1)
|
Materials:-
|
| (a) |
The materials used in
the construction of Small Industrial boilers shall,
except as otherwise provided hereinafter, conform
to the provisions made in Chapter
II of these regulations.
|
| (b) |
Steel plates used in
the construction of the boilers shall be of IS:
2062 grade B or C or equivalent and the plate for
shell and heads shall be not less than 6 mm. in
thickness and the heads as tube sheets for tubes
rolled in shall be at least 8 mm. in thickness.
|
| (c) |
(i)
|
Heads of parts of boilers
when not exposed to direct impact of flame may be
made of cast iron or malleable iron provided they
comply with other requirements of these regulations. |
| |
(ii)
|
The allowable stress
on cast iron or malleable iron shall be based on
the tensile strength of material with a factor of
safety of not less than 4.5.
|
| 2) |
|
Design, construction,
workmanship and the method of computing the maximum
allowable working pressure: |
| (a) |
(i)
|
The construction except
where otherwise specified shall be the same as those
prescribed in the relevant provisions of the preceding
Chapters of these regulations. |
| |
(ii)
|
In the case of fusion
welded boiler neither stress relieving nor radiography
of welded joints is required.
|
| (b) |
(i)
|
In the Small Industrial
boilers unflanged steel tube plate may be inserted
into the shell and welded for the entire thickness as
shown in Fig
XIV/1 with a fillet weld
having a throat not less than 11/4 times the thickness
of the shell or tube sheet whichever is smaller. |
| |
(ii)
|
The minimum thickness
of unflanged welded tube sheets shall be 10 mm.
|
| |
|
t1 = 2 times required
thickness of a seamless shell but never less than
1.25 ts or greater than t.
|
| |
|
|
| |
(iii) |
The temperature of the
heating element of electrically heated steam boilers
shall be so controlled that it shall not exceed
650° C. |
| (e) |
(i)
|
The tubes shall be made
of steel. |
| |
(ii)
|
The tube holes shall
be drilled full size with shells butt straps and
ends bolted up in position or may be punched at
least 13 mm smaller in diameter than full size and
then drilled, reamed or finished full size with
a rotating cutter. The sharp-edges and chips removed,
the plates and butt straps reassembled metal to
metal with pins fittings the holes and with tack
bolts. |
| (3) |
|
Inspection and testing:- |
| |
|
The
Small Industrial Boilers shall be subjected to inspection
during construction and after completion by an Inspecting
Authority. The inspection of the boilers shall be
made at the following stages: |
|
A.
|
|
Shell type Boilers: |
| |
(i)
|
Material
identification and inspection. |
| |
(ii)
|
Inspection of each component
after completing welding and drilling. |
| |
(iii)
|
Assembly of boiler. |
| |
(iv)
|
Hydraulic test:- |
| |
|
(a)
|
Every completed boiler
of riveted construction shall be tested hydraulically
at least twice the working pressure; |
| |
|
(b)
|
In case of a boiler wholly or partly
welded construction, the hydraulic test pressure
shall be equal to two times the maximum allowable
working pressure of the boiler. |
| |
(v)
|
A test coupon shall
be provided by the maker for conducting root and
face bend tests. |
|
B.
|
|
Coil type Boilers, once
through boilers and water tube boilers: |
| |
(i)
|
Identification of materials.
|
| |
(ii) |
Hydraulic test: The pressure
for hydraulic test shall be two times that of the
working pressure of the boiler. |
| (4) |
|
Certificates and Maker’s
Stamps.- |
| (a) |
|
The certificate and
maker’s stamp shall be in conformity with the
provisions of Chapter I of these regulations. |
| (b) |
|
If owing to small size
of the boiler all information cannot be visibly
stamped on the boiler plate, maker’s certificate
accompanying the boiler shall contain the necessary
details, but in all cases name, works number and
the year of the make must be stamped or exhibited
on the boiler. |
