Friction Loss for Roll-Grooved Couplings?

9/12/2019

I had always thought that couplings didn't need to be calculated under NFPA 13, but I'm reviewing a set of calculations which show 1-foot of schedule 40 equivalent for each coupling. This is for a 4-inch main with roll-groove couplings. Any ideas?

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4 Comments

Names.R.Hard

9/12/2019 10:46:44 am

Hmmmm, it looks like it was an old FM requirement from datasheet 2-8N, which seems to no longer be used. I couldn't find any record of it in the FM 2-0 or 3-0..

Looks in 2010 they updated their datasheets.
https://www.sfpe.org/page/2012_Q2_4

It might still be in a current datasheet somewhere, hopefully somebody who knows more can chime in

Max link

9/12/2019 11:49:50 am

Victaulic has a data sheet on roll grooved pipe.

Wayne Ammons

9/13/2019 09:38:09 am

This is no longer a requirement in FM Data Sheets. I spoke with Victaulic concerning their data sheet 26.08 for Roll Grooved Pipe, which references the now obsolete FMDS 2-8N, and was informed that their data sheet has not been updated to reflect this.

Section 2.5.3.4 Grooved Pipe Connections of FMDS 2-0 does not require a friction loss across the roll groove pipe connection like Section 2-5.3.1 of FMDS 2-8N.

Since section 27.2.4.8.1 (1) of NFPA 13, 2019 Edition requires friction loss to be calculated for "pipe, fittings, devices...", I wonder if it is the intent of the committee that the words "pipe" and "fittings" be inclusive of any friction losses created by the joining method?

Wayne Ammons

9/13/2019 11:05:29 am

I posed the question to NFSA's Expert of the Day and here is the response:

Question: Is it the intent of NFPA 13-2019 section 27.2.4.8.1(1) to require any friction losses in hydraulic calculations created by rolled grooves themselves and/or grooved couplings?

The answer to your question is, “No. Like flows through a tee on the run, while there is turbulence in flow, the friction loss is negligible and can be disregarded in the hydraulic calculations.”

If a product has a friction loss equivalent length significantly different than those shown in NFPA 13, it should be documented on the product’s data sheet and that value should be used in the calculations.

(copied with permission)

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