A refrigeration subcontractor detected a 2.4-bar ammonia (NH3) leak on the low-pressure circuit of a brewery’s refrigeration equipment. The valve was appraised by its manufacturer, and a special round was set up every two hours to monitor progress of the leak before the appropriate repairs (expert’s report, order and delivery of a new valve, etc.).

These works were completed 10 days after the leak was first observed. The refrigeration subcontractor drained the 3.4 tonnes of NH3 contained in the installation for transfer into 5 dedicated 1,000-litre containers (whose filling was controlled by a pallet scale truck). The valve was replaced and NH3 reloaded into the installation with an additional 180 kg of NH3; this complement was not directly tied to the leak loss, which was very limited, but intended to replace the alkali generated when pumping down the low-pressure tank.

The leak occurred subsequent to a microcrack in the housing of the DN 200 butterfly valve installed in November 2011 on the facility placed into service in March 2012. Positioned on a gaseous NH3 pipeline, at the end of a tap awaiting possible future extension, this valve revealed a manufacturing defect. NH3 had been released in the vicinity of the “bulge” (widening used as a well with a shaft).

This repair effort caused the brewery to shut down for a full 48 hours. The toxic gas discharge into the atmosphere had remained limited enough to avoid surpassing the facility’s lower NH3 detection chain threshold. The 10 NH3 sensors composing this chain were however closely inspected.