Pressure filter: pump upstream or D/S? 1

[shahyar]

Hi,
If I need to put pump for a pressure filter, what do you recommen, uostream of the filter or downstream of that?
I am interested to hear your experiences.
Thanks

 

[bimr]

There is more involved. You need to know where the water is coming from, where the backwash is going, and where the filtered water is going among other things.

 

[cvg]

upstream so that you can maintain sufficient npsh, if you place it downstream and the filter clogs, your pump will cavitate

 

[zabrab]

cvg is right on. Any potential high headloss equipment should be on the discharge side of the pump.

 

[shahyar]

Thanks Guys.
It makes sense. Just I heard, at the similar conditions,
(Filter+Pump)has more removal efficiency than (Pump+filter).Because some particles "escape" from filter in the latter case. Is that right?

Thanks again

 

[kenvlach]

re "(Filter+Pump)has more removal efficiency than (Pump+filter).Because some particles "escape" from filter in the latter case. Is that right?"

Sometimes true; a strong pump can force flow through & cause channeling in the wrong type of downstream filter, especially if poorly maintained. Whereas, flow will simply cease if clogged filter is on pump inlet side (since max. [Δ]P is less, maybe only 1 atm depending on initial head).

Don't base design on anecdotal comments. For most conditions, filter should be downstream of pump.

 

[bimr]

shahyar (Chemical)

You have provided little information for anyone to make any type of informed comment.

However, you can rest assured that there is no difference in filter efficiency whether the filter preceeds the pump or is after the pump.

The pump location in the process depends on a number of factors such as your discharge pressure, your feed pressure and source, the storage requirements, elevation changes, treatment methods, type of filter, etc. You have not provided any of this information.

 

[sbush]

As the name implies, pressure filters are intended for positive pressure. When you install a pump after the filter, you introduce the potential to create a vacuum condition. Unless the vessel is designed for vacuum service, you should not place the pump after the filter.

Where vacuum filters are used, they typically involve an open top vessel with the pump located after the filter.

Vacuum filters are more efficient than pressure filters at removing very finely divided suspended solids and colloidal particles from water (without filter aid). This is scientifically well documented and, in fact, patents have been awarded based on this phenomenon (none are still in force).

Unless you change the design from pressure filter to gravity filter, then the pump should go before the filter. And, if the pump has the potential to exceed the maximum allowable working pressure of the vessel (for example, if the filter is completely plugged and the pump is deadheaded), then a properly sized pressure relief valve should be installed after the pump.





S. Bush

http://www.water-eg.com