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Technical / Re: BC26 (and possibly other boats) ballast pump problem. Flexible impeller
« Last Post by Sea Simon on 13 May 2024, 10:18 »Imho...Given that this pumps duty is to empty a ballast tank (and so, it's planned to run it dry at some point?), I'm not surprised that this type of flexible lobe pump is starting to struggle as it ages. Never mind the inverted fitment causing sealing issues too!
These pumps depend almost entirely on the flexibility of the vane materials to operate, although casings will wear if pumping gritty/sandy water. I was astounded how much sand came in with the water ballast on my BRe, particularly when I inadvertently left the fill/drain plug out while moored over sand for a few tides. So much sand that I needed to actively flush the tank with a hose, while the boat was on a concrete slipway. Not that the Bre had a pump to fret about, but sand is HEAVY!
All vanes also need to be intact. If a vane is shed, try to find it!
These pumps are known to have relatively low suction capabilities.
Try fitting a new impeller? Apparently there are two different materials used, nitrile rubber or polyurethane.
Copy parts are cheap enough (buy several, you'll need them if you plan to run it dry), they are imho acceptable for this non critical duty (although I wouldn't fit some of these knock-offs to the similar pumps fitted for diesel engine critical cooling systems), and they are easily fitted with simple tools.
An occasional dob of silicon grease (or Johnson pump lube - glycerine) thru that brass plug on the suction port might help lengthen service life?
Try and seal the suction line that is drawing air.
Perhaps fit a foot valve to the suction line, to try to keep fluid in the pump after it stops. The Whale bilge suction strainers can come with a foot (non return) valve incorporated.
These pumps depend almost entirely on the flexibility of the vane materials to operate, although casings will wear if pumping gritty/sandy water. I was astounded how much sand came in with the water ballast on my BRe, particularly when I inadvertently left the fill/drain plug out while moored over sand for a few tides. So much sand that I needed to actively flush the tank with a hose, while the boat was on a concrete slipway. Not that the Bre had a pump to fret about, but sand is HEAVY!
All vanes also need to be intact. If a vane is shed, try to find it!
These pumps are known to have relatively low suction capabilities.
Try fitting a new impeller? Apparently there are two different materials used, nitrile rubber or polyurethane.
Copy parts are cheap enough (buy several, you'll need them if you plan to run it dry), they are imho acceptable for this non critical duty (although I wouldn't fit some of these knock-offs to the similar pumps fitted for diesel engine critical cooling systems), and they are easily fitted with simple tools.
An occasional dob of silicon grease (or Johnson pump lube - glycerine) thru that brass plug on the suction port might help lengthen service life?
Try and seal the suction line that is drawing air.
Perhaps fit a foot valve to the suction line, to try to keep fluid in the pump after it stops. The Whale bilge suction strainers can come with a foot (non return) valve incorporated.