Does anyone have experience with recessed impeller pumps?

[relentlessratt]

I am considering the use of a vertical cantilever recessed impeller pump for a sump application. The pump product has sand, silt, vegetation, BS&W and some amount of sticky oily sludge. what are your experiences with recessed impeller pumps? do you think this is a suitable application?

 

[relentlessratt]

Thanks TenPenny. Will check Vaughn Chopper.

 

[Artisi]

An option is to use a chopper pump in the sump feeding a surface mounted conventional horizontal slurry pump, a complicate arrangement but it works making it a viable option.

 

[MortenA]

I could also suggest a progressive cavity pump e.g. from seepex or mono.

Best regards

Morten

 

[Artisi]

MortenA

with solids upto 3/4 inch ?

 

[relentlessratt]

Guys,
I have a bit of a stumbling block with this application. The sump depth is too much for a true vertical cantilever pump. The drawings i looked at initially indicate depths that are different from what was actually constructed, although they are 'as built' drawings.
In any event, The pump will now have to include a submerged bearing lubricated by an external source of water unless i use a submersible pump.
can someone advise the different types (if there are different types) of submerged water lubricated bearings?

should i use a submersible pump and are they reliable? I don't want to install a pump that will be removed in six months for repairs.

thanks.

 

[Artisi]

Can you fit a suction pipe to the cantilevered pump you were looking at, this means you will level control to start the pump once the impeller and case is flooded and primed and switch at some predetermined lower level.

If using a submerged bearing with an external water source I would go for cutless rubber. You will need to start up the water supply before the pump starts to flush the bearing of any rubbish - this will mean a delayed start on the main pump.

There are recessed or open impeller electric submersibles availble from a number of major manufacturers. Flygt- Toyo -Grindex (if still around)- ABS - and I would think there are a number of US manufacturers - the problem again is , can you get a pump that can achieve the head and turn-down you need.

 

[relentlessratt]

Artisi,
i can get a pump to do the head as required.
i did look at the option of fitting a suction pipe to the cantilever pump but the lowest (normal level) liquid level is more than 8 feet from the top of the pit. Apparently, most cantilever are limited to an 8 feet length and this is with a 6" shaft. So the impeller will not be flooded most of the time which is not a good option.

I've seen the cutless rubber design but the pit usually has a vast range of chemicals from time to time which can of course damage the elastomer used in the bearing. I've also seen some designs with colmonoy and graphalloy bushings. I'm not familiar with these materials. Can anyone share their experience with these materials?

Thanks.

 

[Artisi]

why do you want the impeller flooded ?
With a suction pipe you set the start point higher than the pump case.
Are concerned about priming the pump?
Not knowing what pump you are thinking of using it is more than likely that you can remove any gland / packing etc which allows the case to vent any air in the casing.

 

[relentlessratt]

Artisi,
I'm looking at a TOYO recessed impeller pump -

http://www.toyopumps.com/dec-recessed-impeller-vertical-cantilever-slurry-pump.php

The venting of air is not really an issue since the system discharges to an atmospheric tank. In any event, I don't intend to use any mechanical seal or packing in this application.

I'm thinking that the impeller will have to be below the liquid level at least for initial start if a suction pipe is used. If the liquid level is somewhere in the region of the suction pipe, then the pump will not be primed.

Just to clarify further, the current pumps utilize level control to switch on when the liquid level is high and shuts off when it is low. The high and low level settings operate between 10 feet and 13 feet (using the top of the sump as the datum). So if a Vertical Cantilever pump with a suction pipe is used, then the pump case (impeller) will not be submerged and additional priming will be required. At least that's what i reckon. I may be wrong. Please let me know if i am.
Sadly, I can't change the high level setting because it is dictated by the system and not the pump.
Thanks.