Our client, a major player in the production of nitrogen fertilisers, asked a number of service providers to help it comply with the statutory monitoring requirements for a tank containing concentrated ammonia for the purpose of its reclassification.

CTP environnement was awarded the contract to provide a complete service comprising washing and sand blasting the inside of the tank, which measured 30 m (98 ft) in diameter and stood 35 m (114 ft) high:

• Decontamination of all internal surfaces by spraying with demineralised water using a rotating nozzle (a reduction from more than 100 ppm of residual ammonia to 18 ppm).
• High-pressure washing of the base of the tank (wearing the appropriate protective suits) and disposing of sludge (removed and processed by an approved treatment facility).
• Drying the tank.
• Sand blasting the welds on the base and the ferrules.

Excellent cooperation between the site services and CTP environnement’s teams when producing risk assessments and the operating procedure, as well as implementing preventive measures, made it possible to strictly enforce the safety measures:

• An optional decontamination phase to reduce the level of NH₃ in the atmosphere
• Specific PPE (protective suits with a breathable air pack)
• Continuous ventilation with dust extraction/filtration

The cleaning and sand blasting operation was completed successfully, in accordance with the proposed procedure and time schedule.