In a plastics injection moulding plant the fire load is everywhere: pellets in raw material silos, work-in-progress beside the machines, oil in the hydraulic units and packaged product in the warehouse. Burning plastics release heat quickly, produce dense and toxic smoke and can melt and flow, spreading fire across the floor. As a result, protection in plastics plants is usually stretched hardest in the warehouse rather than the moulding hall.
Hazard classification: NFPA 13 and EN 12845
The NFPA 13 example lists include "plastics manufacturing" among the EH2 examples; in practice, the moulding hall is assessed on the amount of work-in-progress and the machine hydraulics. Under EN 12845 Annex A, plastic product manufacture is usually around OH3, with foam plastics manufacture higher. For storage, the class depends on plastic type (expanded or unexpanded), packaging (cartoned or exposed) and storage height.
| Area | NFPA 13 (typical) | EN 12845 (typical) | Note |
|---|---|---|---|
| Moulding hall (machines) | OH2–EH2 (by WIP and hydraulics) | OH3 | Limit in-hall stock |
| Hydraulic power units | EH1 (combustible fluid) | OH3–HHP | Prefer less-flammable fluid |
| Regrind and pellet preparation | OH2 + dust measures | OH3 + dust measures | Fine dust deposits |
| Raw material store (bags, big bags) | Group A plastics storage | Category III (unexpanded) | Storage criteria by height |
| Finished goods store (cartoned) | Group A cartoned unexpanded/expanded | Category III–IV | Expanded plastics are the hardest case |
| Tool room | OH1–OH2 | OH1–OH2 | Welding and grinding |
For class comparison use the NFPA 13 hazard classification tool, the EN 12845 hazard class finder and, for mapping between standards, FM Global, NFPA and EN 12845 storage class mapping.
System selection
Moulding hall
- Wet pipe sprinklers, allowing for obstructions from crane runways and ducts above the machines.
- Hydraulic units: approved less-flammable fluid, drip trays under machines and pump shutdown on fire. For large units, consider local foam-water or water mist.
- Heater bands and dryers: over-temperature cut-outs and an independent high-limit thermostat against thermal control failure.
- In-hall work-in-progress: boxes and pallets at the machines should be limited and marked so they do not exceed the design assumption of the hall protection.
Warehouse
- ESFR is often the economical choice for high-bay plastics storage, but ceiling height, rack type and commodity must stay within the listing limits. Check with the ESFR suitability checker.
- For expanded or exposed (uncartoned) plastics, ceiling-only protection may not be enough and in-rack sprinklers are needed.
- FM Global based designs assess plastics storage separately: FM DS 8-9 plastic commodity storage. Worked example: plastic raw material warehouse and ESFR.
Silos and pneumatic conveying
Pellets are generally a low dust explosion risk, but fines and "angel hair" generated during pneumatic conveying build up in filters and cyclones. Carry out a dust explosion assessment for filters and granulators: NFPA 652 dust explosion risk.
Water supply and pumps
The warehouse almost always sets the water demand in a plastics plant. ESFR design requires a set number of heads to operate simultaneously at high pressure, which can push pump capacity to several times that of the moulding hall.
- Tank volume: fire water tank sizing; duration by class and standard (90 min for high hazard under EN 12845).
- Diesel pump fuel: diesel fire pump fuel tank calculator.
- K-factor tables for head flow checks: K360 flow table.
- Hydrant demand is added to sprinkler demand; external firefighting on a plastics fire can last a long time.
Detection, alarm and smoke control
- Early detection: plastics fires grow fast. Use beam or aspirating detection in the hall and heat or flame detection at hydraulic units.
- Smoke ventilation: plastics smoke is dense and toxic, and ventilation matters for fire brigade operations. For an initial size use the smoke vent area calculator. In ESFR areas, the vent opening logic must not impair sprinkler performance.
- Interlocks: hydraulic pumps, dryers and pneumatic conveying stop on a fire signal.
- Compartmentation: a fire wall with self-closing doors between warehouse and moulding hall, and fire shutters at conveyor openings.
Turkey: points under the BYKHY
The BYKHY requires sprinklers in industrial buildings by hazard class and compartment area, with additional provisions for high-hazard storage. In plastics plants the insurer's requirement is often more decisive than the regulation.
Common site mistakes
- Warehouse calculated as "general storage" or OH3. Plastics storage criteria not applied.
- Expanded plastic packaging ignored. Even with an unexpanded product, foam packing raises the class.
- Growing in-hall stock. Machine areas turn into small warehouses.
- ESFR listing limits exceeded. Rack height is raised later while the ceiling stays the same.
- Flue spaces closed. Pallets are packed tight and water cannot get down.
- Hydraulic oil leaks not cleaned up.
- Open penetrations in fire walls. Conveyor and cable openings.
Design checklist
| Check | What to look at |
|---|---|
| Commodity | Plastic type, expanded or not, cartoned or exposed, packaging |
| Storage geometry | Rack type, storage height, ceiling height, flue spaces |
| Warehouse protection | ESFR/CMSA suitability, in-rack need |
| Moulding hall | WIP limit, obstructions, hydraulic unit protection |
| Dust | Explosion assessment for filters, cyclones and granulators |
| Compartmentation | Warehouse-to-hall fire wall, doors, penetrations |
| Water supply | Warehouse scenario, pumps, tank volume, hydrants |
| Detection and smoke | Early detection, smoke ventilation, interlocks |
| Operations | Stacking rules, signage, periodic audits |
In a plastics warehouse, the design assumption survives only through operational discipline. Rack height, commodity and flue spaces must stay as the design assumed. Post those assumptions on a sign at the warehouse entrance.
Frequently Asked Questions
What class is an injection moulding hall?
The NFPA 13 examples list plastics manufacturing around EH2; under EN 12845, plastic product manufacture is usually OH3. In-hall work-in-progress and the hydraulic fluid type directly affect the class.
Is ESFR always enough in a plastics warehouse?
No. ESFR can be used when ceiling height, storage height, rack type and commodity are within the listing limits. Expanded or exposed plastics may need in-rack sprinklers.
Why does expanded plastic packaging matter?
Expanded plastics are harder to protect than unexpanded plastics. Even with an unexpanded product, foam packing can raise the commodity class.
Do plastic pellets pose a dust explosion risk?
The pellets themselves are generally low risk; the concern is fines generated during pneumatic conveying and their build-up in filters, cyclones and granulators, which need separate assessment.
SprinkCalc — Fire Sprinkler Design Across Three Standards
SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report.
Download SprinkCalc on the App StoreNFPA 13, NFPA 652, NFPA 72, EN 12845 (Annex A and commodity categories), FM Global DS 8-9 and DS 8-1, Turkish BYKHY. Confirm classes and values against the current edition and the insurer. The findings here are typical defect patterns, not an account of events at any particular site.