Enclosed Pump Selection for Mild Caustic/Acid Solution

[Rogue909]

I have a pump in our manufacturing facility that is exposed to conductive particles (aluminum oxide to be specific) daily. The first pump selected (dayton 4JMW5) was an air cooled guy which shorted out and sparked in the most enthusiastic of ways after approximately 9 months of service. In hindsight, I should have seen the aluminum oxide being an issue.

The pumped material is ph 10 water at 175F used to soak parts to remove machining oils before processing. The loop pulls water up over the tank and pumps through a bag filter to a return. Filter is changed when the pressure unit hits approximately 15psi, on the pump curve that puts it at 100gpm. I'm looking for a replacement pump and want to be a bit smarter this time around. This time I'm looking at enclosed pumps (listed below) but trying to plan a bit more with regards to the environment. The shop (115 on hot day) can exceed the 104 ambient temperature listed by these pump manuals. I'm having difficulty sourcing a pump that meets ambient temperature, pump material selection (SS), and is enclosed.

What other reputable vendors should I be looking at? I've done a cursory search online but I'm hitting dead ends. (PS; I'm not limiting myself to what's available on grainger - it's more of convenient linking to what I'm looking at.)

What other 'gotchas' should I be looking at from an environmental standpoint?

https://www.grainger.com/product/DAYTON-304-Stainless-Steel-3-hp-HP-4JMX9

https://www.grainger.com/product/DAYTON-316-Stainless-Steel-3-hp-HP-5WXU1

https://www.grainger.com/product/DAYTON-316-Stainless-Steel-3-hp-HP-5WXV0

 

[EdStainless]

It isn't the Al3O2 that is causing this, it is likely residue from your caustic.
These salts will be very conductive.
The oxide could be contributing by raising the motor temp and further shortening the insulation life.
We pumped hot alkaline (180F) with fairly normal high temp, high eff, TEFC motors.
They were expensive, something like triple the cost of generic motors.
And they have run for years with no issues. Worth every cent.

Your phrasing infers that the pumps are not at the lowest point in the loop.
This is likely causing some pump cavitation issues.
The suction head requirements for pumping hot water are a real issue.
Even with our pumps below the bottom of the 5' deep tanks we occasionally had cavitation issues.

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P.E. Metallurgy, consulting work welcomed

 

[Rogue909]

I hadn't considered the salt damaging the pump. That's very much right in front of my eyes. Thank you for the obvious observation. I assumed oxides since the unit was regularly filled with particles. While I normally tend towards failure to maintain, in this case I believe the pump was simply incorrectly chosen.

The pump sits on the floor next to the tank. The tank is approx 6' tall (from ground) with liquid level ranging between 4-5'. The suction goes up and over the edge of tank so if the discharge was removed it would siphon dump the contents of tank. In the future we will be updating the tank at the next drain/maintenance to have a bottom outlet to feed the pump.

What pump brand do you have experience with? A motor that costs 3x as much is significantly cheaper than replacing 5x motors + downtime + associated safety scolding for the fireworks display.

 

[EdStainless]

Ours were fairly large, maybe 25-30hp.
They were put together by a local service company.
The motors and pumps were sourced separately.
I don't recall the pump brand.
The motors were Baldor's, 480 3ph, either 1200 or 1800 rpm.
I think that they came with synthetic bearing grease, and epoxy paint.

Our original layout had an elbow between the tank and pump for ease of position.
We ended up redoing it for a straight shot and better flow.


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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

TEFC isn't substantially more expensive than ODP. Maybe you're thinking of TENV? Even TEFC has small vent holes drilled in the motor housing. Deck machinery on tugboats requires TENV.

OP's case sounds like a good example for a submersible pump. Off the shelf sub pumps will be less expensive than a custom order with the TENV motor.

 

[MJCronin]

While I agree with most comments above, I somewhat disagree with Tugboat ...

I believe that the 175F tank operating temperature is too high for usage of most submersible pumps.

In my opinion, a well located seal-less pump with a TEFC motor would be a solution ....

MJCronin
Sr. Process Engineer

 

[TiCl4]

Rogue909,

I would actually go a step further than TEFC and suggest you consider a motor designed for Class 2 locations, which is a hazardous location that is classified for combustible dust exposure. Aluminum oxide isn't combustible, but it would prevent dust exposure on the motor windings. I'm not so sure about the caustic residue causing this, unless you have a leaking seal that is spraying on the motor.

As far as pumps go, I would suggest looking at some Iwaki Sanwa pumps (link below). They are mag-drive pumps in the flow ranges you need and are 316 SS on wetted metal parts. They have a rated temp to 302 F standard, so temp demands are okay there too. You'd need to look at the pump curves to make sure you have the right head, but this is worth a look, at least. We have had good success with them and purchase them with Class 1 Div 1 motors. I assume that Class 2 motors are also available for dust.

The MP541 might be a good first look.

Lastly, be aware that cavitation can be a real killer when dealing with salts. Brief flashing of the water from cavitation can lead to local increases in concentration. This can increase corrosion rates above what may normally be expected and may also lead to precipitation of salts if you are running near the solubility limit. Look carefully at the NSPHr of whatever pump you end up purchasing.

Iwaki Mag Drive Pumps

Here is a brief reference from Grainger on classification zones that pulls from NFPA:
Haz location designation

 

[EdStainless]

We considered subs, but the real high temp ones are designed for deep wells, so they are low flow and high head.
The opposite of what we needed.
We didn't need to use mag drive pumps, but they would be good for this service.

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P.E. Metallurgy, consulting work welcomed