Ductile Iron Pipe Fittings Equivalent Length

[sowhatso]

Can you help me to get the DIP fittings equivalent length , for the sizes 6" , 8" , and 12". I looked for this table but I couldn't find it !!

Thanks in advance ..

 

[katmar]

The pressure drop through a fitting like a bend, tee or a valve is only slightly influenced by the surface roughness of the fitting and most of the pressure drop is due to the geometry of the fitting. You can safely use K values listed for other materials to calculate your pressure drops, provided they are for geometrically similar fittings.

But of course you should not use equivalent lengths tabulated for other materials for DIP. For a given flow through fittings of identical geometry but different materials the pressure drops will be virtually the same. But when you convert this pressure drop back to a length of pipe that would give an equivalent pressure drop then the surface roughness of the pipe is very important because the length of pipe that gives that same pressure drop will vary with the roughness.

This is why in the Crane TP-410 manual the pressure drops are all expressed in K values. The way they generate the K values is to convert the equivalent length of commercial steel pipe to a K value using the friction factor for commercial steel pipe. See Crane pg A-26.

This is just the reverse of what I described above. To convert a pressure drop in a fitting to an equivalent length of pipe I said you must use the roughness (or friction factor) for that pipe. When Crane are working in the opposite direction and are converting the equivalent lengths they determined for commercial steel pipe to K values they need to use the friction factor applicable to the commercial steel pipe in which they measured the equivalent lengths.

Crane did all their work at fully developed turbulent flow, so the friction factors are those for fully developed turbulent flow - again see the table at the top of pg A-26. Unfortunately Crane 410 says that you can then use these K values for laminar flow, but that is not true.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[nackra]

http://www.grpumps.com/upload/AV-06196.pdf

http://www.grpumps.com/education~action~list~type~education.asp

hopefully links work

 

[rconner]

fyi see

http://www.eng-tips.com/viewthread.cfm?qid=133881&page=144