Week 25: Adding return air to the dust collector

Just when you thought we could not add any more piping to the workshop, we have gone ahead and installed a return air system on our new dust collector. This allows the air that gets sucked out of the shop with the dust system to be returned back into the workshop dust free, saving on heating costs and improving general ventilation. It is a small opening (as you can see below in the foreground), but makes a huge difference. 

One of the hazards of fine wood dust is that it is extremely explosive in the right (or perhaps I should say wrong!) circumstances. All dust collection units are equipped with blast gates that allow the force of an explosion to release outside of the building and not blow back into the workshop through the collection piping.

In light of this, a dust collector with a return air system requires an essential feature called a spark detection system. It operates to detect any possible flammable material (a minor spark) and sprays it with water before it reaches the main dust container, avoiding an explosion. You can see the attachments for the spark detection  (waiting to get wired in by the electrician) on the main out-feed pipe below.

The other element necessary is an abort gate on the return air unit, which will automatically shut if a spark is detected. In the case that an explosion does occur, this would prevent any of the fire being forced back into the shop through the return air piping.

Here are some images of the guys installing the outside section of the return air to the main dust collection system on a grey snowy day.