Near Miss when using a automatic Dosage Unit with Caustic

The Incident

While using a Dosing burette with caustic soda, the delivery stopped with the first dose, it did not however refill itself for the next dose. The piston had withdrawn, but no liquid was sucked in, thus the inlet valve had to be blocked. When the apparatus was disconnected the vacuum inside the dosing syringe (a vacuum because no liquid had been sucked in) caused the piston to be rapidly inerted, with the result that the whole assembly broke and the piston landed some feet away. Liquid was sprayed all around, but no personal damage was sustained (PPE prevented any major contamination).

Recommendations

All employees using such apparatus should be informed about this hazard.
The ceramic valves should be replaced by valves made of PTFE, which are better in particular for solutions that may crystallize, such as Caustic Soda.

Lesson Learnt

Personal Protection should be used even in situations, where contact with hazardous chemicals is deemed highly unlikely.