Author Topic: Boom - or the Power of Compressed Air !  (Read 2486 times)

Offline awemawson

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Boom - or the Power of Compressed Air !
« on: February 16, 2017, 12:53:29 PM »
My nice civilised Hydrovane 15 (well I think that it's a 15 but never found a model number on it!) was cutting in a 85 psi and out at 125 psi which has been fine until I got my CNC Plasma Table - the Hypertherm PM45 plasma cutter on it specifies it at 90 psi (although it regulates it lower internally).

So a job yesterday was to tweak the pressure switch on the compressor up just a tad so that it never falls below 90 psi. Often compressor pressure switches - or at least the better ones - have settings for maximum pressure and hysteresis or dead band, thus setting the range from 'cut in' to 'cut out. But not this one - it's a cheapy generic one with only the maximum pressure settable. No problem, increase it from the 125 psi upper limit to a bit nearer the 150 psi that the compressor is rated at. I checked the test pressure of the tank and there was loads of margin, so 'one flat at a time', I tweaked the adjusting nut and cycled the compressor noting where it switched off.

I got it up to about 140 psi when suddenly the Hydrovane would not raise the pressure one iota. I thought I'd done massive internal damage to it, so a bit miffed I left the Portakabin where the compressor is housed, to go in the main workshop to google for technical diagrams of the beast.

As I got to the door, a chap that I have at the moment lowering a massive Laurel hedge called over saying he was glad I was ok as he'd heard the 'loud explosion', and come knocking on the locked workshop door to check I was ok :bugeye:

What explosion - I'd heard nothing ! So I went hunting along the considerable length of my air distribution system and eventually found the culprit. There was a three way Tee joint, where one branch is for future expansion, and the blanking plug had decided it was no longer going to stay put  :bang:
« Last Edit: February 16, 2017, 01:24:36 PM by awemawson »
Andrew Mawson
East Sussex

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #1 on: February 16, 2017, 01:01:47 PM »
Now this is a 'proper official blanking plug' for 25 mm MDPE pipe certified for pressures in excess of what I'm using, so maybe I'd not tightened it quite as much as I should have. The plug is a harder plastic than the pipe, and I suspect that the 'grippers' don't bite into it as much if at all.

So no wonder the poor old Hydrovane couldn't raise pressure  :lol:

However, the huge explosive blast sadly cleared the top of the cupboard where the joint is, knocking to the floor a Prom programmer and my Textronix cable measuring device. Falling onto a hard floor they both have suffered damage, and as they fell, they knocked the polycarbonate safety shields off my Fanuc Tapecut Model M wire EDM machine but luckily they survive the encounter.
« Last Edit: February 16, 2017, 01:28:51 PM by awemawson »
Andrew Mawson
East Sussex

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #2 on: February 16, 2017, 01:03:55 PM »
I replaced the original blanking plug, (which had vanished!) with another from stock, and tightened it up murder tight, but today I found the original way over the other side of the barn. It must have bounced all over the place to get where it was   :bugeye:

Andrew Mawson
East Sussex

Offline Spurry

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Re: Boom - or the Power of Compressed Air !
« Reply #3 on: February 16, 2017, 01:37:29 PM »
If that had have happened to me, I think there would have been a few four letter words involved. :bugeye: I'm surprised you don't stock the cap ends for the 25mm pipe.  :wave:
Pete

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #4 on: February 16, 2017, 01:40:21 PM »
Pete, I do, but that would have involved a stub end of pipe and two inserts, whereas the plug is just ..... a plug  :lol:
Andrew Mawson
East Sussex

Offline hermetic

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Re: Boom - or the Power of Compressed Air !
« Reply #5 on: February 16, 2017, 01:46:59 PM »
 Bad luck Andrew, that damage is a bit of a B*stad, but if you can find the bits, it will fix with Hepworth solvent cement, I have some on the desk as it happens. It actually blew those off the shelf onto the floor?
Phil

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #6 on: February 16, 2017, 02:05:17 PM »
Phil, as I said I wasn't in the workshop when it happened (lucky or I may have had other 'accidents'  :bugeye: )

