Completion of strip down of Schmidt Combo remote control valve – PT 2

BlastOne’s Master Technician, Kerry Cooper, completes the strip down of a Schmidt Combo remote control valve

I continue to undo your bolts, just keep rotating the unit to undo the bolts. Now, just to reiterate on the marking of this — just to ensure that I’ve got it in the right place, I can put two marks on here — one on there so that I know when I reassemble, this where I am in conjunction to what should go where.

There’s no need to mark the bolts, of course, but certainly the body of the unit and the cylinder in the center here needs to be put back in the same place.

Now that these are only finger tight, I can continue to do this. You can do this with gloves on. Keep all of it together so that you’ve got all the washers and nuts so that you don’t get lost in relation to its reassembly.

In the case you’ll get one that’s a little bit tight on the thread, again, use your shifter to undo that, like so. If they remain to be tied, of course, there’s always one and you’ll have to wind it all the way off with the appropriate tool. Let that one go.

Now, go back to the diagonal opposing of that which is this one. You’ll find that there is a little bit of tension on these nuts primarily because we are now undoing a spring inside this particular unit.

The spring is holding the tension on the bolts as we separate them. Now that those two opposing is still there; we’ll remove this one here. There’s the tension on the spring holding that bolt in place so undo the nuts.

See how much easier it is with the appropriate spinner and of course; keep them all together so you don’t lose where you are with the reassembly.

Okay, so now you can see here, looked at once tight and so is this one because that spring is now starting to expand.

For the last two bolts you’ll find, you’ll undo one completely and take it out of the carriage; like so, and it helps if you just push it, hold it together to get those last ones undone.

Remember what I said, keep the washers because you need to reinstate them. You see, it’s trying to separate itself. For this last one, just put it on the bench, push it down, and see if we can undo that nut.

If you can’t do it, don’t panic. Just go and revert back to the original. I’m doing them by spinner to remove them. You can see this is trying to separate itself now. So, that’s the recall on the spring tension.

Just be patient and undo them while holding the head of the bolt. There you go!

If you’ve got a clean work area and you do manage to drop items which I’m very good at, you’ll be able to recover them and see where they are.

If we’re on site, I suggest you put a drop sheet down, some cladding whatever; just so you’ve got a clean work area.

Remove the bolts and sit them in an area so that you know where they are.

To give you an indication of what happens here is — remember the marks we put on there, so the marks there now tell us where we have to line them up.

Remove this end, which is the pressure end, and as you can see here, the cylinder comes out.

There’s the wedge and this here, actually, retains the pressure in the end of that where the pressure comes in.

What that does is that allows the air to travel through the pot; as well as this here coming backwards through here, pinching the hose in this particular environment here.

In the end of this valve, the hoses pinch with that wedge. Just put them to one side.

Is there any wear factors in this?

The only thing you’ll find that wears in there is if you leave the hose that I mentioned. It has to be checked for its integrity. The wall takes integrity of the hose that is poked through here.

You can imagine here’s the hose through here and the wedge is coming in and pinching the hose every time you operate the deadman.

It’s a good idea to start when you start blasting try not to trigger the deadman on and off on and off because this wedge is pinching that hose all the time.

If the hose is undermined and left and the wall of the hose is damaged, it’ll tend to blow a hole in this casing.

What we’re inspecting this casing for is the pinch bar, to say that and see that it is concentric.

Also, to this body to ensure that none of the body has been undermined by abrasive if that hose was broken and left unattended. So that’s fine. We’re happy with that!

What are we looking for in here?

Well, this rubber seat actually seals all that pressure in the bottom here on a seat; so, it’s important that we look at this seat to ensure that it’s still got a nice taper. There’s no big gouges or scratches and the rubber has a chance to seal on that seat and hold that air pressure in there. There’s nothing else you have to worry about here except for a big scour mark or any damage.

What I suggest you do is put that face up because if you put it face down and it’s on a rock or something, you could scratch that. It wouldn’t pay to damage that face edge of this particular end unit Put that to one side. We’re happy with that.

Now, here’s the trick, this is the cylinder that harnesses a lot of air. All this does is go back and forth like this; every time you actuate the deadman back and forth that’s all it does. Now, make note of this particular one here when you pull it out, the reason I say that is because you can be caught unaware in relation to the reassembly of this.

I’ll show you as I dismantle it.

You need to take this rubber off. This rubber seat needs to come off and it should be 7/16th like so anyone. I think I’ve done this before, 7/16th.

So, you’ll find that because that’s a no lock nut. You’ll need to hang on to the wedge and we go.

As you want to do this, take note; because there’s a couple of things you need to reinstate.

There you are. There’s a copper washer, just slide that off and look what’s underneath — this plunger head.

There’s a copper washer and underneath that copper washer is another one of these O-rings and there’s another copper washer.

In essence, what I’m saying too is that, this here has got a copper washer in behind it.

