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Fault finding and initial strip down Schmidt Thompson metering valve – PT 2

BlastOne’s Master Technician, Kerry Cooper, demonstrates fault finding and the initial strip down of the Schmidt Thompson metering valve


So, these breathers, I’ve been kind to check these breathers first to make sure that they’re clear and clean. You can do this on the pot without taking the entire valve out of the system because the breather may be the reason why that piston’s not lifting appropriately to lift the piston off the urethane seat to let the grit go through.

So, what we do is we just check them to see if they’re clear and clean. This one’s really good so, I can actually blow through it. If you wish to give it a wash, blow it back, output it back in.

Do you need thread tape or anything? No, it’s brass and it’s going into a cast aluminium. So, it’ll find its own seat and the thread will settle down in there anyway. So, it’ll go through. It’ll tighten up to the stage where it’s nipped. There’s no need to over tighten because you can actually stretch the brass and you won’t get it back out. So, look and that’s plenty.

So, do the same with the other one. Repeat the step on the other side because there’s two breathers there. Because there’s two exhaust ports. So, there’s quite a bit of air that has to escape from these little fellows.

So, again, you see I check to see if it’s clean and clear. See, if I can blow through it. Give it a blowout. Make sure the threads clean. Popping back in.

Now, I would do this before disassembling this entire valve because that could be the reason you’re stopping.

So, what I’m showing you now is the fundamental process of elimination, primarily, to establish why the valves not lifting off the seat.

So, remember what I said, the air line that goes down from the auto valve to this valve, I’ve taken it off, open the dead man, the air is coming to this. So, something is wrong with this and the biggest problem with these is moisture that don’t like moisture.

So, if you’re getting excessive moisture, you need to install an air prep to diminish the amount of fluid that runs through this.

Now, as far as pulling this apart is concerned, if you think yourself, I’ve never pulled one apart before. What do I do? You can ring the guys on the help desk at Blastone and they’ll run you through this. They’ll email you through a diagram of how to repair this and pull it to pieces.

So, where do I start? I’ve got base bolts and I’ve got a big nut here or plug. So, in essence, remember, this goes around this way. The conical section of the pot comes down here and feeds the grid into this hole.

So, this one here, before I even pull this valve off, I can also undo this plug and see if the grit flows through. Because if you’ve got no grit coming through the pusher line, you can always use this in the inspection port. So, what you’ll need to do is undo this particular plug and see if there is grit in the chamber.

So, another checks you’re doing is a subsequent check that you go through checking items to ensure they work all in line with your process of elimination.

So, if you do have substantial grit coming out of that plug, you will need a sizeable shifter for that to undo that.

What you’ve got to be careful of is that you don’t over tighten it because you can actually split this aluminum housing. So, a little bit of thread tape on it is a good thing and also, you can check the thread while you’re at it to make sure that it’s clear and clean.

So, that’s the plug I would take off while this is on the pot. Now, if the grit starts flowing out, you think, “oh, I can’t get that plug back in. What do I do? What do I do?”

Lay the pot backwards. So, the grit stops flowing out. It enables you to get the plug back on. Just clear the grid out of the thread. Put the plug back on.

So, let’s reinstate that for now. So, what I don’t do is just do it up hand tight and leave it, primarily because, I can put that back in the pot and I’ve forgotten about tightening that up.

Now, that could shoot out at a rate of knots and hurt somebody. So, it pays to reinstate it. It’s not going to impede the breasts in relation to pulling the valve to pieces. What it is going to do is its eliminating one item that I may forget in reassembly that could actually cause somebody some harm, particularly, me.

Now, that plugs put back in, where do I start in disassembling this? Because we’ve established that they are clean and clear and clean, those two little plugs.

So, the best way to do this is to while that big knob is wound backwards. So, it’s well, counterclockwise; righty tighty, lefty loosey. So, I take the tension all the way off it. Now, why I’ve done that is because underneath here is a spring and this spring is putting tension onto the piston. So, when I go to undo these four bolts here, if I leave that knob round all the way in, I’m compressing the spring and putting excessive tension back on this housing that I’m trying to remove.

So, I’ve done that relief, released. Relief the tension on the spring. Will I start there or here? Well, let’s start at the base and it exposes the piston, the sleeve, the seats, and the seals up in here, which is up in this stem here, and then the piston.

So, we’ll go from the bottom up which is easiest way to do this. These will be 9/16th. They are imperial metric. They are imperial not metric on these. So, just hold it nice and still.

Now, if they’re a bit tight to make life a bit easier. If you’re if you’ve got a vise available, by all means, pinch it and hold it safely so that you can undo these items.

But what I am simulating here is a broad cross-section of. Yes, look, I have a vise available but a lot of you guys know that when you’re on site, you don’t have a vise, so, you can actually put your foot on this and hold it still or with a pair of Stillsons. Grab the base of the body itself, hold the Stillsons with your foot and undo it.

So, you notice, I’m using a ring spanner. You can use soffits, or you can, if you’ve only got ring open enders on site, you can use an open ender.

Now, the reason I prefer ring spanner or sockets is less chance of stripping the head of the hex of the bolt and make it very difficult to reassemble and more importantly, make it even more impossible when you go to dismantle the unit.

Now, what I’m taking off here is the hardened pipe or the base, and you can see here that it’s got an impregnation of the seat itself. So, this seat, as you can see, is “look, it’s quite tight, how do I get it out of there?”.

Well, I don’t want to damage it because I don’t want to damage it. I only want to pop it out of there. So, cover the end of the screwdriver with a rag and pick up the lip of the of the neoprene and just pop it out.

Because that’s what they look like that means that the piston in that taper is going to sit into that taper. So, just to pop that out, I’ll just again cover my screwdriver and put that in the side of it and pop it out, like so.

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