Asking The Right Questions (continued)

3. Will it perform reliably?

Dust collection equipment can often be a maintenance headache, but this need not be the case. Reliability problems typically stem from neglecting or misunderstanding details about the unit's performance during the initial selection process or when changes are made in the facility. By following the steps above, engineers can help to ensure more reliable performance from their dust collectors.

Although the site survey and lab analysis typically provide enough data, in some cases the engineer may opt to commission full-scale dust collection testing. Full-scale testing typically requires a large dust sample that is run through dust collectors on a test rig in a simulation of real-life operating conditions. Pressure drop, dust load, filter media and other parameters can be varied to determine the optimal collector design. Full-scale testing is usually limited to analysis of difficult or hard-to-handle dusts, or applications where there is a history of chronic dust collector "upsets".

When selecting equipment, it also helps to be aware of design and technological improvements that can enhance reliability and performance. Examples include:

Horizontal vs. vertical cartridge mounting: Some pleated filter cartridges are mounted horizontally. The biggest problem with horizontal mounting is that the dust does not get cleaned off the top of the filter, causing the dust to blind at least one third of the filter, effectively reducing the functional surface area.

Also, because the incoming dust is dumped on top of the filters, there is no pre-separation of heavy or abrasive particles from the air stream, which can significantly shorten filter life.

An antidote to this problem is a system using vertically mounted cartridges. The best designs incorporate a high, side entry inlet with a series of staggered baffles that distribute the air and also separate out larger particles, dropping them straight into the hopper. This reduces the load on the filters and helps eliminate problems encountered with horizontal mounting by helping to maximizing of the effective surface area.

Advances in pleat spacing: Most dust collection cartridges use tightly packed media configurations. Though they offer high efficiency, much of the media surface area is unavailable for filtering, allowing dust to remain trapped within the filter even after pulse cleaning.

A recently introduced pleating technology makes use of hot melt separators that open up the full length of the pleat, allowing the entire depth of the pleat to be utilized. This design thereby allows significantly higher air flows per sq. foot of media than what has been achieved in the past, effectively maximizing the functional surface area.

Because virtually all the media surface is exposed to the air stream, the filter tolerates more dust between cleaning pulses. The open pleat design also results in significantly lower pressure drop as well as improved dust release characteristics during pulse cleaning, using fewer pulses, and therefore less energy.