Pipeline Cleanout Pigs and Go-Devils
A Go Devil (also known as Pig) is a device that is inserted into a pipeline for the purpose of cleaning; a line scraper. Vertical lines for high-rise work should almost always be cleaned by moving concrete back toward the pump. In the most common method, a go-devil or blow-out ball is inserted at the discharge end of the slickline and a blowout cap is attached. Compressed air may be used to push the concrete out of the line. The blow-out ball must be inserted and the blow-out cap attached before disconnecting the bottom end of the line from the pump or switching the diversion valve to the cleanout line.
Safety precautions: Always be very careful when using compressed air to clean out pumping lines because concrete under pressure will be ejected at a high velocity. It’s particularly dangerous to break back a line that is under pressure. Be sure that the blow-out cap has a bleeder valve installed so that pressure can be relieved if a blockage occurs. Don’t attach a hose to the discharge end of the cleanout line—a hose can recoil violently as the line is blown out. Use a devil catcher and firmly anchor the end of the line so that it won’t whip around as the ball or go-devil is blown into the devil catcher. Also, shield the discharge end with sheets of plywood to prevent workers in the area from getting hit by concrete when the blowout ball exits the pipeline.
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