mud in sandblaster gun

How large is your sandblaster,compressor and tank?

I know you drain your tank regularly because that is where most condensation occurs normally.The compression of the air "Squeezes" the moisture out of the air and it settles to the bottom of the tank.

Vertical tanks have a larger distance from the outlet to the bottom of the tank,so they are a better choice if choosing a tank.

Install a drip leg in the output line;A tee with one leg facing down, and one leg facing up.Use the up facing leg for your output,and run the downward facing tee as far down as possible and install a manual drain valve on the end.

Run the output line up as far as possible before attaching your hose.

Another tank,remote from the main tank will also catch a lot of moisture.

Some desiccants can be regenerated by heating them.Silica gel is one of them.

Is your blaster portable?

I don't recall tank specs at the moment but I'm not seeing that being the problem. I can run 25 feet of hose from the tank, run thru a clear plastic water separator chamber, run another 25 feet of hose and have the described problem. With this configuration I have never found a single drop of water in the clear plastic chamber. The initial 25 feet of hose should allow the compressed air to cool and increase the chance of additional water being squeezed out and being deposited in the clear plastic chamber.

Can you bury part of the airline?This will help cool the line,the more the better,but you must keep in mind the slope of the pipe to prevent low spots becoming tiny reservoirs that will then blow water downstream.You should drain the tank daily.This is critical.A second tank to cool the air and allow for a primary expansion between on/off of the nozzle will help remove more of the moisture.Every time you open the blast nozzle,the pressure will drop a little in the second tank,which will allow some water vapor to condense.

Depending on the amount of air flow, cfm required,you could run the air through a scrap air conditioner condenser coil,and fan cool it.Not as good as refrigerated or water cooled,but better than nothing.

The drip leg should be the first part of your system,and running it as high as possible.Slope the output back toward the drip leg.

The moisture problem is occurring in the supply air moisture and you must minimize the moisture there,not raise the temperature at the outlet.

Certainly chilled air will condense outside in the ambient air,but not inside your head if it is a dry air supply.

Here is a link that may help you.

https://www.airblast.com/news/techtips/tip-12-avoiding-moisture-in-abrasive-blasting-operations

Think about what is happening in a remote tank(receiver).

Air first entering the receiver is decompressed,cooling it a little,then when line pressure is reached,it "squeezes" the air again,releasing some moisture.

When the blaster trigger is opened,the process repeats,pressure drops in the receiver for a short time,and then recovers when the trigger valve is closed..This action will help remove a lot of moisture from the line.

Condensate should be bled from this receiver tank frequently.

This is the simplest way I know to reduce moisture in your air.

If you will provide information about the HP and CFM of the compressor maybe I could be of more help in this situation,perhaps a DIY cooler using compressed air as the cooling source.

Moisture in the airlines is the "enemy" of spray painters, especially auto restorers and anyone else wanting a fine paint job. The Eastwood Co. in PA has many products and tools for restoration folks. If you haven't, check them out for air driers and other interesting goodies. Your local paint supply dealer likely has an abundance of information, but maybe just the brands they handle.

The compressor is an old Sears unit

with these ratings.

I have two sandblaster guns. The cheap one is from Harbor Freight

with these ratings.

I couldn't easily get to the gun I prefer. I have a very old gun that tube feeds from a one gallon hopper. I keep the hopper above the work so the gun only needs to suck upward through about four inches of hose as it curves upward from the gun to the hopper. The ratings tag on the older gun fell off about 25-30 years ago but I would guess that grit volume and air consumption go up by about 50% with respect to Harbor Freight.

I'll have two sources of condensation. Both would be caused by the expanding air cooling the gun. One source would be the "dryer than ambient at STP" air that is at about 100% relative humidity since it is under pressure. The other source would be the ambient air that in the summer is often 90% +/- relative humidity.

The ambient air humidity is squeezed out by compression,and settles to the bottom of the tank.The air above the moisture in the bottom is saturated(100% Relative humidity),which is less than the ambient relative humidity.

