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Re: Fire Sprinkler Thrust Loads

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I recently had the need to look at thrust loads where a large fire water
line turned on a rather weak pipe rack.  To determine the loads, I used NFPA
24 Section 8.6.  It has the figures for thrust anchors for underground
pressure piping.  Since this code is for bell and spigot type piping, I
subtracted the internal water pressure component for the effective thrust.
Be aware that this is thrust for a pipe solid with water (force due to
momentum and change of direction).  If the pipe is empty and you have a
water slug running down the pipe, the thrust force is much larger.

I haven't had FM or any insurance carrier request this type of evaluation
for a building.

Paul F. Blomberg
Jacobs Engineering Group
Phoenix, AZ
(602) 212-5011

From: Joshua Matthews
To: seaint(--nospam--at)
Subject: Re: Fire Sprinkler Thrust Loads
Date: Saturday, October 17, 1998 11:04

I recently spoke with a friend who is a contractor who was being requested
verify that a new metal building that they had constructed be checked for
"thrust" loads in the plumbing of the fire sprinkler system.  The plumbing
braced back (and checked) to the structure for seismic loads but Factory
Mutual has requested that it be checked for "thrust" of the water moving
through the system (particularly at bends in the plumbing). It would seem
most of the forces in the plumbing would be resolved within the plumbing
itself and not be exerted on the structure (two opposing bends might create
tension in the pipe)

I have not heard of this before, has anyone else had this question come up
have any experience with this situation?

Any comments would be appreciated.

Joshua Matthews