TESTING PISTON RINGS AND VALVES.
To ascertain whether the piston rings and valves are leaking or not, first place a block of wood about four inches long upon the guide for cross-head and against the front cylinder head. Then turn the engine “over” until the cross-head comes back tight against the block. This will place the valve of a simple engine in such a position that steam would be admitted to cylinder through front steam port. If a reversing engine, throw the reverse lever in the last notch in end of quadrant that would allow the engine to run “over”. Then take off the back cylinder head, and open the throttle valve wide. If steam blows out past the piston, it would indicate that the rings were not tight. In case steam packing rings are used, they should be refitted or replaced by new ones. If adjustable rings are used, they should be adjusted to stop the leak, care being taken not to get them too tight. If the steam blows out through the back port, the slide valve is not tight and it will require refitting, as will also the valve seat.
If a very small amount of steam blows through, new rings or adjustment would not be necessary, as the waste of steam or back pressure resulting from it would amount to very little.
This test should be tried occasionally with a full head of steam on, to assure of the piston rings and valve being tight, as leaky pistons and valves are very wasteful of steam, sometimes causing priming, and greatly diminishing the power of the engine. Never run your engine with leaky piston or valve. Have them properly fitted at once.
After making the test, and repairing if necessary, replace the cylinder head, and be sure to remove the wood block from the guides.
KNOCKS OR POUNDS.
The Knocks or Pounds of steam engines are frequently caused by lost motion in the crank and wrist-pin boxes, valve rod and valve, cross-head and link; looseness of the piston rod, pillow block or main bearings, follower plate, or eccentrics; the slide valve having not enough or too much lead, the exhaust being cut off too soon or too late, shoulders being worn in each end of the cylinder by the packing rings not traveling over the counter-bore at the end of each stroke; or shoulders may be worn in the guides by the cross-head slides, or they may not be adjusted properly to fit the guides; boiler may foam, causing the water to be drawn over in cylinder; the piston rings may leak, thus causing cushioning; and as the crank approaches the centers, steam occupies the space between the cylinder head and piston, causing a tremendous strain upon the engine; the piston rod being packed too tight, the boxes and pins being worn flat or oval; the key in driving pulley may be loose.
TO REMEDY KNOCKS OR POUNDS
OF A STEAM ENGINE.
While it is hardly possible to prescribe a remedy for all cases, if the following practical methods are closely followed they will be found to be very useful, although in many instances the remedy must be determined by the circumstances of the individual case.