External Heat tracing and insulation.

Is it economical and environmentally positive to provide heat tracing just to keep recycled wash water?

Alternatively is is viable to let it freeze without breaking anything? (Also 6500gal will take a decent time to freeze, so could well be fine depending on what sort of winters you get.)

The puzzle is the unknown weather condition of the cold winter in the area where the tank is.
Suggest to verify the worst winter condition first and apply it to the design for the facility accordingly.

Bury it?

Mound it?

It's the pipes in and out which will freeze first. They need lagging and trace heating.

The rest will depend on how cold it gets,

An internal heater like a pond heater might be enough.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

I'd suggest to contact the tank supplier and see if they have recommendations.
For large steel tanks with regular flow (municipal water tanks, for example), in most cases, the water flowing in from a well or wherever is warm enough that it will keep the tank from freezing. But this is different from just agitating the water that is in it, as that incoming water transfers some warmth in as well.
For tanks with no circulation (fire protection tanks, for example), typical solution is to put some form of heater in/on the tank and also insulate the tank. The heater would generally heat the water in the tank, not the outside shell. The insulation is mainly to reduce the amount and cost of heat required.
A double wall would help, but isn't really intended for that purpose, either.
It might be easier or cheaper to put the tank in some form of enclosure rather than just insulating the tank itself.

Cames

Plastics tanks come in many forms. Appears you have selected a 27 m³, two piece roto moulded high density polyethylene (HDPE).

Plastics are good insulators (PE first practical use was superb electrical insulation (on early radar) 1941).

Air-gaps are also very good insulators.

Double walled is actually a secondary containment (against leakage) from the primary tank - and should be dry and remain dry!.

Pipe work requires at least insulation and possibly trace heating.

It really depends upon how cold and for how long.


Regards

Ed

Ed Clymer
Resinfab & Associates
England

cames ...

You have not bothered to tell us where the tank will be located ... Saudi Arabia ? Nome ?

As is typical with all Third-World postings, there is not enough information here ....

1) For many climates, as stated above, simple burial with an insulated top would be adequate (we are guessing here)

2) Contact the tank vendor ... He has been asked this question before. Stubby tanks like this freeze slowly

3) You probably have a top-mounted pump on the tank to circulate liquid. AS LI states, this is where your freezing will occur, if it occurs at all

4) Consider a small heated shed or structure above the UG tank (for access to tank pump, valves, and level indication ?

5) Consider placing the tank in a concrete vault (like a little basement) ... possibly provide space heaters

6) Consider designing the return Wash Water piping with additional pipe-unions and "space" for a trim heater

Keep us posted on your final solution .... Best Regards

MJCronin
Sr. Process Engineer