Pollution
Humain
Environnement
Economique

The shell-and-tube heat exchanger used to cool a press at a plastic manufacturing plant began leaking. Oil from the press’ cooling circuit flowed into the secondary water cooling circuit. Between 50 and 100 l of hydraulic oil was released to the natural environment. At 8:05 a.m., firefighters informed the operator that the river was being polluted. After identifying the leak, the operator installed a shut-off valve on the stormwater network while the firefighters deployed a containment boom around the oil. That day, a specialist firm pumped out the residues trapped by the dam.

The leak was due to the heat exchanger’s age (installed in 1996) and the degraded mode of cooling. Under normal circumstances, this secondary cooling circuit is connected to the water loop of the plant’s cooling tower (CT). However, at this time of the year the water in this circuit is too hot to guarantee the proper quality of certain products that require cooler temperatures. The circuit was therefore connected to the well, which has cooler water (open-circuit cooling).

Measures taken:

  • Immediately after the event, the cooling circuit was switched back to the CT circuit. The heat exchanger was also replaced, thus eliminating the root cause.
  • Over the medium term, the operator plans to modify the network to make it impossible to connect the heat exchangers of the three presses to the open circuit coming from the well.