I think it's interesting that the FX5 is the only canister that seems to regularly suffers from cavitation. Design flaw?
Sump for Mech - FX5 for Bio
- Thread starter Rockydog
- Start date
cchhcc;2788577; said:
it is because of the high flow rate, and if something obstructs the flow then you get this problem. I my self have never had this problem because I dont use the optional filter pads.
The reason the Fx5 is the only one that suffers from this is due to the highly efficient enclosed bladed impeller design. Straight Open Blade impellers are not very efficient at all at producing negitive pressures. Though the Fx5's impeller can produce a good amount of negitive pressure when the filter clogs which will cause the water to possible "boil" since lower pressure will lower the boiling point of water.
Ask anyone that closes the intake valve while the Fx5 is running and keeping the output valve wide open. If you put your hand on the canister, you can feel it constrict. You can also hear the whole thing make crackle noises. (Nothing to worry about)
Jgray152;2788878; said:
Please tell me you don't really mean "boil."
.....and are you saying its "highly efficient enclosed blade impeller" is unique to this model and can cause cavitation? How is that not a design flaw then? The same doesn't occur when other canisters clog.
I only use my FX5s For BIO also. I just stuff them full of 5 ltrs of Ehfisubstrate and
no filtering pads. Work great with no Micro bubbles. I use AC 110 for Mechanical.
no filtering pads. Work great with no Micro bubbles. I use AC 110 for Mechanical.
Do REALLY mean boil. I said boil because thats kinda what its like on a non scientific note. On a more scientific note, large reduction in pressure is accompinied by flash vapor. With enough reduction in pressure, the water could boil at 50*F or even 90*F
Water boil at 212*F at 14.7 PSI (Atmospheric pressure). Higher altitudes will make the water boil at lower temps, around 210*F. To make water boil at 50*F, you need -15 gauge pressure.
More about vapor cavitation below;
http://www.myplumbingportal.com/CDA/Articles/PME_Back_To_Basics/9c6955c9ff298010VgnVCM100000f932a8c0____
If you wan't to call it a flaw, then go ahead. I never said it wasn't a desgin flaw.
This is because they use a INEFFICIENT open straight blade impeller.
The impeller speed in the Fx5 motor is MUCH slower than the impeller speed in all other canisters with open straight blade impellers.
You know, if I decide to get another Fx5, I may just take the motor apart and find out how I can get the motor to "speed up" a little bit. Or maybe changing the electricity frequency?
What is your definition of inefficient? I suppose you mean the wattage draw vs. flow rate (which is impressive), but the caviation issue seems like a problem. Efficient in one manner and DEficient in another...... or is this a rare situation?
Please read; This article is more toward metal impellers which wear out other than plastic impellers which usually don't. The concept is the same though, just different materials. Doesn't talk about straight bladed impellers at all. Only open vs enclosed.
http://www.pump-zone.com/pumps/pumps/open-versus-enclosed-impellers.html
It will take more energy and revolutions from a open faced straight bladed impeller to move 600 GPH then it will for a enclosed curved bladed impeller.
http://www.pump-zone.com/pumps/pumps/open-versus-enclosed-impellers.html
It will take more energy and revolutions from a open faced straight bladed impeller to move 600 GPH then it will for a enclosed curved bladed impeller.
as long as the filter is properly maintained then there is no cavitation. so really when your filter clogs and you start to get micro bubbles (cavitation) I wouldnt call it a design flaw because it wasnt designed to run all dirty and clogged. when you see the micro bubbles (cavitation) then it means it is time to clean your filter, so I wouldnt call it a design flaw but rather a sign of the filter need to be cleaned maybe a plus over other filters.
