They just seemed backwards Ken.
Then I read Appendix E.
I had made the mistake of thinking it was all about total weight from
the zoi, so smaller pipe would be less weight, and after the
adjustments to load ratings- if 4" at 40' is 'under', 2.5" at 40'
would be 'underer'.
My only conclusion is that I a ashamed of myself for assuming it was
all about total weight and nothing more.
Thanks Dude, Brad.
Quoting Parsley Consulting <[email protected]>:
Brad,
I'm not following your conclusions with the information you've provided.
Remember that the values in Tables 9.3.5.5(a)-(l) are maximum
allowable loads for various types of pipe and spacing of the lateral
braces from each other.
Consider that if you were bracing 4" schedule 10 pipe, and the
lateral braces were spaced greater than 35' apart, but less than 40'
apart the maximum allowable load 769#. It is true that the maximum
allowable load if the lateral braces were spaced closer together,
for example greater than 25' but less than 30', the value from Table
9.3.5.5.2(a) for the maximum allowable Fpw in the ZOI is no 1,071#.
You're of course welcome to tentatively space your lateral braces at
the maximum spacing of 40' per 9.3.5.5.2.2. The very next
paragraph, 9.3.5.5.2.3 mandates that the Fpw cannot exceed the
allowable loads in the tables. As a result of that consideration
you may indeed have to respace the lateral bracing to be closer
together in order to have the resulting ZOI Fpw not exceed the
allowable load.
The tables aren't backwards by any means. The values for, say 2½"
pipe are lower than that for 4" piping - _*at the same brace
spacing*_ - because when the strength of materials calculations are
completed it's obvious that the smaller pipe is susceptible to
significant damage at much lower values.
One very valuable illustration for what these tables are addressing
is that they take into consideration the allowable load between the
lateral braces depending on their spacing.
As I am a member of the hanging and bracing committee please see the
disclaimer below.
sincerely,
*Ken Wagoner, SET
*Parsley Consulting***
*350 West 9th Avenue, Suite 206
*Escondido, California 92025
*****Phone 760-745-6181*
Visit the website <http://www.parsleyconsulting.com/> ***
On 11/27/2017 11:16 AM, [email protected] wrote:
Thanks Ken, yes, I understand this.
And I understand the zone of influence and so forth.
But these Max Load Tables threw me when I got into them more- they
seemed 'backwards'. In terms of calcing the loads in the Z.O.I.,
the 40' spacing will be greater than the 20' spacing. But I read
Appendix E and figured it had to due with pipe deflection, not just
total weight. So If these tables apply I cannot 'tentatively' space
lateral braces at 40'. And I cannot know my calc for 4" main at 40'
works and assume my 2.5" main at 40' works because it is 'less
demanding'.
I hope this makes sense.
thanks again,
Brad
*IMPORTANT NOTICE: This correspondence is not a Formal
Interpretation issued pursuant to NFPA Regulations. Any opinion
expressed is the personal opinion of the author and does not
necessarily represent the official position of the NFPA or its
Technical Committees. In addition, this correspondence is neither
intended, nor should it be relied upon, to provide professional
consultation or services**
**
**It should be noted that the above is my opinion as a member of the
NFPA Automatic Sprinkler System Hanging and Bracing Committee in
accordance with the NFPA Regulations Governing Committee Projects
and should therefore not be considered, nor relied upon, as the
official position of the NFPA or its Committees*
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