PREPARATIONS FOR INSPECTION
(a) At every examination of boiler or the grant of renewal of a certificate, the boiler shall be empty and thoroughly clean in all its parts. Except as provided as for in sub-regulation (f) all doors of manholes, hand holes and sight holes and cleaning plugs and all caps in the headers and mud drums of water tube boilers, all fire bars, bearers, front plates, bridge plates, fire bridges brick arches, oil fuel burners and mechanical stoker fittings shall be removed. All valves and cocks comprising the boiler mounting shall be opened up and taken apart and the valves or cocks ground, when necessary, before the Inspectors visit.
(b) Provision shall, if required by the Inspector, be made for the removal of lagging or brick-work or other concealing part and for the drilling of plates, and for verifying the pressure gauge and safety valve dimensions and weights.
(c) All smoke tubes, exterior of water tubes, smoke boxes, and external flues shall be swept clean.
(d) Provision shall be made for the effective disconnection of all steam and hot water communication with another boiler under steam as required ed in Chapter XI -A of these Regulations.
(e) No blank flange / plug shall be inserted between a safety valve chest and the boiler generally and where it is permitted by the Inspector the blank flange / plug shall be removed in his presence.
(f) At alternative annual inspections and subject to a minimum of three bottom rows or an tubes subject to the first pass of heat being opened up for inspection, the Inspector may at his discretion relax the preparation for inspection called for under (a) above in favour of boilers having an evaporative capacity of 200,000 lbs. per hour and over, and fed either water treated to the satisfaction of the Inspectors.
(g) In the case of forced flow and forced circulation types of boilers, provisions shall be made for checking that proper circulation is maintained through all sections of the circuit by the flow of water.
PREPARATIONS FOR HYDRAULIC TESTS
(a) The chest of all mounting subject to steam pressure shall be in place and shut tight or blank flanged.
(b) The safety valves should invariably be removed and the chest opening blank flanged.
(c) The attachment for the Inspector's pressure gauge shall be in order.
(d) All doors shall be properly jointed and tightened up. The boiler shall be completely filled with water, care being taken to allow all air to escape and, if possible, a preliminary test not exceeding the working pressure of the boiler shall be taken before the Inspector's visit, to test the tightness of the joints.
(e) When a boiler is hydraulically tested for the first time, it shall be entirely cleared of lagging or brickwork, at subsequent tests the lagging or brick work, or portions thereof, shall be removed if required by the Inspector.
*Provided that the Inspector may, at his discretion, allow the lagging and brick work to remain in situ, in case of boilers where the covered parts have been fabricated and tested before erection in position.
PROCEDURE OF HYDRAULIC TESTS
(i) Subject to the provisions of sub regulation (e) of regulation 381, every boiler shall be hydraulically tested after erection at site in presence of the Inspector to 1.25 times the maximum working pressure as certified by the Inspecting Authority in Form II, to be stamped on the boiler, as free from any indication of weakness or defects.
(ii) If all components of the boiler in the manufacturer's premises have not been tested hydraulically as per regulation 268, the test, on completion, shall be taken to 1.5 times the maximum working pressure.
(iii) The temperature of the water used as medium of pressure testing shall not be less than 20°C and greater than 50°C.
(iv) The test pressure shall be raised gradually under proper control at all times so that it never exceeds by more than 6% of the required pressure and maintained for 30 minutes whereupon the pressure shall be reduced to maximum allowable working pressure and maintained for sufficient time to permit close visual inspection for leakage of pressure parts.
(b) The boiler shall satisfactorily withstand such pressure without appreciable leakage or undue deflection or distortion of its parts for at least ten consecutive minutes. If the test is not satisfactory, the working pressure allowable by calculation shall be suitably reduced, unless the owner desires to make such alterations as will enable the boiler to withstand satisfactorily the hydraulic test, in which case the boiler shall again be examined after the alterations have been made, the pressure recalculated, if necessary and the boiler tested to satisfaction of the inspector.
(c) At the first hydraulic test of a boiler prior to the issue of an original certificate deflection measurement shall be made before, during and after test of each furnace length, fire-box and flat end or other plates.
