Muriatic acid flush for lime feed lines.

[Pump2005]

It was recommended to periodically flush our lime feed lines with muriatic acid to dissolve any lime buildup. Anyone done this and how is the proper way to do it while the plant is in operation?

 

[Barrie66]

Pump2005,
When you say lime, do you mean CaCo3 build up? if so you will need to circulate either Hcl or sufphamic (sulfamic) acid through the line at approximately 10%.
We have a mobile acid cart with a tank and mag-drive kynar pump and connect the discharge from the acid pump at the head end of the line and the return from the other end of the pipe back to the tank using plastic flexible hoses.
You will need to circulate the acid solution through the line for at least 40 minutes.
You don't say the pipe size or length. Our pipes are approxiately 30' x 2" dia.
A word about sulphamic acid....
Sulphamic acid or sulfamic acid is a dry crystaline powder similar to sugar and is inert when dry. 25kg bags are available from any chemical supply company. As sulphamic is inert when dry only minimal safety precautions need be taken, you can get the MSDS for it on GOOGLE.

 

[Pump2005]

Its buildup from calcium hydroxide (slurry) pumped through 3/4" braided poly tubing. About 50' of tubing.

 

[Barrie66]

Acid recirc as mentioned previously should work OK. We use this method to get rid of Magnesium Hydroxide in piping as well as the Calcium. However, you would be wise to speak with your chemist before trying it out.

 

[cub3bead]

Since it is poly tubing why don't you just flex it? That should break up the deposit. Use a pressurized clear water source to flush the deposits out. Setting this up as a routine PM activity and the line should stay flowing.

Be careful as the heat of reaction between the lime and acid could be great enough to weaken the poly line and could rupture under excess pressure.

 

[Pump2005]

The tubing is buried in conduit for that 50 plus feet.

 

[kenvlach]

I've used compressed air in combination with tapwater (line pressure, 60-80 psig) to backflush a drainline with lots of precipitation (rinsewater from a hot caustic etch with lots of dissolved Al). After alternating air & water flow, I would then set up surges in the line by opening & closing the outlet valve, i.e., let the line pressurize & un-pressurize quickly. The stuff shoots out, so be careful!
Also, be careful that your system doesn't come apart -- I used an air pressure regulator to drop plant air from 120 down to 70 psig.

 

[cub3bead]

What about using the existing pipe as a fish to pull in a new line? You might want to use some glycerine or a lubricant like thye use to pull electrical wiring.

 

[Pump2005]

Thats what usually has to be done but would rather not let it get to that point. The pumps have automatic flushes when they turn off.