For calculating the K factor for a reducer/ expander and friction factor for materials other than steel, I have below two questions:
- For any reducer, Crane TP-410 says that the K value is independent of size ie. It doesn’t depend on the friction factor. From the formulae it appears that it depends only on the ratio of the bigger to smaller diameters ie. Beta Ratio. The formulae for any other fitting like for a valve are given as product of a ft and Leq/D. The schedule of the pipe remains as schedule 40 for class 300 and lower and is independent of the actual schedule of the pipe in which valve is fitted. However, if we want to estimate the loss through a reducer, say 6”x4” in a schedule 80 pipe (class 150), do we need to consider the actual internal diameters of the reducer ends (6” sch. 80 and 4” sch. 80) or based on the permitted schedule considering class 150 (6” sch. 40 and 4” sch. 40) for estimating Beta Ratio and subsequent theta angle? If we use pipe internal diameters based on actual schedule, do we need to convert the K back to that based on schedule 40 internakl diameter so that it will be equivalent to the ones for other fittings whose K is based on schedule 40 and arithmetic addition can be done for estimating total K?
- All the formulae for estimating the K factor consider the ft for clean commercial pipe. If we have material different from steel, I understand that Leq/D values remain same but the value of ft estimated from graph in A-23 shall be used based on the absolute roughness (epsilon) for the material and the diameter (D) under consideration. Is this understanding correct?
I would be grateful to have your opinion on the above queries.