reduce heat transfer from the furnace to the water. A good part of the nontransferred heat is, as you know, retained by the fireside or waterside deposit. However, some of the heat not properly carried away by the water and not absorbed by the deposits remains with the combustion gases. Therefore, [he temperature of the stack gas rises.
When working in the watersides of a boiler, you should take all possible precautions to keep tools, nuts, bolts, cigarette lighters, and other small objects from sliding down into the tubes. Some required precautions are as follows:
1. Remove all small objects from your pockets before entering the boiler.
2. Keep an inventory of all the tools and equipment you take into the boiler. Ensure that you remove each item and check it off the inventory before closing up the boiler.
3. Do NOT set tools or other articles down in places where you are likely to forget them. For example, you must not leave tools on top of the steam separators or in other places that are easy to reach but hard to see.
4. When an article is lost in the boiler watersides, you must NOT close up or operate the boiler until the article has been located and removed. Even a very small article can interfere with boiler circulation and cause tube ruptures.
Additional precautions for waterside work include the following:
1. Close, wire, and tag all steam, water, and air valves that could possibly admit fluid to the boiler. Disconnect (or otherwise render inoperative) the remote operating valves as well.
2. Be sure that adequate ventilation is provided before entering the waterside of a boiler.
3. Be sure that all portable extension lights are of the watertight globe type, with the globe encased in a rubberized, metal cage. Be sure all lights are grounded and wires are not broken. Examine the wires from end to end to be sure that the insulation is not broken or cracked, exposing the bare wire.
4. Station a person outside the drum whose ONLY duty is to act as tender and to assist personnel working in the drum.
Boiling out is a special waterside cleaning technique. There are two approved methods for boiling out boilers& - the sodium metasilicate pentahydrate method and the trisodium phosphate method. The method used depends upon the purpose of the boiling out. The sodium metasilicate pentahydrate method is used to remove rust-preventive compounds and other preservatives; consequently, this method is used for boiling out (1) newly erected boilers, (2) reactivated boilers, and (3) boilers that have had major tube renewals. The trisodium phosphate method is used when you are boiling out for the removal of oil and for scale softening in preparation for mechanical cleaning.
Many operators faithfully and carefully follow all the procedures and regulations concerning boiler water treatment only to find that the watersides, nevertheless, experience corrosion and pitting. It should come as no great surprise that the fault is not with the treatment methods, but rather the manner in which the boiler is permitted to stand idle. After the pressure drops within an idle boiler, air gradually seeps into the boiler, carrying oxygen with it. The air also contains carbon dioxide that combines with the boiler water to form carbonic acid, which, in turn, lowers the residual causticity of the boiler water. Gradual in-leakage of feedwater can dilute and lower the causticity of the boiler water even further. In addition, condensation within the boiler, on both waterside and firesides, can produce water droplets that are saturated with oxygen and contain no causticity. Conditions within the boiler are now ideal for active and rapid corrosion. The need for protecting boilers that are left idle for any length of time should be obvious.Continue Reading