measuring salt level in salt saturator??

[drbitboy]

> Sodium Chloride has listed solubility of 35.7g per 100ml water at 0 Celsius and 39.12 at 100 Celsius.


I was surprised that the temperature coefficient is so small.



An alternate expession of solubility is the saturated salt percentage by weight (~26%+) and the specific gravities of brine (~1.2) and salt (~2.2), which is what are needed for the weighing formula; but I don't think they are useful here.



Does the undissolved salt turn into cake (loss of surface area)? Or is it sitting on a gravel bed or similar and the fresh water comes in from the bottom which minimizes caking?




Any, I think OceanSoul's solution is the right one. I suspect this need be neither a continuous nor even a frequent measurement: it's a bang-bang control to determine when to add salt.



With the yoyo, I would be concerned about brine in the device. One way to get around that would be the simple-minded idea sketched below, which may or may not work, but which lets the designer control the materials submerged in brine. It would need a PLC or similar to drive a motor to lift the disk regularly and when salt was added. Also, the H2 measurement has a small cosine-near-zero-degrees error, but maybe that is replaced with a prox to indicate when to add salt.


Just too much time on my hands, to go along with all the time spent on this thread!

 

[Saffa]

Does the undissolved salt turn into cake (loss of surface area)? Or is it sitting on a gravel bed or similar and the fresh water comes in from the bottom which minimizes caking?

Nope it just sits at the bottom of the tank and remains crystalline. We normally just add water in from the top but at a high enough rate to mix things up

 

[Tom Jenkins]

I'm not sure moving discs like DrBitBoy's diagram will work without manual intervention. At some point, more salt will be added, and I don't see a way to keep the disc from simply being buried in the new salt unless it is manually raised. I'm also not sure that the salt below the disc will dissolve at the same rate as the surrounding salt layer since it is protected from the brine to some extent. This could keep the disc from falling in coordination with the rest of the layer. Just thinking, and obviously, I have too much free time too!

 

[I_Automation]

This could keep the disc from falling in coordination with the rest of the layer. Just thinking, and obviously, I have too much free time too!

How about grab the cat off the train and give it some snacks on the counterweight regularly, or put a mouse in a cage on the counterweight so he/she keeps it in motion so the salt underneath can dissolve?

Time on my hands here too.

 

[drbitboy]

@Saffa thanks for the feedback about the salt not caking.

I'm not sure moving discs like DrBitBoy's diagram will work without manual intervention. At some point, more salt will be added, and I don't see a way to keep the disc from simply being buried in the new salt unless it is manually raised. I'm also not sure that the salt below the disc will dissolve at the same rate as the surrounding salt layer since it is protected from the brine to some extent. This could keep the disc from falling in coordination with the rest of the layer. Just thinking, and obviously, I have too much free time too!

Ooh, good catch Tom! I had mentioned the need for a motor to lift the disk regularly and when salt was added, but did not think about the effect of the disk on the salt immediately under it (Heisenberg). Maybe the motor would have to to a short lift briefly every few minutes, or maybe if the disk is small enough it won't be an issue (ChemEng is all about surface area, after all).



Or maybe instead of a flat disk, a disk with angled paddles (screw?) that turns (vertical axis) so it can "climb" out of the solid bed but not up into the brine. Hmm, but then there's a 2-DOF mechanism that would need to be immune to precipitating salt; for that matter the lever-disk joint may have the same problem.


Still too much free time. I was just thinking: I have a MicroLogix 1100 and a 5gal pail; salt and water are cheap; ...

 

[drbitboy]

How about grab the cat off the train...

LOL.


Getting into Heath Robinson/Rube Goldberg territory (as if we weren't already there).

 

[cardosocea]

I witnessed the salt delivery yesterday and the yo yo sensor would eventually be destroyed as someone would forget to raise it out of the way.

I also realised that the "port" available isn't available and is filled with the ballcock so I'd need a new tapping point on it.

I'll get in touch with Forbes and ask if they can tap into the tank (there's a high level already) and create 3 points or so for bulk salt probes.