(Actually,they are the same relative humidity when at 100%,but not the same absolute humidity). Relative humidity varies according to pressure and temperature,absolute humidity does not).

When the air pressure is released,the air is now below the saturation point of the ambient air and absorbs the moisture in the bottom of the tank.That combined with the lower temperature at the nozzle will cause condensation to form from the ambient air as well as the supply air.The ambient humidity will cause condensation outside of the nozzle,not inside the nozzle.

A second tank between the nozzle and the main tank will allow the air to drop out some of the moisture by decompression/compression by cycling the pressure as you apply and release the nozzle.The secondary tank will also be cooler than the main tank,allowing more moisture to drop out. It is important to drain the tanks regularly,especially in the morning when it is cool to get out the most water.

This is the best time to do your blasting also.

The hopper is open to atmospheric pressure,so ambient moisture will enter it.

Believe it or not, a small bag of raw rice in a cheese cloth bag or coffee filter will absorb moisture from the air.Put this in the bottom of your sand hopper.

You could also add this to one of your moisture traps,just change it when the rice swells or gets tacky.

Ever notice rice in a salt shaker?It absorbs moisture to keep the salt from clumping.

Survivalists use this method to protect items in long term storage.

I worked with air a lot back when pneumatic systems was king in process control,and nothing is 100 % fool proof unless you want to spend big bucks on refrigerated dryers, large receiver tanks ,blow-down valves with timers,etc. and even these require frequent maintenance.

For a low budget fix,this is about the best you can do.

I hope this helps you.

It's really expensive to dry the air, ask any paint shop, so if you aren't willing to spend the money you just have to live with it....You might be able to draw air from a room you have with a dehumidifier running for a time before you start the compressor, but you would have to keep stopping and drying the air depending on how much time you use the blaster...A heated blaster gun sounds interesting, but you would probably end up having to relocate the handle next to the present handle and insulate the gun, but then you have so much plastic materials to melt, probably need to redesign the whole gun...easier to just go chemical method of cleaning eh?

https://www.compressorworld.com/air-dryers?matchtype=e&network=g&device=c&adposition=&keyword=compressor%20air%20dryers&gclid=Cj0KCQjww4OMBhCUARIsAILndv4F_DOTC4eS98zJQXUmkn4T77B4wtdzURe4HLg2TkWBFbHysCV6xnEaAkvtEALw_wcB

This doesn’t help your immediate problem but will extend the life of you compressor thanks…

sorry, HF was the most handy the grab.

I think heating the blast medium would help some but by the time I figure out how to do that "on the fly" it probably would have been a better solution to heat the gun.

Perhaps you could just raise the air pressure...?...or perhaps mix the blast media with a moisture absorbent...?

I assume you run the air through a desiccant between the compressor and tank.

Can you reuse desiccant by heating it in an oven and driving off the absorbed moisture? That should reduce your cost.

cold winter day when it is in the mid 60s

Cold day & temp in the 60s? That's just an example of global warming; wait multi-million years and it will change again! (I'm from northeast Ohio!)

Well to my way of thinking you could always drag out your water pressure cleaner and attach a wet sandblasting gun to it, problem of mud solved, if not the mess.

Maybe install a large filter housing and fill it with silica gel like they use as a desiccant in power transformers.

too many variables poorly defined...

- Low cost suggestions? "low cost" is kinda vague. For you it may be asking for less than $20.. for me it maybe less than $500.

- Just how much pressure do you have to work with? Can your compressor supply 175 psi at the required volume? if so, have you tried ? ... https://www.jtdryers.com/jt-dryers.html?gclid=EAIaIQobChMIgM_U7Zz98wIVUg6tBh3gNA4XEAAYASAAEgIiPPD_BwE

Normally a 5 hp 2 stage compressor puts out air at a pretty high temperature (will burn flesh quickly). Maybe you are losing too much of this elevated temperature before the gun? But if you are using a much smaller compressor with a larger tank and longer lines, this situation will limit your possible solutions.

