7 replies to this topic

[Suri]

What are your views and experience with side stream filtration for CW systems? Our side stream filters are designed for 3% of the total circulation volume. Is that sufficient enough to handle all the solids in the system?
I've been reading on separators that filters 100% of the CW supply. Since we have found solid particles at our heat exchangers, we are considering changing to 100% filtration from the current side stream filtration. Would this really solve the problem?
I'd appreciate some feedback. Thanks.

[Art Montemayor]

Suri:

Depending on the size, water quality, process criticality, and other factors, I always try to design for 100% cooling water (CW) filtration to process (not the make-up supply). Sometimes this can't be justified; but I always filter critical parts of the process.

I recommend a CW filter such as the Boll Filter design. You can find full information on the
Goggle search engine for Boll filters.

[smalawi]

Hi,

Agree with Arts's note, it really depends on the type of system and process you have.

What did you find in the HX ? is it somthing you filter out or its marine type growth, the later can not be filltered and needs treatment, e.g. Cl injection. It actually grows in the system !

I had good expriance with auto backflash systems from Alfa Laval, it filters 100% excpet when it back washs for short duration.

suggest you contact some of the venders around you, be careful they want to sell so ask for expriance of others in services similar to yours and make your own conlcusion.

cheers,

sm

[santy]

On top of above commments, I actually wonder would there be any other cause which leads to
solid apperance in the heat exchanger.
For instance, the cooling water velocity in the tube side of HEX, normally it is designed to be superior
to 1 m/s (vary depending on design practice in different area/discipline). Tow low velocity could aslo
give trouble in heat exchanger operation because of solid sediment in the pipe/tube. We actually have
this sort of problem on one site. Process engineer was then asked to check the water velocity in
the C.W system.

I just heared of this issue from operation team, I would let you know the real cause of this issue if
I know more from site.

[Ollie]

One process safety note on this topic. If you switch from side stream filtration to full stream filtration the probability that the cooling water flow will be interrupted is increased by a significant factor! This is to be taken into account during Process Hazard Analysis or HAZOP study. Speaking from experience.

Be safe...

Ollie

[katmar]

Forgive me for splitting hairs here, but I think there is a bit of confusion over the terminology being used. We need to distinguish between the terms "screening" and "filtering". When I talk of cooling water screening then I am thinking of a mesh with an opening of about 1/8" (3mm). On the other hand, when I talk of cooling water filtration then I have in mind a sand bed filter.

On the towers that I have worked on, or installed, we have generally gone for 100% screening and 3 to 10% sidestream filtration. So I don't believe the decision is between 100% and partial filtration - you need to decide separately (1) do I need screening, and (2) do I need filtration?

The screening protects the pumps, valves etc from plastic bags, bits of wood, plastic helmets and so on. If you are going to put screens in then you would invariably apply them to 100% of the flow.

The side stream sand filters take the micro-particles (suspended solids) out and help prevent fouling of heat exchange surfaces etc. An alternative to filtration as a way of keeping the suspended solids low is a higher blow down ratio, but with the never ending increases in water prices I guess this is becoming less and less of an option. Generally you will have blow down and filtration and the balance between them is economic.

[Lukman]

Be carefull to increase your CW side stream flow. Please consider increasing of pressure drop through that filter. You may lack of CW flow for your cooling duty after that.

Percentage of CW side stream mainly depends on your CW quality. Or you can use individual filter (strainer) for each equipment mainly the sensitive ones.

[aqology]

What are your views and experience with side stream filtration for CW systems? Our side stream filters are designed for 3% of the total circulation volume. Is that sufficient enough to handle all the solids in the system?
I've been reading on separators that filters 100% of the CW supply. Since we have found solid particles at our heat exchangers, we are considering changing to 100% filtration from the current side stream filtration. Would this really solve the problem?
I'd appreciate some feedback. Thanks.

We have useful information for you to come to a conclusion. Please let's have your contact info.

With warm regards,
Ajai Agarwal
Director & Chief Executive
AQOLOGY TEKNIX
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Alaknanda
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India
Tel. +91-11-42143751,64604044, 65668347
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