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Replacing flange studs under pressure 3
- Thread starter byronm
- Start date
'tis wise to be leary, but it is commonly practiced, even to the point of flame cutting the bolts while the line is under pressure.
The thinking is that if the pipe is not too hot, it is okay...
but you have to look at the piping class, temperature (personnel protection), lethality class, plant operations, etc. to better guage that. When you are completely satisfied with you draft, you go to a different area of the plant and you find that the welder will not touch a natual gas line unless it has gas in it...with the flames pouring our of the joint while being welded...
are you sure the piping forum is the right place for the question?
The thinking is that if the pipe is not too hot, it is okay...
but you have to look at the piping class, temperature (personnel protection), lethality class, plant operations, etc. to better guage that. When you are completely satisfied with you draft, you go to a different area of the plant and you find that the welder will not touch a natual gas line unless it has gas in it...with the flames pouring our of the joint while being welded...
are you sure the piping forum is the right place for the question?
- Thread starter
- #3
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- #4
I work in a large oil refinery. It is common for us to replace studs on flanges that are in-service. We only allow this on flanges with 8 or more studs. For "high risk" streams, we require special review and approval. We define high risk streams as: above auto-ignition, high pressure (above 500 psi), toxic (such as high H2S above IDLH), and vapor cloud potential. For streams that are not high risk and flanges with 8 or more studs, a normal workorder approval process is used with no requirement for engineering review.
Johnny Pellin
Johnny Pellin
- Thread starter
- #6
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- #7
GregLamberson
Petroleum
byronm
We call this Hot Bolting, a pretty standard process, but as it is a higher risk, a written procedure is the way to go. I worked one up not too long ago.
A few things that you should make sure are included: hot bolting is not allowable under SIMOP conditions; cutting of bolts with a torch is not permitted; Operating pressure should be less than 75% of the MAWP as allowed under ANSI B16.5 at the operating temp of the piping or process system being worked on; flange should have a minimum of 8 bolts; process temperature should be between 40°F and 160°F; flanges, piping & equipment need to be properly supported (reuce excessive vibration or pulsation); gasket area should not show signs of leakage; piping, flanges, and bolts should not be severely corroded (to the point of affecting their integrity); existing flange bolts/nuts should be tight and of the right size & grade (one of those “goes without saying” that you really need to say).
I would also insist on a JSA (including a risk assessment).
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
We call this Hot Bolting, a pretty standard process, but as it is a higher risk, a written procedure is the way to go. I worked one up not too long ago.
A few things that you should make sure are included: hot bolting is not allowable under SIMOP conditions; cutting of bolts with a torch is not permitted; Operating pressure should be less than 75% of the MAWP as allowed under ANSI B16.5 at the operating temp of the piping or process system being worked on; flange should have a minimum of 8 bolts; process temperature should be between 40°F and 160°F; flanges, piping & equipment need to be properly supported (reuce excessive vibration or pulsation); gasket area should not show signs of leakage; piping, flanges, and bolts should not be severely corroded (to the point of affecting their integrity); existing flange bolts/nuts should be tight and of the right size & grade (one of those “goes without saying” that you really need to say).
I would also insist on a JSA (including a risk assessment).
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
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- #8
byronm-
The 2008 edition of ASME PCC-2 will be of interest to you. Several new articles have been added in this edition, including Article 3.11: Hot and Half Bolting Removal Procedures. It’s three and a half pages, enough to provide decent guidance. For what its worth, the definition is:
Hot bolting is the sequential removal and replacement of bolts on flanged joints while under reduced operating pressure. It is carried out one bolt at a time in a predetermined cross pattern sequence. Each bolt is fully tensioned before the next one is removed.
Hot bolting can be used to clean, lubricate, and reinstall existing bolts for pre-shutdown activities, replace corroded or damaged bolts, or upgrade the material specification or grade of bolts.
As mentioned in previous posts, it is a fairly common practice. In my experience in a moderate sized refinery we did this on a fairly routine basis with exceptions made as noted above for hazardous services and we were much more careful if we were replacing corroded studs (make sure the remaining studs have sufficient area left to maintain the seal).
Keep an eye on for the 2008 edition. It should be available soon…
jt
The 2008 edition of ASME PCC-2 will be of interest to you. Several new articles have been added in this edition, including Article 3.11: Hot and Half Bolting Removal Procedures. It’s three and a half pages, enough to provide decent guidance. For what its worth, the definition is:
Hot bolting is the sequential removal and replacement of bolts on flanged joints while under reduced operating pressure. It is carried out one bolt at a time in a predetermined cross pattern sequence. Each bolt is fully tensioned before the next one is removed.
Hot bolting can be used to clean, lubricate, and reinstall existing bolts for pre-shutdown activities, replace corroded or damaged bolts, or upgrade the material specification or grade of bolts.
As mentioned in previous posts, it is a fairly common practice. In my experience in a moderate sized refinery we did this on a fairly routine basis with exceptions made as noted above for hazardous services and we were much more careful if we were replacing corroded studs (make sure the remaining studs have sufficient area left to maintain the seal).
Keep an eye on for the 2008 edition. It should be available soon…
jt
I find all of this detail about "hot bolting" very informative and fascinating.
But, IMHO, what is equally interesting is the demand from "byronm's" supervisor requesting the development of a complex and potentially life theatening guideline from people without experience.
In management's view, as far as engineers go, they are all interchangable
The reason..????
Because somewhere, sometime in MBA school they are all indoctrinated to think this way
Welll...ummmm.....design a beam....select a pump......come up with a "hot-bolt" changeout guideline....its all 16 manhours.......just like I have on my little spreadsheet here.
While there are a lot of bright, learned people in these fora, this is the kind of crucially important maintenance guideline that should be developed by an outside industry consultant.
Does no one else see a danger in this type of management approach ?
How many posts have we seen on this forum from newbies who are doing something for the first time and have no where else to turn ?
My opinion only
-MJC
But, IMHO, what is equally interesting is the demand from "byronm's" supervisor requesting the development of a complex and potentially life theatening guideline from people without experience.
In management's view, as far as engineers go, they are all interchangable
The reason..????
Because somewhere, sometime in MBA school they are all indoctrinated to think this way
Welll...ummmm.....design a beam....select a pump......come up with a "hot-bolt" changeout guideline....its all 16 manhours.......just like I have on my little spreadsheet here.
While there are a lot of bright, learned people in these fora, this is the kind of crucially important maintenance guideline that should be developed by an outside industry consultant.
Does no one else see a danger in this type of management approach ?
How many posts have we seen on this forum from newbies who are doing something for the first time and have no where else to turn ?
My opinion only
-MJC
More info here...
- Thread starter
- #11
GregLamberson
Petroleum
MJCronin
On the surface, agree 100%. One would hope though that this person was tasked with being the lead on the effort and is trying to do his/her homework in order to get a good 1st draft completed for review and it would be a multi-discipline effort at the end of the day, at least that is the way it should be done. If someone, anyone is asked to write a potentially life threatening guideline on their own, regardless of the amount of experience, I would find that very troubling as well.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
On the surface, agree 100%. One would hope though that this person was tasked with being the lead on the effort and is trying to do his/her homework in order to get a good 1st draft completed for review and it would be a multi-discipline effort at the end of the day, at least that is the way it should be done. If someone, anyone is asked to write a potentially life threatening guideline on their own, regardless of the amount of experience, I would find that very troubling as well.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
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