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Old 07-30-2009, 07:54 PM
Will I ever get it done?
 

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Yet Another Compressor Question (long)

I have an old Campbell Hausfeld 6 HP, 60 gallon unit. Can't remember exactly when I got it but the U stamp on the tank is from 94. I have always drained it after every use, so the tank is in good condition, but I do plan on retiring it in 5 years.

However, the pump is getting long in the tooth. It won't keep up with my tools, it is noisy, and it is losing oil out of the shaft seal (maybe being forced out by blow-by?).

I decided that since the whole thing is scheduled to be replaced in five years and I am only using it for a hobby, not a business, I would get the HF 5 HP pump. The CFM rating on it at 90 psi is better than the CH at 40 psi. And it is relatively inexpensive.

Tonight I did the preliminary fit up to see what parts I am going to have to buy. I stumbled on two things I am not sure about.

1st Question - The CH unit has 1/2" tubing connecting the pump to the tank. The HF unit is set up for 3/4". I pulled the fitting out of the tank to see what I would need. I was surprised to see the fitting had an integral check valve. Do I need this with the HF unit?

2nd Question - There is a small tube running from the pump to the pressure switch. (see attached photo) There is no provision for this on the new pump. Is it necessary?

Any help or advice you can give will be greatly appreciated. I will even let you tell me how evil and/or stupid I am for buying a Chinese pump!
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Old 07-30-2009, 08:01 PM
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That tube is for the unloader valve. I may be wrong about this, but I believe it vents the pump after it has reached it's cutoff pressure which prevents the pump from restarting under pressure.

I have never seen a tank with a check valve in the inlet fitting, don't know if I would keep it or not.


Vince
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Old 07-30-2009, 08:58 PM
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You are right about the small line on the pressure switch. The check valve has to stay as the small line from the switch vents the larger one leading to the tank. The check valve prevents tank pressure from backing up to the tank.
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Old 07-30-2009, 09:19 PM
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That makes sense, thanks for clearing that up.

Vince
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Old 07-30-2009, 09:42 PM
Will I ever get it done?
 

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So, since the new pump doesn't have a fitting on the head like the old pump, leave the check valve in and tap into the line between the check valve and the pump? The check valve fitting has a side hole that has a pipe plug in it now. I bet that hole is there for pumps without the fitting for the relief tube.
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Old 07-31-2009, 07:06 AM
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Compressor

Hey friend, you're probably right about the plug in the side of the check valve, cause I have set up unloader lines on compressors this way before. Just pull the plug out and make your tubing connection there, It's usually 1/8" npt. You have to have the unloader tube to unload the head pressure off the compressor so it doesn't try to start up under load. If you try to start it under head load, the motor will stall on start up,pull extremely high starting current and cause the motor to fail. I'm kinda curious about that HF comp head,cheap way to save an old compressor. I looked at them one time,the casting seemed kinda junky,please let us know how it works out. You can buy good replacement compressor heads at Graingers, but the cost almost as much as a complete new compressor.olnolan
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Old 07-31-2009, 08:10 AM
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One thing worth looking into, is how the dipper that lubes the bottom end is configured.

Some have a bent, formed piece of ~1/8" wire that is screwed into the bottom cap of the rod. Others have a cast-in dipper that's an integral part of the rod cap.

The wire type can- and given enough time- likely will fail. If I were to use a pump that used the wire dipper, I would look into making a modified version, like a different material for the dipper- something much more reliable than wire. Or, at a minimum, I would carefully cratex the wire to remove ALL traces of stress risers.

I know that after the failure I had, inspection of this critical part would be done often.
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Old 07-31-2009, 04:03 PM
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I am assuming you have the HF V twin pump for 5 HP? If so I have installed two of these, one on a CH compressor like you described. The check valve has already been covered but there is something else here that is going to be just as important and that is the motor you have, it is only 15 AMPs right? That motor is not really powerful enough for that pump at it's (the pump) rated RPM because it is not really 6 HP (6 "peak" HP is not even close to 5 "real" HP never mind 6 HP) it is in fact only about 3 1/2 or maybe a little more. You can still use this pump and it will work quite well however you need to change the pulley on the motor to drop the RPM about 15% from it's rated speed. There are two of those pumps from HF, an Aluminum one and the cast Iron version which is being replaced by the Aluminum version and the two I installed were cast Iron but I think the specs are the same. With either one however you will have to slow it down from the rated speed or your motor will not last long, look at the motor data plate and see if it is indeed 15 AMPs as I would almost bet it is.
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Old 07-31-2009, 09:02 PM
Will I ever get it done?
 

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It is 15 amp. I was wondering if something funny was going on. Based on the pulleys I could find, the pump will be running about 12% slower than its rating. Would using synthetic oil be a help?
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Old 08-01-2009, 11:01 PM
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12% slower should work but it would be a really good idea to check the AMP draw when the pressure is near the cut off point, very easy to do with a clamp type AMP meter and you want to keep the AMPS at no more than 15 at cut-off. I don't know much about the synthetic oils but from what I hear they are a good idea and I use it in both my compressor pumps now however I doubt the synthetic would help with the motor since the problem is going to be the volume of air being compressed.
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