CHAPTER XVIII

THE SAFE OPERATION OF STEAM BOILERS

Many fatal accidents both to life and property have happened due to foolhardy methods in design and operation of the steam boiler. This early became so apparent that rigid governmental inspection of boiler operation was insisted upon. To aid in systematic inspection the Department of Commerce and Labor at Washington has issued general rules and regulations for such supervision under Form 801 entitled Steamboat Inspection Service. Many insurance companies have, too, put into force rigid rules of inspection to safeguard their interests in assuming risks. The most complete publication on the subject, however, is to be found in the recently published report of the Boiler Code Committee of the American Society of Mechanical Engineers, entitled: "Rules for the Construction of Stationary Boilers and for Allowable Working Pressure." These rules have been adopted by law in a number of States, including California where they have been incorporated in the Safety Orders of the State Accident Commission.

In the discussion taken up in this chapter only fundamentals will be considered. The thorough mastering of these fundamentals will, however, enable the reader to understandingly read the deeper discussions alluded to above.

The Inspection Tests Involved. The testing of the water and steam gages, the checking of fittings and appliances, and the trying out of the safety valves and other accessories constitute, of course, important details of boiler inspection. The most important feature, however, is to ascertain by computation the maximum allowable working pressure that may be safely put upon the boiler. After this maximum allowable pressure is ascertained the boiler is subjected to a hydrostatic pressure test by filling the boiler completely with water and then pumping enough additional water into it to raise the pressure to the desired point. This apparatus is held under proper control and the total pressure put upon the boiler is one and one-half times the maximum allowable working pressure.

Thus if the maximum allowable working pressure on a boiler is 160 lbs. per sq. in. above the atmosphere, the test pressure to be applied should be 240 lb. per sq. in.

Many carefully compiled instructions have from time to time been issued by various boiler makers, inspectors, and others interested in economic and safe operation. The instructions compiled by J. B. Warner chief inspector of the San Francisco

FIG. 76. An inspector's testing and proving outfit.

Here is a typical outfit for boiler and power plant inspectors. It consists of a standard test gage, a screw test pump, a gage hand puller, a hand set and other useful conveniences.

department of the Hartford Steam Boiler Inspection and Insurance Company are especially good, and largely the ideas appearing in the following lines come from this source:

Preliminary Precautions. Whenever going on duty in the boiler room, find out, first of all, where the water level is in the boilers. Never lower nor replenish the fires until this is done.

Make sure that the gage glass and gage cocks, and all the connections thereto, are free and in good working order. Do not rely upon the glass altogether, but use the gage cocks also, and try them all, several times a day.

Before starting up the fires, open each door about the setting and look carefully for leaks. If leaks are discovered, either then or at any other time, they should be located and repaired; but cool the boiler off first. If leaking occurs at the fore and aft joints, the inspecting company should be notified at once. This is important, whether the attendant considers the leakage serious or not; and it is especially important when the boiler has a single bottom sheet, or is of the two-sheet type.

After the maximum allowable working steam pressure for the boiler has been computed, the boiler is then submitted to a hydrostatic test of one and one-half times this allowable pressure. The above apparatus is especially adapted for those having frequent occasion to make hydrostatic tests of boilers.

When a boiler has been emptied of water, do not fill it again until it has become cold.

In preparing to get up steam after the boiler has been out of service, be sure that the manhole and hand-hole joints are tight. Do not use gaskets that are thin and hard.

Vent the boiler in some way, first, to permit the escape of air. Then fill the boiler to the proper level, open the dampers, and start the fires. Start them early so as to have the pressure up the required hour, without forcing.

Ventilate the setting thoroughly before lighting the fire. Never turn on the fuel supply when starting up without first

placing in the furnace a lighted torch or a piece of burning waste to ignite the fuel instantly.

Connecting up Boiler Units.-In firing up a boiler that is to be connected with others that are already in service, keep its stop-valve closed until the pressure within the boiler has become exactly equal to that in the steam main. Then open the stop valve a bare crack, and slowly increase the opening until the valve is wide open. The complete operation should occupy two minutes or more. Close the valve at once if there is the slightest evidence of any unusual jar or disturbance about the boiler. See that the steam main to which the boiler is to be connected is thoroughly drained before the valve is opened.

Low Water Encountered.-In case of low water, immediately shut off the oil supply at the burners. Do not turn on the feed under any circumstances, and do not open the safetyvalve nor tamper with it in any way. Let the steam outlets remain as they are. Get your boiler cool before you do anything else.

Avoid Making Repairs Under Pressure.-No repairs of any kind should be made, either to boilers or to piping, while the part upon which the work is to be done is under pressure. This applies to calking, to tightening up bolts under pressure, and to repairs of any kind whatsoever.

The safety-valve must not be set at a pressure higher than that permitted by the insurance company's policy. Try all safety-valves cautiously, every day. If the actual blowing pressure, as shown by the gage, exceeds the pressure at which the valve is supposed to blow, inform the office immediately, so that prompt notice may be sent to the company. The safety-valve pipe should never have a stop-valve upon it.

Removal of Sediment.-To remove sediment from the bottom of the boiler, open the blowoff valve in the morning, or before the circulation has started up. The valve should be opened wide for a few moments, but it should be opened and closed slowly, so as to avoid shocks from water-hammer action. When surface blowoffs are used, they should be opened frequently for a few minutes at a time.

In case of foaming, check the draft and shut off the burners. Shut the stop-valve long enough to find the true level of the water. If this is sufficiently high, blow down some of the water in the boiler, and feed in some fresh. Repeat this several times

if necessary. If the foaming does not stop, cool the boiler off, empty it, and find out the cause of the trouble.

Keep Out Cylinder Oil.-Cylinder oil must be kept out of the boilers, because it is likely to cause overheating of the plates. Oily deposits may be removed, in large measure, by scraping and scrubbing, although more efficient methods of treatment may be required in bad cases. If kerosene is used in a boiler, keep all open lights away from the manholes and handholes, both when applying the kerosene, and upon opening the boiler up afterwards; and ventilate the inside of the boiler thoroughly, after oil has been used in it.

Cooling and Cleaning the Boiler.-In cooling a boiler before emptying it, first let the fire die out, and then close all doors and leave the damper open until the pressure falls to the point at which it is desired to blow. Clean the furnace and let the brickwork cool for at least two hours before opening the blowoff valve. If it is desired to cool the boiler further, after it has been emptied open the manhole and leave everything else as in full actual service the fire doors, front connection doors, and cleaning doors being closed, and the damper and ash-pit doors open. First cool the boiler as explained in the last paragraph. Never blow out under a pressure exceeding ten or (at most) fifteen pounds by the gage. If time will permit, the boiler should be left full of water for two or three days after shutting down. This prevents the scale baking to the tubes so it remains softer and is more easily removed.

The engineer must find out for himself how often his boilers need to be opened and cleaned. In many plants it is necessary to clean every week, while in some favored few it is sufficient to clean every three months. When using kerosene or large amounts of scale solvent, or when (as in the spring-time) the water becomes unusually soft, the boilers must be opened oftener than usual. In washing out a boiler, wash the tubes from above, as well as from below.

Never touch any valve whatsoever, in any part of the room, while a man is inside of a boiler, nor even after he has come out again, until he has reported that his work is finished and that he will not enter the boiler again. It is well to lock the stop-valve and blowoff valve upon every boiler in which a man is working, while other boilers are under steam. Padlocks and chains may be used for this purpose.