The FPSO topside typically includes a nitrogen generation and distribution system. The system should be designed to provide sufficient nitrogen for blanketing and purging of the process system in connection with minor repair/maintenance work, blanketing of methanol tanks, continuous purging of the open drain tank and vent system, intermittent purging of the pipeline pig launcher/receiver system and gas compressor barrier seals. In addition, the closed loop cooling and heating medium expansion vessel shall be pressurized with nitrogen.
Purging for major maintenance operations such as vessel inspections will be carried out using nitrogen supplied in transportable bottles.
The purity of the nitrogen should be a minimum of 98%.
The nitrogen generator capacity should meet the requirements for all the continuous users, and have an excess membrane area of not less than 25%.
The storage capacity of the nitrogen receiver should have capacity for 20 to 30 minutes of normal operations.
The nitrogen generation system should be fed from the conditioned instrument air system.