A closure is a cap that threads or clamps at the open end of pipe. When blowdown stacks are installed in gas pipeline systems, a closure can be used to seal the stack to allow the piping to be pressurized so that it can perform other functions when a blowdown is not needed. If a blowdown is needed, the piping can be valved off, depressurized through small vents, and then the closure can be manually removed to allow a large-volume gas blowdown with the use of valving in the station. Once the blowdown is completed, the closure is then re-installed and the piping can be re-pressurized and used for other purposes. In this case, the closure is used as an alternative to a blowdown valve for sections of pipe where blowdowns are infrequent.