Heating the gun? Nah... Any practical way to "cool" a big enough intermediate pressure tank that has let's say cross-flow to minimize turbulance inside from air flow, so to force water condensation and removal from its bottom? If you have enough space in the garage, an old fridge and a suitable tank to fit inside, combinined with the suggested heating of sandblasting medium could do it for normal duty cycles that is. Any air pressure regulation should be done after the indermediate tank of cource. I also hope your blasting medium, as being probably recycled again and again does not have too much rust, dust and paint particles from previous jobs. That makes things worse. And unhealthy to heat. S.M.

Several times I considered making a "zig-zag" of galvanized steel pipe and placing it in an ice bath to condense moisture out of the pressurized air. When I go to Home Depot or Lowes and price galvanized pipe and fittings my blood pressure goes way up and my inspiration goes way down. It would be a pain to store, a pain to set-up for each use and might not work. I also worry about too much DIY duct tape and bailing wire on a pressure project. I prefer getting my explosions on NetFlix.

A US$1K compressed air dryer seems like the best way to get additional drying of the compressed air. Spending 1K$ and storing it just doesn't make sense for something I want to use 3 or 4 times a year.

I still think that the bottom of the tank and the first oil/water separator get all the liquid water. The oil/water separator mid-line has a clear bowl and has NEVER had a single drop of liquid water in it.

In the summer in Florida you can give someone a cold stare and get water condensing on your eyeballs. I'm starting to feel alone on this but I still think my most significant problem is the expanding air cooling the gun and causing local condensation in the gun.

The problem inside of the nozzle is due to moisture in the compressed air,not the ambient humidity,temperature.Ambient conditions will cause condensation on the outside of the nozzle,such as the work piece.

Water vapor,a gas, is invisible,and hard to remove.

A good test is to partially one on your moisture traps,the ones that look dry, with a handful of rice.Rice will expand when it absorbs moisture,so half full is plenty.

Rice will absorb a lot of moisture,and it is a cheap way to dry your air.

If it gets sticky,it is doing it's job.

Just be sure to put a fine filter after the rice to catch any particles shed by the rice.

You can also regenerate the rice by low heat drying,or as cheap as it is,replace it daily.

Don't let the rice stay in the filter for long periods of time.

Change it at the end of day,or you will have problems removing it later.

Survivalists put rice in their storage containers to absorb moisture.

Works for me.

Good luck.

Check places that deal with automotive painting. they should have a variety of dryers since water causes huge problems with the paint film on automobiles.

I don't think a refrigerator would handle the heat load, maybe an ice maker...?

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2060353.m570.l2632&_nkw=ice+maker&_sacat=11874

Even better I think ...

Water source heat pump exchanger...$55

small low-temp compressor $50

condenser coil $35...

Parts to make one of these, DIY, could be salvaged from an old discarded freezer.The only problem is finding the Freon 11 they used to run on.

Propane has been used as a substitute,but I do not recommend it.

The total heat load? No, of course not. But remember, pressurized air has already gone through the main air tank and has already come down near(?) ambient temperature and has already condensed much of it's water in the main tank. (that needs draining frequently. I also live in high humidity here and in a few days of normal work my tank can be halfway full) Naturally the colder you keep the main tank, the better.(A fan?) Now the idea is to cool air further with low cost in a container that can also be drained. Just cooling it is not enough. That's why I talked about an old fridge which you can find most everywhere cheap. And a vertical air tank to fit inside also cheap. Now if you want to increase the duty cycle, you can add mass inside the fridge (water containers for example) and leave it work overnight. That should give him plenty of time to work the other day. Can't see any other way -with low cost that is- And I think amature use most of the time doesn't justify more expense. Unless you also need al lot of cubes for teqilas. Not a bad idea. (LOL). S.M.

