Cold stress control measures

Measurement and Control The TLVs for cold stress and the windchiU index can be used to evaluate the cold environment. The windchiU index expresses the cooling power of wind on exposed skin as an equivalent temperature. The human body senses cold as a result of both air temperature and wind velocity. 

Other Control Measures Engineering controls can be used to reduce cold stress in the mining enviromnent. These include general or spot heating to increase workplace temperatures warm air jets, radiant heat, or contact with warm plates to keep hands warm work area shielding from air... 

For example, the small amounts of chlorides in most extern pipe insulations can be leached out by exposure to weather and become concentrated at the pipe wall. Temperature may be difficult to measure, let alone control, especially during startup or shutdown when gradients exist. Residual stresses usually are present in a relatively low yield strength material like annealed stainless steel pipe. A pipe bumped in shipment or sprung or cold bent in fitting can have all the stress needed. 

Injection molding machines Resin should be dried < 0.02 %. Do not use resin that has been out of the dryer for > 20 min. Cold molds are difficult to fill and require higher injection pressures. Hot molds, generally, give better finish and less molded-in stress. Melt temperature is very sensitive to very small changes in rpm or back pressure despite sensor or controller set point. Measure with hand held pyrometer or laser sensor. Need slower fill rate for spme-gated parts to prevent blush, splash or jetting. If the walls are > 5 mm, then slow fill helps reduce sinks and voids. 

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