(d) After the application of the hydraulic test the inspector shall carefully examine the boiler inside and outside and satisfy himself that it has satisfactorily withstood the test.
(e) In any case in which the safe working pressure to be allowed for a boiler cannot, owing to peculiar construction of any of its parts, be determined by calculation in the ordinary way, the Inspector shall, under the direction of the Chief Inspector, subject the boiler to hydraulic test for the purpose of determining the fitness of such parts. The amount of the test pressure to be applied in such a case shall not exceed the test pressure prescribed for the least working pressure found by calculation for other parts of the boiler or the intended working pressure whichever less is.
(f) Should any part of the boiler show undue detection or indication of permanent set during the progress of the test, the pressure shall be released immediately such indications are observed. The working pressure for the part shall be 40 per cent of the test pressure applied when the point of permanent set was reached. This procedure shall apply to any boiler at any test.
(g) Hydraulic tests of boilers at subsequent examination shall, except when the Inspector expressly requires otherwise, be made after the inspection. The test pressure to be applied to boilers at such subsequent examinations shall be from one and quarter to one and a half times the working pressure of the boiler.
(h) When the internal construction of size of a boiler does not permit of the Inspector getting inside it or of examining closely all it's parts, he shall see it tested by hydraulic pressure to one and a half times the working pressure at each inspection or the grant or renewal of a certificate.
(i) Water tube locomotive type and all tubular boilers shall be hydraulically tested at each inspection for the grant or renewal of a certificate, unless such test is waived under the orders of the Chief Inspector.
(j) The Inspector may if he considers it necessary, apply a hydraulic test to any boiler at any inspection.
(k) Except in the case of vertical boilers heating surface of which is less than 18.58 sq. m. (200 sq. ft.) portable and vehicular boilers, which do not require re-erection or building in brick work, the hydraulic tests of all boilers shall be conducted only after the erection of the boiler in situ, and all boilers shall after re-erection in a position different from that in which were last examined by hydraulic tested.
(l) A hydraulic test shall also be taken granting an increased pressure certificate and after repairing a boiler. However, in the case of minor repairs to the Water Tube boilers where NDT has been carried out, hydraulic testing may be dispended with provided NDT is carried out by an approved method.
(m) When carrying out hydraulic test, Inspectors shall use pressure gauges supplied by the Chief Inspector.
* Note: These deflection measurements should be entered in the memorandum of Inspection Book before it's submission to the Chief Inspector.
PROCEDURE FOR INSPECTION OF INSTALLED BOILERS
(a) 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.
(b) Scale Oil, etc- Upon entering a boiler, the Inspector shall examine all surfaces of the exposed metal to observe the action caused by the use of water, oil scale solvents, or other substances which may have intentionally or unintentionally gone in with the feed water. Any evidence of oil is dangerous and immediate steps shall be taken to prevent any further entrance of oil into the boiler .Oil or scale in the tubes of water-tube boilers or on plates over the fire of any boiler is particularly bad, often causing them to rupture.
(c) 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.
(d) Stays- All stays, whether diagonal or through, shall be examined to note that they are in even tension. All fastened ends shall be examined to note whether cracks exist where the stays are punched or drilled for rivets or bolts and, if not found in proper tension, the Inspector should recommend their proper tension, the Inspector should recommend their proper adjustment.
(e) Manholes and Other Opening- The manhole and other reinforcing plates, as well as nozzles or other connection flanged or screwed into a boiler, shall be examined internally as well as externally to see that they are not cracked or deformed, and wherever possible observation shall be made for the inside of the boiler, as to the thoroughness with which its pipe connections are made to the boiler. All openings to external attachments, such as water column connections, openings in dry pipes and opening to safety valves, shall be noted to see that they are free from obstructions.
(f) 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.