I'm thinking we are dealing with something like this

That uses 7 cfm of 90 psi air...You need a substantial compressor to meet those specs...

https://www.aircompressorsdirect.com/Porter-Cable-PXCMLC3706056-Air-Compressor/p9201.html

So the compressor may be underpowered...

Possibly, blasters are very demanding and this could indirectrly add to the problem but if I were to risk a -seconds from disaster- specific diagnosis I would start like this. Inside the pressurized tank you have most of the time a 100% relative humidity i.e. the air holds as much water as it can in an "equilibrium" that is mainly dependent on its pressure and temperature. Also marginally diluted water balance is tiped upwards with air flow to and from the tank due to turbulance. Now when temp goes down -and at the place it goes down- local condensation happens. Correct up to this? OK Right after the compressor and before entering the tank there always is some kind of heat exchanger, be it at least a piece of tube with or without fins in front of the motor or compressor crank driven fan. Since this exchanger is very ineficient, the air entering the tank is not that cool yet. But the tank also disperces some heat into the room also very ineficiently, and "tries" to get down to ambient. Now because of the above inefficiencies, even befor blasting starts, the coldest point in the system is actualy the hose, and there is where a lot of condensation happens. Now with the first blast that chunck of water is possibly enough to get blaster medium wet and ruin your day. In my system for example I divert a second hose straight upwards to the third floor on my little electronics lab for blowing dust, small tools etc, and I've noticed condensation on the up direction is NEVER a problem, because condensed water given half a chanse, flows back to the tank. If there are no "pockets" over its root that is.. That is not the case for the horizontal line that is practically useless if you need dry air. Now if I had to do something I'd do some trick like the fridge on last post. Or try a better heat exchanger between tank and compressor but it would have to withstand near 15 bars for safety margin, so it wouldn't be cheap. But before all that I would just blow some air out of the hose, before connecting the blaster to lose the water from there. Who knows? It might be enough to get him going. S.M.

More info will give better suggestions,such as the CFM being used,the pressure,etc.

Still you have not provided critical information about your process.

What is the HP of your compressor?

The air flow required in SCFM?

These are important factors in deciding the best way to solve your problem.

Without that info everyone is working sort of blind.

Does your sandblaster introduce ambient air as well as the grit? I'll call this "auxilliary" air to distinguish it from your compressed air source.

Your compressed air should be dry (relative to ambient) with most water condensed into your compressor tank. During expansion within the spray gun, the remaining moisture of your previously compressed air should not condense.

From my history in painting automotive parts, we experienced "bloom" from the cooling effect of atmospheric drying of paint solvents.

What you may be experiencing is the cooling (by the release of the compressed air) causing the humidity in the auxiliary air air to condense, making your "mud". You might like to reduce the humidity of your auxiliary air and I see two ways to achieve this.

For small and infrequent jobs, you might create an environment where the auxiliary air is released air from your compressor, back at atmospheric. Essentially using the compressor as the de-humidifyer.

The second is similar to the "fridge" option suggested by others, having this auxiliary air coming through some cooling device, even as simple as a copper coil in an esky of ice. This should hopefully remove enough of the humidity in the auxiliary air so that it doesn't condense.

If you are sandblasting in an enclosed cabinet, then simply running the gun with no sand for "as long as it takes" to purge the high humidity ambient air inside the cabinet that becomes your auxiliary air once you start blasting will provide you with a dry air aux feed to the nozzle system. You would need to repeat each time you open the cabinet.

Go to 8:55 about mud....

$4.

https://www.harborfreight.com/disposable-inline-moisture-filter-63951.html

Compressors usually have cooling fins between the compressor and the tank, to cool the air going into the tank. Remove them. The air in the tank will now be hotter, with a higher dew point, maybe enough to stay dry in the gun. Insulate the tank and those same lines to keep the heat from escaping.

Compressors have an 'unloader' to ease the load on the motor at startup. Maybe you can connect the unloader at the bottom of the tank, so it drains the condensate every time it unloads. This may be impossible, since there is a check valve between the unloader and the tank.