Steam Turbines A Book of Instruction for the Adjustment and Operation of the Principal Types of this Class of Prime Movers

Excerpt

"Of the making of books there is no end." This seems especially true of steam-turbine books, but the book which really appeals to the operating engineer, the man who may have a turbine unloaded, set up, put in operation, and the builders' representative out of reach before the man who is to operate it fully realizes that he has a new type of prime mover on his hands, with which he has little or no acquaintance, has not been written. There has been much published, both descriptive and theoretical, about the turbine, but so far as the writer knows, there is nothing in print that tells the man on the job about the details of the turbine in plain language, and how to handle these details when they need handling. The operating engineer does not care why the moving buckets are made of a certain curvature, but he does care about the distance between the moving bucket and the stationary one, and he wants to know how to measure that distance, how to alter the clearance, if necessary, to prevent rubbing. He doesn't care anything about the area of the step-bearing, but he does want to know the way to get at the bearing to take it down and put it up again, etc.

The lack of literature along this line is the writer's apology for what follows. The Curtis 1500-kilowatt steam turbine will be taken first and treated "from the ground up."

On entering a turbine plant on the ground floor, the attention is at once attracted by a multiplicity of pumps, accumulators and piping. These are called "auxiliaries" and will be passed for the present to be taken up later, for though of standard types their use is comparatively new in power-plant practice, and the engineer will find that more interruptions of service will come from the auxiliaries than from the turbine itself.

It is impractical for the manufacturers to make complete foundation drawings, as they are not familiar with the lay-out of pipes and the relative position of other apparatus in the station. All that the manufacturers' drawing is intended to do is to show the customer where it will be necessary for him to locate his foundation bolts and opening for access to the step-bearing.

FIG. 1

Fig. shows the builders' foundation drawing, with the addition of several horizontal and radial tubes introduced to give passage for the various pipes which must go to the middle of the foundation. Entering through the sides of the masonry they do not block the passage, which must be as free as possible when any work is to be done on the step-bearing, or lower guide-bearing. Entering the passage in the foundation, a large screw is seen passing up through a circular block of cast iron with a 3/4-inch pipe passing through it. This is the step-supporting screw. It supports the lower half of the step-bearing, which in turn supports the entire revolving part of the machine. It is used to hold the wheels at a proper hight in the casing, and adjust the clearance between the moving and stationary buckets. The large block which with its threaded bronze bushing forms the nut for the screw is called the cover-plate, and is held to the base of the machine by eight 1-1/2-inch cap-screws. On the upper side are two dowel-pins which enter the lower step and keep it from turning. (See Figs. and .)

FIG. 2

FIG. 3

The step-blocks are very common-looking chunks of cast iron, as will be seen by reference to Fig. . The block with straight sides (the lower one in the illustration) has the two dowel holes to match the pins spoken of, with a hole through the center threaded for 3/4-inch pipe. The step-lubricant is forced up through this hole and out between the raised edges in a film, floating the rotating parts of the machine on a frictionless disk of oil or water. The upper step-block has two dowel-pins, also a key which fits into a slot across the bottom end of the shaft.

FIG. 4

The upper side of the top block is counterbored to fit the end of the shaft. The counterbore centers the block. The dowel-pins steer the key into the key-way across the end of the shaft, and the key compels the block to turn with the shaft. There is also a threaded hole in the under side of the top block....