How much forcing is allowed when connecting flanges
How much forcing is allowed when connecting flanges
(OP)
We have burner fuel gas piping to be connected to the burner inlets and it was found that the flanges aren't perfectly level. Production people of course pull and push and manage to get the flanges closed but my question is in this case, the line and the bolting connection itself is under tension, so how much of this tension can we tolerate and how does it change depending on pipe size or pressure rating?
More info: the line size is 3/4" (haven't got all the papers on me right now and do not remember pipe class and w.thck.)
More info: the line size is 3/4" (haven't got all the papers on me right now and do not remember pipe class and w.thck.)





RE: How much forcing is allowed when connecting flanges
RE: How much forcing is allowed when connecting flanges
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
Thanks
RE: How much forcing is allowed when connecting flanges
2 mm stretch / 400 mm = .005
Stress = 0.005 * E = 150,000 psi
... rip.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
RE: How much forcing is allowed when connecting flanges
elongation, Δ
Δ = P * L / A / E
P = axial load
A = cross-sectional Area
L = length
E = Young's modulus = 30,000,000 psi for Grade B steel pipe.
P/A = stress = {Δ]/L * E
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
The problem, of course, was that the very systems where coldspring would do the most good (large diameter steam systems) were the most difficult to physically "spring". Come-alongs and hydraulic jacks were used to perform the "spring" along with welded lugs attached to the pipe
Coldspring was discussed in the "Piping Handbook" by Nayaar
The US nuclear power program has also struggled with this issue during the plant construction salad days of the 1980s.
As I recall, the de-facto ruling from the utilities/USNRC was that the spring could be ignored if it could be performed by one man without any assistance from jacks, come-alongs, levers or similar devices....
Just my recollection....
RE: How much forcing is allowed when connecting flanges
I think I'll just go with the flo...
RE: How much forcing is allowed when connecting flanges
BigInch just gave you the equation (awfully nice of him wasn't it, there's a way you can thank him); you need to make a decision as to whether that's ok or not -- your pipe, your decision. You have a small diameter pipe (3/4") and a short length (400 mm.) Is it within your piping allowable? You also don't mention how far out of alignment it is, which is a pretty critical dimension.
Which leads me to another question -- whenever I see mixed units and a new user, I start wondering if it's a student problem. Please come back and reassure us that this isn't a homework assignment.
Reason I'm asking is that I know
RE: How much forcing is allowed when connecting flanges
There was no rotational misalignment in my example. You'd have to add bending stress to correct a rotational misalignment. Moment required to do so /section modulus.
Even if cold spring is allowed, you cannot overstress the pipe (even though that would be in the opposite sense from the loaded condition) during installation. So, no. This pipe is far too stiff to consider rectifying any misalignment by coldspring.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
The misalignment isn't that great 2mm max I would say. Almost always one guy can manage to get the job done without any help of come alongs or chain blocks.
Perhaps I should communicate this data to someone in our head office...(which always aggravates the CM on site of course).
RE: How much forcing is allowed when connecting flanges
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
With only a 2mm displacemnt and a 3/4" line, I wouldn't be that worried. That seems to be within the boundaries of what could be nudged in place without much problem. But as a long term fix, can the piping be moved over by the 2 mm?
Interesting cases are when you see people trying to align two 12" diameter pipes off by 2" -- and one of them is rigidly restrained at one end. Crew of six big guys sweating with come alongs. It totally amazed me.
RE: How much forcing is allowed when connecting flanges
RE: How much forcing is allowed when connecting flanges
RE: How much forcing is allowed when connecting flanges
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
RE: How much forcing is allowed when connecting flanges
Seems to answer the OP's original question...
RE: How much forcing is allowed when connecting flanges
Most common for me are high compression loads anyway.
Go for it.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
RE: How much forcing is allowed when connecting flanges
RE: How much forcing is allowed when connecting flanges
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: How much forcing is allowed when connecting flanges
http://www.hss.doe.gov/IndepOversight/docs/guidanc...
(I told you that it was my "recollection".....I'm a gettin old)
RE: How much forcing is allowed when connecting flanges
Watts Bar plant:
http://pbadupws.nrc.gov/docs/ML0725/ML072540717.pd...