PRIMING.
Priming in a steam boiler is the carrying over of large quantities of water by the steam to the engine, and may occur in a perfectly clean boiler. It is usually caused by too great a demand on the capacity of the boiler, too sudden and fierce firing, or after steam pressure is lowering, an increasing demand is made for it. It is usually a radical defect in the construction or capacity of the boiler, and is most frequently the result of insufficient steam space, small evaporating capacity, and lack of good circulation.
Priming is indicated by the water rising and lowering in the glass gauge more or less violently, by the clicking sound in the steam cylinder of engine as the piston forces the water from end to end, and by the regular shower of water falling from the exhaust.
Q. How do you remedy priming?
A. There are several remedies for priming, none of which will apply effectually in all cases. Where insufficient capacity is the cause, the only remedy is a larger boiler. In others, it may be prevented by carrying the water level lower, if same can be done with safety, or taking steam from side of dome instead of top, or increasing the size of steam pipe, or taking out the top row of flues, and in boilers that have no steam dome, a long dry pipe with perforated top may be of benefit.
Q. What are other causes and remedies for priming?
A. The piston rings may leak badly. If they do, they should be replaced, or made to fit cylinder perfectly. The cylinder may be badly cut by the rings. If it is, it should be re-bored and new piston rings put in.
The slide valve may be cut, and leak. In this case the valve will need re-planing and scraping, also the valve seat. If the valve is not properly set, it may also cause priming. The exhaust nozzle may be clogged with burnt oil and sediment; if it is, clean it out thoroughly.