Air Pumps

[Gallagher]

I have a few elementry questions on air pumps.
These may sound so obvious to be stupid, but here goes. I bought a refurbished Secoh EL80 - 17 air pump, that, according to the rep pumps ~ 85 lpm. There is a small bleeder nut on it that I plugged. Then I got to thinking maybe I shouldn't have, as it could create to much back preasure.
How does one tell if there is to much back preasure?
What determines the number of air stones, or bottom drain one can run on a give air pump? It's certainly obvious that if your not getting any air at the other end then you need to reduce the number of outlets, but there has to be a optimum number but how do you arrive at this number?

[PapaBear]

This link gives the perfomance curves for the EL-80 pump.
http://www.septicsuppliesinc.com/ima...reformance.jpg
But the answer to your question really depends on the air capacity of your air rings/fritters and the operating depth for each. 85 lpm performance is at 3.5' head (1.5psig)

[Gallagher]

Quote: Originally Posted by PapaBear This link gives the perfomance curves for the EL-80 pump. http://www.septicsuppliesinc.com/ima...reformance.jpg But the answer to your question really depends on the air capacity of your air rings/fritters and the operating depth for each. 85 lpm performance is at 3.5' head (1.5psig)

Thanks PaPa,
I have the p curves. How do you figger the rest out. In other words given that most airstone and DYS air rings don't prvide a air capasity etc. it's tough to know if you're stressing the motor or it's running eficiently.

How about a temp indicator? since all motors have a running temp, if that temp got over a certain level you'd know your setpu was creating to much back presure and you could open the bleed valve.
Jim

[PapaBear]

Running temperature for the motor or air either one will vary with ambient conditions so that wouldn't work. (you could calculate it based on pump discharge temperature, but you'd have to have graphs for K factors, N factors, Supercompressibility,... . It ain't worth the bother) If you want to you can install a pressure guage in the discharge line, but it will have to be sensitive enough to measure inches of water column or ounces for it to do you any good. It might be just as cheap to find a small flowmeter. I've been out of the loop on lab equipment for several years now so I'm not sure who a good source for an inexpensive one would be. Most of my sources for stuff like that were high end petrochemical specialty outlets. Way too expensive for what you want to do.

[bekko]

To measure air flow, turn a container with a known volume (brim full) upside down under water. Place the airstone at the desired depth. Move the inverted container over the airstone and measure how long it takes the air to displace all the water in the container. Express results in lpm, gpm, cfm, or whatever. Since the inverted container becomes buoyant as it fills with air, you sometimes need three hands to keep it in position to capture all the rising bubbles.

The lower the pressure, the more air you get per kilowatt-hour. You want enough pressure to be able to regulate the flow through the deepest airstone, but any more is a needless expense.

I don't think it will save you any electricity, but using the pressure relief valve on a pump will definitely save wear and tear on the rubber diaphragm.

Look for back-pressure specifications on the airstone or diffuser. You have to add that back-pressure (in psi) to the maximum depth you want to aerate (also in psi) before reading the pump curve.

-steveh

[tewa]

hi gallagher

you can get air back pressure gauges like this that tell you the amount of back pressure/resistance on your air pump

http://www.boddingtonkoi.com/Back-Pressure-Gauge-Assembly_30.htm

http://koikit.biz/acatalog/Valves_and_accessories.html




tewa