Equivalent pipe length of reducing elbows & tees

Question

Equivalent pipe length of reducing elbows & tees

MeckMan (Mechanical)

(OP)

3 Jun 02 13:47

I am trying to perform hydraulic calculations on our fire sprinkler system and would require the equivalent pipe length of reducing elbows and tees.

Where can I find such information?

In the absence of any such information, in the case of the reducing elbow, can I assume a standard elbow with a reducer on one end?

Thanks in advance.

vpl (Nuclear) · Answer 1 · 2002-06-03 14:23:17

Do you have Crane 410 (Flow of Fluids)?

Patricia Lougheed

rusman (Chemical) · Answer 2 · 2002-06-03 22:15:47

You can also refer to API RP 14E. It does give some equivalent length for the fittings.

MeckMan (Mechanical) · Answer 3 · 2002-06-11 09:43:23

I do have Crane 410-C but there is no mention of REDUCING elbows (i.e. 1" inlet x 1/2" outlet).

I am not familiar with API RP 14E.  I will look into it for further reference.

Besides, I have been reading more into NFPA 13 regarding the calculations of Sprinkler Systems.  Section 6-4.4.5 (c) states "calculate the loss of reducing elbows based on the equivalent feet value of the smallest outlet.  Use the equivalent feet value for the standard elbow on any abrupt 90-degree turn, such as screw-type pattern."

Furthermore, subsection (d) states that "friction loss shall be excluded for the fitting directly connected to a sprinkler".  The Handbook further states that "On branch lines with upright or pendent sprinklers screwed into the line tee, the fitting losses associated with the line tee are excluded from the calculations because it is assumed that one fitting (i.e. reducing elbow) is included in the approval tests of a sprinkler.  The presence of this fitting is accounted for by the sprinkler's K factor."

Thanks to all for your help.

Woka (Mechanical) · Answer 4 · 2002-06-20 19:47:12

Whenever I have reducing fittings (tees, elbows) I always show the change in direction going through the smaller diameter, so you seem to be on the right track...

Incidentally, do you ever make an allowance for grooved couplings in the pipeline...if so, what?

MeckMan (Mechanical) · Answer 5 · 2002-06-21 10:16:28

Thanks Woka,

I have calculated sprinkler systems using rolled grooved couplings such as Victaulic, and no I have not made any allowance for friction losses. The reason for this is that I used Victaulic couplings for only larger pipe sizes (>2-1/2"). All other smaller pipe sizes were welded due to their short lengths.

I presume cut grooved, as oposed to rolled grooved, would cause even less friction because the inside of the pipe would not have the "bump" made by rolling sch. 5 or 10 pipes.

Regards

mross (Chemical) · Answer 6 · 2002-06-21 15:29:01

If you want to do accurately this by hand then use either the K values published in "Handbook of Hydraulic Resistance- IE Idelchik" or
"Internal Flow Systems - DS Miller".

There are several software packages that will do this for you. Try searching on Google using "fluid flow software".

Hope this helps.

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Equivalent pipe length of reducing elbows & tees