by reconstructing the cooling towers, which at present do not offer the proper amount of cooling surface. The screens used were heavy galvanized wire of about 3/16-inch mesh, which became coated in a short time, and must be thoroughly cleaned to permit the water to drop through them. The supply of cooling water was taken from a 30-inch pipe line several miles long and fed from a spring. The amount of water varied considerably and was at times quite insufficient for the load on the plant. Instead of meeting this condition with the best apparatus possible, a chain of difficulties were added to it, with the results given.
Acceleration, rate of,147Adjustment, axial,65making,66Air-pump, examining,163Allis-Chalmers Co. steam turbine,41Auxiliaries,2,154special,165Auxiliary plant for consumption test,137spring on governor dome,28Axial adjustment,65Baffler,36functions,39Bearings, main,69Blades, construction details,44inspecting,104Blading, Allis-Chalmers turbine,48Westinghouse-Parsons turbine,59,92Blueprints, studying,11Buckets, moving,14stationary,14Bushings,36Carbon packing,19ring,20Central gravity oiling system,111Circulating pump fails to meet guarantee,172Clearance,15,150adjusting,18between moving and stationary buckets,4gages,17measuring,18radial,63Comma lashing,95Condensers,108,131jet,154Conditions for successful operation,105Cooling water supply limited,177Coupling,127Cover-plate,4-plate, lowering,9Curtis turbine,11turbine in practice,1setting valves,31,32De Laval turbines,118Draining system,105Dummy leakage,115pistons,63,65rings,43,113,114Equalizing pipes,64Exhaust end of turbine,107pipe,107Expanding nozzles,14Feed-pipes,164Flow, rate,38Foundation drawings,2rings,44,46Fourth-stage wheel,14Franklin, Thomas,112,137,154Gages, calibrating and adjusting,169clearance,17for test work,165Generator,53Glands, examination for scale,104packing,71,77regulation,148Governor, Allis-Chalmers turbine,48Curtis turbine,27,31improved, Westinghouse-Parsons turbine,83-rods, adjusting,35safety-stop,86Westinghouse-Parsons turbine,80Grinding,38Guide-bearing, lower,9Gump, Walter B.,172Holly draining system,106Horseshoe shim,8Hot-well regulation,148Inspection,103Intermediate,14Jacking ring,8Jet condenser,154Johnson, Fred L.,1,31Leakage,118Load variation,144Lower guide-bearing,9Lubrication,51Measuring tanks,171Mechanical valve-gear,32Nozzles, expanding,14Oil,57,103,109amount passing through bearings,122consumption, high,175detecting water in,122pressure,122-temperature curve,123Oil, testing,110velocity of flow,122Oiling,87system, importance,119Operation, Allis-Chalmers turbine,54,55successful,105Operations in handling turbine plant,146Overload valve,28Packing, carbon,19glands,71ring, self-centering,14Parsons type of turbine,41Passage in foundation,2Peep-holes,15,18Piping,171changing,179inspection,164Pressure,63gages,166in glands,57Pump, circulating, fails to meet guarantee,172inspection,164Radial clearance,63Rateau turbines,118Relief valves,31valves, importance,159Ring, carbon,20Rotor, Westinghouse-Parsons turbine,59Running,99Safety-stop,22-stop governor,86Saucer steps,39Screw, step-bearing,18step-supporting,4Separators,105Setting spindle and cylinder for minimum leakage,115valves in Curtis turbine,31,32Shaft, holding up while removing support,8Shield-plate,26,36Shim, horseshoe,8Shroud rings,44,46Shrouding on buckets and intermediates,18Shutting down,101Special turbine features,127Spindle, lifting,96removing,104Spraying mechanism,158Stage valves,28,31Starting up,54,95Step-bearing, lowering to examine,8-bearing screw,18-blocks,4-lubricant,4-pressure,38-supporting screw,4-water, flow,38Stopping turbine,56Sub-base,8Superheated steam,105Test loads,141necessary features,163Testing oil,110preparing turbine for,145steam turbine,112,137,152Thermometer, calibrating and testing,169oil,125Thrust-block,118Top block,4Troubles with steam turbine auxiliaries,172Turbine features, special,127Vacuum,152raising,107test,135Valve-gear,83-gear, mechanical,22,32operation during consumption test,138overload,28relief,31importance,159setting in Curtis turbine,31,32stage,28,31Vapor bound pumps,178Water, cooling, limited,177in oil, detecting,122-measurement readings,148pressure,101service,126importance,119tests of condenser,133used in glands,57,76Westinghouse-Parsons steam turbine,58Wheels,14lower or fourth-stage,14position,18