Repacking breathing air filters

[frogman62]

I have received several question regarding a past scubaboard posting in which I suggested using e a ratio of 60% 13x, 10% Hop, and 20% AC, with 10% remaining for filter felt and foam Is that the standard across the board?

My response has been "I don't know that the numbers are perfectly accurate. I simply measured the three chemicals ( Linde 13X, hopcalite, and activated carbon) in different length commercial filters and that was about as close as I could come to a relationship.
The large manufacturers have much more expertise than I do and they may weigh the chemical to get a consistent amount. I think if you watch your cartridges as most of us do - and change them on the conservative side, the difference between accurate weight and volume relationship is sufficient.
The other factor is that we fill in many environments -- dry and cool and hot and humid and each has a more profound effect on the chemical expiration rate than the exact Content".

I always recommend using manufacturers filters if you have a commercial shop or fill for other individuals.

I would invite members comments since many pack their own filters.
Jim Shelden

 

[frogman62]

I guess no one cares ,agrees or disagrees .
Jim

 

[Camerone]

Happily, this is all answered in the great article here: Scuba Engineer - Filter System Design. Getting the filter packed right is pretty simple math.

Empirically, my goal is to make sure I run out of 13x capacity before I come anywhere close to running out of activated carbon or hopcalite capacity. Why? Because moisture is the easiest thing to measure in the line with a continuous "eyeball" and indicator disk; we simply know hopcalite and carbon need to be very dry to work properly. So, as long as I have excess capacity for HC and AC, and change when the moisture content begins to rise (well before the saturation point of the 13x or the HC/AC), I will always be good to go.

Not too hard... FWIW, your rules of thumb are pretty decent enough and don't require me to get out the mass balance every time I repack my stack.

 

[frogman62]

Thanks, I' won't ask again
Jim

 

[rcontrera]

I'm with you Jim. I have quit making suggestions on how to repack a filter. Way back in the day ... when I had my shop ... we packed our own filters. Everybody did! And we used a ratio of 3 to 1 13X to AC. But, when LF came out with filter cartridges and set standards for filtration , we went to the cartridges and let THEM inherit the liability.

Now, because of liability, I sell repackable filter canisters but supply zero "official" advice on how to fill them.

 

[frogman62]

Thanks, Ray, I send one packed but heavy on the 13X so they have an example - and extra filter felt from McMaster-Carr.
Jim