If you have ever experienceda chamber fire in your plant, chances are it involved either the heatingsystems and elements or tire/envelope contamination.

Heating system elements suchas fan motors, thermostats, electrical contacts, baffles, etc. can overheat anda fire may result. Contamination can come from sealants and lubricants usedduring tire mounting and break down. Four words can prevent most chamber fires:inspect, monitor, maintain and chart. Inspect casings and envelopes, monitorand maintain your chamber, and chart the curing process.

Inspect envelopes andcasings.

Inspect all envelopes. It isbest to use inner/outer envelopes, as they may isolate and contain some vaporsduring the initial vacuum stage (necessary for inner/outer envelopes). The useof inner envelopes in conjunction with outer envelopes can significantly reducethe chance of a fire due to contaminants inside the tire casing.

Chemicals and/or flammableitems are sometimes found in the inner liner area of envelopes. Wheninspecting, treat any unknown smells or substances found in the casing withcaution. If you are not sure of what they are, ask someone who may know or putthe casing to one side for investigation. If you detect anything unusual insidethe casing, it is recommended that you thoroughly clean it with water or someother nonflammable material to remove contaminants.

Monitor chamber during theentire curing process.

You need to monitor thechamber at regular intervals, as well as what is placed in the chamber. Manychemicals that do not react well with heat come into contact with tires andalso are around a retread factory. While chemical fire problems are usuallyisolated to a particular tire (and/or the tires on either side), they too canget out of control.

Maintain heating systems andchambers (steam, gas, electric).

Not all problems evolve fromcontaminants. Chamber fires can develop from such things as fan motors stoppingand faulty thermostats. This is the reason for constant nursing from start-upto blow down. It’s better to be safe than sorry.

Besides the normal cycletime, this monitoring should involve:

• Calibrating temperaturegauges (at regular intervals)

• Checking to be surethermostats are working correctly at pre-set differentials

• Making sure electricheating elements, fan, motor bearings, shaft interlock, etc. are in goodcondition

Chart the curing process.

Cycle time charts must becreated to ensure that monitoring is being performed as expected, including thechecking of charts, pressure, heat and clock time degradation, etc. Teachemployees how to adjust and regulate the chamber if necessary.

Documented causes of chamberfires

(not to be considered allinclusive – submitted by Woodrow Turman of Hules Banda Rubber Co.)

• Fan motor stopped eitherfrom loss of power, bearings seized or motor burn out

• Fan shaft bearings lockedup

• Fan loose on the shaft dueto key shearing

• Tire jammed against fan.Tire hanger into fan shroud

• Fan running backward dueto improper wiring during replacement or maintenance

• Paper or other flammablematerials left in chamber

• Excessive dust or dirt inthe chamber

• Cal rod failing andshorting out in air duct

• Grease or oil on envelopesor in tires being cured

• Flammable stop leak orseal coating on tire liners or envelope

• A can of spray lubricantleft in chamber

• Heavy grease on trolleyrollers

What do you do in the eventof a fire?

• Shut off all power to thechamber – electricity, steam, gas, etc.

• Do not open the door underany circumstances.

• Call the fire department.Explain to them what the contents are when they arrive.

Best practices for retreadplants

• Train employees annuallyand cross-train where possible.

• Do not use flammablechemicals/solvents such as heptane for cleaning or inspecting.

• Monitor curing processfrom start to finish. Do not run chambers after hours and/or unmonitored.

• Check with customers anddetermine whether run-flat or some other sealant is allowed to be used by theirdrivers.

• Inspect casings and cleanwith non-flammable materials.

• Contact the local firedepartment for training in emergency firefighting (tire, chamber and rubberdust fires). If possible, remind firefighters not to open the chamber door inan attempt to fight a fire inside; this will reduce the chance of a “backdraft”or flare-up of the fire.

• Usenon-flammable/water-based tire paint.

• Inspect envelopes on aregular basis.

• Shut down plant annuallyto perform maintenance on chambers and all equipment.

– Courtesy of Zurich NorthAmerica  –https://secure.zurichna.com/zdu