Pollution
Humain
Environnement
Economique

A leak was detected on a line feeding the compressor with cracked gases in a petrochemical plant. The line (DN 500, P 10 bar, T 30 °C) contained flammable gases (5% 1-3 butadiene, 4% benzene and H2S) circulating with a maximum flow rate of 140 t/h. The leak was located in the middle of a 150 x 110 mm non-insulated, externally corroded section with a puncture measuring 10 mm long and a few tenths of a mm wide, with an estimated leak rate of 5 kg/h. Because the section was at a height of 6 m (on the 3rd floor of the compressor), the operator had installed scaffolding and preformed sheet metal (200 x 300 mm) applied with a waterproof paste and maintained by clamps.

Since the piping could not be isolated and a drop in the steam cracker’s load had no significant effect on the leakage rate, the facility operator installed fire hoses and monitors to abate the leaking product, which was also diluted by the steam injected nearby. Surveillance patrols were implemented, and work in the leak area was suspended pending the installation of a waterproof fixture, the construction of which was completed within 48 hours. Explosimetry measurements were negative, except in the area surrounding the leak.

According to the facility operator, the origin of the leak was external corrosion due to a leak on the steam tracing system of a line positioned just above the corroded section. The last thickness measurements carried out on this section 8 years prior, indicated a minimum thickness of 5.9 mm for a design thickness of 2.9 mm.