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Dangers in Venting Calorimeters

The incident

As a small calorimeter bomb was released from holder (noted to be stuck), contents sprayed all over arm.

Summary

A TSUTM [Thermal Screening Unit by Hazard Evaluation Labs Ltd.] equipment has been used for a quite violent gas producing reaction.  At the end of the run, the system was cooled and vented normally, and the trasnducer reading was zero.  However it was noted that the bomb was stuck, so visor and gaultlets were worn, but failed to stop the spurting as the bomb broke free.  Although the gauge was reading zero, a blockage in the line meant that the pressure in the bomb was high.

Discussion

This is a particular problem with these calorimeters, and it is not limited to the device supplied by HEL Ltd.  The ARCTM [Accellerating Rate Calorimeter by Columbia Scientific and later by Heath Scientific] uses similar bombs and similar problems have been seen it this kit as well.  The problem arises by the fact a gassy reaction will foam out of the bomb into the narrow tube to the transducer, as it cools so it solidifies, thus making the only way to release the pressure it to remove the bomb.  One way to reduce the risk is to only undo the nut half a turn or so, and then apply force on top of the bomb (the fork of a small spanner, with a thick rod to act as a fulcrum is ideal), this restricts the apature and slows the gas flow.

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