Method for determining loads on Pipe Racks 2

[Tioch]

I've recently been tasked with assigning loads for a rather long pipe rack. Since I'm relatively new (less than 1 yr out of college), I was wondering what method is the best way to find loads on pipe supports. I have access to ASME 31.1 and 31.3. What I have for this are line sizes and velocities, as well as lengths. I figured I'd appeal to some other experienced engineers for some assistance while I muck through the codes and standards. Thanks

 

[pmover]

Tioch,

first of all, congrats on the graduation and highly recommend you listen & observe from the "sourdoughs" (seasoned technical personnel) of your firm/industry. your professional development will grow.

as far as the loads, do not forget the weight of the transported fluid, + any additional loads (i.e. wind, earthquake, etc.) necessary for the design of pipe racks. fluid velocities are important in designing for thrust blocks (tees and pipe bends - elbows).

keep mucking through the codes, you will find useful information there.

meanwhile, good luck!
-pmover

 

[StephenA]

Don't forget expansion / contraction loads due to temperature.

StephenA

 

[1969grad]

Look at the pipe hanger chapter in Grinnell's Piping Design and Engineering book. (Note: Grinnell has been bought by someone else but that is title on the book in most engineers bookcase.)

Add the weight of the pipe, insulation and contents for the dead loads plus the wind and seismic loads from ASCE 7. Even though the pipe may normally flow gas, the weight of water during hydrotest has to be accounted for.

Longitudinal stresses have to be limited per the piping codes.

The allowable deflection of the pipe span is a much often discussed topic in the forum so I suggest you do a search of other threads. The piping codes do not specify the max deflection other than as it relates to the above stresses so you will have to use some engineering judgement considering your application.

 

[LSThill]

good technical reference sorce is COADE ENGINEERING SOFTWARE DISCUSSION FORM:

http://www.coade.com/support_discussion.asp

LST

 

[superpiper]

A common problem.
Often given by the structural engineer to help him start the design.

My advise is this. think simple.
Your rack should be designed for dead load only.
give the strucutral engineer a X-sectional drawing of your rack showing the position and size of all lines on it.
(normal piping rules of large lines at the edge and allow 1/3 for future expansion apply here)
Use standard tables to asses the weight of pipe (Filled)
including insulation (most of the old pipers will have this chart) or look on pipingdesigners.com
The structural engineer will probably allow 1/3 of deadweight for sliding forces on the support beams.
Dont assume you know where the support shoe will be for large lines. all support beams should be capable of taking the max support load (i.e pipes are not supported on every beam)
For Stress critical lines, forces are to be calculated seperatly and it is probably more cost efficient to 'upgrade' any particular structural supports as required.
It is not a bad idea if you have large relief forces etc etc on the rack to give the structural department a heads up on these forces befor inception.

 

[stanier]

You may also need to consider the following:

Cable ladders mounted on the rack will add a significant load.

If any of the lines are subjected to surge then the dynamic loads could impact on the structure. Best to desig the piping systems to avoid surge problems. Some steam lines may exhibit such forces when they start up.

Check out the facility to make sure no one has a long term plan to add a whole new tier to the rack when they build the next plant.