TR2/3/3A sandblasting the tr3

I am starting to think my air compressor tank is too small for the amount of work I want. The tank is round and about 2 feet by 4 feet, and does not hold 125psi for very long and as result the sand blasting becomes weaker with the air pressure drop. A guy I used to work with back in the day suggested getting an old hot water tank and putting that in line to increase volume of air. That sounds logical, but I was hoping for some suggestions, perhaps I could purchase a secondary tank at HF or something and put that in line. Any thoughts

I have a 15 gallon compressor and have a 33 gallon holding tank for it. I still run out of air even doing relatively small parts in a cabinet blaster...I have learned to be somewhat patient waiting for the tanks to recharge. What I really need is a higher hp compressor with better a better cfm rating.

Cheers
Tush

I would be concerned with an old water tank holding that much pressure. They usually have a lot of rust in them. It would cost some bucks, but those large vertical compressors have a really large tank and would do the job. The down side is they take up more space, takes at least two people to move them and the cost. Its a lot cheaper to sand by hand if your up to it.

Regulating the pressure down to about 70-75 psi on the blast cabinet will allow it to run longer. You shouldn't notice any difference in how it cleans. We did this at work on our blast cabinets and it helped a lot. More storage will also help, but as mentioned above, more compressor is sometimes the only answer.

Below is a chart that shows how much cfm you need at what pressure and at what nozzle size you using. A rule of thumb is it takes about 1 HP to make 3-4 cfm.
Also, worn out nozzles use more air, as the size of the hole gets larger as they wear out.

https://surfacefinishingcompany.com/site/wp-content/uploads/2009/10/Charts-and-Tables.pdf

Once the compressor starts running, you have used all of the "stored" air. A larger tank will delay the start of the compressor, After that it does little good for blasting. The 2 things that are never big enough are compressors and garages.

The motor is 3hp, and I probably made a mistake by using ¼ fittings and larger/long hose. The hose and fitting were from the pipe line job when it shut down years ago plus the hose is probably fifty longer than it needs to be. Do you think if I went to 3/16 fittings and shorter hose it would make much difference?

I don't think it will make much of a noticeable difference.

Cheers
Tush

If you are running out of air, a shorter hose in larger diameter should just help you run out of air faster. That's not the fix you were looking for. I have a 3.5 HP 220V compressor with 60 gal tank. Harbor Freight. It leaks a lot of oil but does the job. It is good for running the blasting cabinet, with occasional breaks. It is not good for sandblasting outdoors - that takes a lot of air. I have problems with moisture accumulating very rapidly in the summer, even in dry Sacramento. Moisture causes the blast cabinet gun to spit and spray sort of intermittently. Gotta drain the moisture separator frequently. If I were to do it again, I'd save a few more bucks and go to a 5 HP with 60 gal tank and not buy the cheap noisy leaky HF model. But, we all work within our means.

Pat

sp53 said:

The motor is 3hp,

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Is that before or after the law got after them for lying about air compressor "hp" ? I used to have a compressor that was roughly about one actual horsepower; but it said "2.5 hp" in big letters on the side. And it was totally pitiful for trying to sand blast. The problem was compounded because it was a single stage compressor, and would only run up to about 125 psi. My point is that you can't really tell much by the "hp" rating of the compressor.

Adding a bigger tank will give you a longer run time from a full tank; but then it will also take longer to recover. Not really a net benefit in my book, unless perhaps you only do very small simple parts that could be done on a single tank of air.

FWIW, I found a used upright compressor on Craigslist for $500. Rated "7.5hp", actual is probably under 5hp (judging by how much power it draws). It will keep up with my modest blast cabinet, never run out of air. Since I didn't have room for it in the garage (nor want to listen to the noise), I mounted it out in the back yard and ran an air line along the side of the house. Works great, I just need to finish the remote controls so I don't have to walk out back to open the valve & flip the switch when I want air

M_Pied_Lourd said:

I don't think it will make much of a noticeable difference.

Cheers
Tush

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I agree with Tush. It would be relatively easy to calculate the volume of air in the hose (3.14 x 5/16 sq. x length = not much).
Here's my experience in the light of some of the previous comments. Reducing the air volume helps a lot. Use the smallest nozzle you can get to work. Reducing the air pressure also works, set the regulator to 75 or the lowest that will work for you. Increasing the CFM works. Borrow another compressor and tee it into you tank or rent a bigger compressor for bigger jobs.
Increasing the volume has it's problems. The larger the storage, the longer the useful pressure but also the longer it takes to recharge. Usually, with an inadequate compressor, the charge time is much greater than the work time, so you won't gain much. In addition, the constantly running compressor will overheat and so will the air ( not too inconvenient with sandblasting but not good for the compressor).
Sandblasters use a lot of air. For comparison, my compressor, 3.5 hp and 10.5 cfm with an 80 gal. tank is adequate for small projects only. it works OK with the siphon blaster but taxes the air system with the 100lb pressure unit. I've set the regulator at 70 lbs and use small nozzles and I still send the bigger stuff out.
For what it's worth,
Tom

Steve, running a sand blaster on 3hp is a loosing proposition. I am running a 5hp, and have burned through 4 compressors. The problem is the duty cycles for these (home depot) light series of compressors is only 50%. So, regardless of the tank size, we are overworking these dinky little things. Mine runs continuously at a sustained 60 psi when I'm working. The 60 psi is fine, since I don't need that much pressure on my parts,but the continuous duty cycle kills the compressor rings.

I have learned to stretch mine by only blasting one tank and then grabbing a water while the compressor cuts off and cools for 10-15 minutes. I change the oil daily when I'm blasting. Using these precautions I can get about a year out of my compressors.

If you are serious about blasting, the continuous duty compressors start at $1400 and go up...that's compressor only, no tank. It's also huge. I have no room in the garage for one, so I just fork out $300 a year for the cheap single stage Junkers. Interestingly, the continuous duty will run on your 3 or 5 HP motor. The motor is better prepared for the beating than the compressor.

You need to use an ASME designed air receiver tank to store compressed air (just like the tank the compressor is mounted on.) Compressed air is not like incompressible water being stored; it holds an enormous amount of energy and using a tank not designed for air storage could be fatal.

Also, never use PVC or CPVC piping for compressed air. A pipe failure will result in the shattering of the plastic material and can cause serious injury. There is a lot of energy stored in compressed air and it can be very dangerous.

This is probably the minimum you can use for sandblasting. https://www.northerntool.com/shop/tools/product_200596488_200596488 I use a similar one for doing some soda blasting and blowing out lawn sprinkler systems.

Rgb said:

You need to use an ASME designed air receiver tank to store compressed air (just like the tank the compressor is mounted on.) Compressed air is not like incompressible water being stored; it holds an enormous amount of energy and using a tank not designed for air storage could be fatal.

Also, never use PVC or CPVC piping for compressed air. A pipe failure will result in the shattering of the plastic material and can cause serious injury. There is a lot of energy stored in compressed air and it can be very dangerous.

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Very true! We used to design the tanks so they can crack and leak out before they burst. A certified tank is a must!

Moisture is a real problem. Once you have enough to spray water with the media, you are creating flash rust! I did the front and back clips on my tr3. To help with the water, I got out an old wash tub, added about 10 gal. of cold water (ice cubes would help) and a 25ft length of 1/2 " copper coil. Input is from the compressor and output thru an automatic trap to the blaster. The idea is to get the compressed air temperature lower than its dew point, the lower the better. A good commercial dryer will try for -55F!

when actively using my compressor I crack the drain on the bottom of the moisture separator and let it bleed out moisture as I work.