Water Filter Cartridge End Cap Installation

You may need a thermoset adhesive instead of a thermoplasitic.

Can you send a picture? How much internal pressure? Operating temperature?

Why not weld it?

This is more about sealing than welding, I think.

Well then, this might be just the thing...

http://www.royaladhesives.com/presentations/RAS_FilterAdhesives.pdf

Instead of putting a "Band-Aid" on the problems with your cartridges, why not just buy quality ones that meet your operational and environmental specifications and constraints?

IMO, from the information that you have provided it seems to me that the ones that you have on hand are or inferior quality.

Use a perforated polypropylene tube as the core and pressure fit the caps on to the core.

Thanks for the input Solar Eagle, especially the Hardman Adhesive connection. They appear to have a FDA approved casting urethane with low viscosity (haven't found costs yet, though). Lyn, you are right, sealing is the most important aspect for this installation. These filters are for field and home use and will see 30-90 psi and water up to 160F (but may see 180 F in shipping dry). We can get a seal (mixing paraffin wax with hotmelt glue to lower viscosity) and get pre-cast caps to stay on the media, but it is too labor intensive, too artisan and we have to automate. Merely welding poly cores to poly caps will not address the media sealing issue (and some filters we make use carbon cores). Thanks again.

You should be looking to NSF for certification of any filters dealing with drinking water. The NSF is supported by EPA, Health Canada, World Health. and many other organizations including FDA. Once you get NSF certification, your product can be used in many jurisdictions. Sorry, I am not versed enough in the sealants to help in that aspect of your question so I leave that to others to answer.

Dear Evannen,

I can exactly visualize your problem. I am involved an industry for design and manufacture activated carbon filter blocks with PP end cap assembled for point of use water filters.

Filter cartridges manufactured by our company have NSF and WQA approvals and used globally.

We done extensive experimentation for assembly of PP end cap to Carbon with various adhesives including epoxies, UV cure we are convinced that nothing compares EVA hot melt for ease, food grade, no solvent emission, inexpensive wide availability and more than enough bond strength.

You need to work with glue manufacturers for zeroing on the exact EVA type meeting melt viscosity etc.

There could be many other type of adhesive and method which can do the job but nothing can be as inexpensive and amenable to mass production.

Thank you Krishnan,

Did your experimentation include any cap casting directly onto carbon filters, or did your company do any cost/benefit analysis related to this process? Since we are in the scaleup transition period, we want to weigh the options before the capitol investment. Casting would obviously cost more but we would eliminate some QC issues, temperature concerns and process steps. The hope is for a castable low viscosity resin with a short curing time that will meet FDA criteria and is not prohibitively expensive. We have an idea what mold tooling costs are, but want to explore outside the box too, like is it possible to have a quartz mold with UV curable adhesive? Is there an adhesive with low viscosity that can be potted in endcaps that will harden with sonication through the caps? We would like to eliminate the hotmelt altogether, but you may be right in that we will return to EVA for the reasons you site.

We have after several experimentations settled for Semi automation for the filter candle assembly. Our experience need not necessarily be ideal for you. Here in India we have more than plenty of semi-skilled work force readily available, especially women ideally suited for the kind of mass production technology. This again, I repeat, is unique to social conditions of India. The assembly techniques we have adapted using PP cap semi automatically assembled with EVA adhesive is extremely cost effective and meet the quality certification requirements WQA/NSF. We have tried UV cure adhesives with transparent caps, but it is not a cost effective solution, carbon being porous tend to consume more of expensive adhesive. We foresee no problem what so ever scaling up production with our existing methods. Semi automation allow for the flexibility of redeployment of work force to balance peak and off peak demands of the market. Last but not the least; our company has the satisfaction of providing life sustaining social benefits by employing many economically weaker women.

Those are really good points for our consideration, Krishnan.

You mentioned the UV glue getting consumed by carbon during installation. Can you give me an idea how far the glue penetrated your carbon (granular or block?) over what time, and how fast the UV cure?

I cannot really recollect the fine details of the UV cure bonding trials, since it was quite a while back.

We tried bonding transparent cap to block of granular activated carbon.

Obvious advantage of UV adhesive was almost instantaneous bond. Pressure application is essential during the bond.

Good luck.