Running
While the turbine is running, it should have a certain amount of careful attention. This, of course, does not mean that the engineer must stand over it every minute of the day, but he must frequently inspect such parts as the lubricators, the oiling system, the water supply to the glands and the oil-cooling coil, the pilot valve, etc. He must see that the oil is up in the reservoir and showing in the gage glass provided for that purpose, and that the oil is flowing freely through the bearings, by opening the pet cocks in the top of the bearing covers. An ample supply of oil should always be in the machine to keep the suction in the tank covered.
Care must be taken that the pump does not draw too much air. This can usually be discovered by the bubbling up of the air in the governor case, when more oil should be added.
It is well to note from time to time the temperature of the bearings, but no alarm need be occasioned because they feel warm to the touch; in fact, a bearing is all right as long as the hand can be borne upon it even momentarily. The oil coming from the bearings should be preferably about 120 degrees Fahrenheit and never exceed 160 degrees.
It should generally be seen that the oil-cooling coil is effective in keeping the oil cool. Sometimes the cooling water deposits mud on the cooling surface, as well as the oil depositing a vaseline-like substance, which interferes with the cooling effect. The bearing may become unduly heated because of this, when the coil should be taken out at the first opportunity and cleaned on the outside and blown out by steam on the inside, if this latter is possible. If this does not reduce the temperature, either the oil has been in use too long without being filtered, or the quality of the oil is not good.
Should a bearing give trouble, the first symptom will be burning oil which will smoke and give off dense white fumes which can be very readily seen and smelled. However, trouble with the bearings is one of the most unlikely things to be encountered, and, if it occurs, it is due to some radical cause, such as the bearings being pinched by their caps, or grit and foreign matter being allowed to get into the oil.
If a bearing gets hot, be assured that there is some very radical cause for it which should be immediately discovered and removed. Never, under any circumstances, imagine that you can nurse a bearing, that has heated, into good behavior. Turbine bearings are either all right or all wrong. There are no halfway measures.
The oil strainer should also be occasionally taken apart and thoroughly cleaned, which operation may be performed, if necessary, while the turbine is in operation. The screens should be cleaned by being removed from their case and thoroughly blown out with steam. In the case of a new machine, this may have to be done every two or three hours. In course of time, this need only be repeated perhaps once a week. The amount of dirt found will be an indication of the frequency with which this cleaning is necessary.
The proper water pressure, about five pounds per square inch, must be maintained at the glands. Any failure of this will mean that there is some big leak in the piping, or that the water is not flowing properly.
The pilot valve must be working freely, causing but little kick on the governor, and should be lubricated from time to time with good oil.
Should it become necessary, while operating, to shut down the condenser and change over to non-condensing operation, particular care should be observed that the change is not made too suddenly to non-condensing, as all the low-pressure sections of the turbine must be raised to a much higher temperature. While this may not cause an accident, it is well to avoid the stresses which necessarily result from the sudden change of temperature. The same reasons, of course, do not hold good in changing from non-condensing to condensing.