Filtration method for 10 micron range

[stewbaby]

Having problem with prefiltering on our diesel coalescer system. The coalescer is used to remove gross water from the diesel to storage off a crude unit. The coalescer elements require protection from particulates larger than 10 micron so prefilter is required. Since bag filters have served us well in other applications, we installed a four bag prefilter with 10 micron absolute welded seam bags (design is 150 GPM).

Problem, our diesel off the unit is much dirtier in the 20 to 30 micron range than we ever expected. Operators are having to change bags daily. Curious on opinions or experience related to if we should switch to cartridge filtration or spread out bag change schedule by installing say a 18 bag unit.

What are pros and cons between bag and cartridge filtration of oil?

 

[orenda1168]

Stewbaby:

Consider going with an initial 20-30 micron nominal bag filter grouping, followed in series with the 10 micron absolute bags. "Get the rocks out before you worry about the dust".

Orenda

 

[StoneCold]

stewbaby
One thing I recently learned about bag filters may help you. When you buy a bag filter that is rated at 10 microns it is really only stops particals that are 20 micron or larger. Does not make any sence but that is how it is. I would try dropping the bag filters down to 5 micron and see how things go.

StoneCold

 

[HEC]

stewbaby,

perhaps also consider wsing a wedge wire style filter that can be fitted with a cleaning device. Johnsson screens have filters of this style that may be useful for your application. I would agree with orenda1168 also and look at coarse filtration prior to the finer filters.

Mark Hutton

 

[jmj5152]

Stewbaby: There are backwashable stacked disc filters that would work well for you. The discs are held together by compressed air, and filtration occurs radially, inward. When pressure drop is high, the pressure is relieved on the air, and the discs come apart , resulting in an air type backwash, with very small volumes of process liquid wasted.

 

[vonbad]

Stewbaby,
I recently read a thread (thread378-116447) similiar to your request.

I am assuming this is a full flow filtration requirement. The only practical way is to use staging filters.

How much fluid are you processing at a time?

 

[stewbaby]

I'll have to look into the backwashable stacked disc, I'm not familiar with it. May be something we can use.

StoneCold...Yes, tried 5 microns that we already stocked at first then learned that they were "nominal"...these filters lasted for a long time but didn't protect the coalescer. Curently using 10 micron "absolutes" that catch 98% of over 10 micron...coalescer is protected but filter changeout in 4 bag unit is a headache (often enough that operators are going to lynch me)!

Orenda1168...This was also my first thought but my system curve can't handle the pressure increase that would be created by another filter in series. Upstream heat exchanger's design is 100 PSI and relief valve is set at 90 PSI. We can't even take full advantage of current filters 20 PSI recommended change-out DP, if we don't change filters at 15 PSI DP we risk lifting relief and making wastewater treatment and environmental guys very unhappy. Without major changes to minimize piping loss or redesign heat exchanger, looks like I'm stuck with going with same amount of filter usage per give interval, but can minimize times operations has to go into filter vessel by exchanging 4 bag unit with 12 or 16 bag unit.

Glad that no one recommended cartridge filters. I felt bags had a much greater capacity and acceptance in dirty services but wanted to check.

System is flowing 150 GPM of diesel 24/7/365.

Thanks to all for your time and recommendations.

 

[HEC]

Stewbaby
I see that you aer backed into a corner with the system pressure drops. have you considered putting some coarse strainers directly after the supply pump, ie before relief valves and heat exchangers. This would achieve the coarse filtration required and reduce the load on finer filters and solve the pressure drop problem.
Regards
Mark Hutton
hutton4eng@picknowl.com.au

 

[vonbad]

Stewbaby,
I meant to get back with you but have been tied up and wanted a minute to think about your application. Bag vs cartridges are a trade off and really the best is dependent on the particular application.

I (and I do not know if it's appropriate here) work for a company that manufacture filtration systems for hot oils (HTF) as our main core business. We supply both bag and cartridge vessels. Again, dependent on the application.

Bags do have a higher capacity for contaminants and really apt for full in line filtration (which I do not recommend unless absolutely necessary as it could lead into a lot of problems and process operation). Cartridges tend to be more flexible for applications. Again each application is different.

I see that you also came into the realm of absolute and nominal sizes. If you ever decide to change suppliers have the new supplier EVALUATE bag to determine the exact rating.

Unfortunately, I do not know enough about the process "The coalescer is used to remove gross water from the diesel to storage off a crude unit" to be of more help.

 

[stewbaby]

HEC, yes all this talk has helped me think "outside the box" and pushed my thoughts back upstream in the system. I had been hesitant due to temperature concerns to go back upstream but you hit on it...a fine mesh strainer may do the trick. I'll need to do some more particulate load testing to see what mesh (if any) will be effective.

Vonbad, I guess the coalescer info is really to much info. Overall goal is to filter an...apparently much dirtier than I would have guessed...150 GPM, 100F, continues flow (24/7/365), diesel stream down to 10 micron range (to protect a coalescer, it plugs if exposed to higher than 10 micron stuff). Bypass in place so filter can be changed on run.

Existing 4 bag filter vessel with 10 micron bags is an operational headache due to need to change filters daily and filter bag cost get up there. My options seem to be 1) install strainer upstream to catch gross solids before DP is an issue, 2) install larger filter vessel so frequency of opening is less (still same number of bags/year so same $ in bags) or 3)Somehow remove pressure drop in system so a staged prefilter, say 30 micron, can be inserted upstream of existing prefilter (may be possible by going to a pilot relief or relocating a control valve). Also, JMJ5152, I need to look into the backwashable stacked filters option.

Thanks all for your help. This process really helps you think.

 

[aspearin1]

Stewbaby,
I wish I had come across this post sooner. (Took a little eng-tips leave). I'm at risk of being red flagged with this one, but I develop bag filter products, and I've evaluated many competitor bags. Consider the following products: DuoFLO (

http://www.cuno.com),

Hayflow (

http://www.haywardfilter.com),

or another similar product called Excalibur (Flotrends.com). These are all bag filter elements with a 70% increase in filtration area. This cuts the flux substantially, cuts the hold-up volume by 400%, and at least doubles the life. I think a 1 micron bag filter will suit your process well. Each of these bags will likely retrofit into your existing housing. In essence, this style of filter will make your 4-round housing equivalent to about a 7-round housing. Hayflow and DuoFLO are near identical and they use extra thick bag media. The Excalibur filter uses thinner media and is sewn, but it outprices both the DuoFLO and Hayflow.

I presume for high efficiency bag filters you are using either 3M or Hayward, which run $50- $100 a piece. They are regarded as the market leaders for high efficiency bag filtration. The DuoFLO, HayFlow and Excalibur run between $7 and $20. If you can get the efficiency you need from one of these 1 micron rated bags, the payback would be nice.

If you are interested, I'd be willing to talk offline. Let me konw, and I can forward some contact information.

In the meantime, I suggest you do a web Google search on the bags I mentioned above.
Good Luck.


ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee