TIRE CLINIC
from the November/December 2007 issue of
Today's Tire Industry |
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| Tire Clinic is a monthy feature addressing reader inquires related to tire retreading, repairing, and service. |
Q:
I have been told that I should install a larger pressurevrelief valve on my precure chamber. What is thevreason?
A:
On many of the early precure chambers the relief valve was designed to relieve excessive air pressure from a leaking or defective pressure regulator. If you are unfortunate enough to have a chamber fire, the pressure from the fire can increase extremely fast and possibly overcome the capacity of your relief valve. If your relief valve is small, I would suggest leaving it in place and installing a much higher capacity relief valve along with the original valve. You may want to set the second larger valve to relieve at five PSI greater than the original valve. Check with your compressor or boiler supplier for the proper relief valve.
Q: We have had two fires in our dust collector in the last year. We have not had this problem before. What could be causing this to happen?
A: Fires in a dust collection system are, in most cases, caused by pockets of fine dust that accumulate near the buffing rasp. When the rasp blades strike a small rock or nail embedded in the casing being buffed, it causes a spark that will ignite the fine dust. The highvelocity air will supply more oxygen to the fire causing it to quickly spread. Try to eliminate any areas where fine dust can accumulate and remove any rocks or nails from casings before buffing. If you have a fire, turn off the blower and use a dry chemical to spray into the intake and turn the dust collector on for five seconds to pull the chemical into the collector.
Q: I have several truck casings that do not have a DOT code. They appear to be in good condition and were manufactured in Japan. Can I legally retread these casings?
A: A truck casing does not have to have a new tire DOT number to be retreadable, but it cannot be used on public highways unless it has a retread DOT code. I should warn you that if a new tire DOT code has been removed and the tire is retreaded, the liability exposure is much greater. If the tire is involved in an accident, the plaintiff’s attorney may claim that the DOT code was removed because the tire was defective.
Q: We have used several different brands of precure
envelopes, but we have never been happy with the
number of cures we get. What can we do to obtain
more cures per envelope?
A: Lowering the curing temperature will increase the envelope life, but it will also increase your curing time. Improper handling and storage of envelopes is one of the major reasons for short envelope life, as is allowing the envelope to come in contact with any sharp corners or angles, especially where heat can damage them. If the envelope is a poor fit on the tire, it will wrinkle and sometimes develop creases that will cause early failure. The proper amount of lubricant can reduce the chance of the envelope being torn while it is being removed from the tire.
