Ensuring LNG Liquefaction Facilitys System Cleanliness: Pipe Air Blowing as a Build It Clean Attribute

Air Blowing is one of the most efficient methods of cleaning piping systems. In this technique a large-volume, clean system is selected as an air reservoir (a vessel or large-bore piping such as a reservoir header) and used to store dry air, which is then released into smaller open-ended piping systems where the velocity will significantly exceed the normal operational velocity, thus resulting in debris removal. This system of cleaning is used on sections of the LNG facility where it is necessary to keep the pipe-work dry, such as Propane, Mixed Refrigerant (MR), Natural Gas (NG) circuits and Instrument Air (IA) lines. It is also used on large bore systems where a sufficient flow of water is not possible. Air blowing in a LNG facility also serves the purpose of removing free water from the piping in order to prevent excessive use of gas for defrosting. In air blowing pipe-work, the objective is to maintain a high air velocity through the line for an extended period. To achieve this it is normal to include some large volume vessel (reactor, column, etc. ) in the circuit to be blown. The circuit is then pressured up with air, and then rapidly vented out at an open end with the vessel in the circuit acting as an air reservoir to sustain the blow over a longer period. The velocity achieved during air blowing shall have the required drag force (preferably 1.1 to 1.5 times) higher than drag force during operation.