Slower Speed = Less Noise

[Kraig]

I recently acquired a Belaire 318VL compressor and would like to know if I slow it down a bit will it be quieter.

This thing is a bit overkill for me at 7.5HP, and 25CFm at 100PSI on a 80 gallon tank, when occasional sand blasting will probably be the biggest air hog I use, but the price was right. That said it's a bit loud.

I added insulator feet and could build a intake silencer to cut down on the gulping affect, but wonder if I slowed the pump a bit if this would help too.

It runs a T39 pump and based on my Calcs turns at 1400 RPM with the Baldor motor turning at 3450 rpm. The pump min speed is 700 rpm, so if I added a smaller pulley to slow the pump would this be a good thing and worth the effort? I am thinking the down side would be slower catch up when running it wide open, but this thing will fill the 80 gallon tank to 175 PSI in 8 min so a bit more time running for I will use it for is not a big deal to me.
Thoughts?

Thanks

 

[larry_g]

http://www.mastertoolrepair.com/new...-p-633.html?osCsid=u8d8v9ni1mhvs36u16ssii3k14

The above link does indeed show this pump runs in the 700-1400 rpm range. So you will have no problems in slowing it down. On a quick look I did not find the noise level published for these compressors but if you can find them then compare the 5 hp to the 7.5 hp and I'd bet that if you slowed down to the 5 hp speed you would also run at the 5hp noise level.

lg
no neat sig line

 

[md21722]

Slowing it down may help, but if its an aluminum housing I'm not sure you'll ever get it as quiet as a heavy cast iron housing. The best 5 HP compressors have cast iron pumps that weigh 175 pounds or more. Using a smaller motor shieve (pulley) will slow the pump down. Just keep it above 700 RPM. Even though they are splash lubricated they have a minimum RPM for sufficient lubrication.

 

[firworks]

I think a big part of why the California Air Tools compressors are so quiet is because they run at lower RPMs. Might be an improvement if you can run your compressor slower but it'll charge slower too of course.

 

[Kraig]

By my calculation I can go to a 3.25" power side pulley and bring the RPM down to 800 on the pump side. This will give me a margin of error of 100 RPM over what is required for lubrication. I think this will be worth a try to see if the noise is improved, or I may need to sell it and pick up a 60 gallon Quincy that runs slower and quieter, or so I am told. None of them are silent that I have found in this style anyway.

Anyone made their own intake silencer from say 4" and 2" steel pipe. My understanding is if you can cut down on the gulping affect that makes the most noise you will make a huge different there as well.

Thanks

 

[ttpete]

By my calculation I can go to a 3.25" power side pulley and bring the RPM down to 800 on the pump side. This will give me a margin of error of 100 RPM over what is required for lubrication. I think this will be worth a try to see if the noise is improved, or I may need to sell it and pick up a 60 gallon Quincy that runs slower and quieter, or so I am told. None of them are silent that I have found in this style anyway.

Anyone made their own intake silencer from say 4" and 2" steel pipe. My understanding is if you can cut down on the gulping affect that makes the most noise you will make a huge different there as well.

Thanks

The shop next to ours just ran the intake pipe out the wall and put an air cleaner on it.

 

[Mohawk Dave]

We just put our air compressor on the cheap HF rubber pads that are made to stand on at your workbench.

WAY QUIETER....just the simple harmonics from getting it off the concrete slab.

I say do all available mods to quiet it down.

 

[ttpete]

We just put our air compressor on the cheap HF rubber pads that are made to stand on at your workbench.

WAY QUIETER....just the simple harmonics from getting it off the concrete slab.

I say do all available mods to quiet it down.

I have mine on Ford Taurus silicone gel engine mounts.

 

[redmondjp]

Do a search on this site - there are tons of threads about this topic, with plenty of suggestions about remote intakes, mufflers, etc. A lot of noise does come from the intake so just remote-mounting it (preferably with a rubber house coupling at the pump so as not to transmit vibration into the remote intake piping and whatever it touches) helps a lot.

 

[roguegts]

Can you build a closet around it? We built one, minimal insulation, if you "duct" the air through the walls properly It's so quiet we had to wire in an outside indicator light so you knew when the compressor was on.

 

[Kraig]

Just to followup on this, I purchased a 3.25" pulley for the drive motor bringing the speed down to an estimated 800-850 rpm. I don't have a way to measure the exact noise level, but I can tell you it's half or more the noise. It does slow down the tank fill rate, but I have not measured that completely yet. If it takes 1-12 min to fill versus the prior 8 I am okay to save some sanity with the noise.