If we just grab the screwdriver and pop that out so you can see what I’m talking about. There it is. There’s the O-ring. There’s the copper washer.

If you put a kit in this, what you’ll find is, you’ll get an O-ring, copper washer, O-ring, copper washer.

Ensure that you put them back in that order because the O-rings seal that particular rubber — both sides.

It’s imperative that it is sealed. Put them to one side.

Remember what I said, if it’s second-hand, put it to one side so you don’t get it mixed up with the new stuff. So, there’s the second-hand part.

Now this shaft here, we have to inspect this shaft for damage.

If there’s any scaring or sacrificial damage to this shaft, it can be rendered null and void; primarily, because it has to seal on the inside of this particular backing plate.

You’ll see now why I’ve marked that backing plate because, look, the backing plate comes out like so – there’s an O-ring behind it. But what can happen is this whole unit could go back together with this inner round out this way.

The consequence of that is that when you actuate it, there’s not enough travel distance for this piston to pinch your hose off; so that is stopping the travel distance of the host of the crimp edge — for the hose, I should say. This actually goes around that way. Now, you can see why I’ve marked it.

Also, look at this face plate, there’s a step in it to accommodate the O-ring.

The O-ring seals this particular unit so that air doesn’t escape around its circumference.

Also, in this particular unit, when you’re putting a kit in there, you’ll see there’s a bronze bush.

On the other side of that, you’ll find that there’s a recess or a ring land. What is in there is another O-ring; so, the O-rings that are here, there’s also an O-ring in that recess and that’s designed to seal that piston as the piston travels through.

When we reassemble this, we don’t use grease, any cease, any wet lure because whatsoever we use a product called graphite dust.

Graphite dust is not a product that accumulates if it gets moisture on it. It tends to coagulate slightly but it still remains as a lubricant — same as graphite grease.

Graphite dust is the only item I use to reassemble these, primarily, because it’s a good dry lubricant.

If there is moisture in there that doesn’t coagulate to the situation where it impedes the actuation of this particular unit.

If you use grease and it gets dust in there, the dust becomes aggressive and abrades the stem of the piston and any other rubbers that are in this particular unit. Sit at the one side.

This particular item here is the piston itself. This piston runs in this barrel (oh! it doesn’t fit. oh no! That’s right, it went that way.)

You’ve got to be conscious of how you pull this apart as to how it goes back together. Remember, if you mark these items, it’s easy to establish which one went where. (Oh no! That doesn’t go there; it hasn’t got two marks)

This one goes here. It’s got two marks. Slide the piston out and you’ll see that the piston has an O-ring on it so this ring is actually a sergeant seal and it’s designed in such a manner that the sergeant seal has two lips.

If you think to yourself, I can’t take the seal off — which way did it go?

It’s easy to remember that when you put a sergeant seal or a chevron seal back in, the two lips face the pressure.

So, where would the pressure be in this chamber?

Well, if we go back to this again; you’ll find that – that was where the return line was before the deadman. The return line, when you actuate the deadman, fills this chamber and pushes this backwards.

The chevron seal always faces the pressure. Remember, it goes this way — so that way — that chevron seal must face towards the spring. If you’re worried about it, as you’ll flip it off, just take a photo in case you forget.

This recess, in this particular piston, has to be wiped clean and the new seal doused again with graphite dust.

And in here, when you put them back on – don’t use spinners, screwdrivers – just stretch the O-ring and slide it back over the surface so that it pops back into place.

If it rolls on you, just bring it together like this, pop it up and slide it backwards. Back over that recess so that you can re-establish its correct installation.

So, you see, so it’s relatively easy to do it by hand because it is a rubber composition. It will stretch but go back into place quite easily.

Is there anything I need to do else here? Not really!

No, just make sure it’s clear and clean and there’s no contaminants left in there. The one thing I am looking for, though, is in this particular cylinder where that i-ring runs.
I’m looking for any sacrificial damage.

What could be the sacrificial damage?

Well, ultimately, if this garden enters into this area; say for example, I took that little breather out because it was blocked and didn’t replace it, garnet can end up in this particular cylinder if garnet and air are traveling back and forth on the ear abrasive.

The abrasion will actually put scours and there will be vertical scales in this cylinder.

If you’re on site and you don’t have another cylinder, what I suggest you do is get some 600 wet and dry, some kerosene or any type of wet lubricant even oil –allied oil. And you can’t rub the marks out like this. You actually have to do it in a circular motion.

Just to take the edge off those scours, you can reassemble it but you know, eventually, you have to replace the cylinder if there’s scour marks in there.

It works exactly the same as the bore in the engine of your car.

If there’s scours in there, it has to be either re-board; which in this case, we don’t bother because there’s not a tolerance there to accommodate a bigger O-ring.

If it’s scoured, you replace it. But to get you out of trouble; if you take the sharp edges off the scouring, that’s ultimately enough to get you started and back up and running.

Don’t forget on the other side of this, is your O-ring.

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