[Sorry for the late reply, but I've been out of the office and
dealing with other priorities.]
We do not require an additional hydraulic safety margin in SC in our
reviews at the state level. We decided not to implement a "one size
fits all" solution with an across the board safety factor that would
exceed the NFPA minimum requirements, and not just because we
understand the safety margin built into the code requirements
already, but because some local water authorities that are providing
the water supply data to the designers are already adjusting it down
to account for the daily and seasonal fluctuations on that system.
The (2013) NFPA Automatic Sprinkler Systems Handbook has some good
related information seen in the commentary/FAQs to 2013 NFPA 13
23.2.1.1 and in A.23.2.1.1.
We currently rely on the engineer of record to determine the
appropriate water supply and use their own professional judgment in
choosing the margin that is appropriate to allow on a specific
project. The (2013) NFPA Automatic Sprinkler Systems Handbook has
good commentary [such as seen in the commentary to 2013 NFPA 13
24.1.2] that supports our questioning of the validity of water
supply information used in certain cases where we suspect it is not
appropriate. If, in our reviewer's opinion, a demand is too close
to the curve or is too far beyond the last known flow point, we may
question how accurately bouncing needles on test gauges can be read
during a flow test or how well they know the water supply purveyor's
system fluctuations and capabilities [including their tanks and
pumps, capacities and settings] and how much confidence they have in
us being able to witness equivalent or better flow test results if a
repeated flow test were conducted to verify the acceptability after
the system is installed and prior to issuance of the CO. We have
seen such verification flow tests cause a redesign [with a fire
pump] after verification flow testing proved the flow test used in
the initial design was not adequate...
Personally, I would prefer a trend of moving away from the standard
of one point in time flow tests on public water supplies, to using
[where available] the water provider's own water supply system model
[which incorporates their own internal validation testing],
especially if they are able to specify a level of water supply
flow/pressure normally available 365/24/7 on their system at a
specific point in the water supply near the site. If the standard
required in the plan submittal documentation a copy of such public
water system information, where applicable, it might help us better
police whether even a perfectly designed and installed water system
will still be able to fail under normal conditions due to a lack of
its most precious/essential resource...water. The building owner,
their insurance company, the fire service etc. is expecting to get a
fire sprinkler system that meets the minimum code requirements all
year round and be fully functional at that level all year long, not
just during certain parts of the year.
I hope you find this point of view of interest to the conversation,
even if it is a few days late.
Feel free to email me directly off-thread, if that is your preference.
Respectfully,
David Blackwell
David Blackwell, P.E.
Chief Engineer
(803)896-9833
Office of State Fire Marshal
141 Monticello Trail | Columbia, SC 29203
http://statefire.llr.sc.gov/
(803)896-9800
"Our firefighting starts with plan review..."
From: Sprinklerforum
[mailto:[email protected]] On Behalf Of
Mark Sornsin [FAR]
Sent: Monday, June 18, 2018 11:34 AM
To: '[email protected]'
Subject: RE: Safety Margin
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All of the horror stories in the world do not change the fact that
requiring a specific safety margin for calculations is difficult to
justify in an internationally recognized standard. I could see
Annex language offering pros for a margin and maybe giving examples
of when one might be considered.
In my view it’s the responsibility of the person engineering the
system to make this call. In this industry 99% of the time that is
the designer working for the low-bid contractor. The designer who
may or may not be NICET certified, depending on the rules of the
jurisdiction in which they are working. The point is the person with
the most knowledge of the local conditions should be making this
call. In an ideal world, when you have someone specifying the
design parameters for a bid project, it would be the specifying
engineer. I also realize that this is fantasy 98% of the time, which
is a stain on the engineering profession, but that’s a different
rant. We can’t expect to codify a requirement like this in a
standard that needs to apply throughout the world. It would require
specific numbers and these will vary on local conditions. Instead it
is the engineer/designers responsibility to become familiar with
local conditions and adjust accordingly. The example of reduced
water levels in municipal water towers is a great one. Not all
cities engage in this practice, but where they do the designer needs
to know what the minimum static pressures can be. Or the local
reviewing authority needs to adopt specific requirements to match
their local conditions.
But the real problem comes when a contractor is bidding on a job
with no real engineering guidance and no local amendments to account
for special local conditions. The low-bid contractor or will be the
one who assumes their water test is valid despite having taken it at
the highest possible pressure of the day/season. And a specific
safety margin requirement in NFPA 13 cannot guarantee proper
correction for this error.
[Visit our Website at www.SummitCoUS.com]<http://www.SummitCoUS.com>
Mark Sornsin
Sr. Fire Protection Engineer
Direct: 701-499-1391
Cell: 701-526-8585
From: Sprinklerforum
[mailto:[email protected]] On Behalf Of
Scott Futrell
Sent: Saturday, June 16, 2018 9:51 AM
To: [email protected]
Subject: RE: Safety Margin
As a plan specifier, plan reviewer and an investigator I see designs
right to the supply and then as-built conditions far worse (read
more demanding) than the design submitted with the calcs. This is
not a regional observation.
