Pressure Retaining Items 1

A pressure retaining item in code space is an item that is designed to contain pressure (either internal or externally applied).

As usual, metengr has provided the correct answer. Just a compliment, the demister support ring is not classified as pressure retaining item. However, the demister can see at times, significant differential pressure, hence the support ring has to be designed for that additional force applied on demister.
Cheers,
gr2vessels

See ASME VIII Div. 1 U-1(e)(2.

Example: in horizontal three phase separator (water & oil) the vertical baffle retain pressure of column liquid on one side. This baffle shall pass a test by filling with water on one side, prior to the hydrostatic pressure test of the separator.

Regards

r6155

If it is necessary for the vessel to be hydro'd, it is a pressure retaining item. Demister = not needed = not Pressure Retaining
Studs and nuts on manway = needed = Pressure Retaining

I am a bit unsure of how the hydrotest could make an internal support ring a pressure retaining component, with or without demister installed. Am I reading correctly, that if the vessel has to be hydrotested, then the support ring mentioned in the OP is a pressure retaining item?
Cheers,
gr2vessels

Not only. It is also a bit confusing to reverse the requirement, Duwe6.
Pressure retaining components are required to be hydrotested with the whole vessel, it's not the requirement for hydrotesting that makes an item a pressure retaining component!

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I was trying to simplify the way to recognize Pressure-Retaining vs. non-pressure retaining items welded to the pressure boundary. The internal support ring that gr2vessels mentiones could be either. If the ring is part of the Design Calc's for either the pressure or vacuum rating of that vessel, it is a Pressure-Retaining item.

If the ring is simply in the vessel to hold up a tray or demister, it is a non-Pressure Retaining item that is welded to the pressure boundary. This question comes up a lot on rings on the OD of a vessel.

If the OD ring is just to keep the insulation from slipping, it is Non-Pressure retaining, and would not be 'needed' for the hydro. [yes, all welding to the vessel pressure boundary should be done prior to hydro, but it is not mandatory]. Any contractor with a qualified WPS and a certified welder can weld or cut on these rings.

If these OD rings are used in the vessel calc's, like using them as stiffeners to achieve a Full-Vacuum rating, they have become a Pressure-Retaining item. Only a contractor with a complete "R"-stamp [or "U"-stamp] program may cut or weld on the rings. And when done, complete an "R-1" or "R-2" form, with the concurrence of their AI. They are just as important to the vessel as the heads or shell.

The support ring for demister was mentioed by the Original Poster (OP), not me. The question seems to be straight forward, clip or support ring for a demister. Since no vacuum or any other condition was mentioned, the ring is not a pressure retaining part. As for how the internal support ring can turn into an insulation support ring, no comments. By the way, where is hhmh2004 to tell us if we managed to clarify his problem or managed to confuse him?
Cheers,
gr2vessels

For internal pressure:

1) Pressure retaining parts:

Shell, heads, flanges, gaskets, nozzles, nozzle reiforcing pad (internal)...; means surface in contact with product.

2) Non pressure retaining parts:

bolts flanges ( bolt is retaining the flange, not the pressure ), stiffening rings, nozzle reinforcinga pads (external)

Regards

r6155

r6155,

You said flange bolts, stiffening rings, and external nozzle repads are non-pressure retaining parts. Where the hell did you get this idea??? How can you retain the pressure at flange joints without bolts? Now aside from thickening the vessel shell, how can you prevent your vessel from buckling due to external pressure without stiffening rings?

All vessel parts that are subject to stress due to internal or external pressure are considered pressure retaining items. Vessel shell, heads, nozzles, manways, flange bolts, stiffening rings, nozzle repads, etc. are among them.

Now back to the original poster's question about support clips/rings for demister pad...
Support clips for demisters are not pressure retaining items. For demister support rings, I echo what Duwe6 has said. If the demister support ring was considered as a stiffening ring in vessel design, then it is a pressure retaining item. Otherwise, it is not.

a) UG-82 LUGS AND FITTING ATTACHMENTS
All lugs, brackets, saddle type nozzles, manhole frames,
reinforcement around openings, and other appurtenances
shall be formed and fitted to conform reasonably to the
curvature of the shell or surface to which they are attached

Reinforcement around opening is an attachment, not a pressure retaining part. ¿How can a reinforcement around opening with a telltale hole be considered pressure retaining part? Telltale hole is for not retain pressure !!!!!! .

