Pipe support Span 2

[B.L.Smith]

Hi,
In many project distance between main beams of piperacks are 6 meters. According to the project pipe support span table, the allowable span for gas lines 12” and above based on line thickness, temperature, and insulation is a minimum of 12 meters. Which of these approaches is the best practice:

1-Supporting all pipes every 6 meters according to piperack beams regardless of the pipe span table. This approach causes the distribution of piping loads on all beams and the size of main beams reduces, but the supporting cost including material, welding, and NDE increases.

2-Supporting lines according to pipe support span table e.g. for 12”-20” every 12 meters and for 24” and above every 18 meters. This causes low costs of pipe support material and construction but increases the cost of the structure material.

 

[LittleInch]

Define "best"??

Lowest CAPEX, OPEX, materials, support sizes etc etc

Also depends how may pipes you have of different size mixes so there is no "best" only one more thing to complicate life.

But sure if you had a decent number of larger pipes then support them every 12 or 18m and only put in smaller supports for the smaller lines.

But then you have two different types of supports and what happens then in the future when you need to add more lines? big or small?

You could probably make an argument for both options, make only one type / size of support - simplifies life or different types - might save you a few $ in material but I guess adds more to construction.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

LittleInch summarised the problem and solution well.

To generalise even more so, refineries and chemical plants have a mixture of all sizes of pipe and years of experience in building those things has resulted in a "standard span" of 20ft. If you're building piperacks and cable trays, you most likely have similar requirements. Use 20ft spans, unless you have specific loads or unusual pipe requirements and can justify something different. No need to reinvent the wheel for that. Why mess up a good system, especially when its not likely to save a lot and you need to build pipe racks quickly, even before you start pipe fab. Standard sizes for cable trays have similar spans. Can you find cable trays that span 40ft?

 

[HTURKAK]

Typical approach, provide piperack main frames at every 6.0 m . My experience, the bay length in the range of 6.0 to 9.0 meters. If necessary,( for small dia pipes , cable trays ) provide secondary beams supported by horizontal strut beams. Optimum spacing should be around 6.0 m. If this is a real question, you may post more details ( width, height of PR, no. of storeys, pipe sizes etc..) and get better responds.

 

[StressGuy]

Maybe I'm just seeing this differently, but I don't think folks are answering the question you are asking. I read that your pipe rack is going to be built at 6m spacing and you have a line that can span 12m. You appear to be asking if you should support at the 6m spacing, or just use every other support and use the 12m spacing that the line can handle.

The question seems to be about "pipe support material" - indicating to me that all your lines will be on some kind of shoe. If there are no shoes, then the line is going to sit wherever the steel is.

As you indicate, if you go with the longer span, then the structure where the shoes are will need to be designed for two spans worth of load. You benefit by having few shoes to fabricate and less welding for the shoes to the pipe.

In general, if this is a common use pipe rack with lines of various sizes, I would go with supporting at each bent. CSA benefits from having common designs for each bent. While you theoretically spend more on shoes, you also have more chances for errors - i.e. did the shoe land at the right bent? Did construction put shoes at each bent anyway and now you have to rush to order more?

On the other and, if you had a case of this being a single line and all the steel being installed was just for that line, then it would make sense to take advantage of the longer span capability and put the supports farther apart.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.