For some time now ive been searching for a solution to pre-heating the oil. None of my options seem that trouble free.
History -
#1: 90ltr plastic clip top with waste paper basket set into the top, and port about 4 inches up from the bottom
This was fine for liquid veg, but as soon as there was any solids, i had to pump hot oil over the top of them, whilst pumping from the base. No pre-heat, just a feed drum. Easy to clean the basket, but impossible to fully drain the drum, as the port was not on the absolute base.
#2: 205ltr clip top with coil of PEX pipe in it.
Took ages to heat. No need to bleed the air from pipework. No way of draining water. Had to be largly taken apart to clean.
#3: 205ltr clip top with radiator in it.
Quicker to heat. Rad needed to be bled, which is impossible when its submerged (this probably wouldnt be an issue for a long term install). No way of draining water, and, again, hard to clean.
#4: Same as above, but with bermuda baxi exchanger.
Same issues as above, but with the minor advantage that the heat exchanger could be put on top of a drum of solid oil, and it would melt its way to the bottom under its own weight. Harder to clean than above, as the heat exchangers weigh a lot!
#5: Water heated melting prongs, made from 22 and 15mm pipes.
I tried these for melting solid oil out of 30 and 60 ltr clip top drums. They work, but are slow, and its easier just to get the shovel out.
#6: I had an idea of an insulated cupboard with rads inside it. I have the cupboard, and the rads, but ive never gotten arround to it.
#7: A 205ltr bung top, turned up-side down, and the 3/4" bsp port fitted with a drain valve, a copper coil fitted, and take off port in the side. The top was cut to hold the waste paper basket used in the very first feed tank.
This works ok, but still akward for melting solids. The hole for the waste paper basket is just the same size as the OD of a 20ltr can, so these can be hung through the hole also. But, again, not much good for melting a load of solids, as you have to keep feeding small amounts to the basket. So i added...
#8: A wheely bin with the baxi heat exchanger dropped into it.
I could then shovel solids into this, leave them to melt, slowly (but i dont mind slow if im not having to watch it!) and then pump to whereever. I intended to pump through the waste paper basked, but my mono has a strainer on the inlet, and, if the solids are melted slowly, any junk either sinks or floats, so there's nothing to filter out anyhow.
But the baxi heat exchanger still has to be lifted out for cleaning, there's no way of draining water, and its not that space efficient.
#9: I considered 2-off clip 205ltr clip tops, with 'false' bottoms, with water pumped through the base, and the ports added to the sides. Again, not bother with strainers, just shovel in solids, and clean occasionally. Or possibly the same but with copper coils, although i thought that the false bases would give more surface area, and also be easier to clean out... possibly.
#10: My current plan- Ive been quite impressed with the clarity that long slow heating / settling with water has affoded the solids, so im focussing on not bothering with strainers, but just making a pre-heat tank thats easy to clean.
I think the next job will be a 6x4x2 heating oil tank, cut in half, to give a (well, two) 2x4 tanks, with a depth of 3 feet, and a brimmed volume of 600ltrs.
600lts will give me a good bit of storage if i dont want to process for a while, and, if full, could probably be dealt with with two 250ltr back to back batches.
I plan to weld some angle arround the top lip for stability, and to support a two part lid of some sort One part of the lid will be removed for loading, and both for cleaning.
Im not yet fixed on the heating arrangements, but i think ill go for rads fixed to the sides of the tank. Placing them flat on the base would heat the oil better, but create issues with bleeding the air, and more issues with cleaning. Ill try and use single skin units, without convectors, so as not to trap crud.
As for cleaning, as the tank is large, it cant just be tipped out, but its dimensions would be much easier to hook stuff out of than a 205ltr drum. So i figure on making up a scoop / sieve thing, like a commercial chip scoop, with a long handle.
I will fit a wide bore water drain at the base, in an accessible place, so that, if it ever does get horribly blocked, i have access to rod it. And an oil take off higher up.
Jules has a tank very similar to this, but with electric heating, but its taken me some experimentation to get to pretty much the same place, i think!
