RK2 Skimmers

[swsaltwater]

So after watching the performormance of the RK2 skimmer I bought 2 years ago become less and less I decided to mod it. I put a new dart needleweel "orca" pump on it and bypassed the mazzai injector. In about 3 mins the perfomance went way up and I had to lower the water level 10 inches. I have a few kinks to work out but would highly recommend anyone here running an RK2 in their store to consider changing it up. I am thinking of adding another orca dart to the feed. We are working with coralvue to make a large commercial hurricone soon but until then this will work much better.

 

[Anonymous]

Cool! What was the model RK2?

 

[coralite1]

I know that weak performance from commercial scale RK2 skimmers has been a problem for many institutions. I'll be watching this thread to read more about your RK2 mod with the reeflo needle wheel pumps.

 

[Anonymous]

Neat. Pictures? What scfh does the orca draw? Are you feeding it with ambient or pressurized air?

I would think converting both pumps to orcas would be even better, but you may not be able to draw as much air through the feed pump due to the increased head.

 

[swsaltwater]

I am going to add a single piston air pump to the mix just so i can open up the recirc water flow a bit. I can easily tell it will work better. I have the RK 25PE, about 6-7 feet tall and runs off the regular dart. I am feeding it with a mag 36 for now but will change to the dart I pulled off. Maybe use the mazzai on that for the feed. If that all fails I am waiting on coralvue to build us some 5 feet tall hurricones with 2 dart gold pumps on each. The dart gold pulls 50-60 SCFH. The regular dart seems to be in the 30-40 range. With a piston pump I can run them at 100scfh according to manufacturer.

There is a union on the dart pump RK2 has installed from the factory. All you have to do is tap it an add a valved air intake. I will work this more as I go to get it angled more toward the NW. I will post pics soon.

 

[swsaltwater]

Question for the water pressure experts out there. The water tower in the RK2 is 5 feet tall about 18" in diamter. Does that head pressure affect the pump since both the intake and output are under simular pressure(output 6 inches higher into the skimmer body then the intake). Does it decrease the output any? I am mostly just curious since the output is higher then the intake the natural action would be water syphoning from the top one to the low one like a powerless pool filter, but the pressure on the bottom one should be greater correct?

 

[Anonymous]

Question for the water pressure experts out there. The water tower in the RK2 is 5 feet tall about 18" in diamter. Does that head pressure affect the pump since both the intake and output are under simular pressure(output 6 inches higher into the skimmer body then the intake). Does it decrease the output any? I am mostly just curious since the output is higher then the intake the natural action would be water syphoning from the top one to the low one like a powerless pool filter, but the pressure on the bottom one should be greater correct?

If you're talking about the recirculating pump there will not be any head due to gravity that affects the pump performance, regardless of the skimmer height, pump location, intake and output locations, etc. There will be some head pressure from any pipe bends, elbows, length, etc. of course.

It gets tricky, however, when you do something like punch an air hole in the line like, say, on a needlewheel skimmer intake on a recirculating loop. The air intake IS affected by the height of the water level in the skimmer above it, and if you had a very tall column of water above that air intake you may need to use pressurized air. Ideally you would locate a needlwheel pump up as close to the top of the water surface as possible to diminish this.

HTH.

 

[ctenophore]

I am going to add a single piston air pump to the mix just so i can open up the recirc water flow a bit. I can easily tell it will work better. I have the RK 25PE, about 6-7 feet tall and runs off the regular dart. I am feeding it with a mag 36 for now but will change to the dart I pulled off. Maybe use the mazzai on that for the feed. If that all fails I am waiting on coralvue to build us some 5 feet tall hurricones with 2 dart gold pumps on each. The dart gold pulls 50-60 SCFH. The regular dart seems to be in the 30-40 range. With a piston pump I can run them at 100scfh according to manufacturer.

There is a union on the dart pump RK2 has installed from the factory. All you have to do is tap it an add a valved air intake. I will work this more as I go to get it angled more toward the NW. I will post pics soon.

Hi all,

I am the developer of the Orca needlewheel, so I will try to give some guidance based on testing we did while developing this impeller.

Early on, we thought the piston pump was necessary to get the Dart to draw air at anything beyond about 42" head pressure. The problem with the air pump was that it tended to cause large air bubbles to make it past the impeller and consequently disrupt the foam head. We found that restricting the water with a gate valve before the air intake solves this problem fairly well. It creates a stronger suction on the air pipe and seemingly smaller bubbles as well (although the latter effect is hard to measure).

So before you add the piston pump (we used an alita-40), try a gate valve before the air intake you tapped into the union. Like this: skimmerbody<--pump<--air<--gatevalve<--skimmerbody
(See this for an example, roughly equivalent to RK75PE in size)

If the Dart/Orca doesn't do it for you, contact Chris @ ReeFlo and ask about the Hammerhead NW impellers. I have been running early prototype needlewheels on two 8' tall skimmers (7' of head, see link above) for about 2 years of continuous duty each, and they have performed admirably. We haven't opened up the HH to general availability yet since it is a rather specialized part which costs a lot to machine (the Orca impellers are molded but the HH are milled delrin). I remember having a good discussion with the RK2 brothers about these impellers a few MACNAs ago but nothing ended up happening.

