DIY home processing plant

[UFO]

But remember, the plastic processor folks are using these because they're cheap and convenient. Anything that adds cost and *shudder* engineering prowess is out of the question

Which is curious, as a hot water heater is both cheaper and stronger. It just happens to not follow the mass marketing concept that the user cannot participate in the building process, and plastic is cheaper to ship.

 

[UFO]

Ok i just looked up HPDE on mcmastercarr's website. It's usable temperature range is -40 to 140 degrees F and doesn't start to reach is softening temp until 253 degrees F. It has a tensile strength of 4000psi and excellent impact resistence (won't crack, just deform). Although i'm confused as to why you'd choose this one since it's not rated for use with products containing gasonline, benzene (most fuels i'm aware of have this in it), alcohols, chlorine, etc.
Just for fun since school starts next week and i need the mental exercise i'll whip up some numbers for an ideal container with this material using those numbers i'll see what i come up with.
By the way, and it's probably expensive, but check out Polyetherimide. Rated for use up to 340 degrees F and has a tensile of 16,000psi.......nice.

Excellent. There is nothing fundamentally wrong with plastics, but they should be engineered specifically for the application. There is just too much risk inherent with using heaters and supporting large quantities of a hot caustic solution. I recall a case where someone fitted a plastic reactor with an electric heating element, where the base heated up enough to deform the plastic, and dump the load. This would obviously never happen with steel.

 

[Darkeyesuk2000]

I hear what your saying UFO.
But would you not agree there is a difference between some one who knows what their doing asposed to someone who dont.
If someone is negligent using or installing equipment.
whos fault is it.
the person or the makers of the equipment?

 

[Murphy2000]

I hear what your saying UFO.
But would you not agree there is a difference between some one who knows what their doing asposed to someone who dont.

Of course there is a difference.. but how that difference applies to various activities is what's in question.

If someone is negligent using or installing equipment.
whos fault is it.
the person or the makers of the equipment?

That depends on what kind of equipment it is. Think of a coffee maker. How many times have you left the heater on when the pot was empty? User negligence right? How would you feel if that coffee maker burned your home down while you were at work?

Same kind of thing...

There's a difference between user negligence and faulty design.. That difference is a very fine line that can be adjusted in one direction or the other by the price of your lawyer.

How that line applies to different products is something no one here is going to be able to answer.

 

[robzuk]

But remember, the plastic processor folks are using these because they're cheap and convenient. Anything that adds cost and *shudder* engineering prowess is out of the question

You hit the nail on the head with that one. We're all looking to save a buck here and there, but my safety and my familys saftey DO NOT come with a price tag!! I made part of my reactor out of 55 gallon drums and as soon as I find an inexpensive source for stainless containers, I'll go to them with an element in that instead of a hot water heater.

 

[1fastredsc]

Ok, so i finally got around to running some numbers today. Here's the run down of it.

So 55 gal translates to about 7.35 cubic ft using .13368 ft^3/gal.

Next assume an average diameter for the inside of the container, i choose about 1.5 ft.

Now i use the v=d^2*pi*h/4 and i solve for h which is the height of the container. (btw, if your not used to see it this way, normally that's written as r^2*pi*h, however r=radius=half of diameter=d/2, so if you replace the r with d/2 you get d^2/4) Solving for h i get a height of 4.16ft.

Now i use P=gamma*h, which is used to find the maximum pressure on the outside wall of a container with fluid, gamma is specific weight of the fluid (i used the specific weight of SAE 30 weight oil) and h is depth of the fluid which reaches maximum at the bottom, therefore the bottom has the most pressure. So using this in a maximum condition i get 237lb/ft^2 or 1.65psi.

Lastly we treat this container as a thin walled axisymmetrical container and use sigma=P*r/t where p is pressure, r is mean radius, and t is thickness of container wall. I get 2133 lb/ft^2 of stress or 14.8 psi with the assumtion that the wall thickness is 1 inch. If you go half inch, it's double the stress or 29.6psi, etc.

Now this assumes that the container is resting on the bottom of the container (sitting on the floor or on a stand that supports it from the bottom), if you suspend the container from the top, then i must add in the forces of the fluid weight also trying to pull the bottom of the container off which changes my calculations by adding on a single axis tensile stress to the container.

I think the only real challenge is picking a plastic material that is both safe for use with oils and alcohols, and can withstand enough temperature to not reach it's softening point. Something i've been reading is that some batch makers need to heat up the oil to get water out which requires temperatures in excess of 210F or slightly above which changes most of my assumptions. Plus as someone else mentioned stainless containers are cheap, or even normal steel containers are easy to find at the dump and even cheaper or free. This was more than anything else an excercise to prove against that old idea that plastics suck and metal is always better no matter what.

 

[1fastredsc]

\
That depends on what kind of equipment it is. Think of a coffee maker. How many times have you left the heater on when the pot was empty? User negligence right? How would you feel if that coffee maker burned your home down while you were at work?

Because of engineers being blamed for cheap designs instead of the bean counters in accounting that ordered the cheaper design/parts, you'll find that almost impossible these days (engineers no longer sign off on things that they don't approve of). In one of my experiments i needed a heating element so i bought a 15 dollar coffee makers at walmart and ripped it apart. I was pleasantly surprised to find that it had an inline thermo switch that would break the circuit once 115 degrees C was acheived at the element itself (it had it's specs written on the little device, plus i ran it's part number on google to make sure ). So if left on with no fluid to absorb the thermal energy it's putting out it would reach 115 and stay there (actually cycle between it's close circuit temp and open circuit temp).

BTW i know your just using that instance for arguement, however i'm in the mood to be difficult today .

 

[bayshorecs]

Just a side note, most people also go through either a dewater and/or a demeth process when making fuel so the temps are really 180F to 220F which is getting closer to the limits of the "cheap" plastic barrels must use and get for free.

Either way, if everything goes perfect, plastic would be fine. If everything does not go perfect, you have a can of worms on your hands. In a steel container (unsealed), you know where your fuel is if there is a problem. With plastic, the melting temp will cause fuel to pour out of the barrel, on the floor, and take your house away. There are pictures to show that can happen.

If you are safe with your processes, you should be ok. Plastic just has a lower tolerance for error than steel.

Also, there are newer designs of appleseeds to handle the fumes, heating, etc problems a prior poster listed. And, cheaper to build (and in my book, safer) than purchasing some of the "commercial" processors. Heck, just look at the pictures and buy all the parts yourself! It would still be cheaper than alot of the markups I have seen!

Just my two cents. Each to their own.

 

[gottdi]

tinfoil hats?

I swears it works, buy my plans and youze be safe as can be. Don't buy those others or use thoses freebees youse see. Just buy mine. I swears they work.

 

[comp]

interesting read