Is ESFR Appropriate for Cable Manufacturing?

5/19/2023

Can ESFR Be Used for Extra Hazard Group 2?

ust before I saw that discussion on the forum I was confronted with a nearly finished, similar situation.

A new technical plant for manufacturing of large-diameter high voltage cables. Huge amount of PE in the next-to-outer layer, and the sprinkler designer have based the fire protection on ESFR due to ‘’all the plastics’’ and generally large ceiling heights – variation between 40 and 55 feet – and a wish for ‘’maximum flexibility’’, by using table values for UUP for the respective ceiling height.

NFPA 13 – 2019 is to be used for the design.

The manufacturing process starts with a thin single wire and ends in an obvious UUP commodity.

In my mind this is mostly a production risk to be protected with spray sprinklers and density/area calculations, or CMSA-sprinkler parameters where the ceiling height permits it, especially as most of the fire load is moving cables, without automatic stop because the alarm could be undesirable or false.

It was said that cables during production would be directed up towards the ceiling, turn and twist on large diameter wheels, and also have large horizontal stretches before they run down into the next machine that may put on a new metal screening or extruding the outer PE layer before PVC or similar outer layer. Obviously a multi-stage production that in the end makes one large cable from 3 or more smaller cables.

As I have seen in earlier discussions, the understanding of the text in chapter 23.1.1 saying ‘’ESFR sprinkler shall be permitted to protect : …. Any storage arrangement OH1, OH2, EH1, and EH2 design criteria’’ must be vital for the understanding.

I don’t feel the actual situation is a storage arrangement, but if so, what is the target for the wording design criteria?

I suspect there will be ‘’longitudinal flue spaces’’ between the cables, transvers flue spaces are not possible. Some places there will be cable(s) in conflict with the minimum 300 mm horizontal distance from a storage suppression sprinkler rule.

However, this is the first time I have been presented for a ‘’ceiling only’’ option with 1 or 2 intermediate levels ESFRs having water shields.

And (luckily !?) someone had found the FM DS 8-9 Table 17b and put in K 480 storage sprinklers in the part of the manufacturing building with the highest ceiling.

Hopefully this is not the only cable manufacturing plant in the world, and I would greatly appreciate other views on this subject.

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4 Comments

Pete H

5/19/2023 06:49:07 am

I see where you were going with this, at first I also thought:

"If we look at Table 15.2.2.5(a) it gives us design densities for group a plastics in certain arrangements. If we have less than 12'-0" of storage (but over 5'-0") with a 15'-0" ceiling of an expanded exposed stable group a plastic, it is supposed to be protected as per EH2 densities. And then the densities only get greater as the storage height and building height increase and ESFR is still good for this protection. So in terms of sheer function, the sprinkler should be adequate for the hazard as long as it is properly spaced and enough water is present to meet the calculation."

But, ultimately even with that said: by code: no. Straight up no. As you stated 23.1.1 in 2019 and 12.6.7.2 (equivalent in 2016) specifically states that it is for any storage arrangement in chapter 13 referencing eh2 design criteria, not just eh2 design criteria. 8.4.6.6. (2016) specifically calls out ESFR sprinklers designed to meet any criteria in chapter 12 through 20 shall be permitted to protect light and ordinary hazard occupancies. They do not include Extra Hazard occupancies specifically.

Looking at the handbook for this section, it informs us "ESFR sprinklers are not permitted to protect flammable or combustible liquids and/or shielded storage arrangements that are part of the defining criteria for extra hazard occupancy use groups" so it seems right out.

Jesse

5/19/2023 09:14:24 am

The short answer is, no ESFR is not intended for occupancy hazard classes EH1 and EH2.

In 23.1.1(3) its says (3) Any storage arrangement OH1, OH2, EH1, and EH2
design criteria

This refers to where earlier chapter allow for protection of some misc. storage arrays using EH1 and EH2 design criteria protection. The reason for this likely being able to protect WIP storage in manufacturing. However, we don't have an option to protect EH1 or EH2 with a suppression mode design approach - just a control mode design approach.

It doesn't sound like this is a storage occupancy hazard class. I can tell you after having spent many moons in insurance loss control engineering, the UW would want to see a different protection scheme.

Anthony

5/19/2023 10:02:39 am

As Jesse and Pete have mentioned storage is not the same as production. Production has a different set of hazards as compared to storage. Specifically the area required to be protected.

Franck

5/19/2023 10:13:02 am

As ESFR are extremely good at protecting storage activities (when adequately designed), they might not be suitable for some production activities. This is why it has been excluded, for example, with EH Gr 1 & 2.
The reason is that they are operating on a very limited area (12 sprinklers), where some production may have a quick laterla spread of fire and open more sprinklers at the ceiling level. This is the case, in particular, with the use of flammable/combustible liquids, hydraulic units with high pressure... which fall under the EH classification.
So while ESFR can be fully adequate to control a fire in an "office like" occupancy, or a fire involving an electrical cabinet (I have some return of experience for this last one), the system might be quickly overtaxed with some other activities.

In your case, could the fire spreads quickly along the cables being processed, thus operating many sprinklers before stopping the production line? Not to speak about the height of the building (you are speaking of 40 to 55 ft) and possible multiple obstructions.
I would personnaly not go for an ESFR protection in your situation.

Is ESFR Appropriate for Cable Manufacturing?

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