Tools, Sharpening and Power Machinery - Air comp: Compression nuts / fittings.

I've got a medium-size compressor that I run at 120 psi at the tank. It has a compression nut and a compression fitting between the tank and the pump.

Here's my ?. Both are made of brass and aluminum. I assume I should tighten them both considerably to force the aluminum sleeve to 'seal' the joint, but not too much to strip the brass nuts.

Sound about right? (Thanks)

These fittings need to be tightened just enough to not leak.

Are yours leaking?
It is common for the tubing to crack just above the ferrule.
If yours won't stop leaaking it would be a good idea to take it apart to examine it.

It is common for the tubing to crack just above the ferrule.

Funny you should mention that. My copper discharge tube sheared off right at the ferrule. :(

This is why I am not too fond of compression fittings on air compressors.
They do not fare well when there is a lot of vibration.

On most smaller compressors the discharge pipe is usually too short to just cut off the end and install a new ferrule.

This is why I am not too fond of compression fittings on air compressors.
They do not fare well when there is a lot of vibration.

On most smaller compressors the discharge pipe is usually too short to just cut off the end and install a new ferrule.

In all fareness to the manufacturer, it did last 9 years of daily use before shearing off. I order several spare parts.

Would you consider a pump rebuild kit a good purchase to keep the compressor at optimal performance?

Nine years of daily use would be considered commercial use and certainly is good service.

You only describe your compressor as medium sized but that could be any number of pump types.
If a smaller compressor like a 5 hp home type or smaller I find it preferable to just replace the pump when it starts to show signs of wearing out.

You can often tell if the pump is loosing efficiency when the head runs hotter than usual under continuous running.

Since you're being so kind and helpful. Here's the URL for the compressor I have. I'm providing this for information only, since the compressor is obsolete I hope it's okay. I believe we have it regulated at ~135-140 psi.

http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?xi=xi&ItemKey=5Z639

It is directly connected to a chiller unit, if that matters.

We use it to "drive" a pneumatic screenprinting press. The press has an interesting feature that it's base is a 'secondary' reservoir of ~20 gallons. Regulated at just over 100 psi.

Only other high demand we put on it is blowdrying out water from wet (water only) screens once washed out. We should probably have it regulated seperately at a lower psi, but we use a defusion nozzle to bleed off alot of the pressure wastefully. (sorry)

We have a few other little toys hooked up to it, but nothing a household compressor couldn't handle.

Oh... And the head is running a little hotter than normal, but I did need a new air filter and oil change, so I don't think it's excessive. Unless the air filter and oil change doesn't cool it off a little.

I do really appreciate your thoughts, comments, suggestions, etc.

I'm with Greg here, avoid compression fittings. Flare fittings hold up so much better. You can do this - get a couple of flare fittings in the same pipe size, since they are usually longer than compression fittings you can reuse the discharge tube. Just a thought.

Yes, nice to see air used to its potential.

Your compressor being a two stage may be a bit beyond a simple parts change to "tune it up".

Considering how important this unit is to you I might suggest either pricing a rebuild by a competant shop or even better, put a new pump on it.
Even two stage pumps have come down in price the last few years.
Keep a clean filter and do frequent oil changes and you will likely get many more years service out of it.

As much as I too think flare is better I have never bought a flaring tool to work anything over 5/8" tube size (plumbers 1/2").

As much as I too think flare is better I have never bought a flaring tool to work anything over 5/8" tube size (plumbers 1/2").

Oops, I haven't thought of that. On a 2-stage 7hp pump, that is likely a 3/4 tube. May require a purchase of a special tool.

Your compressor being a two stage may be a bit beyond a simple parts change to "tune it up".

I plan on replacing the rings and gaskets as well as checking all the seals. What else really is there?

Oil leaking from the crankcase breather hole when the unit is running would give you a clue whether there was excess crancase pressure from worn rings and oil seeping from tightened mating surfaces would require gaskets to be replaced.