(g) Lap Joints, Fire Crack- Lap-joint boilers are apt to crack where the plates lap in the longitudinal or straight seam; if there is any evidence of leakage or other distress at this point, it shall be thoroughly investigated and, if necessary rivets removed or the plate slotted in order to determine whether cracks exist in the seam. Any cracks noted in shell plates are usually dangerous except fire cracks that run from the edge of the plate into the rivet holes of girth seams. A limited number of such fire cracks is not usually a very serious matter.
(h) Testing Stay bolts- The Inspector shall test stay bolts by tapping one end of each bolt with a hammer and when practicable a hammer or other heavy tool should be held on the opposite end to make the test more effective.
(i) 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.
(j) Ligaments between Tube Holes- The ligaments between tube holes in the heads of all types of fire-tube boilers and in shells of water-tube boilers should be examined. If leakage is noted, it may denote a broken ligament.
(k) Steam Pockets- Steam pockets on surfaces are sometimes found in new or replacement work, and wherever, this is possible or likely the Inspector should make observation and, if any are found, recommend the necessary changes.
(l) 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
off pipes with their connections and fittings, because the expansion and contraction due to rapid change in temperature and water-hammer action create a great strain upon the entire blow off system, which is more pronounced when a number of blow off pipes are joined in one common discharge. The freedom of the blow off connection on each boiler shall be tested whenever possible by opening the valve for a few seconds, at which time it can be determined whether there is excessive vibration. Blow off pipes should be free from external dampness to prevent corrosion.
(m) Water Column- The piping to the water column shall be carefully noted to see that there is no chance of water being pocketed in the piping forming the steam connection to the water column. The steam -pipe should preferably drain towards to the water column. The water pipe connection to the water column must drain towards the boiler.
The relative position of the water column to the fire surfaces of the boiler shall be observed to examin to determine their operating condition.
(n) Baffling-Water-Tube Boilers- In Water-Tube boilers, it should be noted, as far as possible, whether or not the proper baffling is in place. In many types of boilers the absence of baffling often causes high temperatures on portions of the boiler structure which are not intended to be exposed to such temperatures, from which a dangerous condition may result. The location of combustion arches with respect to tube surfaces shall be carefully noted. These are sometimes arranged so as to cause the flame to impinge on a particular part of a boiler and produces overheating of the material and consequent danger of the rupture of the part.
(o) Localization of Heat- Localization of heat brought about by improper or defective burner or stoker installation or operation creating a blow pipe effect upon the boiler, shall be condemned.
(p) Suspended Boilers-Freedom of Expansion- Where boilers are suspended the supports and setting shall be carefully examined specially at points where the boiler structure comes near the setting walls or floor. Often accumulation of ash and soot will bind the boiler structure at such points and produce excessive strains on the structure owing to the expansion of the parts under operating conditions.
(q) Safety Valves- As the safety valves are the most important attachments on the boiler, they shall be inspected with the utmost caution. There should be no accumulations of rust scale, or other foreign substances located in the casings so as to interfere with the free operation of valves. The setting and freedom of the safety valves should be tested preferably by raising the
steam pressure to the blow-in-off point, or if this cannot be done, the valves shall be tested by means of the try levers to certain if they are free. Where the steam discharged from a safety valve is led through a pipe the Inspector shall determine at the time the valve is operating whether or not the drain, opening in the discharge pipe is free and in accordance with the Regulations.
If the Inspector deems it necessary, in order to determine the freedom of discharge from a safety valve, the discharge connections should be removed. Under no circumstances should a stop valve be permitted between a boiler and its safety valve.
(r) Steam Gauges- The steam gauges on all boilers shall be removed and the Inspector shall test them and compare their readings with a standard test gauge. The readings of the steam gauges shall be observed and compared when making an inspection with steam on the boiler, where several boilers are in service connected to a common steam main. The location of the steam gauges shall be noted to see whether or not it is exposed to high temperature either externally, as would be the case if placed dose to the smoke flue or other high heated part of the boiler or setting, or exposed to heat internally due to lack of protection of the gauge spring with a proper siphon or trap to prevent steam from coming in contact with the spring. The Inspector shall see that the provisions are made for blowing out the pipe leading to the steam gauge.
Last Updated Date :- 24-07-2019
Page last updated on: 18-10-2021