Nozzle insert design 2

[mechnas]

In general for the pressure vessels according to ASME Sec VIII Div. 1 Code, all the nozzle inserts were designed in circular shapes to avoid the stress intensification factor. A renowed pressure vessel fabricated have changed the design of the nozzle inserts to square shaped based on their fabrication convenience. Please advise whether ASME code permit accptance to sqaure or rectangular shaped nozzle inserts.

 

[XL83NL]

Please provide a skecth or more details on what you mean by an insert. This is how I understand an insert;

 

[mechnas]

Please see the attached file.

 

[ll23]

IMHO, I think that its a good practice avoid square inserts, unless the corrners were round it.
I´m not the more experience here but I think that here is a good point to justify my prevoius comment.

"UG-36 OPENINGS IN PRESSURE VESSELS
(a) Shape of Opening[sup]23[/sup]
(1) Openings in cylindrical or conical portions of vessels,
or in formed heads, shall preferably be circular, elliptical,
or obround.[sup]24[/sup] When the long dimension of an
elliptical or obround opening exceeds twice the short
dimensions, the reinforcement across the short dimensions
shall be increased as necessary to provide against excessive
distortion due to twisting moment.
(2) Openings may be of other shapes than those given
in (1) above, and all corners shall be provided with a
suitable radius. When the openings are of such proportions
that their strength cannot be computed with assurance of
accuracy, or when doubt exists as to the safety of a vessel
with such openings, the part of the vessel affected shall
be subjected to a proof hydrostatic test as prescribed in
UG-101."

 

[BenStewart]

If this were a repair and you were to follow PCC-2 for insert plates, Article 2.1, it states that where rectangular and square insert plates are used the corners should be rounded to a radius and provides what that radius should be as a function of plate thickness.

 

[mechnas]

1) The case under consideration is for the new pressure vessel under fabrication. Please help me out where we can accept the square shaped inserts.

2) PCC-2 is related to the repairs, however, it provides guidelines that the corners shall be executed with radius which is a function of thickness of the vessel plates. I think in the new vessel this should not be considered.

3) The vessel under consideration is a vertical vessel with following conditions:
Design Temp : 565 deg. C
Design Pressure: 4.34 barg at bottom/ ground level.

Looking for the expert opinion please.

 

[TGS4]

Depending in your materials of construction, your design temperature of 565C (1050F) is quite likely in the creep regime. Square insert plates should be avoided at (almost) all costs for equipment in creep. The very high discontinuity stresses will be far in excess of those envisioned by a DBR Code such as ASME Section VIII, Division 1. I would stay as circular as possible.

The provision in UG-36(a)(2) is quite clear prohibiting shapes without adequate radii, but even those provisions are liberal w.r.t. creep.

 

[mechnas]

The material of construction is SA-387 Gr.11 Cl. 2 having thickness of 33 mm cladded with SS 410s material. The length and dia. of pressure vessle is 39 meters and 5.6 meters.

 

[SnTMan]

I would not accept any insert plate that did not at least have generously radiused corners. Period.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand