DIY Flash Dryer Safety

I’m getting a lot of hits on the flash dryer post, so I figured I better get rolling on the articles I stated I’d be working on. First off, I want to take on the safety aspect, as usually in the DIY realm, this is where the biggest deficiencies exist. There are four main things to be concerned with, electrical shock hazards, fire hazards, tip over hazards, and explosion hazards.

Electrical Shock is probably the biggest danger of DIY devices, as few DIYers have been through product safety testing, nor are they aware of how dangerous some oversights can be.

First of all, a DIY unit should be grounded. Commercially produced devices running on 120V can usually get away without a grounded plug, if they adhere to a more rigorous set of safety standards, and the associated qualification tests associated with such standards. Since most DIYers do not have the equipment for such testing, and secondly, since grounding the chassis, and all associated metal parts is such an easy thing to do, its really the only way to go. And of course, along with grounding, a fuse to protect the primary wiring is critical.

The second aspect to consider is spacing… namely the distance between any open electrical contact, and the chassis. There is no reason one should have an open electrical terminal within 1/2″ of the chassis in a DIY design. Otoh, I have seen many units, where if it were not for a layer of 0.010″ electrical tape, a terminal or other electrical contact would short to the cover. In addition, being flash dryers operate at high temperatures, it would be prudent to keep the electrical wires in the hot zone at least 1/2″ from the chassis, even if it means spending a few bucks on high temperature standoffs for the wire harness(s).

Lastly is the issue of wiring. PVC insulated wire has no place in the hot zone, nor do insulated crimp on connectors. The hot zone is a place where high temperature wire is a must, even if it means some hoop jumping to acquire it. It may be that a small quantity can be acquired from a appliance repairman, or possibly a relatively new used appliance that is on its way to the scrap heap…. (movers do drop them at times, and its often possible to by a new damaged oven for $20-$50, pull the wires, and then send it off for recycling).

Fire hazards are another concern. Within the hot zone, wood is not an option, nor are most plastics. The same applies to wires and other internal components. In addition, a over temperature cutout, or thermal fuse of some nature is a must. Its not that you wont leave the room when the unit is on… but distractions are a real concern. If you turn away from the dryer to adjust the press, and it overheats, and you cant get back to it in a timely fashion…. you will appreciate the thermal cutout in a huge way. Along the same thought process, any insulation you use should have a temperature rating equal to or greater than the thermal cutout. One should also consider the design, such that there are not any places where lint or other contamination can build up, and thus prove a potential fire.

Tip Over is a concern, in large part due to the physical attributes of the flash dryer and its stand. A challenge is to figure out what type of scenarios could occur which would result in the unit tipping over. Certainly if one pushed hard enough, one could tip over must any unit, short of having 200lbs of concrete in its base plate. By the same token, a simple bump should not result in the unit crashing to the floor. A reasonable compromise might be to consider the ASTM tip over requirements for furniture. Namely, a 50lb weight is place on the center front of the unit in its most likely to tip over state. I think such an approach while not totally tip over proof in the event of a someone falling onto or into the flash dryer, most assuredly will provide protection from common bumps and encounters.

Explosion hazards are a common thing we ran into with industrial systems, albeit such materials should be far beyond the scope of a DIYer.

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