Want to make a pump for acid

[Shaun @ Tru6]

1 out of 10 MFI lines I get are fully or partially clogged. I want to make a closed system pump that will cycle hydrochloric acid through the line, maybe using compressed air as the pump like in a blast cabinet.

Now I'm running .30 welding wire through lines and then compressed air, multiple times, and while that works, it is extremely slow and painful.

I envision clear tubing at each end connected to a pump. I could even see putting some glass bead in the system to burnish the walls.

Any ideas?

[id10t]

Have you considered an ultrasonic cleaner? If you start playing with acids not only will you have safety issues to deal with but the EPA, etc. may have oversight...

[Oh Haha]

How much line pressure do you think you need? I'm thinking an old pool filter pump might be usable.

[Hugh R]

Get one of these, you can adjust stroke (amount) and time period (how often).

Walchem Metering Pump Overview

[fanaudical]

I second Hugh's recommendation. I have a parts washer in my garage running a similar metering pump - works great.

I'm not familiar with the MFI lines. What are those made from? HCl will strip most all metals and plating as well on the ends of the lines. Have you considered using a solvent like Seafoam instead of the acid?

[Hugh R]

Don't use compressed air with acid, you get acid mist in the air if a line ruptures, then you have a real physical and possibly skin/lung/eye safety mess.

Consider something like this.
LMI Milton Roy P121 358TI Electromagnetic Dosing Metering Pump Chemical | eBay

[Shaun @ Tru6]

Thank you Gentlemen, and thank you Hugh, I'll talk with the seller and see if it will take 20% HCl and if so, order a Milton Roy pump.

Steve, good suggestion, I am currently looking for an ultrasonic cleaner that will accept a 911 case half. But I'm not even sure an ultrasonic cleaner would work. I think most lines are rusted on the inside. And the acid I use is pretty weak stuff. When it's used up I just dump a box of baking soda in the bath and it's fine to go down the drain according to the EPA.

Fan, MFI lines are from the mechanical fuel injection systems for 69-73 E's and S's, RS's and was used last on the SCRS.

I actually use the acid for what you describe, removing plating. Parts are then surface prepped and plated. Here are some lines in the process.

What's nice about the HCl is it dissolves rust very effectively so it should be the best solution for making sure the lines are 100%. The issue is if one line isn't completely free, that cylinder will run lean which could cause catastrophic failure.

[Mark Henry]

I'm cleaning bigger ID tube (3/8 to 1"), but glass bead cleans even heavy rust in seconds.

[fanaudical]

Metal lines - I get it. If steel, HCl will strip both the rust and steel. You might try phosphoric acid (which is commercially available as rust stripper - doesn't attack the steel but will still remove plating).

[Shaun @ Tru6]

Thanks. I like the HCl (muriatic) and in the concentration and time I'm using, it's OK on steel. You may be a chemist, I have a friend who is, and is also a Pelican who does a ton of fabrication/restoration) and he recommended the HCl.

Of course pot metal will dissolve almost instantly and I'm careful with brazings too.

[rusnak]

That would be like using a small radiator boil out tank w/ a gas burner? Maybe try taking the lines to a radiator shop and test the process...

[Shaun @ Tru6]

Good idea but this is something I want to do in-house, mostly for quality control, then for cost.

[Bob Kontak]

Originally Posted by rusnak

That would be like using a small radiator boil out tank w/ a gas burner? Maybe try taking the lines to a radiator shop and test the process...

For discussion, what is used in a radiator shop hot tank?

[dad911]

You can make a pump out of silicon tubing, and a simple dc motor or hand crank. Used to have one like this for model airplane fuel.



Edit: found it. http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXB889&P=ML

[Tobra]

What do you use to neutralize the acid afterward?

[Shaun @ Tru6]

water goes through lines and then they go in the tumbler. When they come out of the tumbler (with recirculating water and soap and other things in the media), more water goes through and then compressed air, dry inside and out like middle pics above. Then they they go in the low humidity room until plating day.

