The reason that some collectors had filter cartridges laying horizontally on their side was to overcome the upward can velocity effects that occured in traditional baghouses and early cartridge collectors. Air would enter the hopper and flow up into the filter housing. The dust could only be cleaned off the filters if the up flowing air was slow enough to allow the dust to fight back down through the air stream. This system worked well on heavy dusts, but not on light dusts like weld smoke and fumed silica. It was devised that if you laid the filters horizontally, moving the clean air plenum to one side of the collector, you could expose the dirty air plenum to the top of the collector and thus bring the air into the top of the dust collector. This resulted in a down flow effect helping overcome the upward can velocity issue.However, the down flow style collector presented many limitations in its inherent nature of laying a filter on its side. The biggest problem is that the dust does not get cleaned off the top of the filter. The dust blinds at least 1/3 of the entire filter because it cannot be cleaned off. This increases the air to media ratio in the collector and has caused premature failure of the filters in many instances. Many operation and maintenance manuals from horizontal cartridge filter manufacturers recommend opening up the collector and rotating the filters monthly to overcome this problem. See figure 1 here. Another major issue with horizontal cartridges is that 100% of the incoming dust is dumped on top of the filters.
Vertical cartridges allow you to overcome upward interstitial can velocities without turning the filters on their side and wasting much of the filter. You cross flow the air into the side of the collector. This is achieved with a high entry inlet that brings the air into the dust collector at the same height as the cartridges themselves. The air is first sent through a series of staggered channel baffles that distribute the air and also act as a classifier, separating out the larger particles and dropping them straight into the hopper without ever seeing the filters. Since the air is brought into the collector at the cartridge level, there is no longer air flowing upward towards the filters. This system combines the benefit of the old down flow style air pattern without turning the filters on their sides and wasting a large portion of the media. For more information, continue reading here.
