[Richard Beale]

It’s been a long time, but as promised I have feedback for you on the success of the shop fabrication of 1½” and below SW piping. The general consensus from fabrication and construction is that it is working out well, largely due to the fact that the use of 3D CAD for the modelling of these small bore lines produces a high degree of accuracy in the pipe routing.

The negatives are that the fabricators find it a challenge to move it through the shop efficiently due to fit-up time taking longer than welding time, so they have to schedule the small bore with some larger bore to balance the shop activity. No spool fabricator would outright say it, but inference is that if all they were sent were small bore piping orders they wouldn’t be too interested in the work, but provided they have lots of large bore butt weld spools to fabricate to go along with it, they’re happy to accommodate it.

Damage in shipping and handling is more likely than that of large bore spools and consequently there’s invariably some field repair required at site. To reduce this likelihood the maximum spool length that has been adopted is 20ft (6m) as opposed to the more common 40ft (12m) for large bore.

Overall though, it does save time in the field and has proven to be a worthwhile endeavor.

[Richard Beale]

It’s been a long time, but as promised I have feedback for you on the success of the shop fabrication of 1½” and below SW piping. The general consensus from fabrication and construction is that it is working out well, largely due to the fact that the use of 3D CAD for the modelling of these small bore lines produces a high degree of accuracy in the pipe routing.

The negatives are that the fabricators find it a challenge to move it through the shop efficiently due to fit-up time taking longer than welding time, so they have to schedule the small bore with some larger bore to balance the shop activity. No spool fabricator would outright say it, but inference is that if all they were sent were small bore piping orders they wouldn’t be too interested in the work, but provided they have lots of large bore butt weld spools to fabricate to go along with it, they’re happy to accommodate it.

Damage in shipping and handling is more likely than that of large bore spools and consequently there’s invariably some field repair required at site. To reduce this likelihood the maximum spool length that has been adopted is 20ft (6m) as opposed to the more common 40ft (12m) for large bore.

Overall though, it does save time in the field and has proven to be a worthwhile endeavor.

[Richard Beale]

I found these articles on the internet that may help answer your question.
http://turbolab.tamu.edu/proc/turboproc … 19-134.pdf
http://turbolab.tamu.edu/proc/turboproc … l28019.pdf

I’m most certainly no expert in these matters, but I do have some thoughts, so take the following as only the thoughts of someone who has been involved in piping design for many years and continue to seek expert advice.

It seems to me that there is a big difference between a natural frequency or harmonic vibration that occurs in piping connected to such as a reciprocating compressor and the violent and sudden vibration encountered by the piping ahead of such as a slug catcher; the former being uniform, constant and predictable, and the latter being non uniform and varying in frequency and intensity. I think you’ll find that the design considerations for the two scenarios are quite different.

In short, I believe that you will find that your initial question about natural frequency can’t be correlated to your subsequent example of condensate water hammer in a steam line during start-up.

Keep in mind that I’m speculating to generate further thought. We all live and learn, so please share your findings with us.

[Richard Beale]

I found these articles on the internet that may help answer your question.
http://turbolab.tamu.edu/proc/turboproc … 19-134.pdf
http://turbolab.tamu.edu/proc/turboproc … l28019.pdf

I’m most certainly no expert in these matters, but I do have some thoughts, so take the following as only the thoughts of someone who has been involved in piping design for many years and continue to seek expert advice.

It seems to me that there is a big difference between a natural frequency or harmonic vibration that occurs in piping connected to such as a reciprocating compressor and the violent and sudden vibration encountered by the piping ahead of such as a slug catcher; the former being uniform, constant and predictable, and the latter being non uniform and varying in frequency and intensity. I think you’ll find that the design considerations for the two scenarios are quite different.

In short, I believe that you will find that your initial question about natural frequency can’t be correlated to your subsequent example of condensate water hammer in a steam line during start-up.

Keep in mind that I’m speculating to generate further thought. We all live and learn, so please share your findings with us.

[Richard Beale]

It’s so that the flow is as near as is possible to an equal distribution to each unit.

