A METHOD OF PREPARING A SYSTEM FOR MAINTENANCE

摘要

A method of preparing a system (100) for a maintenance operation, said system (100) comprising - a first subsystem (110) containing a super-atmospheric gas, - a second subsystem (120) connected with said first subsystem (110), and - a third subsystem (130) between the first and second subsystems; via intermediate subsystems (170a, 170b) comprising valve seats with a vent opening (246) in between. The intermediate subsystems are for example ball valves. To avoid gas escaping from the system (100), subatmospheric is applied to the vent openings (246) to discharge the gas and prevent it from leaking.