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Fire prevention for food manufacturing

28 October 2010

Fire prevention is a big issue in food manufacturing and processing, particularly where the application of heat is an integral part of the process, writes Chad Relf of Industrial Design

However, not only are the requirements of each plant different but within each plant there are multiple applications that demand unique measures for detection, suppression and control. Here Chad Relf, of fire safety system specialists Industrial Design, outlines some typical applications explains how to achieve effective detection and fire extinguishant in each case.

The first step in assessing fire safety in a food processing plant is to gather as much information as possible about the application. We look at the process or equipment that needs protection and ask a member of the client’s team to demonstrate it and explain its operation and to identify any specific areas of risk.

Once the type and location of the detection mechanism is determined we decide where to put storage cylinders, pipe work and nozzles to get the optimum performance from the system whilst taking into account any restrictions caused by the equipment or processes. As part of this process the customer’s production programme and shift patterns need to be discussed to try and minimise any disruptive effect that the installation of the equipment may cause.

In the food and beverage industry, we often come across packaging machinery where they use heat based shrink wrapping and carton sealing processes, which have been known to cause fires. Product can get jammed on the conveyor and, because heat is applied in the chamber, the jammed item will burst into flames. In addition mechanical faults, such as bearings running hot, can generate sufficient heat to cause a fire in a device such as a polythene film packaging machine.

In these applications we would normally use ultra violet or infra-red detection to provide a very rapid alert; required because of the quick burning process. The extinguishing system would probably be carbon dioxide applied using the local application method to extinguish the fire and cool the residue.

Another issue in food plants is deep fat frying; which is of course a common process applied to everything from potato chips and vegetables to meats and fish. The problems here are caused when the oil is raised above its flash point or when ultra heated product that has been immersed in oil for an extended period is exposed to the air. The latter often happens during cleaning, when the oil is emptied out of the vat and the product residue left in the bottom spontaneously combusts.

Here we recommend the use of heat detectors, to detect the rise in temperature, and carbon dioxide for extinguishing. This suffocates the fire by preventing oxygen from supporting re-ignition as well as cooling the combustion source to below its spontaneous combustion level. As an alternative to carbon dioxide, we also consider water mist. The water turns to steam during discharge and combines with the by-products of combustion to create a fire suffocating blanket. This also provides a cooling effect, thus reducing the oil’s temperature.

Compliance issues must also be considered. All systems should comply with current appropriate legislation (e.g. EN15004, BS5306 and BS5839) unless otherwise agreed with the appropriate authority. This may further depend on the Customer’s in house regulations, site location and insurance company requirements.

Health and safety is a primary concern with all systems, both during the installation phase and during the ongoing use of the completed system. Risk assessments and method statements need to written, agreed and complied with during the installation phase and the system user must likewise adhere to agreed procedures during its ongoing use.

The essence of the problem is that where you have extreme heat there is the risk of fire. Nevertheless, by attending to the individual demands of each application and, as in the examples we have discussed, the individual needs of the machines, unique designs can be produced which share a common result; effective detection, suppression and control.

* Chad Relf is a project engineer at fire safety system specialists Industrial Design Ltd. The company is based in Oxfordshire, where Chad also lives.

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