Hi peeps
Hope you don’t mind if I join in with discussion. I’ve been a skimmer freak for many years now and although Deltec skimmer design is down Wolfgang the skimmer guru at Deltec rather than D-D I find skimmer design extremely interesting so hope I can add my views on the subject.
With regards to air pollutants I personally run my air through carbon as I take air from outside the house due to Ph suppression during the winter months when the house is shut up.
As I live in a rural area near fields there is always a danger of crop spraying or neighbours using weed killers or bug powder so it essential if taking air from outside if you live in a street, near industry or agriculture.
Skimmer design is tricky for sure, historically designs have always been limited by the amount of air that could physically injected into the body. When we look back at lime wood diffusers for instance the skimmer design relied on long thin bodies with thin neck designs.
Although these skimmers were not particularly efficient due to the fact that the amount of air was limited to the air pump used and lime wood diffuser life their saving grace was contact time and steady/gentle foam build.
The next big thing came with the needle wheel pump; a new era came about with the new taller skimmers that could handle more air. Cup and neck sizes increased although the amount of air the pumps could shift was still limited to around 800 lt/hour so neck sizes were still quite small and bodies tall to make the most of contact time. The tall Aquamedic skimmers were a prime example, two large pumps, very tall body and thin conical neck to make the most of the available foam at the head.
Beckett skimmers were quite popular as although quite power hungry they could inject far more air than old school needle wheels.
Deltec did offset the need for very tall skimmers by using more pumps on a wider shorter body to increase the air whilst increasing capacity within the body. The neck sizes were also larger to account for the increase in air. Try this on a skimmer with a narrow neck and it would have continually flooded. We also have to look at air to water ratio’s of the pump, most of the time the pumps were shifting lots of water and not a great deal of air creating chaotic conditions inside the skimmer, something modern designs avoid like the plague and another reason that skimmers couldn’t be made smaller.
Modern skimmers are easier to site due to the more compact size and you’ll notice that the better designs rely on wide bodies, diffuser plates, high air to water ratio at the recirc pump, efficient design of inlet and outlet so dirty water doesn’t keep getting re skimmed, better level adjustments and wide neck designs.
Skimmers now force huge amounts of air through them whilst keeping chaotic behaviour inside the skimmer nominal so bubbles can enter the neck to form good foam without popping too early and protein draining back into the skimmer. Neck size is also key as if the neck is too large the foam causes scum to build and can’t remain stable to force its way into the cup, too narrow and the cup will flood and you may have to reduce air/pump size.
Bubble size is also important, it’s far better to have a pump producing very small bubble size and greater surface area than to use a larger pump that looks to be producing more air due to volume but with larger bubbles.
So basically it’s a balancing act between
1 Amount of air
2 body size
3 bubble size
4 flow through the skimmer
5 neck size
Not that difficult to do with the older taller designs as you can default to lots of contact time but not so simple when trying to optimise more compact skimmers.
Sorry for going over a little history there but I think it helps us understand the latest tech even if its going over old ground.
