Tony,
With respect,
A plastic tank is NOT suitable for a biodiesel reaction vessel.
I have spent almost 20 years as an industrial engineer designing process systems. If I ever designed a biodiesel processor using a plastic tank, not only would my reputation be a joke but if an accident ever happened, I could be charged with negligence. It wouldn't be hard to convince a jury of peers that plastic tanks processing automotive fuel is a bad idea.
Now I realize that these rules don't apply to a home owners property but common sense is just that. Hot oil + Flammable Methanol + Caustic materials + Plastic tanks to hold it all is not a good combination.
Anyone who uses a plastic tank is taking a huge risk and those who sell them give the biodiesel movement a bad name.
The only reason these plastic processors are allowed is because the laws have not caught up.
Have you ever seen a plastic Diesel Fuel tank that is manufactured by a real corporation? No local fire marshal would allow it.. No heating elements there either.
Those who use plastic tanks do so for several reasons:
1. Lack of skill to build a real tank.
2. Lack of profit margin to sell a real tank
3. Convenience
All the ingredients for a catastrophe are there.
And then it happens:
Quote:
Originally Posted by Tony From West Oz  Murphy,
While I agree that you should never heat a plastic tank with anything which can attain temperatures in excess of the working temperature specified for the tank, I disagree about the suitability for use as a reaction vessel.
With oil preheating performed before adding to the plastic processor, the plastic processor would be no more of a fire hazard than a steel tank.
Where the hazard comes in, is where people use high wattage, poorly designed electric heating elements to heat vegetable oil in the plastic reaction vessel. Even with a thermostat, the element temperatue can exceed the safe working temperature of the tank, causing it to distort and leak, potentially exposing the heating element and causing ignition temperature to be reached quickly.
A sitable heating element should not be able to exceed the safe working temperature of the tank and never reach ignition temperature for biodiesel. Even with a high wattage element, this is possible to achieve. It just needs to be designed for the purpose.
Features of such a design may include a large diameter tube enclosing the element, with a heat transfer fluid between, a 2 stage thermostat, which prevents the heat transfer medium exceeding the maximum working temperature and a fail safe temperature fuse which cuts off the heat if the design temperature is exceeded for more than 20 seconds (more or less).
Such a heating element could be safely used with a plastic tank.
Regards,
Tony |