UG-37(g)..If the holes are plugged, the plugging material used shall not be capable
of sustaining pressure between the reinforcing plate and the vessel wall.

b)Stiffening ring is not a pressure part

UHT-28 STRUCTURAL ATTACHMENTS AND
STIFFENING RINGS
(a) Except as permitted in (b) below, all structural
attachments and stiffening rings which are welded directly
to pressure parts shall be made of materials of specified
minimum yield strength within +/-20% of that of the material
to which they are attached.

c)U-1(e)(3) pressure retaining covers for vessel openings, such as manhole or handhole covers, and bolted covers with their attaching bolting and nuts;

Flanges bolt retain the cover, and the cover retain the pressure.

Bolt is an attachment, not a pressure part

d) Several terms are used
1) Pressure part
2) Pressure retaining part
3) Load-carrying nonpressure part


e)Pressure retaining part: a part stressed due to pressure that any defect would produce a leak

More information, please see ASME VIII Div. 2

Regards

r6155

r6155,

Wow! You are interpreting the words "pressure part" or "pressure retaining part" literally, i.e. parts that are exposed to the pressure. And you've taken the time to copy and paste some clauses in the ASME Code to prove that some vessel items that were called "attachments" are not pressure parts.

Like I said before, all vessel parts that are subject to stress due to internal and external pressure are considered pressure retaining items or pressure parts. Also, parts that are "attached" to the vessel and are essential to the integrity of the vessel to withstand the pressure are considered pressure parts. These "attached" pressure parts include stiffening rings, reinforcement pads, bolting, etc.

Now since you are interpreting the ASME Code "literally", have a look at UG-14(a) or UG-82(a). (You did a copy & paste on UG-82, but you only copied the first paragraph. Have a look at what is written after that first paragraph)

doct9960

1) sorry, a mistake occur in my post:

"b)Stiffening ring is not a pressure part" must be read "b) Stiffening ring is not a pressure retaining part"

"Bolt is an attachment, not a pressure part" must be read "Bolt is an attachment, not a pressure retaining part".

2)Please, ¿have you any official interpretation, Code Case or definition between "pressure part", "pressure retaining part" and "primary pressure retaining boundary"?

Regards

r6155

doct9960

1) sorry, a mistake occur in my post:

"b)Stiffening ring is not a pressure part" must be read "b) Stiffening ring is not a pressure retaining part"

"Bolt is an attachment, not a pressure part" must be read "Bolt is an attachment, not a pressure retaining part".

2)Please, ¿have you any official interpretation, Code Case or definition between "pressure part", "pressure retaining part" and "primary pressure retaining boundary"?

Regards

r6155

r6155,

I mostly work with ASME VIII-1 vessels. I have not seen any definitions of "pressure part" or "pressure retaining part" or "pressure boundary" in ASME VIII-1. You will have to get the intended meaning of these terms from the ASME VIII-1 paragraph or rule they are mentioned. As for the term "primary pressure retaining boundary", I don't believe it is mentioned in ASME VIII-1.

Since there are no formal definitions for the above terminologies in ASME VIII-1, there would be no Interpretation on definition. There are, however, lots of Interpretations on existing "rules" concerning pressure parts, pressure retaining parts, or pressure boundary. You could browse through 61 volumes of the Interpretations and find out for yourself.

Other Codes like ASME III-1 might enlighten you (or confuse you more) about the definition of "pressure parts" or "pressure retaining parts" or "pressure boundary". Grab a copy of that Code and check it out. You could also read chapters 7.1.2 and 7.1.3 in Rao's book...
Cheers!

Please, r6155, do not insist on your position, that may only cause confusiopn to non experts.
I confirm that what doct9960 and others say above corresponds to the position of any expert in the field.
If you know the difference and the exact definition of pressure part or pressure retaining part please provide yours with all relevant references to codes.
For us experts the only definition that matters is that a pressure part or pressure retaining part (call it whatever you like) is an element of a pressure vessel whose strength is required to insure the integrity of the vessel when pressurized.
And of course, stiffening rings and bolts are pressure retaining parts!

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In my opinion, there may be a subtle difference between "pressure containing components" and "pressure retaining components". However they are all pressure parts, and ASME BPV codes seem to use these terms indiscriminately.

I agree with Doct9960. Components subject to stresses due to pressure are pressure parts as implicitly defined by UG-4. Of course flange bolts, vacuum stiffener rings and nozzle repads are pressure parts.