COMMON DEFECTS.
As maintaining unbroken speed on the water put in motion is the first essential in keeping an injector in good working-order, any thing that has a tendency to reduce that speed will jeopardize its action. A variety of influences combine to reduce the original efficiency of an injector. Those with fixed nozzles are constructed with the orifices of a certain size, and in the proportion to each other which experiment has demonstrated to be best for feeding with the varied steam-pressures. When these orifices get worn out of the proper size, the injector will work badly; and nothing will cure it but new tubes. The tubes sometimes get loose inside the shell of the injector, and drop down out of line. The water will then strike against the side of the next tube, or on some point out of the true line, scattering it into spray, which contains no energy to force itself into the boiler. A machinist examining a defective injector, should always make sure that the tubes are not loose. Injectors that suffer from this defect will not work without a high pressure of steam. Injectors suffering from incrusted water-passages will generally work best with the steam low. Cases of the latter kind are common in calcareous districts. I have known instances where injectors got so incrusted with lime that the passages were almost closed.
Joints about injectors that are kept tight by packing must be closely watched. Many an injector that failed to work satisfactorily has been entirely cured by packing the ram-gland.