The Pressure Cooker Problem

The laboratory was recently contacted by a solicitor who told us that in the previous three months, their client had purchases a new pressure cooker. We were told that while the pressure cooker was in use, a ‘substantial jet of steam came out from just under the lid of the pressure cooker and in so-doing, injured the person who was preparing dinner and standing beside the pressure cooker at the time of the incident’. The complainant put the failure down to a ‘catastrophic failure of the lid of the pressure cooker’.

We requested that we visit the injured party, speak with them and take the pressure cooker back to the laboratory. The examination of the components of pressure cooker was undertaken by our forensic engineer. The plastic handles and the steam relief valve on the lid were found to be unremarkable with all seals in place and in excellent condition.

It was found that the 22 cm metal mating surfaces (body and lid) of the pressure cooker were undamaged and mated correctly. Upon examining the mating face of silicone rubber ring whilst still in place within the lid of the pressure cooker, it was found that the silicone sealing ring appeared intact and undamaged. Removing the silicone ring and closely examining it by eye, showed an incision which commenced on the side of the ring

Our technical report was sent to the injured parties solicitor, which in its conclusions, opined that the ring was damaged by a serrated knife.

After re-examining the entire surface of the ring using our Axio-Zoom V16 digital materials microscope, we decided to make a through-cut 15 mm each side of the incision and in so doing, removing a piece of the ring for further inspection.

Placing the specimen in our electron microscope allowed us to gently open the incision and examine the incision more closely.

Examining the inside face of the incision showed linear striated marks  which were equidistant.

What was the result?

Our technical report was sent to the injured parties solicitor, which in its conclusions, opined that the ring was damaged by a serrated knife and that it is likely that this damage occurred whilst the silicone ring was being washed.

This case is typical of the types of matter which our laboratory are asked to investigate. Having an encyclopedic knowledge of materials and the modes of failures of these materials, enables us to elucidate the facts of an occurrence.

Have you had a material failure? Then Contact us today, and let our expertise work for you!