Filter Bags: Pulse Jet Bags: Bottom Load Design

Pulse jet bags are cleaned using compressed air to mechanically "pulse" or snap the bag periodically so that the built up filter cake is discharged and the flow through the media is returned to its higher “in service” permeability. Pulse jet bags are installed on wire cage supports and filter from the outside/ in.
In the bottom load design, bags are pre-installed on their cages and then attached to a mounting thimble or cup which hangs down from the underside of the tube sheet. The tube sheet is a metal plate with regularly spaced holes which serves as the top of the gas tight metal box known as a dust collector. The top edge of the bottom loading bag is normally tucked into the cage and the entire assembly is attached to the thimble or cup with a hose clamp.

Installation of bottom loading bags is more difficult because of being on the dirty side of the collector and having no catwalks or surfaces on which to stand. Some bottom loaders are on the top of large storage bins on tall silos which make installation potentially dangerous. Bottom loader collectors are frequently used when headroom above the collector is not adequate for top removal design bags.

Bottom loading bags are less expensive than comparable size top loaders because the top is plain with no special attachment features.