Pump keeps kicking out 3

[iqbalnaq]

Hi
I work in pulp and paper and am troubleshooting a pump. It is a centrifugal pump 9" impeller (goulds 3196mtx); motor 3HP, 1760RPM, 3phase constant speed induction motor, 575V, 3.2A. The flow rate we are putting out is 23gpm. The motor is the right size for application (meets the pump curves)

The problem is the motor keeps kicking out. It is pumping polysulfides orange liquor (pulp and paper jargon). We think it is scale build up in the pump that is causing the motor to trip.We do an acid wash once a year right now. It is a time intensive process and increasing the frequency is a bit difficult. Putting in a bigger motor seems unreasonable as we don't know if the amps drawn by the motor ever level out.
Any pumps out there in the market which decrease the rate of scale build up.
Or maybe there is some other reason for the kick outs.
Thanks
Naqshe Iqbal E.I.T

 

[Artisi]

On 6th August you said "We just opened the pump and found very little scale build-up. The impeller was not rubbing against scale in the housing."

So what is happening now, why have you now asked how to reduce scale build up?



It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Artisi]

One possible option is a rubber lined pump, this is sometimes a solution but cannot be guaranteed. Also sourcing a small pump with high temp. elastomers maynot be possible.
You will need to talk with a slurry pump manufacturer and ask their advice.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

Reading this again, it struck me that one thing not considered is whether to increase the flow through the pump by say double your current flow by means of a return line either to pump inlet line or back to original tank. You would waste a bit of energy, but the additional velocity and operating more in the centre of your pump curve would be helpful and the increased efficiency means that at double your flow, you would only increase power by 50%.

Given you have a control valve on level control, the loss of a few feet of head shouldn't make any real difference.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[iqbalnaq]

I think when we opened the pump the flush affect knocked some of the scale inside the pump. That is why we didn't see any scale rubbing against the impeller. That will also explain when the pump kicks out the amps drawn by motor go down.

Scale is the only possibility I can think of. After acid wash amps go down, after flushing the pump with water amps go down.
As for rubber pump, or a coating we are worried it will chip off and enter our pulp stream.

I was thinking of an impeller with a scraper vane on it. That might prevent buildup.

Increasing the flow will increase the efficiency, but might not help with scaling. Or maybe more fluid will prevent scale build up. Will try that.
Thanks

 

[LittleInch]

It's not guaranteed, but at low flows you get all sorts if strange Eddy flows within the pump which are much reduced at higher flow rates.

Let us know if it helps.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way