unload HCL35% solution

[rika kose]

A client uses centrifugal pump to unload HCL35% solution tanker.
But the pump can not prime. Client makes a side branch pipe to a bucket in the suction line of the pump.
Operating:
1. Connect the unloading hose with bottom valve of the tanker
2. open the discharge valve and start the pump
3. Open the branch pipe and let HCL35% fill the bucket around 2L then the pump starts pumping
4. Close the side branch
So, it shows that the pump can not be filled by gravity (Gas/air in the suction lines). We solve the problem by installing a self-prime pump.
My question is that why the pump cannot be filled. Due to physical properties of the solution?
The similar installation is used to unload other materials, never had the same problem.

 

[rika kose]

sketch

 

[pierreick]

Hi,
Standard unloading station attached, have a look
Pierre

 

[shvet]

My question is that why the pump cannot be filled.

Pump and suction line can be filled from an external source of a liquid or vacuum. After filling this external source is isolated and pump operates as normal.
Your kind of arrangement is a common situation and is widely spread in industry.

Note that your kind of pump installation arrangement normally is avoided for pumping a such hazardous liquids like HCl because of need to handle these sources of liquid/vacuum and this means to handle (in your case) might become expensive option as a result of corrosion and acute toxicity.

 

[rika kose]

In other unloading cases, when the suction hose is connected, the liquid will fill the pump by gravity.
Is that becasue HCL35% vapor pressure is too high, so they need to evacuate the gas/air in the suction line first? Or the pump doesn't work.

 

[shvet]

Or the pump doesn't work.

1/ Pumped liquid cools zone where rotating details attached to shaft are in contact with motionless details attached to casing. In case of "dry" start of pump these details will overheat and shaft seal become broken.
2/ Centrifugal pump can not selfprime gas. Only liquid. For vacuum selfpriming design see page 70 in a handbook attached.

 

[EdStainless]

You may need a vent on the outlet line.
And you need to check the amount of restriction posed by the valve on the pump inlet side.
Remember the density of this fluid, that could also be part of your issue.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[jari001]

Hopefully the physical property data here can give you a better idea of what's happening to the solution throughout the unloading process.

https://ordspub.epa.gov/ords/guideme_ext/f?p=guideme:gd:::::gd:hcl_6

 

[LittleInch]

The key seems to be the relatively low head from the tanker to the pump inlet isn't enough to flow the air through the pump until it sees liquid and can operate.

You therefore either need an auto vent valve on the inlet to the pump or a vacuum connection to fill the inlet system. Or make the tanker higher or the pump lower.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pierreick]

Hi,
You may check for: centrifugal pump priming pot using your favorite search engine .

http://www.rhodekpumps.com/equipments/priming_pot.html

BTW the company supplying the material should be equipped with relevant pump to transfer the liquid from truck to tank. You want to talk to them.
Good luck
Pierre