Dear Sir,

Please guide on the question below for a Section I (2007 ed.) boiler drum.

For a 2:1 Ellipsoidal dished head having an obround manhole welded in similar fashion like Fig. PG-28 and having an internal manhole cover:

- Do we consider the thickness as per PG29.1 "t=5PL/4.8S" because it is a 'segment of a sphere'? Is it?

- Or do we consider the minimum thickness of this head as per PG -29.7 'at least as thick as the required thickness of a seamless shell of the same diameter as provided in PG-27.2.2' ?

In this case the reinforcement as per PG -33 has to be checked and if sufficient without any additional reinforcement (i.e. with contribution from manhole wall (A2, A3) and dished head thickness (A1) above the minimum needed as per PG-27.2.2), the head thickness shall be same as for a blank unstayed head (PG-29.5).

The subsequent provisions of PG-29.7 shall not apply since the manhole is not 'flanged in'. These provisions say "If a flanged-in manhole that meets the Code requirements is placed in an ellipsoidal head, the thickness of the head shall be the same as for a head dished to a segment of a sphere (see PG-29.1 and PG-29.5) with a dish radius equal to eight-tenths the diameter of the shell and with the added thickness for the manhole as specified in PG-29.3."

Are any other checks needed?

Thanks for your guidance in this matter in advance.

regards

mechtech

the term of dish head in PG-29 equals to torispherical head, you have to use 29.7 for hemiellipsoidal head.

Mechtech,

Just calculate the thickness of the head using formula PG-27.2.2 & perform reinforcement calculations as per PG-32 to PG-38, that is it.
If results are okay, then PG-29.7 is fully satisfied. You are using 2:1 semiellipsoidal head & manhole is not flanged-in, you have to comply with 1st paragraph of PG-29.7 only. Please also refer to, PG-28, PG-44 & especially PG-44.3.

Hope that helps.

Regards,

Nasir

_________________
Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

From Nasir. QUOTE <manhole is not flanged-in> UNQUOTE

Dear all.
I think useful to describe what a flanged-in manhole is, apparently youngsters do not know because now, the contrary of time ago, it is easier to weld a ring than to forge it into the head.
Sect.I used to have sketch, with dimensions, of the flanged-in manhole. You may see it in Sect.VIII Div.1 Fig.UG-38, called "Flued in" .
Mauro