Explosion Isolation in Food & Beverage

A food plant is a network of connected vessels, and that connection is what turns one explosion into several.

A dust collector, a silo and a mill joined by ducts share their pressure. An ignition in any one of them sends a flame front along every pipe that leaves it, and the receiving vessel is hit by a flame travelling fast into a cloud that is already stirred up. The second event is usually worse than the first.

In food plants the problem is widespread because the dusts are explosible almost without exception: flour, starch, sugar, milk powder and cocoa all qualify, and the plants are full of ducts.

An explosion that stays in the vessel where it started.

Practically: every connection between protected vessels carries a device that stops flame and pressure propagation, the device sits at a distance where it can still act, and its function is verified on a schedule rather than assumed.

Devices that can be cleaned in the changeover window the plant actually has, because an isolation device in a food line is a product contact surface and an allergen item as well as a safety component.

A grain and feed plant has the same map problem in a different place: the aspiration ducts are left unisolated, and the filter becomes the route the flame takes.

The design starts with a drawing of what is connected to what, because isolation is a property of the network rather than of a machine.

Each connection then gets a device suited to it. A fast-acting valve detects the pressure rise or the flame optically and closes within milliseconds. A chemical barrier injects a suppressant across the duct. A rotary valve with a certificate acts as a passive barrier, provided its clearances and the number of blades in contact meet the certified conditions.

The minimum installation distance is the figure that decides whether any of this works, and it comes from the device certificate. Too close, and the device cannot complete its action before the flame arrives; too far, and the pressure has already propagated.

Hygiene sets the rest. The device sits in a product line, so it has to be cleanable to the plant standard, and a chemical barrier has to be compatible with food contact.

Testing is the part that quietly decides whether the concept is real. A device that cannot be function tested in place will not be tested, and an untested detection based system is an assumption rather than a protection. That requirement belongs in the selection, alongside the distance and the dust severity.

• Draw the network first, select devices second.
• Respect the certified minimum distance.
• Choose a device that can be cleaned in a food line.
• Test the function on a schedule.
• Function testing in place included in the selection, not left to the maintenance plan.
• Devices treated as product contact surfaces and entered in the allergen matrix.
• Rotary valve clearances and blade contact checked against the certificate, not the catalogue.

• The connection map, because an unprotected duct defeats every other device.
• Dust characteristics, measured for the actual product, which set the severity.
• Available distance, which often decides the device type by itself.
• Cleanability and whether the device can be opened in the changeover window.
• Food contact compatibility of any suppressant.
• Testing regime: a device that cannot be function tested in place will not be tested.
• Changeover window, which decides whether a device can realistically be cleaned at the required frequency.