Care and use of Blast Nozzles

BlastOne’s Master Technician, Kerry Cooper, discusses how to use and care for blast nozzles

So, this is an ultra-tough nozzle – the silicon carbide, silicon nitride. Both have good wear, non-wear factors. Also, they’re quite resilient and robust as far as a blast nozzle is concerned.

The important thing to remember though because it’s hard, I wouldn’t recommend you drop this. So, when you’re finished for the day blasting, what I suggest you don’t do is just drop the hose and walk away. Because when you drop this, you’re making it susceptible to cracking and damage of the nozzle.

What’s the outcome of that is, it wears prematurely and also too, it doesn’t appropriate the role of the garnet and the abrasive to exhaust in the appropriate manner on the exhaust side of this nozzle.

So, you have to look after them. Keep them clean. Make sure that they are not damaged and also, what I do like about these particular nozzles where the thread starts on the back of this, it’s actually flat. So, it’s flat all the way through and it gives me a slight lip surface on the back of the nozzle.

So, what that means is that if I cut this hose, this blast hose and feed the blast hose all the way back to the nozzle holder, there’s a shoulder inside here that that blast hose comes up to.

So, say for example, I was on site and I forgot to get some nozzle gaskets. Uh-oh! I forgot the nozzle gaskets. What do I do? I can’t blast.

It’s not quite true because if this hose has been cut square and what we do with this nozzle holder is that we make sure the hoses cut squares and goes all the way through to the shoulder in the back of the nozzle holder then we use these grab screws.

So, these grab screws are purely that. They just grab the hose. They do not penetrate the hose wall. If the screw penetrates and comes all the way through the blast hose, you’ve undermined the integrity of the blast hose.

Also, too, the screw hanging down in a stream of velocity of grit and air, the grit will hit where the protrusion of the screw is and ultimately come out in the back of this nozzle holder. So, me as the operator, I’ve got my hand. Admittedly, I have gloves on but also too, it can actually impregnate the glove and get me.

So, it’s important to remember that when we change these nozzle holders, we cut the whole square. We utilized the grab screws and also too, as a secondary holding factor, we will utilize silicon.

So, a smear of silicon up the nozzle holder, put all the screws in and make sure you put all the screws in then ensure that the hose has been cut and comes all the way through to the shoulder and the nozzle holder. Because if I forgot my nozzle gaskets, I can actually screw this particular nozzle, the ultra-tough nozzle, all the way in and make the nozzle seat on the hose itself. So, there’s nothing wrong with that. That’s a good way to do it.

What I do suggest you do is because it’s a dry abrasive that you’re using and say for example, the relative humidity is high, you’ll find that the grip becomes sticky around these sorts of areas.

What I suggest you do is smear a little bit of graphite dust on there. So, graphite dust is a dry lubricant and enables me to screw that in and out easily. Because what I suggest to do is after every blasting shift is you unscrew this nozzle, and this is everyday I’m talking.

Take that nozzle out and check to ensure that it’s still maintaining a full face. It’s a circular shape and the wear factor on the edge of this particular flat edge has been checked to ensure that it hasn’t been undermined by grit and air passing through that edge.

Also, to check this hose section in here to ensure that that is being sealed as well when you screw the hose or the nozzle back in there. So, by doing that, that’ll keep you safe. Why? Because you are the blaster hanging on to this all day.

So, as I mentioned, there’s the blast nozzle. I’ve just described how to ascertain the wear factor on your nozzle. I’ve just described what types of nozzles they are. I’ve described how to check the pressure in that.

With the pressure gauge, the gauge is utilized. Remember, don’t put it in that way because the grid will fill up the hole. The venturi hole in them gauged or the hypodermic needle. So, always put the needle and gauge in this way and operating the deadman, you can check then to see where the pressure is, how your pressure is going.

So, as I mentioned earlier, I didn’t have a hundred psi when I was blasting. I’ve just established possibly that it may have been the blast nozzle wear and because the wear factor in the nozzle has increased and the holes become larger and I’ve ascertained that from this particular gauge, I changed the nozzle to a new nozzle.

Again, I impregnate the hose with the needle. Operate the deadman and check to see what pressure I’ve got now. If the pressure is increased but only slightly, I still need to go back and check all the lines that facilitate the air pressure within this pot.

So, I may walk back through the line or get an associate to walk back while I’m operating this from a safe distance from me and ensure that there are no leaks in all the gaskets.

The one thing to remember too, with the air prep, is that on the bottom of the air prep, there’s a leak off valve on the bottom of that. If you have that open too far that can affect the total outcome of this. You only want them to weep a small amount of air.

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