Existing ESFR Sprinklers With FM Global Criteria?

1/31/2022

We have a project that has carpet storage, per FM Global Sheet 8-30, Table 1. In that table, there are different K-Factor options with corresponding minimum pressures.

The existing sprinkler system has k-16.8 ESFR sprinklers.

My question is whether or not I can utilize the existing k-16.8 ESFR sprinklers and just calculate them to meet the requirements of FM Global?

In this case, it's showing a minimum required demand of 30 sprinklers at only 7 psi. Am I looking at this wrong?

Thanks in advance.

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13 Comments

Alex

1/31/2022 06:54:57 am

Hi,

Yes, you can utilize the existing system if it works hydraulically.

From your question, I cannot confirm your storage arrangement/height/sprinkler type. But you are reading the table correctly: 20@7 means you need 20 sprinklers operating at 7psi.

Thanks,
Alex

Franck

1/31/2022 11:21:51 am

No, you can't use ESFR if you are using FM data sheet 8.30. The table is with standard spray sprinklers only.

Alex

1/31/2022 01:16:51 pm

Hi Frank,

Great catch. Looks like I jumped the gun on my response this morning.

Alex

Jay

1/31/2022 04:33:28 pm

Where does the table say cmda sprinklers are required? FM classifies sprinklers as either storage or nonstorage sprinklers. Many ESFR sprinklers are FM approved storage sprinklers, which can be used in accordance with 8-30 table 1 as a quick response sprinkler.

Glenn Berger

1/31/2022 08:09:56 am

The use of 7 psi for ESFR sprinklers does not sound right. Need to use the required minimum pressure for the sprinkler type utilized.

Franck

1/31/2022 11:23:03 am

Hi Glenn
This is because the table is not intended to be used with ESFR.
You're fully right, ESFR at 7 psi does not sound good at all...

Jesse

1/31/2022 08:18:45 am

I just did a rolled carpet storage using FM 8-30.

The answer is "probably not". The FM design criteria are CMSA. That sprinkler is listed for ESFR. They are two entirely separate design approaches being control-mode and suppression-mode. So unless that sprinkler carries a listing for CMSA as well (which it doesn't), it has to be ESFR.

The 7-psi is indeed correct and you're balancing ceiling level sprinklers with the i-rack automatic sprinklers.

While hydraulically you may get it to calc, that ESFR sprinkler is dependent upon its end-head pressure required in its listing. You providing less psi to CMSA sprinklers.

Jesse

1/31/2022 08:21:09 am

Sorry, my answer was kinda convoluted.

No, you can't use that K=16.8 ESFR sprinkler. You may be able to use a K=16.8 sprinkler but it needs to be listed for CMSA, not ESFR.

My last FM 8-30 project I used K=11.2 with K=8 in-rack

1/31/2022 08:23:29 am

You are going about this properly, the only two issues I see are the following:

1. Are the current sprinklers FM approved?
2. Are the sprinklers too old to be used and should they be changed out or have representative testing performed? Since ESFRs use fast response elements, it is required after 20 years as per NFPA 25, not sure if FM Global has a similar requirement.

Franck

1/31/2022 11:24:41 am

No, you can't use ESFR if you are using FM data sheet 8.30.
The table is with standard spray sprinklers only.

2/2/2022 08:36:09 am

I cannot see where DS 8-30 talks about using only "Standard Spray Sprinklers" only. DS 8-30 says for the automatic sprinkler protection to use ceiling and in-rack sprinklers as per DS 2-0, and DS 8-9. DS 8-9 redirects to the following:

"2.3.3.2.1 Use only FM Approved sprinklers listed in the Approval Guide under the heading of Storage
Sprinklers (Ceiling-Level) for any ceiling-level sprinkler options in this data sheet."

So since this occupancy is storage, and we are using a storage data sheet this leads us to using a storage sprinkler head. For example, the JL17, and ESFR sprinkler, is considered a Quick Response storage head by the FM Approval Guide.

Franck

1/31/2022 11:20:04 am

As indicated by some above, the table 1 is not for ESFR but standard spray sprinkler (in the CMDA mode).

A few years ago, FM Global abandonned the use of density/area to go for a number of operating heads at a given pressure. And they apply that to standard sprinklers (not only CMSA or ESFR).

Roughly, when 30 sprinklers are indicated, this corresponds to the "old" 3000 sq ft area of application, while 20 sprinklers corresponds to 2000 sq ft.
And 7 psi is indicated as this is the minimum operating pressure for a sprinkler. This corresponds to a density of 0.3 gpm/sq ft with K11.2.
And then, as the minimum operating pressure for a spray sprinkler is 7 psi, you have the same pressure demand whatever the K factor above 11.2. Which is strange as the larger the orifice, the better should be the control, but the higher the density required by FM...

As a summary, what you read in table 1 is that you need a minimum density of 0.3/3000 or 0.3/2000 with IRAS, and you need a K-factor of 11.2 or more.

If you have the opportunity to have access to old version of the data sheet, at a time where FM was using density/area, you would find some very different demand... ranging from 0.2/2000 (when one level of IRAS was added for the configuration not requiring IRAS), to 0.3/3000.
With a demand of 0.25/3000 for the cubicle racks arrangement up to 15 ft (ceiling sprinklers only). But the densities of 0.2 or 0.25 gpm/sq ft are not achievable with K11.2 sprinklers, as the minimum operating pressure is 7 psi...

I know this is confusing for those who are used to NFPA 13 approach!
And this leads to many misinterpration in the field when not checked by FM Global engineers !

Franck

2/1/2022 04:47:11 am

Note also that sprinklers have minimum and maximum operating pressures.
Max is generally 175 psi.
Min is generally 7 psi for spray sprinklers.
But the minimum pressure can be slightly higher depending on the typê of sprinklers.
K25 ESFR can be listed to operate as low as 15 psi, but some other are listed to operate at least at 50 psi.
You need to check the manufacturer's data sheet to find out this minimum operating pressure.

The delivered pressure has an effect on the water droplet size as well as the delivered water spray pattern.
A too high pressure would result in finely divided droplets and non-uniform water distribution.
A too low pressure may result in an unacceptable water velocity and a too small water spray distribution pattern (elliptical shape at very high pressures).
For spray sprinklers, the best results, in term of homogeneous spray pattern, are obtained for a pressure between 0.5 bars (7 psi) and 4.8 bars (70 psi).

As ESFR have a larger orifice, a too small pressure can have adverse effect on the water droplet size and velocity and then on their efficiency to extinguish the fire (which is the aim of ESFR).

Existing ESFR Sprinklers With FM Global Criteria?

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