Adjustable Dip Pipe in Pressurised Vessel

[malc_t7]

Hi All
I'm working on a process design that involves settling a suspension in a vessel, and removal of the supernatant above the settled bed. The settled bed volume varies batch-to-batch, and as much of the supernatant as possible needs to be removed before moving to the next step. The proposal is to have an adjustable dip tube that can be manually lowered to just above the bed, and use a pump to draw off the supernatant. However, finding a design for an adjustable dip tube that can be fitted to a pressurised vessel, and maintaining the pressure rating of the vessel is proving difficult. Does anyone have any recommendations, or experience with a similar requirement?
Thanks.

 

[LittleInch]

Why not use a floating suction arm instead?
Problem with a dip tube is surely that it will suck up some of the bed material when it starts flowing?

Then when it touches the bottom layer it just stops.

How variable in depth is the layer?

 

[malc_t7]

Thanks for the reply. I think the main problem there would be that the system needs to be relatively hygienic (it's not a pharmaceutical but a product that is used in the pharmaceutical industry), so needs to be fully cleanable.

The current thinking is that the dip tube will have a 'deflector plate' on the bottom to stop sucking up the bed. The dip tube can then be retracted to a set position, where full coverage can be achieved by the vessel sprayballs.

The bed depth can vary by +/-200L, so roughly +/- 6cm.

 

[LittleInch]

Well depending on your amount you can have left, why not simply have say three or four dip tubes of different length fitted permanently at say 1.5 to 2 cm intervals then use which ever one is best?

Sliding or even turning things which are under pressure is difficult and very bespoke.

 

[EngrPaper]

I second having multiple dip tubes. Having some manner of variable component would add complexity and error to a process that could essentially just be a hot swap.

 

[malc_t7]

Thanks for the replies. Multiple static dip tubes is a good suggestion. I just wanted to check that there wasn't an existing solution that I wasn't aware of.