Roots blower overloading, tripping breaker

[APRSOLUTIONS]

Hello, I run Recycling plant here in Florida. We use our roots blower in a unique way. We pump air into a water tank that cleans the plastic. The Piping runs through a manifold into several pipes that feed the tank with air. The Pipes have holes in the bottom of them and blow the air towards the bottom of the tank to create a vortex swirling the water and cleaning the plastic. For the past 18 months we have had no issues. However, we had to shut down for about 6 months and now on startup the blower will work for a few minutes then trip the breaker. It is over amping. We have not changed the configuration at all since the shut down and dont' know why this is happening now. Any suggestions. ?? It is a RAI-65 with a 20hp Motor.

 

[LittleInch]

This looks like your blower?

http://www.pdblowers.com/admin/uploads/65_urai_pressure_performance_curve.pdf

On that basis it seems you might either have a small blockage causing even a small increase in pressure taking you over your 20 hp or you have a reduction in flow.

You need to be able to measure flow and pressure, or at least pressure and speed of your blower to see where you are on the power curves in the link above.

My guess is that in 6 months downtime something has blocked up some of your pipes or holes.

Has anything else changed? - Depth of water, viscosity of whtever is in the tank?

do you have any filters inlet or outlet which could be clogged? did anyone stuff a rag down the pipe to seal it when you mothballed the plant? Are all the manifolds still connected as before? Anything else different which could give you a rise in pressure, even of one or two psi

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1gibson]

Piping loads distorting the blower casing? Can you spin it by hand and feel for any rubs or tight spots? Unbolt the piping and see where it wants to be, was it forced into place?

 

[APRSOLUTIONS]

No Thing changed, However I think you may be right. We put a value on the end of one of the pipes and it seems to have cured it. We were amping at 40+ with no water and around 50 with water. Once we opened the valve we are steady at 20-24 amps. So I guess its time to clean the pipes?

 

[APRSOLUTIONS]

Gotta say, This thread or website is pretty awesome

 

[LittleInch]

Looks like it. I would still put a pressure guage on the outlet so that you can monitor this or simply see whether you've cleaned it enough. If you know the rpm of your motor (4 pole 60 htz is 1800 rpm , 4 pole 50 htz is 1500) then you can read off from the chart what the downstream pressure needs to be to be within your 20 hp

It can seem counter intuitive but for a PD blower like this the less flow / higher pressure the more power it uses. As its a fixed speed motor then the motor will simply take whatever it needs to try and maintain a fixed speed.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Probably some of the plastic bits were sucked into the piping when the air was turn off. Now, the material is plugging the piping.

Coarse Bubble Aeration are clog resistant:

http://www.xylemwatersolutions.com/...ion/Coarse Bubble Aeration/Pages/default.aspx

 

[APRSOLUTIONS]

Interesting. Thank everyone for their help. Questions for Bimr though That system you suggested seems interesting, But if the System is submerged how do you prevent backflow when turned off.

 

[Compositepro]

Any unnecessary air pressure will cost you a lot of money, over time. A 20 hp motor will cost roughly a minimum of $1.50 per hour to operate at full load ($0.10/kW-hr). Given your amp readings, your system is probably capable of operating at less than 10 hp (remember, an electric motor consumes only as much power as is being used, not what the name plate says).

 

[LittleInch]

Be sure and tell us what the upshot is - feedback / update is greatly appreciated. A photo of what the tanks look like when the air is going through them would be instructive and interesting.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.