[Fakes]

I have a tank which contains a solution of 32% urea in water. In the hose that i use to fill tanks of buses with this solution i noticed a dry white substance. I analysed the content of this solution and the content of calcium is bigger than the specifications. I have 2 questions:
a) I am almost sure that the supplier' product is ok and i have a calcium infestation in my tank (plastic). From dirt? Or maybe from the plastic material?
b) Is this white substance in the edge of the hose urea or has something to do with the increased percentage of calcium?

[Babcock_Hall]

I am not certain.  However, urea is in equilibrium with ammonium isocyanate, and one might consider what its properties are.

[magician4]

we're talking AdBlue here, aren't we?

..which is a > 35% solution of urea in water, technically at a typical pH 7-8

storing it in tanks however might, after  while, invite some microorganism to feast on it, and cause some kind of hydrolysis or another: this should  be generating NH₃ , NH₄⁺ and HCO₃^- / CO₃^2- (usually in low concentrations, but anyway causing the pH to rise to 9-10 should it come to that)

neither plastics nor the urea however will generate Ca²⁺ : this needs to be introduced from elsewhere *⁾, but could be source for CaCO₃ should the pH become really alkaline here
... and its quite insoluble

another explanation might be, that the urea in AdBlue is of high concentration already, and might precipitate when further concentrated (evaporation of solvent from the hose)
However, this precipitation should be easily re - soluble in water, and you might test for that

hence:
your substance is easily soluble in water?  urea
its insoluble in water  CaCO₃

that's what I think you might wish to investigate

regards

Ingo

*)
for example, somebody pilfering from your storage and covering it up by refilling it with "normal" water, which is of rich calcium content usually, instead of using demineralized water

[silverz89]

What kind of water feed is the Urea dissolved into? Particle free? Reverse Osmosis? you may want to sample the hardness of your source water to verify that there is no calcium being introduced to the system from there.