I'm doing a project where i have to specify some minor los values. i have source on these values but can someone tell me where i can find out the typical variance in these values. eg the loss coefficient for a 90 bend is 1.5+/- x. where can i find out what is x? thanks for you help

Clifford,

This is a very good question, and one that the Navy made me answer several many years ago while working at Electric Boat. I was able to obatin some data from a series of tests on 90 degree elbows that indicated that for new, clean pipe the vatiarion in K-factor is about 5%. Needless to say, the Navy made us assume that the variation was about 10% for flow calculation purposes

I'm not sure if this data is readily available. You might be able to contact fitting and valve manufacturers to find out if they have documentation on their test programs that would indicate variation in measured pressure drop data.

This really only applies to new, clean pipe. After it's been in service all bets are off. After a year there will be a big difference in pressure drop through an elbow that's in a chilled water system, and another that's in a system transporting raw sewage.

Regards, Alton Reich