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Old 10-30-2013, 09:57 PM
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Everyone's favorite. Another compressor help question.

Hello All,
I recently purchased a used Dayton Speedaire compressor on Craigslist.
I will try to be as brief as possible, but detailed.
Low down in a nut shell:
Dayton Speedaire Model #5Z399B
80 Gallon, 17.1 @ 175 psi max.
Originally (OEM) 5 hp, 3 phase, "US Motor" motor, 1735 rpm, 6 3/4" pulley.
Swapped for 7 1/2 hp, 1 phase, "Baldor" motor, 1725 rpm, 4 3/4" pulley.

Problem(s)
Purrs like a kitten to 75-80 psi (according to tank gauge), then the safety valve that is on the intake tube cylinder starts blowin'. OEM valve is a .075 psi, which I replaced w/ a new one today. Same problem still. Thought maybe the spring was "soft" in the old one.
Only other small yet somewhat significant problem is the small copper line that runs from the tank fill tube to the pressure switch leaks a tiny bit @ the compression fitting on the switch end of the line. I will try and repair that tomorrow eve.
Could the tank psi gauge be bad? The whole assembly, meaning the on/off switch, pressure switch junction all thread directly to the tank. I would not think a small leak in the pressure switch would effect the tank pressure gauge to that degree (100 psi out of calibration?).
Another reason I wonder about the gauge is because once it fills to a so called 75-80 psi and the valve starts blowin', I shut the compressor down and start draining it through what will ultimately my main line valve, once all assembled.
Currently I have approximately 16" of 1/2" galvinized pipe with a ball valve in the middle.
I opened it approximatley 1/4 of the way and it took roughly 1 hour plus to drain? For 75-80 psi?
Seems like there is a bit more pressure in the tank than that, to me?

Any ideas where to go beyond repairing the pressure switch line, I'm lost!? Thank you in advance!!! SG.

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Old 10-30-2013, 10:44 PM
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Pressure gauges are not expensive. buy one and find out what you really have in that tank. You are going to have to have a regulator anyway. install a regulator and see what it says you have.

John
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Old 10-30-2013, 11:34 PM
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Hi John,
Thanks for the feedback.
I plan to purchase a new pressure gauge as my next attempt to chase the problem, if repairing the pressure switch line does not fix it? Like so many of us, I'm on a tight budget and every penny counts. Every one spent towards getting this compressor going is one less penny to complete auto projects already in the works.
I do actually have a regulator. A Prevost TMPSM203 single stage regulator & water trap.
I ran it w/ my previous compressor which was a POS Craftsman roadside freebie. $20 worth of bearings got me a couple years even though I knew I was beatin' it. Regulator works awesome & connecting it @ the end of a 50' run from the tank gave me virtually no moisture in the trap through most PNW seasons.
I have to ask though, because I'm puzzled. Unless I have a regulator that can take more psi (My Prevost is 145 max psi) than my max tank psi it can't be used as a gauge w/out potentially damaging the reg, correct?
Otherwise my regulator is only good for reading the psi I have it set @?
If my reg was good to 200 psi I could understand what your saying, but @ 145 psi max, I don't want to take the chance.
Thanks again!! SG
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Old 10-31-2013, 08:27 AM
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Quote:
Originally Posted by SquirrelyGig View Post
Hi John,
Thanks for the feedback.
I plan to purchase a new pressure gauge as my next attempt to chase the problem, if repairing the pressure switch line does not fix it? Like so many of us, I'm on a tight budget and every penny counts. Every one spent towards getting this compressor going is one less penny to complete auto projects already in the works.
I do actually have a regulator. A Prevost TMPSM203 single stage regulator & water trap.
I ran it w/ my previous compressor which was a POS Craftsman roadside freebie. $20 worth of bearings got me a couple years even though I knew I was beatin' it. Regulator works awesome & connecting it @ the end of a 50' run from the tank gave me virtually no moisture in the trap through most PNW seasons.
I have to ask though, because I'm puzzled. Unless I have a regulator that can take more psi (My Prevost is 145 max psi) than my max tank psi it can't be used as a gauge w/out potentially damaging the reg, correct?
Otherwise my regulator is only good for reading the psi I have it set @?
If my reg was good to 200 psi I could understand what your saying, but @ 145 psi max, I don't want to take the chance.
Thanks again!! SG
You are correct in what you are saying SG. If I remember correctly you said the pop off valve was working at 75-80 lbs. I just thought that you could set your regulater at 145 or what ever maximum is and if the the regulator says it is up to 145 when the pop off valve operates you will know the tank gauge is off. If the regulater is the same as the tank then you will know you have a bad pop off valve.

John
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Old 10-31-2013, 10:39 PM
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I'm @ somewhat of a loss? I replaced the tank pressure gauge today w/ one I picked up @ Grainger Supply and the valve starts blowin' @ 60 psi according to the new gauge? 75 to 80 psi on the old one? The old gauge actually seems more accurate as the valve is rated @ 75 psi.
I'm pondering a new "theory".
Although my replacement 7 1/2 hp motor is rated @ 10 rpm slower than the original 5 hp, it also has a 2" smaller pulley on it (4 3/4" vs. 6 3/4"). Is it possible the motor is turning the pump @ enough (or too many) rpm's that it is backing up the intake line, so to speak?
Thus creating enough pressure in the pipe or cylinder create enough back pressure to blow the valve? Perhaps I should try putting the 6 3/4" pulley on to slow it down a bit? Not sure?
Otherwise, I think I'm gonna' have to lean towards it being something internal w/ the pump? A valve or something?
Boy! All of the sudden I feel like this post is full of question marks??? Thanks in advance for any input. SG

Last edited by SquirrelyGig; 10-31-2013 at 10:44 PM.
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Old 11-02-2013, 09:37 PM
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Well, I pulled off the cylinder head today & seperated it from the valve plate. A good # of the gaskets on the high pressure cylinder were in bad shape and the reed valves were all gunked up and could not have been operating properly.
On top of that, there were sections where the gasket was missing between the valve plate & cylinder as well as on top between the cylinder head & valve plate.

