Informational content provided by Jamie at ImmersionHeaters.uk.
In addition to all the requirements for water immersion heaters, for oil heaters our target is to get the watts density down, requiring more element or less power, that is the compromise facing the customer, who is always right, even when they are wrong!
For HEAVY INDUSTRIAL OILS we are aiming for <=12w/in².
For LIGHT COOKING OILS we are good with up to 25w/in².
If we stray above this, the sheathe temperature is too high, the oil caremelizes onto the elements, thus preventing dissipation of the heat, so it gets hotter & more stuff sticks, until something goes BANG!
The OIL Range has many benefits, including bespoke screwplug size, immersed length, double stat pockets, etc, all with a 2 week leadtime. The 8mm elements can be double looped to fill your maximum available immersed length with a large overall length of element.
On 2″BSP & above screwplugs, the elements drop from the screwplug to your maximum available immersed length, before looping back up to within a few inches of the screwplug (taking care not to stray into the cold section), before dropping back to full immersed length, then returning back up to the screwplug. This allows us to fit nearly twice the length of element possible in a plain U bent element. For example, in 24″ of maximum immersed length, we could use an 84″ element double looped. Thus, nearly halving the resultant watt density.
If you are in the privilidged position of having a very large tank with a massive space available for immersed length, you may choose not to double loop, but to have plain U bent elements over a meter in length.
But for most folks, size is important! And this is where compromise is required to achieve the target watt densities shown above.