MotoGP
Marine/Ocean
- Jul 14, 2003
- 23
Yet again, time for me to make a concerted plea for all of your weclomed mentoring...
I am working on my first LNG project. I have no previous expriences with either Steam System piping design or Cryogenic (o/a -160 deg. C) System piping systems and their installation. Even so, I will be charged (in the future) with the responsibility of inspecting the joint fabrication and installation of these systems in the field, and it's scaring the socks off of me.
Taking either one of these systems into account, both of them utilizing material alloys of Stainless Steel:
(1-a) When visually inspecting the Cryogenic and Steam Systems' welded joint areas prior to welding, another project had a "be-all-end-all" i.d. alignment (and gap fit-up) tolerance of 2mm +/- 1mm of the drawing requirements. Later, this allowable alignment limit changed to 3mm +2mm / -1mm (I guess this an "improved, be-all-end-all" requirement). I've been trying my level best to reverse-engineer the employed method(s) used for determination of an allowable gap fit-up and allowable i.d. misalignment for these systems, but I can't seem to find anyone who really understands this topic (or, if they do, they are not willing to share it with the likes of me). I would really have much fewer sleepless nights if I could understand how to determine, on my own, when a pipe that is fit-up has a correct gap between the facing weld prep's, and to determine the allowable limits for alignment, and, most importantly (at least for me), the engineering reason(s) as to why this is so...not to just simply stare at somebody with a blank expression and regurgitate the "drawing requirement" and pretend I know the reasoning behind it. The hippocracy I'm facing just makes me thoroughly disgusted with myself...
(1-b) Can I apply these same engineering principles to determination of the misalignment of weld neck flanges?
Some some field personnel (hereafter, labeled as "guys") seem to take a subjective approach to this issue, and eye-ball the installation and ask the poor pipe welder to release and re-fit the flange, while other guys seem to let the same degree of misalignment fall into their repertoire of acceptability. It all seems like such a "black art" to me.
(1-c) Can these fit-up requirements also be comfortably applied to all diameters of piping and piping appurtenances? If so, as is what seems to be the case on the subject project, I don't really understand how these requirements can be placed on 25mm dia. piping through 400mm dia. piping. Terribly simple question for you all, I know, but, would someone kindly explain this to me?
(2) Also, I have noticed that many guys do not check the facing bevel geometry on the prepared ends of piping. Is having symmetrical weld preparation bevels and lands, on mating butt-ends of pipe, a limitless consideration, or are people just not excercising "due diligence" in these piping inspections? Some other reason(s) that you can think of?
(3) Re: Steam Piping Systems
In like stead of the "seemingly" little attention paid to checking the bevel angles on the butt-ends of piping, guys do not seem to be too concerned about checking the location of anchors, stops, and support points on the installed steam piping. Naively, I would think that this would be extremely important...maybe it's because Piping installation is considered a "mechanical" responsibility, while the supporting elements are considered to be a "structural" responsibility...I just don't understand this one, either. I guess that there sould be an allowable limit of deviation from the designed location (right?).
Finally, the last question (for now)...appropriate chorus, fanfare, applause, etc.
(4) Does any reference exist, as far as you are all aware of, that could provide me with some field guide as to the range of the "normally expected" to the "absolutely unacceptable" areas of discoloration as found in the HAZ of the pipe weld joint? I guess that I never had to deal with this issue on good-ol' mild steel pipe, but the stainless steel piping shows a variety of light blue-to-deep violet discoloration, and sometimes hues of brown in the HAZ...I don't know if I should beware of any colors in the HAZ of butt-welded piping that would indicate either an inappropriate amount of heat applied during the welding of the joint, or, if any form of discoloration in this area is "normal" and not to spend any time investigating it.
"Why-oh-why doesn't he simply ask someone these questions where he is working?", a reasonable engineer would ask.
My response would, in this case, include:
a) I am the only native-English speaking person on this project, located in Asia.
b) The area that I am living is remote, and although Charles Berlitz has helped me in many ways to communicate, he has nothing to offer me in terms of a technical vocabulary.
c) English expressions that are either vulgar or profane are widely used here, and universally understood by everyone, but, so far, this has made a very small contribution to my level of understanding of the subject issues.
d) Previous projects have taught me that the preponderance of people that I have worked with before are either "too busy" to mentor me, or, are too willing to provide me with erroneous information and are incapable of uttering the words "I don't know". I figure that it's better to try and get answers on my own.
