Air rumbling

The operators in the Esso Lago Refinery in Aruba used to blow nitrogen into the water inlet line to coolers. It s safer to use nitrogen than air, in case there is a tube leak. They just coupled a 1-inch hose to the water inlet nozzle and blew in nitrogen for 10 minutes every day. I call this "air rumbling." It helps to clean the tubes. 

Release at high velocity into zone of very rapid air morion Grinding, abrasive blasting, rumbling, hot shakeout 2.5 to 10... 

Combustion instability noise can occur if too much steam or air is added in the base of the flame. So, overaerating the waste gas stream in a flare, causes the flame to periodically lift from the flare tip. This periodic lifting and reattachment of the flame from the flare tip is the mechanism that drives the low frequency rumbling noise. Usually, combustion instability noise can... 

Molten lead passed as drops through a card or colander perforated with numerous holes— 1448 for the smallest shot — and fell into water which usually contained a little sodium sulphide. This coated the shot with a thin layer of sulphide of a lustrous black metallic colour which remained permanent in moist air. The size of the shot depended not only on the diameter of the holes in the colander, but also on the initial temperature and composition of the molten metal. The shot was sorted by sieves and by rolling down an inclined plane, the imperfectly shaped pellets remaining behind. Finally the shot was polished by rolling with plumbago in a barrel or rumble. 

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