Kellogg 331TVX and 10 HP Tecumseh

[Aefriot]

I purchased a two-stage air compressor from a sale at a farm.

Originally a 220V 3 PH 3 HP electric motor powered by a phase converter on a 60 gallon tank in their barn. I don't know how long the compressor sat before I purchased it.

I live off-grid and need to operate the compressor with an engine. I chose a Tecumseh 10 PH snowblower engine because it has electric start I connect to my truck's 24V battery for starting. A toggle switch is used to short the ignition to shut the engine off. I have since installed the compressor on a field truck for mobile use on the farm. Engine pulley is 3.5" (10.99" circumference) and pump pulley is 18" (56.52" circumference) giving ratio of 5.14:1 or 3000 engine rpm (peak torque) : 583 pump RPM. Pump RPM is a bit under the 590 rpm recommended for 150 PSI.

I cannot seem to find a manual for the Kellogg 331TVX pump so I must ask those who may be familiar with them or something similar.

My issues:

1) The compressor does not appear to "kick-off" at my desired 150 PSI. It continues to build pressure beyond the 175 lb. safety valve pressure I feel comfortable with. How do I change unloader PSI?

2) Is the Tecumseh 10 HP engine large enough? According to what I can find, a 5 HP electric motor is the size of choice. Being gasoline operated, I determined if I doubled that figure it should work fine. It did not appear to have trouble pumping up to pop-off pressure of 175 lb., but it did seem to overheat upon a second operation to re-test the operation of the compressor. I do not believe the fins are plugged since I have blown them free of debris. Perhaps it is in need of a rebuild.

3) Where in the air circuit do I connect the engine throttle whip? I currently have it in the unloader circuit (disconnected from the engine, but it appears to pulse with the compressor and slowly extends which I don't believe would be the proper method of throttle operation.

I have since put my MEP-802A generator on the service truck along with a 80 GPM water pump and 200 gal. water tote.

4) Should I forgo the gasoline engine and just power an electric motor by installing a pressure switch? The diesel would be cheaper to operate, but more expensive to rebuild in the long run so would a small engine be cheaper in the long run? Also, it would be easy to make an auto-starter for the small engine compared to the MEP. I know there is a difference between economical and cheap. Just looking for your experiences on the matter.
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[MacMcMacmac]

You need something like this control valve:

https://www.amazon.ca/dp/B01N37U7EN/?tag=atomicindus04-20

It is a combination check valve, throttle control valve and atmospheric exhaust valve. Screw it into the inlet of the tank, put your discharge from the compressor into the top port. Once it hits cut out pressure, the pilot valve trips which sends a control signal to the whip to throttle down your motor, and dumps any air the compressor is still producing. Keep the line coming down from your head to the port on the back of the machine, but remove the control whip from it. There should just be a 90 degree compression fitting at the back cover to receive the line. If you throttle down the compressor enough, it may actuate the flyweight governor inside the back case which controls another blow off valve which will help your compressor freewheel even more by dumping even more air at idle. Make sure you do not go below about 400rpm at idle on the compressor to ensure proper splash lubrication of the pump.

10hp is plenty. This will be be a very nice rig when the controls are sorted.

 

[Aefriot]

Thank you for the reply. You reaffirmed what I was thinking after my post. I had bought one a while back when I was planning the build. Now I hope my throttle whip reaches. I could reorder a new, longer one or I may just extend the port from the control valve.

I don't know why I didn't install it to begin with. Perhaps it was that I read the pump had a unloader circuit. Not having worked with better quality pumps before, my thoughts were that the unloader would pressurize, disengage the flywheel from the crankshaft to allow it to free-wheel. Flawed thinking. Anyhow, I do have the control valve.

Once again, Thank You

<edit> Thank you for the valuable info on the minimum rpm on the pump. I completely forgot about that reducing rpm too far would have a negative impact on the lubrication. </edit>

 

[Monza Harry]

To help with your power question, you guessed really close, the gas/(diesel?) conversion is 5/9ths. So your 10HP Tecumseh would be rated at 50/9 or 5.5HP. This isn't because the IC engine makes less power, it is due to the fact it should be turninga 1800 RPM not the nominal 3600 RPM and then choose pulleys to keep your pump under 900 RPM ie: 2:1. Unless this engine was on a genset or compressor before it will likely need a governer adjustment to maintain that 1800 RPM. Thanx to the other poster for the min. RPM information, really good to know. Harry

 

[Aefriot]

Sometimes I can guess with the best of them! I didn't think about lowering the rpm to 1800 though. I bought the pulley to run the engine at 3000 rpm and the pump about 590 rpm. If torque didn't do the job...horsepower was going to. I tend to do a lot of things by educated guess. Others' education and my guess.

I have installed the new control valve on the compressor but need to get some 1/8" and 3/8" plugs to seal up the holes that now have nothing in them. One day at a time!
Also, the throttle whip doesn't quite make it to where it needs to be and it goes in the wrong direction. Maybe I'll just make a linkage to work from where it does reach. More fun!

 

[MacMcMacmac]

The motor must turn it's rated speed. At 3600 rpm, it makes the same torque as the 5hp electric motor at 1800rpm. Do not slow down the motor or it will not work. You did the right thing to use a smaller drive pulley on the motor to get the correct pump rpm.

The 400 rpm minimum compressor speed is when the compressor is up to pressure and the motor throttles down. This is a conservative guess. The compressor may actually be ok to spin slower than this since it somewhat pressure lubricated. It has an oiler ring which feeds oil to the crank through ports. Centrifugal force then creates the oil pressure. You should contact a Kellogg dealer or find the proper literature to know for sure.

Here is a good RPM reference guide for pressure vs pump rpm for many Kellogg pumps.

http://www.aircompeq.com/ka.htm

 

[MacMcMacmac]

Hmm, if you are turning 590 pump rpm at 3000rpm on the motor, idling at 400 rpm would see you still turning ~2000 rpm on the motor at throttle down. This may not be terribly satisfactory for you. It would be in your interest to find out exactly how slow you can safely turn this pump.

BTW, you could always mount the control whip where you need it and run a copper or plastic air line to it from the control valve.

 

[Aefriot]

I'm on hold for now. I have to hear back from an authority on Kellogg pumps.

Thank you!