Thanks to all of you again for saving my tail...
Best Regards,
Pete
I am working on my first LNG project. I have no previous expriences with either Steam System piping design or Cryogenic (o/a -160 deg. C) System piping systems and their installation. Even so, I will be charged (in the future) with the responsibility of inspecting the joint fabrication and installation of these systems in the field, and it's scaring the socks off of me.
Taking either one of these systems into account, both of them utilizing material alloys of Stainless Steel:
(1-a) When visually inspecting the Cryogenic and Steam Systems' welded joint areas prior to welding, another project had a "be-all-end-all" i.d. alignment (and gap fit-up) tolerance of 2mm +/- 1mm of the drawing requirements. Later, this allowable alignment limit changed to 3mm +2mm / -1mm (I guess this an "improved, be-all-end-all" requirement). I've been trying my level best to reverse-engineer the employed method(s) used for determination of an allowable gap fit-up and allowable i.d. misalignment for these systems, but I can't seem to find anyone who really understands this topic (or, if they do, they are not willing to share it with the likes of me). I would really have much fewer sleepless nights if I could understand how to determine, on my own, when a pipe that is fit-up has a correct gap between the facing weld prep's, and to determine the allowable limits for alignment, and, most importantly (at least for me), the engineering reason(s) as to why this is so...not to just simply stare at somebody with a blank expression and regurgitate the "drawing requirement" and pretend I know the reasoning behind it. The hippocracy I'm facing just makes me thoroughly disgusted with myself...
(1-b) Can I apply these same engineering principles to determination of the misalignment of weld neck flanges?
Some some field personnel (hereafter, labeled as "guys") seem to take a subjective approach to this issue, and eye-ball the installation and ask the poor pipe welder to release and re-fit the flange, while other guys seem to let the same degree of misalignment fall into their repertoire of acceptability. It all seems like such a "black art" to me.
(1-c) Can these fit-up requirements also be comfortably applied to all diameters of piping and piping appurtenances? If so, as is what seems to be the case on the subject project, I don't really understand how these requirements can be placed on 25mm dia. piping through 400mm dia. piping. Terribly simple question for you all, I know, but, would someone kindly explain this to me?
(2) Also, I have noticed that many guys do not check the facing bevel geometry on the prepared ends of piping. Is having symmetrical weld preparation bevels and lands, on mating butt-ends of pipe, a limitless consideration, or are people just not excercising "due diligence" in these piping inspections? Some other reason(s) that you can think of?
(3) Re: Steam Piping Systems
In like stead of the "seemingly" little attention paid to checking the bevel angles on the butt-ends of piping, guys do not seem to be too concerned about checking the location of anchors, stops, and support points on the installed steam piping. Naively, I would think that this would be extremely important...maybe it's because Piping installation is considered a "mechanical" responsibility, while the supporting elements are considered to be a "structural" responsibility...I just don't understand this one, either. I guess that there sould be an allowable limit of deviation from the designed location (right?).
Finally, the last question (for now)...appropriate chorus, fanfare, applause, etc.
(4) Does any reference exist, as far as you are all aware of, that could provide me with some field guide as to the range of the "normally expected" to the "absolutely unacceptable" areas of discoloration as found in the HAZ of the pipe weld joint? I guess that I never had to deal with this issue on good-ol' mild steel pipe, but the stainless steel piping shows a variety of light blue-to-deep violet discoloration, and sometimes hues of brown in the HAZ...I don't know if I should beware of any colors in the HAZ of butt-welded piping that would indicate either an inappropriate amount of heat applied during the welding of the joint, or, if any form of discoloration in this area is "normal" and not to spend any time investigating it.
"Why-oh-why doesn't he simply ask someone these questions where he is working?", a reasonable engineer would ask.
My response would, in this case, include:
a) I am the only native-English speaking person on this project, located in Asia.
b) The area that I am living is remote, and although Charles Berlitz has helped me in many ways to communicate, he has nothing to offer me in terms of a technical vocabulary.
c) English expressions that are either vulgar or profane are widely used here, and universally understood by everyone, but, so far, this has made a very small contribution to my level of understanding of the subject issues.
d) Previous projects have taught me that the preponderance of people that I have worked with before are either "too busy" to mentor me, or, are too willing to provide me with erroneous information and are incapable of uttering the words "I don't know". I figure that it's better to try and get answers on my own.
Thanks to all of you again for saving my tail...
Best Regards,
Pete
