Dust Collection Return Air

A discussion of heat loss and comfort with a closed-loop recirculating dust collector that dumps outdoors. April 19, 2011

We are installing a 60hp fan and baghouse/cyclone outdoors and returning filtered air to the shop. I am expecting the winter heat loss to be considerable here in western NY. Does anyone have experience with insulating outdoor piping? I am considering spraying urethane foam on the cyclone and wrapping pipes with foil faced bubble wrap.

Forum Responses
(Dust Collection Forum)
From contributor T:
Have no experience with your specific question, but wanted to ask - have you put in a blast gate and suppression system to protect against a fire or explosion in the baghouse coming through the return into the building? This is a big risk that is often overlooked and could result in injury or death if a spark made it into the system.

From the original questioner:
One of the reasons we are installing this new (to us) system is for the risks you point out. The new system is a Carter-Day baghouse with explosion vents. We have installed an abort gate to divert smoke/fire to outdoors in the case of a problem as well as a backdraft gate on the inlet side. When we are done, there will be spark detection and corresponding deluge water spray in the ducts. Thanks for the observations.

From contributor G:
The spray urethane that I am familiar with degrades rather quickly in sunlight. In a couple or three years, your cyclone might look rather leprous and most of the insulation may have fallen off. If you can either find a sunproof foam or cover it, that would be better. Does the manufacturer have any suggestions? Does the manufacturer either warn against or void warrantee for what you propose? Check with them.

From contributor D:
Go to your vendor as suggested. I have set up several dust systems over the years, and the conventional thought from the vendors was that the velocity of the air did not allow for the heat to migrate much. Little to no heat loss. We are in central Indiana.

In winter, the return air felt cold, but that was due to velocity. We put an adjustable louver frame over the outlet, and could direct it up in the winter, to circulate the heated air rising up to the ceiling, and down in the summer, to add to air movement in the shop.