I found a defect in the casting / machining of the cylinder head. there was a tiny ridge on one of the "mating" surfaces. It had allowed the gasket to blow out @ some point and only got worse from there.
I could tell that is where the problem originated based on the coloring of the casting. Again long enough to let oil seep through and gum up the reed valves and such. I was able to take it down just enough with a light file and it should be fine now.
I have to now source all the gaskets. I have found a few kits on line that will give me the majority of them.
The only thing I'm not sure of, is I need a few others as well that I don't think
are in the kit. I don't know that they sell them individually.
That would leave me buying the entire valve plate assembly, which is about $300 through Grainger & a couple online retailers.
Oh well even if that is the case I'm still into this thing way, way below buying the equivelent new. Other than time, but in thjis case I'm learning so there's value.
May be a couple weeks to a month, but I'll let ya' know how things turn out. SG.
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Old 11-03-2013, 10:22 AM
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Compressor

Is the blow off valve in between the cylinders. Or is it mounted between the compressor and the tank. If its between the cylinders then it is working correctly a piston compressor will just keep making air. So if the high pressure side is messed up the low pressure side just keeps making air and when it gets to the pressure setting of the blow off valve the blow off pops. But the pressure switch hasn't reached full pressure yet so the motor keeps running. You can make gaskets for the high side from gasket material from NAPA. get the gaskets seal up and it should work OK. It is very typical for compressors to have a blow off in between the cylinders set at 75 psi And a larger blow off on the discharge side at what the rating of the tank is. 200 psi is the norm. If the blow off is mounted between the compressor and the tank or on the tank then it is the wrong psi. It should be close to what the tank is rated at. The tank will have a plate attached to it and on the plate should be the pressure its rated at. It is always a good idea to have one mounted on the tank or discharge line. If the contacts in the pressure switch were to say weld their self together then the compressor will just keep building air until it explodes or the lines burst. No fun inside a shop. Keep it safe use the right blow offs or don't use the compressor until you can get it right. I don't want to see someone get hurt. I hope this helps Bill
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Old 11-07-2013, 08:53 PM
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Hey Ironpony,
There are 2. The 75 psi one is is in the intake manifold, right before entering the smaller high compression cylinder. The 200 psi one is next to the pressure switch.
The problem is clearly related to the bad gaskets.
The local Grainger ordered in the closest gasket set they can get which is a correct set for my pump. It just does not appear to have all that I need or that some have slightly changed design. It should be in tomorrow & I will be able to verify what it actually contains.
Their image on the net may be a generic photo. One of the Grainger guys even said that what they have in their database is often a generic photo. I must physically verify.
The part # that is listed on their site parts list through a google search corelates to a current Campbell Hausfeld part #. However, Grainger apparently has their own internal #'s beyond that. Again according to the guy that helped me previously.
I'm not holding my breathe. I think I will still have to make a few.
The worst being 2 molded rubber gaskets.
The paper one's won't be a problem. I know the kit contains the proper cylinder head to valve plate & valve plate to cylinder gaskets.
Again, worst case scenario is I have to buy the new valve plate assembly, which is not cheap, but I'm still way ahead in the overall cost vs buying the same compressor new.
I'd sure like to put the money towards the rigs though!! Cost will delay getting busy. If I have to buy the valve plate assembly, the compressor will probably out live me after that!! I will stay updated as possible.
Thank you IP for your feedback. I appreciate it!! SG.
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Old 11-07-2013, 10:18 PM
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Your new pulley is spinning the compressor motor 42% slower than the original. This really should not cause any trouble, other than taking a few extra minutes to top up the tank.

HOWEVER, having said that, if you are going to be drawing air from the tank at the full rated output of the compressor motor, then you will need to switch back to the 6 3/4" pulley. The 10 motor RPM won't make a blind bit of difference at all.

The smaller pulley will be producing about 9.9 CFM at your rated pressure of 175 PSI. What that means is if you only need 9.9 CFM on a steady basis you are OK. If you need more, then you will need to switch pulleys. Incidentally, a larger pulley is easier on the drive belt(s). I have to wonder out loud if the belt might slip with that small of a pulley with 7 1/2 horses tugging at it.
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Old 11-07-2013, 11:48 PM
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Hi C-cab dreamer,
Yeah I did the math and w/ the 4 3/4" pulley I am @ about 500 rpm's vs approximately 750 or so w/ the original 5 hp, 6 3/4" pulley. Still seems to fill relatively quickly though. @ least to 75-80 psi, coincidering my current situation.
I plan to reconfigure the pulley situation @ some point. For now I'd just be happy to get back to work. I'm concidering taking the 6 3/4" pulley to my local NAPA & having the machine shop bore out center to fit the 7 1/2 horse shaft.
There's plenty of meat on the thing that it can be done.
Thank you for your input!! SG.
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Old 11-07-2013, 11:54 PM
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Yes, no doubt at all that the compressor will be putting out plenty of air.

Good idea to get the larger pulley machined. One less problem when you do get it all back together again. Good luck!
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