Labour Commissioner
Government of NCT of Delhi

General Instructions- It is essential to have every part of the boiler that is accessible, open and properly prepared for examination, internally and externally. All boilers have openings through which an examination may be made and which for operation are closed. all such parts shall be opened whether for access to water surfaces, or heater surfaces. In cooling a boiler down for inspection or repairs, the water should not be withdrawn until the setting is sufficiency cooled to avoid damage to the boiler and when possible allowed to cool down naturally.

It is not necessary, in order to comply with ordinary prudence, to remove insulation material, masonry, or fixed parts of the boiler, unless defects or deterioration peculiar to certain types of in accessible parts of boilers are suspected and where there is moisture or vapour showing through the covering should be removed at once and a complete investigation made. Particular attention should be paid to the external parts of boilers in the way of seating blocks, especially when the situation is damp.

Saddle tanks and engine fittings of locomotive type boilers should be removed to facilitate the inspection of the parts underneath at the first inspection, and at any reasonable period afterwards if the Inspector cannot otherwise satisfy himself as to the condition of those parts. Upon sufficient visible evidence or suspicion due to age or other causes, every effort shall be made to discover the true condition, even to the removal of insulating material, masonry or fixed parts of a boiler. Sometimes drilling or cutting away of parts is justifiable and necessary to positively determine this condition.

The Inspector should, whenever the size permits, go inside it and make a thorough inspection of all its internal parts. Before doing so, he should of course, satisfy himself that proper provision has been made for disconnecting the boiler from any other boiler under steam. Should he find that proper provision for disconnection has not been made or that the boiler has not been properly cleaned, or scaled, or that is unreasonably hot, he should decline to proceed with the inspection and should report the facts to the Chief Inspector for orders. When a boiler is of such a size or its construction is such that the Inspector cannot go inside it, there should be sufficient sight holes or hand holes provided to enable him to see the principal internal parts; if any important part of a boiler is so constructed that the Inspector cannot examine it, he should report the facts to the Chief Inspector for orders.

In the case of forced circulation and forced flow boilers which are not accessible to close visual inspection, the Inspector should, besides thorough examination, ensure by the flow of water that proper circulation is maintained through all sections of the water circuits.

Corrosion, Grooving- A given amount of corrosion along or immediately adjacent to a seam is more serious than a similar amount of corrosion in the solid plates away the seams. Grooving along longitudinal seam is especially significant as grooving or cracks are likely to occur at points where the circulation of the water is poor and such places should be examined most carefully for evidences of corrosive action.

If the inspector decides that a boiler in one or more of its parts is no longer fit for the pressure approved for it, he must without delay report his proposal for reducing the pressure to the Chief Inspector and at the same time submit his calculation for the wasted parts for check and approval of pressure.

With regard to the pitting and wasting of shell plates, the Inspector should bear in mind that shell plates may become reduce in thickness to an appreciable extent and still be stronger than longitudinal seams.

All flanging shall be thoroughly inspected and particularly the flanges of circular and plates that are not stayed. Internal grooving in the fillet of such heads and external grooving in the outer surfaces of heads concave to pressure is very common since there is slight movement in the heads of this character which produces this kind of defect. Some types of boilers have what is known as the OG or reversed flange construction in some of their parts that may be inaccessible to the eye, but the condition shall be determined by the insertion of a mirror which at a proper angle will reflect back to the eye the condition of such a place, or any other feasible manner.

Fire Surface-Bulging, Blistering, Leaks- Particular attention shall be given to the plate or tube surface exposed to the fire. The Inspector shall observe whether any part of the boiler has become deformed during operation by bulging or blistering; the former is a distortion of the entire thickness of the plate or tube where it takes place, while the latter is a lamination or separation of the plate due to forging material being embedded in the ingot before the plate is rolled. if bulges or blisters are of such size as would seriously weaken the plate or tube and especially when the leakage is noted coming from those defects, the boiler shall be discontinued from service until the defective part or parts have received proper repairs.

Careful observation shall be made to detect leakage from any portion of the boiler structure, particularly in the vicinity of seams and tube ends. Fire tubes sometimes blister but rarely collapse, the Inspector should look through the tubes for such defects and if they are found with a sufficient degree of distortion they should be removed.

Tube- Their defects, etc.-
(i) Tubes in horizontal fire tube boilers deteriorate more rapidly at the ends toward the fire, and they should be carefully tapped with a light hammer on their outer surface to ascertain whether there has been serious reduction in thickness. The tubes of vertical tubular boilers are more susceptible to deterioration as the upper ends open when reposed to the products of combustion without water protection. They should be reached as far as possible either through the hand holes if any, or inspected at the ends.

(ii) The surfaces should be carefully examined to detect bulges or cracks, or any evidences or defective welds. Where there is a strong draft the tubes may become thinned by corrosion produced by the impingement or particles of fuel and ash, or the improper use of soot blowers. A leak from a tube frequently causes serious corrosive action on a number of tubes in its immediate vicinity.

(iii) Where short tubes or nipples are employed in joining drums or headers, there is a tendency for waste products of the furnace to lodge in the junction points and such deposits are likely to cause corrosion if moisture is present. All such places should be thoroughly cleaned and examined.

Pipe Connection and Fittings- The steam and water pipes, including connections to the water column, shall be examined for leaks, and if any are found it should be determined whether they are the result of excessive strains due to expansion and contraction, or other causes. The general arrangement of the piping in regard to the provisions, for expansion and drainage, as well as adequate support at the proper points, shall be carefully noted. The location of the various stop valves shall be observed to see that water will not be pocketed when the valves are closed and thereby establish cause for water-hammer action.

The arrangement of connections between individual boilers and the main steam pipes shall be especially noted to see that any change of position of the boiler due to setting or other causes, will not produce an undue strain on the piping.

It shall be ascertained whether all pipe connections to the boiler possess the proper strength in their fastenings, whether tapped into the boiler, a fitting, or flange rivetted to the boiler.

The Inspector shall determine whether there is provision for the expansion and contraction of such piping, and that there is no undue vibration tending to crystallize the parts subjected to it. This includes all steam and water pipe and special attention should be given to the blow