Fire Detection Design in Industrial Facilities

Why office solutions don't work in factories

Standard optical smoke detectors are designed based on the assumption that smoke will rise and form a layer at the ceiling. This assumption holds true in offices. In production areas, it breaks down for four separate reasons:

• Ceiling height. As smoke rises, it cools and mixes with surrounding air, becoming diluted. After reaching a certain height, by the time it reaches the ceiling, it loses the density needed to trigger the detector; this is called thermal stratification. In high-ceiling warehouses, flame can become visible before the ceiling-mounted detector responds.
• Air movement. Ventilation, process aspiration, and drafts from large doors carry smoke away from the detector. In areas with high air changes per hour, smoke goes to the exhaust intake rather than the ceiling.
• Ambient contamination. Dust, oil vapor, exhaust, welding smoke, and cooking vapor both contaminate and trigger the optical chamber. A contaminated detector first produces false alarms, then enters a fault condition.
• Inaccessibility. In high-rack warehouses, above suspended ceilings, or on operating machinery, cleaning the detector requires stopping production; a detector that cannot be maintained becomes a detector that doesn't exist after some time.

Environment - technology matching

The table below summarizes the industrial premises most frequently encountered in the field and the preferred detection type for that premise. Final selection is always made following survey and risk assessment; the table is a starting point.

Zoning: the real work of detection

In an industrial project, the panel's zone map should be debated more than device selection. The reason is simple: what a signal means depends on which zone it comes from. The flame detector on the filling line is not just there to sound the siren, but to cut off the feed to that line.

Typical chains we establish in practice:

• Flame detector -> process shutdown. Flammable liquid transfer and filling closes with the alarm signal; otherwise suppression is applied to a fire whose supply continues.
• Smoke detection -> ventilation and damper. Continued aspiration operation carries smoke to adjacent premises and feeds the fire.
• Spark detection -> in-line suppression and valve. There is no human in this chain; duration is measured in milliseconds, operator approval via panel is not awaited.
• General alarm -> elevator, door, and turnstile. If there is card-access passage on the evacuation route in an industrial facility, unless it is released at alarm, the escape route remains only on paper.

Each of these chains must be tested individually in acceptance testing. A facility without scenario testing appears to have the system "working"; in a real fire, only the siren sounds.

Explosive atmosphere: zone map first

In volumes containing flammable gas, vapor, or combustible dust, equipment selection depends on explosive atmosphere zone classification. Zones are divided as Zone 0-1-2 for gas/vapor and Zone 20-21-22 for dusts, with each zone permitting different protection types.

Three approaches are used in practice:

1. Certified device. The detector itself is certified for the relevant zone. This is the most straightforward solution; product options are limited.
2. Intrinsically safe (Ex ia) circuit. Standard-type device is powered through a safety barrier located outside the zone; energy in the circuit is limited to a level insufficient for ignition.
3. De-energized detection. In fiber optic heat detection and pneumatic line-type detection, there is no electricity in the sensor line; they do not create ignition sources within the zone, so they do not require barriers.

The zone map is found in the facility's explosion protection document. Detection design carried out without this document in hand returns during inspection, not during commissioning.

Five most common errors in industrial projects

1. Height is overlooked. A point detector selected with office logic is mounted at a location under a ceiling exceeding ten meters where smoke cannot reach it. The project provides coverage on paper, not in the field.
2. Optical detector is placed in a dirty environment. In wood workshops, flour mills, and foundries, the optical chamber becomes contaminated within a few months. The correct answer is usually heat-based detection, ASD, or flame detector.
3. Quotation is based on unit quantity. Unit-based comparison equates the area covered by one beam detector with twenty point detectors and makes the technology difference invisible. Comparison should be made on covered area and detection time. based on
4. Maintenance access is not considered. A device installed over a crane runway, directly above an operating line, or under a ceiling without platform access is skipped at the first periodic maintenance and creates a permanent gap in the system.
5. Suppression is tendered separately from detection. If the detection signal cannot trigger suppression, both systems remain incomplete; especially in gas and in-panel applications, the triggering logic must be a shared document of both operations.

Where to start in an existing facility

For a new facility, design is built from scratch. In an operating facility, the sequence is as follows: first, a zone-based risk survey is conducted and it is measured which zones the existing system actually covers. Then, blind spots, false alarm sources, and disabled zones are listed. Generally, the resulting table shows that rather than rebuilding the system, it is necessary to reinforce three or four critical zones with correct technology.

To determine your facility's risk map, measure the coverage of your existing system, or design detection for a new process line, you can write to us or reach us at 0312 385 15 66. For our nationwide field service and periodic maintenance coverage, see the service areas page.