Additionally, I am aware of communities that lower elevated tank
levels 20’ in winter to lower heating costs. Contractors in those
areas do NOT adjust flow tests for this seasonal variation.
No safety margin what-so-ever in NFPA 13 is unreasonable for a
design standard.
Arguments on the floor including ‘requiring all systems to have
back-up power’ were ridiculous.
Scott
Office: (763) 425-1001 x2
Cell: (612) 759-5556
From: Sprinklerforum
[mailto:[email protected]] On Behalf Of
Steve Leyton
Sent: Friday, June 15, 2018 2:16 PM
To:
[email protected]<mailto:[email protected]>
Subject: RE: Safety Margin
That was the conversation on the floor of the code hearing. The
concerns underscored by the CAM were not about whether safety factor
is a good practice, it was that a fixed minimum value as high as 10
PSI could trigger all sorts of cost-impact consequences,
particularly in areas where pressures are middling to poor – in
Rhode Island, 10 PSI could be 25-30% of the available pressure.
In the West, due primarily to the politics of drought, water
districts are using models in lieu of physical flow tests. Prudent
and conservative programming makes it possible for them to issue
safeguarded values from which it’s not necessary to reduce the
available pressure. For ex., City of San Diego uses a three-level
safety factor in their (highly accurate) models: starting with
legacy drought water levels in the reservoirs, then factor the
highest seasonal demand, then the highest peak day demand of that
season. The values we’re getting are usually significantly lower
than what can be measured on the hydrant, and this practice isn’t
without controversy because there are obvious complications that can
and do occur, particularly with existing systems based on 20-year
old (and older) pressures that were physically measured (with crappy
equipment) when first designed and built.
But if modeling becomes the new normal, prudent water district
engineering departments and fire departments they serve can
coordinate manipulating data to include reasonable safety factors.
The range of variation in pressures, accuracy of flow test
equipment, the use of modeling in many areas … there are too many
variables to set a fixed minimum safety factor based on PSI, IMHO.
SML
From: Sprinklerforum
[mailto:[email protected]] On Behalf Of
Parsley Consulting
Sent: Friday, June 15, 2018 12:00 PM
To:
[email protected]<mailto:[email protected]>
Subject: Re: Safety Margin
Richard,
If my memory is accurate of the issues raised in the discussion that
ambiguity was a part of the differing viewpoints.
Some argued that 10 psi was not workable in their locale as their
pressures were so limited that an imposition of 10 psi was simply to
drastic and would result in much larger pipe sizes as a result.
Others argued that 10 psi was not enough, and in their area 10 psi
didn't equal 10%, and there was some reluctance to base their
designs on a pressure greater than 90% of the available.
It was quite a discussion.
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 06/15/2018 10:23 AM, Richard Carr wrote:
Even though it is not in NFPA most AHJ’s require some sort of safety
margin, 10%, 10 psi which we have had to provide for a long time so
most designers know to leave safety margin in the calc’s. it would
be nice if they all used the same amount.
Richard M. Carr, SET
Project Manager/Design
Diboco Fire Sprinklers, Inc.
325 Jackson Loop Road
Flat Rock, NC 28731
[email protected]<mailto:[email protected]>
828-696-3400
828-696-2288 Fax
828-708-9118 Mobile
[cid:[email protected]]
[cid:[email protected]]
From: Sprinklerforum
<[email protected]><mailto:[email protected]> On Behalf Of Parsley
Consulting
Sent: Friday, June 15, 2018 1:22 PM
To:
[email protected]<mailto:[email protected]>
Subject: Safety Margin
Scott,
Based on the material which was presented to the -24 and -291
committee meetings I believed the proposed safety margin and the
means to calculate that margin there was some merit in the proposal.
For reasons I don't quite remember the PI was voted down at the 2nd
draft meeting. I listened to some of the discussion, and there were
some good points made. I'm not terribly surprised it failed at the
convention level. Perhaps the attendees were following the lead of
the technical committees, and declining to overrule their decision.
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 06/15/2018 8:09 AM, Scott Futrell wrote:
Only that the 'safety margin' inclusion in the 2019 edition of NFPA
13 failed, so it won't be included or required.
I consider this unfortunate, but I'd guess that not everyone on the
forum would agree.
Scott
Office: (763) 425-1001 x2
Cell: (612) 759-5556
-----Original Message-----
From: Sprinklerforum
[mailto:[email protected]] On Behalf Of
[email protected]<mailto:[email protected]>
Sent: Thursday, June 14, 2018 5:46 PM
To:
[email protected]<mailto:[email protected]>
Subject: NFPA Vegas Convention
I didn't make it again this year.
"Caputo" is the only speaker name I recognized.
Anybody have any earthshaking epiphanies?
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