Fire Drill

[Painter1]

Shortly into my first session with the new system a heat controller failed in the full open position and quickly over-cooked the material.

Having a plan for such a situation is something to think about as this could happen to any of us. The smoke and fumes from burning plastic cause burning of the nasal passages and eyes and it happens quickly. Nasty stuff.

I hit the off switch and pulled the plug on the equipment. The vent fan was already on, but I quickly opened the window at one end of the shop and punched the button for the overhead door at the other end on my way out. But the master circuit breaker had popped and when I pulled the t-handle to open the overhead I did it too hard and it hit a ceiling light fixture as it overran the track a bit, spraying fluorescent bulb fragments.

What a mess. Solvent alcohol helps remove the burnt residue but I'm not sure yet how to completely clear all the plumbing. Did some wire damage too.

Not sure what the problem was as the controller is set at 315 F. Originally I thought it was a bad temp controller. The temp sensor may have come dislodged, since the reading never went over 315 but the unit kept heating.

[Baitjunkys]

These systems need a high limit fail safe before someone gets hurt. This stuff is extremly unfriendly at that stage. Be like a fireman walking into a burning house with no oxy mask. If you start feeling funny, get to the doctor, its nothing to play with. I smoked a pot of plastic one time using a controller on a presto pot bypassing the oem controller. Ill never do that again. Nor sell something capable of doing that.

[DaveMc1]

It's a bad thermocouple that caused it. Had it happen a few times, I now keep several spares on hand incase this happens again. 

[Frank]

Are you sure it was set to F and not C? Makes a big difference.

[McLuvin175]

There is something to consider; there are many types of thermocouples K, T, B, etc. I have always used J-type thermocouples. Most temperature controllers need to be programmed or set to the appropriate type of thermocouple being used. If they are not they will work but give incorrect temperature readings, so even if it says its 315F on your controller it might be 400F in actuality if not set up correctly, double check that. If the thermocouple probe became detached then you definitely will get erroneous readings leading to a run away system. That should be easy to determine. 

 

Depending on your system there is a possibility that your contacts that control the heaters locked close. This can happen with direct contact relays though it is rare. It is less likely in something like a mercury relay or solid state relay. If the contacts are internal to the temperature controller then that is harder to check. You will have to use a volt meter to see if the output signal coincides with the temperature controller output when it cycles during heating, there usually is a light indicating that the controller is sending a output signal. Check that too.

 

If your system got hot enough to carbonize the plastic then you dont have many good options. Strong solvents can dislodge some gooey plastic but the hard stuff is another matter. You might have to disassemble the unit and ream/clean all the fittings to make sure they are unobstructed by burnt plastic. Been there done that and its no fun. That burnt plastic never stops stinking.

 

I have a friend who burned down his garage and almost his house. Lost all of his lure making supplies he accumulated over the years. Never determined the cause but he had just finished doing some pouring. Its a reminder to be careful with this stuff. Keep a fire extinguisher handy and hope you will never have to use it.