Working with Sulfuric Acid

The answer really depends on the materials of construction, pump internal volumes and speeds etc. Your initial problem is flushing before even thinking of neutralization, if it is necessary. Baking soda solution is my recommendation for that.

One "safer" method is to run progressively lower concentrations through it; start with an almost empty closed top drum and slowly trickle cold water into it (yes, I know that's backwards!!), preferably through a dip tube below the acid level, while the pump is continually recirculating back into the drum until you are below 1% acid level, then flush with water. This will leave you with a fair amount of diluted acid though.

Or, you can run a bit of denatured or isopropyl alcohol through if it's compatible with the pump materials. This will not react nearly as fast as or to the extent of water. Follow it up with a cold water flush.

WHY would you want to neutralize, at all?

Run it dry, and pack away for winter.

Next spring, immerse and run.

I have to presume, that the pump is acid resistant.

If it were not acid-resistant, it would not be available in the Spring...

How about passing air through it?

What does the owner's manual suggest?

rota chem manual

Hayward Pool

Pool Pilot

LMI Acid Pumps

Hanainst dosing pumps

Texel Magnatex acid pumps (go to "downloads") for your model.

Is this helpful?

The LMI site only mentions diaphragm replacement, but that's the same as storing for the season, in my book of life.

"Carefully depressurize, drain, and disconnect the discharge

line (see Section 8.1 in this manual). Place the Foot Valve

into a container of water or other neutralizing solution. Turn

the pump on to flush the head assembly. Once the pump head

has been flushed, lift the Foot Valve out of the solution and

continue to pump air into the pump head until the pump head

is purged of water or neutralizing solution."

I didn't bother looking at any of the rest, since LMI's are all I've ever specified, when I did such things.

Bulk of the heat of dilution in the case of sulphuric acid would have happened already at 35% dilution. Not much heat will be liberated by flushing with water. This can be checked by adding water to a small volume (Less than an ounce) of the water in a beaker.

So you are saying that with 35% sulfuric and the pump drained of all acid that when I flush with plain water, heat should not be a problem? I've worked with 98% before and did not dare do anything like this. So maybe flush will cold water as long as the pump is purged of acid? It is an LMI pump by the way.

And thanks to all who posted. Some of you went to considerable trouble with links and all. This my first time on the site...nice work!

It's a pleasure to help someone with a legitimate question, who just doesn't want us to do their job, or homework, for them.

Welcome.

I think you are worrying too much about the heat. Even at 50% most of the heat of solution has already been taken care of. Rinse the pump out if you feel this is necessary. If you are worried about freeze protection, the 35% solution has a fairly low freeze point. As long as your pump is fabricated from the correct materials for the job, these will not degrade in dilute sulfuric acid. I have sulfuric acid pumps that remain pumping 93% sulfuric 24/7 for at least 200 days/year. When idle, I simply leave the acid in the lines and the pump, no problem. No maintenance issues.

In view of all the notes, I feel comfortable in my note #3, that a pump can be packed away uncleaned, only drained.

The pump IS acid resistant.

The sulphuric acid is strongly hygroscopic. It will maintain its water content during storage with no trouble whatsoever. And be ready to service next year, without any fancy footwork.

Well, this does change my thinking a bit. If draining and not flushing clean is a common practice with these pumps then I could just store the pump without any cleaning. Maybe just disconnect it and seal the inlet and outlet.

I guess I'm just to obsessive about taking care of my equipment!

Many chemical dosing pumps run 24/7 until the diaphragm fails.

While I may not be able to build a strong case for flushing and storing, I'd not store a pump full of acid residue for any length of time. I believe that will shorten the life of the pump, as the water evaporates and the acid concentration rises.

Rinse, before storage.

I used to use LMI pumps as these were the most durable, but they have changed the materials in these with the new cartridge ball checks, and they will not put Viton in the ball cartridges - bad. I do have good experience with the latest round of Walchem pumps as far as precision of dosing, durability of the materials, excellent. Also, Walchem pumps use a double ball check cartridge (of the right stuff), which means they pick up suction from running dry very easily. I don't recommend leaving any chemical pump set up out in the weather if you live where there are dust storms, as dirt is the enemy of any pump made.