[Richard Beale]

Hi Tayo,
I hadn’t heard of these either, so I did a Google search. NORSOK are standards developed by the Norwegian petroleum industry. From what I’ve seen, there appears to be a heavy reference to ASME and other internationally recognized standards. I couldn’t find anything specifically on weldolets, but if you try your own search you may have better luck than myself. I would also request more information from whoever is specifying these. My guess is that it is most likely a client request.

Good luck.

[Richard Beale]

Thank you cj.abhijit and Jop. This confirms for me what I was thinking. It’s been many years since I worked on a project with a site plan, and I wasn’t turning up much with a Google search. Specifically, the conversation I had was surrounding as-builting the plot plans in existing facilities. I am of the belief that we should be maintaining up to date plot plans, whereas others believe an up to date site drawing is sufficient. The site drawing that they’re referring to is actually a survey drawing that shows roads, buildings, tankage, etc., and other features such as camps, but does not include equipment tag numbers, nor any equipment inside the buildings.

My argument is that nobody refers to a survey drawing for new project development, and everybody revises the existing plot plan. Currently we have multiple CAD files of the original plot plan, each reflecting a different project and I’m pushing to have them combined into one updated drawing.

[Richard Beale]

Have a look at ERCB Directive 056, in particular page 299 of 335, Appendix 6 Spacing Diagram. You may find what you’re looking for in this document.

http://www.ercb.ca/directives/Directive056.pdf

[Richard Beale]

The biggest mistake was to not have the master P&ID stick file in the piping area, so that the pipers were made aware immediately of the proposed process design changes. I’m surmising, but I’m willing to bet that this little omission has caused some design and stress rework and possible schedule delays. I’m also quite sure that not all of the changes are necessary nor approved by the project management team. At the least, if I were the piping lead, I’d be speaking with the project manager to firstly secure approvals before making any piping changes that result from these new mark-ups, and secondly to make it clear that I’ll be trending all rework that affects my budgeted hours. Also, while I would do my best for it not to be the case, that I’m not going to be responsible for any schedule delays that may result from this.

[Richard Beale]

H Jop,
I believe that some construction work packages have been issued with the small bore as shop fabricated, but I’m not sure how it’s working out. I will check and get back to the forum.

[Richard Beale]

Thanks 11echo,
I totally understand now. I haven’t seen these Gruvloks used for tie-ins, but it all makes sense, including the definitions of cold and hot tap.

Many thanks again for taking the time to explain this in more detail.

[Richard Beale]

Hi hc,
Listen to the advice of experience given here; you’re right on the money. I was taught that support placement was part of my job. As Jop points out, the major structures, primarily the piperacks, has to be decided well ahead of time. The modern equivalent to what I used to do manually, and share with the structural group through study drawings, is temporary steel in the 3D models, or “white steel” as it’s sometimes referred to, placed by the piping designers for the structural designers to follow.

I remember a brief two year stint many years ago that I spent in the pulp and paper industry coming from the oil and gas industry. I was chastised for placing pipe supports and coordinating these with the structural group because there was a separate pipe support group that dealt with this. I saw the fruits of their labour when I went to the field; pipe hangers to the ceiling blocking the run of an overhead crane.

[Richard Beale]

[quote]FYI …I see a fair amount of “cold” connections being use these days, usually on low temp critical commodities …fuel gas, vapor recovery headers, vacuum lines, exotic alloy pipe, etc. These are “saddles” that are held in place with U-bolts, the branch connection on these saddles have a large/thick O-ring type gasket to seal this attachment, these tend to be on the smaller size (biggest I’ve seen is 4″).

I’ve never seen or heard of this, and I’m having a hard time visualizing it. Half saddle or full saddle? Are the O-rings on the saddle or the branch? If on the saddle, are there two halves to the saddle and how would the seam be sealed? If on the branch, how do you seal the saddle on the header (surely U-bolts alone won’t suffice), and what type of connection forms the branch? There must be cutting involved into the header, much like the removal of a hot tap coupon?

