Double Interlock Preaction Allowed Below ESFR?

12/17/2024

With a wet ESFR system overhead, would a double interlock in rack system be permitted below?

I would assume linear heat detection would be installed in the racks, not at the roof?

These are oil storage racks and foam tray storage racks that require in-rack sprinklers. The customer has a problem with forklift/sprinkler head interaction. If allowed, I would assume the rack and overhead systems would need to be balanced.

Thanks in advance.

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4 Comments

Anthony

12/17/2024 09:20:42 am

Yes this would be permitted. I have seen this in areas where forklift drivers, despite their diligence and accuracy, continue to smash the in-rack sprinklers causing system discharge.

Andrew Davis

12/19/2024 08:16:55 am

As a former forklift driver, I apologize for my fellows

Dan Wilder

12/17/2024 11:25:28 am

If the rack storage is independent of the overhead...

NFPA 13-22' 25.6.2.1 indicates the system type shall only be wet.

I don't see any other required or not-allowed criteria from a quick keyword search.

If it's using foam, NFPA 30-24' 16.4.2.1. states the system shall immediately discharge from the sprinkler but can use a DIPA.

Jose R Figueroa

12/17/2024 02:00:04 pm

I offer these general considerations, we need more details such rack storage high, rack configuration (single? Double?), design characteristics, etc.

1. Double Interlock in-Rack System:
- A double interlock pre-action sprinkler system is typically allowed beneath an ESFR system, provided it meets specific design requirements.
- A double interlock system activates under two conditions: a detection event (like a smoke or heat detection) and a sprinkler head activation due to sufficient heat.
- The advantage is minimizing water damage and accidental activations, which is crucial in environments with high-value or sensitive inventory.

2. Linear Heat Detection:
- Linear heat detection is a suitable choice for in-rack systems as it accurately detects heat along the racks' length, providing prompt detection of rising temperatures.
- It’s often installed within the racks themselves rather than only at the roof level to ensure early detection of a fire at its source, especially in complex rack arrangements.

3. Forklift/Sprinkler Head Interaction:
- Interaction between forklifts and sprinkler heads is a common issue. Installing protective cages around the sprinkler heads, implementing strategic rack design, and using recessed or flush-mounted sprinkler heads can minimize this risk.
- Regular training and awareness programs for forklift operators can further reduce accidental damage.

4. System Balancing:
- Balancing the overhead and in-rack systems is crucial to ensure simultaneous and effective operation during a fire event.
- Professional hydraulic calculations should be performed to verify that both systems can operate together without compromising overall firefighting efficacy.

5. Compliance and Consultation:
- Always consult with a fire protection engineer or specialist who understands local fire codes and standards (such as NFPA 13 or similar such as FM DS 8-9, AJH depending on the region).
- Confirm that your designs align with any jurisdiction-specific requirements and obtain necessary approvals from local authorities or fire marshals.

By coordinating with a qualified professional and stakeholders, you can develop a cohesive system that optimizes fire protection while addressing operational challenges

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Double Interlock Preaction Allowed Below ESFR?

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