EndSuction pump with Plan 11
EndSuction pump with Plan 11
(OP)
Is it possible to operate an Endsuction suction single stage centrifugal pump with fully enclosed impeller , with out balance holes and back wear-ring, on API seal plan 11?
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EndSuction pump with Plan 11
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RE: EndSuction pump with Plan 11
It is easy to prove. Run the pump with no seal flush and measure the seal chamber pressure. Compare this to the discharge pressure to see how much differential you have.
Johnny Pellin
RE: EndSuction pump with Plan 11
The intention is to increase the seal chamber pressure. API 682 6.1.2.14 recommends to raise vapour pressure margin by "raising seal chamber pressure by removing the back wear ring and plugging impeller balance holes".
The fluid is clean and we have seal failure due to flashing and dry running.
RE: EndSuction pump with Plan 11
Johnny Pellin
RE: EndSuction pump with Plan 11
yes. The extra axial thrust load will be taken care of. When discussed with a pump manufacturer, they indicated that this might lead to dead-heading the seal chamber? Is it industry practice to do this type of modification?
RE: EndSuction pump with Plan 11
You do have an alternative if you just want to build more seal chamber pressure to avoid flashing. You can add a close clearance floating bushing at the bottom of the seal chamber and let your Plan 11 flush build additional pressure. This is less risky in terms of thrust loads. We have done this successfully on pumps with a tendency to flashing in the seal chamber. The bushing can be a separate assembly installed in the bottom of the box. Or, it can be built onto the seal cartridge. If we decided to go this way, you might want to add a gauge for seal chamber pressure and ask your operators to monitor this pressure. If the bushing opens up and the seal chamber pressure drops, you could be right back into the same boat with flashing. Removing the balance holes and back wear rings is a more certain way to increase chamber pressure.
Johnny Pellin
RE: EndSuction pump with Plan 11