Matt, to answer your question about the 600PEs, you'd need a couple of hammerheads minimum. You could try two and see where that gets you, I'm guessing about 10' head pressure on that body? I can't say what sort of air draw you would get at that height. We haven't developed an air intake curve for that pump yet. I would have to find a 10-12' tall vessel to test the pump on, probably a length of 12" PVC duct pipe would work. That would certainly be an interesting test.

Hope this helps.
Justin

 

[Anonymous]

Hey Justin, thanks for the detailed response.

A few (perhaps) dumb questions,

1) Would restricting the intake of the pump with a gate valve cause cavitation?
2) How about restricting the air pressure with a needle valve instead?
3) How about moving the NW pump to a higher location with the same intake and output locations to put less head pressure on the air intake?

I'll send you a PM about the Hammerheads.

Thanks again!

 

[ctenophore]

Hey Justin, thanks for the detailed response.

A few (perhaps) dumb questions,

1) Would restricting the intake of the pump with a gate valve cause cavitation?
2) How about restricting the air pressure with a needle valve instead?
3) How about moving the NW pump to a higher location with the same intake and output locations to put less head pressure on the air intake?

I'll send you a PM about the Hammerheads.

Thanks again!

Definitely not dumb questions! We tried the same things

1) Yes, I think it does cavitate some- which probably helps small bubble production. That decreased pressure is what helps draw in more air at higher head. Hard to tell exactly what's going on inside without an acrylic gate valve & venturi.

2) Not enough air and too much water causes the pump to work really hard spinning the impeller- a lot of drag on the pins. We use the square pin approach since the sharp edges cause cavitation from the shearing of the water. Round pins might work better with air restriction, but square pins caused the pump to run really hot, around 450 watts. Valving back the water allows you to tune the wattage on the pump too, which correlates with air intake. I gate mine back until the pump is running at about 320 watts, which seems to correspond to the best air intake as well. I forget the exact numbers but it is around 100 scfh.

3) We looked at this too, but then you get bubble recombination and less throughput since the bubbles need to travel through several feet of pipe, and there is friction loss to deal with. The skimmers always skimmed best when the output of the pump was as close as possible to sticking straight into the side of the body. Obviously the lower the point of bubble injection the better, to maximize contact time. In general, this idea would probably work well if the tradeoffs were considered- on the 600PEs, maybe put the pump ~3' from the bottom, and use 3 or 4" pipe to return the bubbles to the body. Also, it could work out that an air pump might help a hammerhead at 10' head so that is has the same behavior as what I've gotten at 7'.

 

[Anonymous]

Thanks Justin!

I'll send you a PM about the Hammerheads.

Put me in that loop please!

 

[Anonymous]

Hey Justin, thanks for the detailed response.

A few (perhaps) dumb questions,

1) Would restricting the intake of the pump with a gate valve cause cavitation?
2) How about restricting the air pressure with a needle valve instead?
3) How about moving the NW pump to a higher location with the same intake and output locations to put less head pressure on the air intake?

I'll send you a PM about the Hammerheads.

Thanks again!

Definitely not dumb questions! We tried the same things

1) Yes, I think it does cavitate some- which probably helps small bubble production. That decreased pressure is what helps draw in more air at higher head. Hard to tell exactly what's going on inside without an acrylic gate valve & venturi.

2) Not enough air and too much water causes the pump to work really hard spinning the impeller- a lot of drag on the pins. We use the square pin approach since the sharp edges cause cavitation from the shearing of the water. Round pins might work better with air restriction, but square pins caused the pump to run really hot, around 450 watts. Valving back the water allows you to tune the wattage on the pump too, which correlates with air intake. I gate mine back until the pump is running at about 320 watts, which seems to correspond to the best air intake as well. I forget the exact numbers but it is around 100 scfh.

3) We looked at this too, but then you get bubble recombination and less throughput since the bubbles need to travel through several feet of pipe, and there is friction loss to deal with. The skimmers always skimmed best when the output of the pump was as close as possible to sticking straight into the side of the body. Obviously the lower the point of bubble injection the better, to maximize contact time. In general, this idea would probably work well if the tradeoffs were considered- on the 600PEs, maybe put the pump ~3' from the bottom, and use 3 or 4" pipe to return the bubbles to the body. Also, it could work out that an air pump might help a hammerhead at 10' head so that is has the same behavior as what I've gotten at 7'.

1) Cool!
2) Hmm, so this is where I get lost...are you tuning the wattage draw on the pump via the gate valve, or electrically? How do you read the wattage?
3) Makes sense, I hadn't considered bubble recombination.

 

[Anonymous]

Thanks Justin!

I'll send you a PM about the Hammerheads.

Put me in that loop please!

Yup.

 

[ctenophore]

2) Hmm, so this is where I get lost...are you tuning the wattage draw on the pump via the gate valve, or electrically? How do you read the wattage?

Oops, sorry. I just use a Kill-a-watt and watch the wattage as I adjust the gate valve.

