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TOPIC: Equal and Cascade/ Tree type arrangement Air cooler

5 years 7 months ago #8403

  • Er.piping
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What is the differnence between Equal distribution and Cascade or Tree type piping arrangement in Air cooler inlet/Outlet.
Who decides the requirement process, Stress or Piping.

Re: Equal and Cascade/ Tree type arrangement Air cooler 5 years 7 months ago #7062

  • Jop
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Two issues here:
A- Who is responsible?
and
B- What is the proper arrangement?

Lets take "A" first, Who: This is a primarily a Process responsibility. They indicate on the P&ID what they want. It may not be right but it is what they think they want. Then Piping Design looks at the P&ID requirements (valving, etc), the actual equipment (size, number of tube bundles, number of inlets/outlets, inlet/outlet location), the flow (the location of the inlet fluid/gas source & the location of the outlet fluid.gas destination), the physical complexion of the Plot arrangement, Support requirements vs. support options and arrives at a proper workable solution. Pipe Stress then looks at the overall design, does any required analysis and may or may not call for changes to pipe routing or support locations.

Now "B" Proper arrangement: In my opinion "Equal distribution, Cascade and Tree type" are all the same. In reality there is "Equal Distribution" and "Balanced Flow"
- "Equal Distribution": is where one line (from the source) splits once (1 becomes 2), then these two lines split again (2 becomes 4), then these four lines each split (4 becomes 8 ), then these eight lines split (8 becomes 16). You see where this is going? What is the Air Cooler has an odd number of tube bundles? What is it has an even number of tube bundles but it is not 2,4,8 or 16?
The same complex path is repeated in reverse on the outlet side. Building this kind of "Tree" arrangement is very costly both in piping materials but the Structural Supports to hold it all up to maintain free draining. On the positive side this works with the Air Cooler Tube arrangement having either an even number of tube passes or an odd number of tube passes.

- "Balanced Flow": is where the inlet line comes in as a Header on one end (Example: the inlet end or North end) of the total Air Cooler arrangement, the Header travels from left to right past all the inlet nozzles, then there are shorter branch lines to each inlet nozzle, as the header travels past the branch lines the Header is reduced in size as the rate of flow decreases. On the other end of the Tube Bundle (the Outlet end or South end) the outlet branches are also short and connect to a Header which travels along the South end, increasing in size as it travels left to right past the outlet nozzles. When you look at each and every path from the Inlet Header at the far left through all the tube bundles to the outlet header at the far right you will see that there is Balanced flow (distance) for all paths With this type of arrangement the Air Cooler Tube arrangement needs an odd number of tube passes. This allows for differential thermal expansion in the inlet and outlet headers. With this method the problems of pipe support is simplified thus reducing the cost a great deal.

Always ask the Process Engineer, What is more important, distribution or cost?
Do it once and Do it Right

Re: Equal and Cascade/ Tree type arrangement Air cooler 5 years 7 months ago #7064

  • Jop
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For additional information on Air Cooler piping go here:
www.red-bag.com/design-standards/340-bn-...piping-and-data.html

Please note:Near the bottom of the write-up there are four sketches showing Inlet and Outlet manifolds
Detail III is close to what I recommend except they do not have the inlet header and outlet header shown correctly
Do it once and Do it Right

Re: Equal and Cascade/ Tree type arrangement Air cooler 5 years 7 months ago #7065

  • Er.piping
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Dear Jop,
I cannot thank you enough for the flawless explaination that you’ve been offering on this forum.
Thanks again..!!
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