Getting more back on topic, it is very gracious of you to share your friends comments. Not to be contrary, because I too agree that the world is full of differring interpretations of terminology, but I have to agree with your friend. Hot tapping by my definition is welding onto and cutting into a live line while it remains in service. Cold tapping is joining into a line taken out of service, either by spool replacement between two flanges, with the added branch as you describe, or cutting a tee or O’let into the line by welding. The former requiring of a cold work permit (no welding) and the latter requiring of a hot work permit (welding required).

[Richard Beale]

I’m not sure what you mean by a test vent. If you’re referring to hydro-test vents and drains, then the answer is yes.

[Richard Beale]

Hi raybuckner,

I agree with both 11echo and Jop, but I would like to expand on their answers. I believe that the answer to your question lies primarily in the state government legislation. In Alberta, Canada, I know of two government legislations that speak to pressure equipment, which includes process piping. The first is the Safety Codes Act and the second is the Pressure Equipment Safety Regulation; the second of which is more specific to your question. We also have the Engineering and Geoscience Professions Act which requires that all engineering work done in Alberta must have the stamped approval of a licenced professional engineer, or (unique to Alberta I think) a licenced technologist that has passed the scutiny of a joint engineering society and technology society panel of examiners. No doubt Minnesota has similar, if not identical, legislation, as do all states and provinces in North America and other countries throughout the world. By these acts it is a legal obligation of owners, designers, manufacturers and constructors to meet the requirements of the listed codes, which includes B31.3. It is also a legal requirement to have traceability of compliance. As Jop has said, the B31 codes speak to stress analysis. Such things as expansion loops, anchors and guides, and bellows and expansion joints design and placement clearly require the services of an experienced stress engineer. I cannot see how code compliance can be documented and traced, in accordance with government regulations, by any other means than that of having a professional engineer stamp the piping configurations as is detailed in the piping arrangements and/or the isometrics. Additionally, with respect to 11echo, a civil/structural engineer requires the input of a stress engineer as to the static and dynamic loadings that will be imposed by the piping on the structure in order to design their structures and piling.

Another code compliance requirement that I can think of, that can also only be ensured by an engineering review of the piping layouts, is pressure safety. For instance, when installed on the piping systems, PSV’s that protect equipment cannot be located any further away than a 3% pressure drop between the equipment and the PSV.

Leaving aside any legislation, I think that it is almost common sense that if an engineer is required to do, oversee, or approve the designs, then it is also necessary for the engineer to sign-off on and stamp the designs. I can’t speak for the rest of the world, but in Alberta it is common practice to stamp the piping designs; so-much-so that constructors will refuse to build without them.

The only debate I’ve seen recently surrounding the stamping of piping drawings is whether or not to stamp the piping arrangements or the isometrics or both. This, however, is a debate generated by the advent of 3D CAD and not a debate as to whether or not to stamp piping drawings, but rather which ones to stamp.

In the past, in the manual and even the 2D CAD drafting world, it was common practice to stamp the piping arrangements only and consider the isometrics as secondary construction documents that reflected a compilation of already signed and stamped information, and not requiring of stamping. But that was when we were doing fully dimensioned plans and sections that included all anchors and guides placement. Nowadays, with automatically generated isometrics from the model databases, piping arrangements are often plans only with minimal detail or not produced at all, and the isometrics are no longer generated by the efforts of a manual drafter from the copying of the piping arrangements and compilation of BOMs by reading the piping specs.

Rather, commonly speaking, because of the automatic isometric generation, what I see now are stamped isometrics issued for construction, and unstamped piping arrangements that are plans only issued for information, although, this does vary somewhat according to client requirements.

For your information, I have attached the below links to the Alberta legislation to which I have referred. No doubt you can do a Google search and find the applicable Minnesota legislation.

http://www.qp.alberta.ca/documents/Acts/S01.pdf

http://www.qp.alberta.ca/documents/Regs/2006_049.pdf

http://www.qp.alberta.ca/documents/Acts/E11.pdf

Please let us know of any developments and/or decisions that the engineering company(ies) you work for make. I think we’d all be really interested in a follow up of the rational and concerns behind not wanting to stamp the piping drawings.

Best wishes,
Flowr8

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