Larry Bachus
(a.k.a. “Pump Guy”)

Hi Larry,

I attended your seminar in Houston earlier this year. It was definitely worth its weight in 316SS. I work in sales at a pump distributorship. We sell a variety of pumps.

One of my customers has a challenging application. They are pumping a slurry of 22-percent hydrochloric acid (HCL) at 190 F with iron fines up to about one-inch diameter.

I spoke with my supplier. They said their Hastelloy-C slurry pump would be eaten up by this service. They pointed me to a rubber-lined slurry pump instead.

Do you have experience with HCL acid slurry? Can you recommend a centrifugal pump for this service? Any insight would be helpful.

Thanks,

Mark V.
Pump Distributor

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Mark,

Something doesn’t seem right. Why would a chemical company with staff chemical engineers, who must pump slurry of hot hydrochloric acid (HCL), ask the pump salesman about the correct metallurgical compatibility?

Isn’t this like visiting a grocery store and asking the check-out clerk what you should buy to put into your refrigerator? Would you visit an automobile dealership and ask the car salesman to recommend the car you should drive?

You didn’t make your customer pump hydrochloric acid with iron slurry; it was your customer’s decision. I’d think your customer would tell you the metallurgy they want for their pump and liquid.

You indicate in your message that you (or your company) distribute pumps and the HCL slurry application belongs to your customer. I used to work in a similar capacity. I operated a contract pump repair shop about 20 years ago.

Many of my customers were pharmaceutical chemical plants, and frequently they pumped HCL at different concentrations and temperatures. I’ll tell you what I remember about pump metallurgy and chemical compatibility.

A chemical plant that pumps HCL usually also pumps brine and caustic soda. Brine is sodium chloride (NaCl). Caustic soda is sodium hydroxide (NaOH). Liquid and gaseous chlorine (Cl2) and hydrogen (H2) might be present and pumped as byproducts. Along with these liquids are the pumps associated with the power house, cooling water, and fire water.

Some chemical plants will standardize on one or two metallurgies that cover all liquids in the plant. Other plants will mate specific metallurgy to each liquid.

Depending on the concentrations of the various liquids in an HCL plant, we rebuilt pumps made of everything from carbon steel, stainless, hastelloy, titanium, and plastic (polymer). But metallurgy and chemical compatibility wasn’t my decision; it was the chemical engineer’s decision.

We rebuilt pumps on a contract basis for two industrial bleach plants (sodium hypochlorite, NaClO3). These plants use large quantities of concentrated HCL. Hastelloy was really popular for pumps, seals, pipe, valves, instrumentation, and tanks.

As for pump metallurgy with acids, it is most important not to mix and combine different metals in the wetted parts of a pump. For instance, you don’t want to install a stainless steel mechanical seal into a Hastelloy pump. Be sure all wetted components are the same metallurgy. This applies to set screws, clip rings, wear bands, lock rings, pins, keys, and any other wetted metal.

I stayed away from offering opinions on metal compatibility. A company that handles and pumps 22 percent HCL in a slurry with iron filings at 190 F must have a chemical engineer on payroll and on-site. Ask the chemical engineer. Let the pump metallurgy be his or her decision.

However, if your customer was recently acquired by another company that has no experience with hot HCL slurry, and the company’s recently graduated chemical engineer is at the home office in a different time zone, then some of the metallurgy decisions may fall onto you.

Inquire about the metallurgy of the pipes, valves, flanges, nuts, bolts, accessories, instrumentation, and tanks in the HCL application. If the pipes, valves and tanks are Hastelloy, you’ll want a Hastelloy pump and wetted parts. If the piping system and instrumentation is made of 316 stainless, you’ll want 316 stainless for the pump and parts.

If the pipes and tanks are polymer (PVC, HDPE), or other component like fiberglass, rubber lined, or glass (for ultra-pure), you’ll want an equal pump, parts, and a mechanical seal with no metal components in contact with the liquid.

Glass and glass-lined pumps, pipe and components are unlikely with HCL slurry. HCL cuts and etches glass, and the iron filings would break the glass – I use it only as an example.

And while you’re at it, ask the engineer about chemical compatibility between the HCL and secondary seals, gaskets and o-rings. Even if you get the metallurgy right, an incorrect or inadequate o-ring will still cause your pump to leak.

Good luck,
Larry Bachus

Larry Bachus, founder of pump services firm Bachus Company Inc., is a regular contributor to Flow Control magazine. He is a pump consultant, lecturer, and inventor based in Nashville, Tenn. Mr. Bachus is a retired member of ASME and lectures in both English and Spanish. He can be reached at larry@bachusinc.com.