The reed valves and seats would be likely where you would see more wear.
If there is enough wear on the valves themselves to cause overheating and excess running time in addition to replacing the valves you might need to either replace the valve plate or have it resurfaced.

Thank you Greg.

I do believe there is more oil coming out the breather hole, but I am changing the oil this weekend and will wipe everything done at that time to monitor.

If you wouldn't mind doing one last (hopefully easy) favor, could you look at this link to see if this kit looks to be complete for a pump rebuild.

http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611704034

Moderators: Again, I apologize for linking to a commercial site but it is the vendor that I've always dealt with since purchasing my compressor from them.

Links to other sites are not a problem.

That kit looks like it will do it.
Make sure you stagger the ring gaps before inserting the pistons.
Not sure about your model but you might be able to just pull the jugs off the pistons and leave the connecting rods attached to the crankshaft.

Greg,

How long do you think this rebuild will take? I'm guessing 3 hours without any surprises. Maybe 5 hours "taking my time".

Also, how much should I expect to pay a professional to do the work?

I'm leaning towards the self rebuild, but I'd like to hear your opinion on the subject. I'd much rather spend a weekend and $172 than most other choices I've seen so far. Do you have other suggestions (based upon information I've provided) ?

It looks like a replacement compressor would run $1,500-2,000 for a comparable unit.

Will (should) the rebuild kit buy me 3-5 more years on the compressor?

I'm just trying to decide the best fix.

I appreciate all your help.

Thanks,
Jeff

It all depends on how much of a perfectionist you are. You're going to find that cleaning carbon and burnt oil off the piston faces and valves may require an extensive soak time in a parts washer. Don't forget that the cylinders should be deglazed in order for the rings to seat properly. And the baked on gaskets have to be ground off thoroughly. If you just go for a straight replacement of rings and gaskets, you may do it within a day, but if you want to clean everything inside, you'll have more to disassemble, wash and put back together.

Since this is your bread and butter and you don't have a back-up (correct me if I'm wrong), contract a pro. Specify what you want done and make sure they do it. And see if they can provide a rental while yours is getting fixed.

I'm in agreement that if this compressor is important to you DIY is not the way to go.
You cannot expect to spend the hundred or so dollars on a repair kit and come out with a dependable result without commiting to the time it takes to fully research the methods and tools necessary to do the job.

Experience is a good teacher but can you afford to mess this pump up?

Although I really appreciate the feedback, I still can't determine the proper route.

I can DIY for probably $350 in parts and tools.
I can hire a professional for ?????.
I can get a new compressor for $2,000.

markiz37 - I did consider the delays in cleaning, so I anticipated doing this over Thanksgiving. That would allow me several days to "make adjustments" as needed.

I would (finances permitting) get a new pump, maybe even a better pump than the OEM. Then I would rebuild the old one taking my time and enjoying the process. No pressure to have it back in the shop Monday morning in tip-top shape or waiting a week for a worn-out bushing replacement or something like that. This will set you back the most, but you'll stay in business, have fun and have a back-up pump eventually. Good luck.

markiz37 said: I would (finances permitting) get a new pump, maybe even a better pump than the OEM.

I'd love to buy a new pump. Could you advise me on how to locate one? The manufacturer does not have the pump any longer. It was discountinued a few years ago. It would be great to have 2 pumps for the compressor. I couldn't imagine a better situation after 9 years of service.

You will not have a problem with replacing this pump... This is a popular 2-stage pump made by Campbell-Hausfeld, that ends up on a lot of flagship Speedaire, CH and Husky models. It may have gone through a mod or two in the last 9 years and may have changed the model number - just make sure the mounting holes and the hp rating are still the same.

Markiz,

(edited)

You're right... I just had to play 20 questions until they located the pump only part #. I had a part # that included alot more than just the pump. My part # was never a stocked part.

I'm still looking at close to $1,500, but now it is for a brand new pump, the parts and tools to rebuild my old pump, new pads and a bunch of spare parts.

I'm just so happy and thank you! You didn't "answer" all my questions, but you absolutely helped me make my decisions on the best course of action.