Recommending on pipe guide support distance, special on marine case?

[nickcaiyh]

Dear all warm-hearted friends,
I am a new comer and this is the first time on posting.
Would you like to do me a favor on my questions for piping supports? For critical piping, the guide or the axial stop was set according to pipe stress analysis result, but for non-critical ones, is there a recommended distances or some advises for guide support?
I undertanded that the guide supports were set on considerring about wind load and seismic, so do we have a method on calculation, does the guide distance should be seperated treated for horizontal piping and vertical piping?
Is there a special consideration for marine case? As our projects is the topside on a FPSO.
I wish I have expressed my question clearly.
That's very kind of anyone of you could give me any suggestion.
Thanks very much!

 

[LittleInch]

As you haven't had a response I'll try this out. I don't really understand the difference between "critical" and "non critical". If a non critical pipe falls off the support it will become critical pretty fast... It is difficult to be precise, but a guide every 3 or 4 supports is quite common for horizontal piping, but if you have more extreme loads such as exposed piping or marine movements, this may be every one in two or one in three. A vertical support tends to be a guide all the time as there is no vertical component..

It's sometimes good to put in a specific example with drawings / sketches rather than just a relatively vague question as the answers tend to be relatively vague as well.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[racookpe1978]

I just inspected a tiny 1" drain pipe coming off of a 12 inch diameter main steam line at a power plant. The larger "critical" pipe was moving under service conditions - as you would expect.

The small 1 inch promptly moved also the same distance; and pulled three angle iron "non-critical" support right out of the concrete, sagged, and created a critical low point which could not drain.

 

[tmartin125]

I work for a marine engineering company and we use ASTM F708 as a pipe support standard for most of piping applications. Not sure if this is what you are asking because I didn't fully understand the question.

 

[nickcaiyh]

Great thanks to LittleInch,racookpe1978 and tmartin125 to my questions, I have benifited a lot from all of you.
I would like to explain more details, the critical pipes means that the pipes which will be analysis piping stress by computer software such as CAESAR II, the rest ones were of non-critical category.
We are now excutiving a FLNG project and our scope was topside, as not all of the pipes will detailed calculated by CAESAR II, so for normal temperature and non-large bore pipes, we need to have a practice on pipe safty span and pipe guide distance. I understood that these shall be different from on-shore engineering, as the pipes were installed on a floating barge, and we lack of these experience.
This forum provided me a platform on knowledge learning, and I found people were all kind-hearted to help solve question and offer best suggestion.
Thanks a million again for all of you!

 

[pennpiper]

nickcaiyh,
To put a guide on every second or every third pipe support will have to consider the spacing of the supports and the line sizes..
The missing information here is the spacing of the pipe supports and the line sizes.
It may just be that you will need to place a guide on every pipe support.

Sometimes its possible to do all the right things and still get bad results

 

[racookpe1978]

An old designer (before programs really worked - as if they do now!)- once told me, "Topside, eh? Plan for the worst case wave and ice conditions. Then double it. Maybe it won't break. "

 

[nickcaiyh]

Pennpiper,

Thank you very much for your responds, I decide to setup one guide on every second pipe restain like you said. As the project was a kind of offshore, so I think that was not too conservative.

I am tring to find a recommended table with the size, safty span and guide distance, it seems no result in any standard until Tmartin125 suggested me on ASTM F708. That was a great refference. I would like to follow the Table-8 and also the guide distance will be easy.