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Reg. 572, Reg. 573, Reg. 574
Raised manhole frames, cover plates and
joint bolts
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Raised circular manhole frames not exceeding 16 inches
in diameter shall not be less than ¾ inch thick
in all parts.
The circular cover plates and joint flanges for such
frames shall be not less than-
1 inch thick for pressures not exceeding 120 pounds
per square inch.
1- 1/8 inches thick for pressures exceeding 120 pounds
per square inch but not exceeding 200 pounds per square
inch.
1 ¼ inches thick for pressure exceeding 200 pounds
but not exceeding 250 pounds per square inch.
For pressure exceeding 250 pounds per square inch, raised
circular manhole frames shall not be fitted.
The cover plates shall be secured by at least sixteen
steel bolts not less than 1 inch diameter, such that
the stress in the bolts due to steam pressure shall not exceed:-
5,000 pounds per square inch for 1 inch bolts.
6,000 pounds per square inch for 1- 1/8 inches bolts.
6,500 pounds per square inch for 1 ¼ inches bolts.
For the purpose of calculation the pressure shall be
assumed to act on the whole area within the pitch circle
of the bolts and the bolt area at the bottom of the
screw thread shall be taken.
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Reg. 573
Stand Pipes and branches-
| a) |
The
thickness and bolting of all flanges for joining the
mountings and fittings
shall be in accordance with the dimensions as laid down in
Appendix- E to these regulations. In no case, however,
shall the thickness of flanges be less than 13 mm. |
| b) |
| (i) |
The Wall thickness of
nozzles and other connections shall not be less
than that specified for the applicable loading,
namely, internal pressure, bending and static loads. |
| (ii) |
The pressure loading
shall be determined by regulation 564, but in no
case shall the thickness be less than that calculated
by the following formula:-
| t = 0.04D + 2.5 mm |
(equation XII/10) |
where, t is the thickness of standpipe and D is
the outside diameter of connection. If the branch
is connected by screwing, the thickness ‘t’
shall be measured at the root of the thread. |
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| c) |
Where
a double flanged steam pipe is tapered, the thickness
of flange joining the boiler and fitting shall correspond
to the bore of pipe at the flange connection in accordance
with Appendix-E to these regulations. |
Reg. 574
Stayed Flat surfaces (other than Crowns
of Vertical Boilers).
Stayed heads/ Braced and stayed surfaces.
For various braced
and stayed flat plates and those which by these regulations
require staying as flat surfaces with braces or stay bolts
of uniform diameter symmetrically spaced, the thickness
should be calculate by the following formula; namely:-
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__________
e
=
Cd Ö
P
+
e1
Ö f1
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Where,
P=design pressure in kgf/cm²
e=thickness, in mm.
d=diameter of the largest circle taken between staying
points of the plate (in mm)
f1=0.85 f (f as defined in regulation 271), kfg/cm²
e1=additional thickness equal to 0.75 mm (0.03 in)
C=coefficient having the following values:-
| 1) |
C=0.33 for flanged connections;
NOTE:
d is the diameter of the largest circle taken from
the commencement of the curvature of the flange. |
| 2) |
C=0.40 for stays screwed
in plate with nut or screwed and welded, or plain
end strength welded on the outside; |
| 3) |
C=0.33 for screwed bar
stays with washer of not less than 3.5 times the
diameter of bar stay; |
| 4) |
C=0.31 for screwed bar
stays with reinforcing plate, washer and nut on
the outside.
NOTES:
1. If the plate is stayed in any other way,
average values of C shall be taken into account.
2. If the plate is flame swept, the thickness shall
be increased by 10%.
3. The welding materials used in the manufacture of
these plates shall not have the ultimate tensile
strength less than that of the plate used.
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