Repairing an Evaporator That Doesn't Heat Up Anymore. Lab Hacks




About: museum visit pic

I was asked to see if I could fix an evaporator that has a heating capability that wont heat up anymore.
I'm a IT/Electronics technician.
The evaporator was well out of warranty and a repair person would have to come from the US (at substantial expense and time), I live and work in Canada.
I only have a few pictures of the evaporator apart, but you should get the idea of what was done, through the explanation.

Don't try  this if you do not have permission, authorization or the equipment is still under warranty!

Note : I originally had called this piece of  lab equipment a centrifuge, it turns out it is actually an evaporator.
Sorry for any confusion that may have resulted from my error. JP


Step 1: Taking the Evaporator Apart.

Don't try  this if you do not have permission, authorization or the equipment is still under warranty.

Try to obtain a manual and schematic of the evaporator, we were lucky and the vendor was able to supply us with a schematic, exploded parts diagram and a manual.
Unplug the unit and disconnect any other hoses or cables attached.
Assemble the tools needed, I used nut drivers, Cresent wench, assorted screwdrivers, Fluke DVM, wire cutters, wire crimpers, pocket knife. Repair items: nylon insulated butt splice, heat shrink and Ty-raps.

Step 2: Trouble Shooting the Centrifuge.

Having the schematic diagram, I was quickly able to find the heating circuit and plan my trouble shooting.
I traced the components in the heating circuit and found that the: inline fuse was good, the over-temperature cut out had continuity, and the heating element had continuity.
I then traced the wiring for the heating circuit back to the control board and found that one wire was good and one wire was intermittent.
Next I traced the route of the selected wire.

Step 3: Trouble Shooting Success!

I traced the intermittent wire to the location near this black clamp, years of operation at high speed and vibration had weakened the wire to the breaking point.
If you look closely, in the second photo you will see some slight discolouration in the wire that is pulled out from the rest.
The wire was then checked again for continuity and found to be intermittent still.

Step 4: The Repair

I cut out the damaged section of the wire (about 1/2 inch long).
Because it is Teflon Insulated high temperature wire I had to use my knife to strip off about 3/8 inch of the insulation off of both pieces of the wire for the nylon butt connector.
Then I slid a 4 inch piece of heat shrink over the wire, the butt connector was crimped on and the heat shrink slid over the repair.
I then Ty-rapped the completed repair to the other wires. The repaired wire did not go back under the clamp, because this is where the trouble started in the first place. It did follow its original route to protect it from the inner workings of the evaporator though.

Step 5: Testing

After it was put back together, it was tested by the Lab technicians and it worked like it was supposed to.
The evaporator has been use several times since the repair and has worked perfectly in the lab.
Thank you to Kim H. for the additional photos.

Don't try  this if you do not have permission, authorization or the equipment is still under warranty!



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