[fanaudical]

I'm not a chemist, I just play one at work occasionally. (I'm a mechanical engineer with some history with chemical handling for various industries.)

I agree with your friend that HCl is a reasonable choice for what you're doing (providing you're careful with using low concentrations). I was suggesting phosphoric because concentration control gets less critical. Your process described above seems sound for neutralizing the acid after cleaning (which is important). Hopefully your soap is of the caustic variety to help kill the acid.

Trust me on this one - Pumping HCl (even dilute) through those lines at high flow rates may result in tapering (wall thickness reduction) at the entrance/exit of the line and potentially in tight bends. Rough guess based on line size is that ~250 mL/min is a safe flow rate. I recommend orienting lines during flush so that you flow from bottom-to-top to purge bubbles.

Not that I think this is a concern here, but one interesting thing that happens with HCl cleaning of high-strength steels is hydrogen embrittlement. I don't recommend cleaning any fasteners with HCl unless you're also going to do some things to mitigate that.

My understanding is that radiator shop "hot tanks" used sodium hydroxide (aka "caustic soda") back in the day before aluminum radiators became so prevalent. Sodium hydroxide cleaning solutions work well on copper, iron, steel, but etch(or worse) aluminum allows.

Those lines are beautiful, by the way.

[SCadaddle]

I'd try a vat with nothing but full strength Pine Sol. Not a no name generic brand, get the real deal. Soak those lines for an hour, remove, rinse with water and I bet you'll be surprised. Better yet, take one of those lines that can't be salvaged and test it first. Something you can cut open and see what the inside of the line looks like.

[unclebilly]

Use a diaphragm pump like Hugh suggested. We had something similar at the pilot plant at Tec Cominco 20 years ago for pumping concentrated HCl.

You may be able to get an iron control package to inhibit the acid attack on the lines - these are typically organic acids that coat the metal to passivity the surface temporarily. The acid eats the deposits, not your steel. We do this all the time in the oil patch - I could get you a simple and easily obtainable inhibitor if you want - pm me.

[Shaun @ Tru6]

Thanks for the great write-up here. You are correct on hydrogen embrittlement, as a precaution everything I do is baked. With zinc plating the process itself is a significantly greater threat than stripping. I do a lot of cadmium plating which, given the chemistry both of my platers use, results in lower if any embrittlement. My cadmium is also closer in appearance to 1970s zinc so while more expensive, tends to be the plating of choice for my customers.

I've been stripping anodize on early window frames with sodium hydroxide but am bringing bright dip and anodizing in-house soon, so phosphoric acid will be readily available. In probably 20,000 fasteners plated so far, I haven't had any customer problems, but it's always best to use the safest methods possible.

Thanks again, always great to learn new things.

Originally Posted by fanaudical

I'm not a chemist, I just play one at work occasionally. (I'm a mechanical engineer with some history with chemical handling for various industries.)

I agree with your friend that HCl is a reasonable choice for what you're doing (providing you're careful with using low concentrations). I was suggesting phosphoric because concentration control gets less critical. Your process described above seems sound for neutralizing the acid after cleaning (which is important). Hopefully your soap is of the caustic variety to help kill the acid.

Trust me on this one - Pumping HCl (even dilute) through those lines at high flow rates may result in tapering (wall thickness reduction) at the entrance/exit of the line and potentially in tight bends. Rough guess based on line size is that ~250 mL/min is a safe flow rate. I recommend orienting lines during flush so that you flow from bottom-to-top to purge bubbles.

Not that I think this is a concern here, but one interesting thing that happens with HCl cleaning of high-strength steels is hydrogen embrittlement. I don't recommend cleaning any fasteners with HCl unless you're also going to do some things to mitigate that.

My understanding is that radiator shop "hot tanks" used sodium hydroxide (aka "caustic soda") back in the day before aluminum radiators became so prevalent. Sodium hydroxide cleaning solutions work well on copper, iron, steel, but etch(or worse) aluminum allows.

Those lines are beautiful, by the way.