You can no longer hear it in the house and even at the top of the pressure range, 150PSI, you can have a conversation next to it. Really impressed with this $26 adjustment to make this things really.

 

[larry_g]

http://www.garagejournal.com/forum/showthread.php?t=48204&page=8

In the link above is one members solution to compressor intake noise. Scroll down to the middle of the page.

lg
no neat sig line

 

[zkling]

Well... you would really be best putting a 1725rpm motor on there. Also realize that CFM is proportional to speed so, it will take 2x the amount of time to fill. Just watch belt slip.

 

[Josey Wales]

Slow it down.

 

[Kraig]

Not really sure how a slower motor would not accomplish the same thing as a smaller pulley that reduces the RPM of the pump. That as a Baldor motor is $700 and I pad half this for the AC to begin with.

It now takes 12.5 min to fill the 80 gallon tank to 150 PSI, so I don't think this method has cost me that much on CFM rating when this thing puts out 25CFM at 100PSI and 22.5 at 150 PSI in original form. It's way over kill for my small garage and occasional use but nice to have when needed and nice for it to not be heard all over the cul-de-sac.

 

[ttpete]

An intake silencer will also help with the noise.

 

[Kraig]

Yes, a intake silencer is the next thing, but it's now just lump lump sound as the piston draws the air in, it's far from mind numbing to be around.

BTW - Someone mentioned belt slip due to the smaller drive pulley, but based on my calculating of the belt arc on the new pulley I have 129 degrees of contact, 9 degrees over the recommended 120, so I think that will also work out just fine. With two drive belts on this thing slip should be no more than it was prior.

Thanks

 

[zkling]

Not really sure how a slower motor would not accomplish the same thing as a smaller pulley that reduces the RPM of the pump. That as a Baldor motor is $700 and I pad half this for the AC to begin with.

It now takes 12.5 min to fill the 80 gallon tank to 150 PSI, so I don't think this method has cost me that much on CFM rating when this thing puts out 25CFM at 100PSI and 22.5 at 150 PSI in original form. It's way over kill for my small garage and occasional use but nice to have when needed and nice for it to not be heard all over the cul-de-sac.

Well, as I mentioned in my post, it would be BEST to have fitted a 1725rpm motor, you don't have to. Price is a concern, I completely understand that. The only thing you have to watch is the belt slip since you have quite a large speed ratio in one step with a now even shorter pulley center to center distance which will allow for less wrap on the pinion pulley. It will probably be fine, just something to keep an eye on.

They run the pumps faster to get more CFM out of them for marketing. There could also be a duty cycle issue, but not sure on that pump. Maybe something to ask the maker.

 

[Kraig]

Well, as I mentioned in my post, it would be BEST to have fitted a 1725rpm motor, you don't have to. Price is a concern, I completely understand that. The only thing you have to watch is the belt slip since you have quite a large speed ratio in one step with a now even shorter pulley center to center distance which will allow for less wrap on the pinion pulley. It will probably be fine, just something to keep an eye on.

They run the pumps faster to get more CFM out of them for marketing.

Thank you for the heads up on this though! Def not something I was considering originally! I used a shorter belts and I pushed the motor back as far out as it can go in the Adj limits to maintain as much contact as I could, though to be honest it just seemed to make sense, the contact patch was not on my radar. Always learning something new...

Th duty cycle is 100% on this 7.5HP motor.

 

[Kraig]

So I got the thing chugging along very nicely and the noise level is great. However, I was changing the oil just as a precaution to know where I am with all areas on this thing, and after firing it up noticed a small leak from the aftercooler. Small O ring was burnt. Replaced that $.69 easy enough. I then tightened all the couplers south of the aftercooler to be certain they were good to go. In running my hand around the pump feeling for air leaks, I found air coming out of the breather for the crankcase. There was an audible pulse to it way more than I would assume should be coming out from the typical agitation of the pistons and what not. Not to mention the pulse was instroke with the pump noise from the intake. Not good!

So has anyone rebuilt an IMC T39 pump successfully? Kit is $225, + rod bearings at $25 each for another $200 and then there is the valve plates at $75 a pop, so your into it for $575 and you have not even started the work. This assumes a quality rebuild and that nothing is out of shape and the rings are just worn and pistons and cylinders are good. Seems to me a new unit at $790 + shipping would be a safer proposition and far less time consuming.

Are there other brand pumps that would work as well?

Still money ahead on this so I'm disappointed, but not pissed, yet.