 

[swsaltwater]

I am not getting much cavitation but I only have the ball valve cranked to where it is pulling 30scfh. I did not want to go more figuring too much water restriction would be a bad thing and burn it up. I was looking to order an alita 40 last night, so far so good and wish I knew about the hammerhead before I started this mod. I asked the RK2 guys if anyone ever moded one to a NW and they laughed and said you can pull more then 20scfh on a NW or something to that affect. Mazzai sure is BS old tech and I wish they would update to a NW and bubble plate design. Thanks for the info as before I started I found zilch on Moding an RK2. Thought I was the only one that realized they were no good. You should call up the LA wholesalers and sell them NW's to fix their RK2's......They think they work good but have no idea the potential since my orca 250 was far outperforming my stock RK2.

Your NW's rock btw.............Bubbleking who????

 

[ctenophore]

I am not getting much cavitation but I only have the ball valve cranked to where it is pulling 30scfh. I did not want to go more figuring too much water restriction would be a bad thing and burn it up. I was looking to order an alita 40 last night, so far so good and wish I knew about the hammerhead before I started this mod. I asked the RK2 guys if anyone ever moded one to a NW and they laughed and said you can pull more then 20scfh on a NW or something to that affect. Mazzai sure is BS old tech and I wish they would update to a NW and bubble plate design. Thanks for the info as before I started I found zilch on Moding an RK2. Thought I was the only one that realized they were no good. You should call up the LA wholesalers and sell them NW's to fix their RK2's......They think they work good but have no idea the potential since my orca 250 was far outperforming my stock RK2.

Your NW's rock btw.............Bubbleking who????

Plug the pump into a kill-a-watt to watch the power draw as you tweak it, that way you will be sure not to burn up the motor. Try to keep it below 140 watts; you should be able to get 110-120 watts by restricting water intake.

I'm not sure where they get the 20 scfh claim, but they weren't laughing when I showed them the pics of the prototypes in action a few years ago. That fiberglass skimmer with the hammerhead I mentioned above pulls twice as much crud at 1/4 the elec. consumption of a 75PE. I'm not so much concerned with airflow numbers as much as what's in the bucket at the end of the day.

 

[pyrrhus]

I have heard of issues with the shaft seals on the reeflo pumps when running Ozone on a NW pump. Do any of you have any experiences with this? Is there an upgraded seal available? Alternate methods of ozone injection to consider with this type of skimmer?

 

[ctenophore]

I have heard of issues with the shaft seals on the reeflo pumps when running Ozone on a NW pump. Do any of you have any experiences with this? Is there an upgraded seal available? Alternate methods of ozone injection to consider with this type of skimmer?

I have not heard of that, but to be honest I have never run ozone on any of the prototype or production NW pumps. I suppose it is possible, but I would guess that silicon carbide is ozone safe. The impellers themselves are either molded polycarbonate (Darts, I believe) or Delrin. Both of those materials are ozone safe.

 

[Shawn Wilson]

Are there any updates. I'm looking at moding an RK2 25 PE.

Is the hammerhead NW available now?
What size air intake port are you tapping into the intake?
What kind of valve will give me good control of air intake?
Are the seals holding up to ozone?
Is there a NW feed pump I could use and leave the stock venturi as it is?

I have found that NW don't move much water and the head pressure is limited for feed applications (not closed loop). The guidelines from RK2 call for 25 GPM (1500 GPH) throughput/feed for 2 minute dwell time, but I see many are using much large feed pumps. I tried ATB and they have no idea how much water their NW pumps move much less anything about head pressure. The RK2 I'm working with has a 3/4 HP Pentair Seahorse as a feed pump now (3700 GPH @ 30' head) which is way over the recommended throughput. I was thinking of feeding it with a Panworld HD 70 and swapping out the Dart & Mazzai for a Hammerhead NW.

I will be using a 560 MG ozonizer (Ozotech model# OZ4PC10-V/SW) with their heated air drier (Ozotech model# IQ40 Dryer). I looked at the RK 1000 MG ozonizer but I can't justify the price. Any suggestions?

 

[ctenophore]

They're not currently in production. We are thinking about cutting them in our machine shop rather than outsource them, so if you're interested let me know the time frame and I will schedule it on the project list accordingly.

For air intake, I am simply using 1/2" CPVC (5/8" OD) tapped directly into the machined venturi. It is not regulated but a 1/2" gate valve would be my choice. Most are made from PVC & HDPE so should be reasonably ozone safe.

I have not used ozone in any of the skimmers we've built around the Hammerhead NW. I run ozone in a separate ozone reactor. Some details here:
http://www.avastmarine.com/cb/2010/05/o ... tor-build/

I don't have water volume info on the hammerhead NW either, but I would venture to guess that this pump could easily move 1500 gph @ 7' head. This would be very easy to measure, just put a 7' vertical pipe on the output and record time to fill a known volume.

I use clearwater's CD10/AD, has a built in air dryer. Has been performing perfectly for the past 6 months or so. Rated at 1.3g/hr with ambient air through their regenerative dryer. I only have it at 30% output and it is keeping 3000 gallons sparking clear. I suspect the higher efficiency of the dedicated o3 reactor plays a role.

Hope this helps.

Justin