4 replies to this topic

In the equation K=f * L/D, is L/D constant for pipe sizes over and above 24"? I see a chart in Crane Technical Paper 410 but it only goes to 24". This is for pipe sizes over 24". Thanks.

[pleckner]

We need more specifics. Are you just concerned about straight pipe or are there fittings involved? What fittings do you see being part of the system?

We need more specifics. Are you just concerned about straight pipe or are there fittings involved? What fittings do you see being part of the system?

Long Radius 90 degree elbows for instance. I see that L/D for a butterfly valve changes with changes in size, but does this happen with an elbow? Or, what would the L/D be for even a butterfly valve beyond 24"? For pipe sizes that go over and beyond the standard 24". Thanks.

[pleckner]

What you want to do is calculate your L/D from K/ft, where ft is the friction factor at full turbulent flow. For the elbow, you would probably use an r/d of 1.5 and this corresponds to a K of 14ft (chart on page A-29). So L/D would be 14. For these larger sizes, you can get ft from the graph on page A-23.

But warning! These large pipes are not Schedule 40 so you need to adjust the K value for the new Schedule basis. See page 2-10.

I think you could benefit from my paper on K values and equivalent lengths. You can get this paper from this site:

http://www.cheresour.../eqlength.shtml

Thank you soo much for your helpful responses.