So whether it was the impact of the 'blanking plug bullet' or the blast of air, or more likely a bit of both that did it I'm uncertain. But yes they were knocked off completely.  The Textronix TDR 'scope powers up, but reports 'screen temperature alarm' but is ok if you accept the error and continue - I'd imagine that a sensor has been destroyed or perhaps ripped off by the impact. I haven't ventured too near the Prom programmer - actually I can't remember actually using that one - it was a 'too good to ignore' bargain sometime.
Andrew Mawson
East Sussex

Offline tom osselton

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Re: Boom - or the Power of Compressed Air !
« Reply #7 on: February 16, 2017, 03:41:25 PM »
Glad to hear you wern't in there!

Offline jcs0001

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Re: Boom - or the Power of Compressed Air !
« Reply #8 on: February 16, 2017, 03:58:44 PM »
That's one you can laugh about since no one was injured.  It reminds me of a test I did on a 7 ft piece of 2 1/2 in. firehose with compressed air.  It was plugged at one end with a cast iron nipple with a pipe plug on it - the other end with a cast iron plug with a schraeder valve.  Both nipples were held with a couple of adjustable clamps tightened to the n'th degree.  Anyway I had pressured it up to about 75 psi or so and left it out on my back deck.  Figured I'd leave it a few hours and then check the pressure.

I did not account for the sun shining on the blue firehose :doh:

When I came back a couple of hours later the end plug and nipple were missing.  It had been pointed in the general direction of the back fence.  I looked all over and never found the plug or nipple - didn't ask the neighbours as I was afraid of the answer.

It must have been a fairly spectacular blast but unfortunately/fortunately no one was around to see or hear it.

John.

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #9 on: February 16, 2017, 04:03:27 PM »
Glad to hear you wern't in there!

So was I  :lol:

I suppose in a much smaller room it could have caused ear damage let alone being hit by flying debris  :bugeye:
Andrew Mawson
East Sussex

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #10 on: February 16, 2017, 04:07:05 PM »
John, I worry about that effect on the tyres of my Ifor Williams 3.5 ton trailer. It has smallish wheels but they are pumped up to 90 psi. In the sun or after a long run I'm willing to bet they rise in pressure considerably. The only consolation is that they are multi-mega number of ply's - can't remember the number but many more than any other tyre I've owned.
Andrew Mawson
East Sussex

Offline appletree

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Re: Boom - or the Power of Compressed Air !
« Reply #11 on: February 16, 2017, 04:40:10 PM »
Lucky escape, not being there, you do the research, work in a methodical informed manner etc etc and s**t happens. never under estimate the distruction of pneumatics, hydraulics are a damp squib by comparison although much more powerful

Phil


Offline tom osselton

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Re: Boom - or the Power of Compressed Air !
« Reply #12 on: February 17, 2017, 01:16:42 AM »
John, I worry about that effect on the tyres of my Ifor Williams 3.5 ton trailer. It has smallish wheels but they are pumped up to 90 psi. In the sun or after a long run I'm willing to bet they rise in pressure considerably. The only consolation is that they are multi-mega number of ply's - can't remember the number but many more than any other tyre I've owned.
I've been behind a semi trailer that blew a tire, scary stuff a good portion of it missed us by around 4feet at window level!
I've seen on mythbusters the tire going through the front window!

Offline JerryNotts

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Re: Boom - or the Power of Compressed Air !
« Reply #13 on: February 18, 2017, 06:26:16 AM »
If that had have happened to me, I think there would have been a few four letter words involved. :bugeye: I'm surprised you don't stock the cap ends for the 25mm pipe.  :wave:
Pete

I was reading 'Churchill - The Power of Words' last evening. As you know WSC had a way of putting things so that his meaning was clear but could not cause offence. He wrote in his boiok ' My Early Life' about wrenching his shoulder when disembarking from a boat at Bombay in 1896, "I ....made a few remarks of a general character, mostly beginning with the earlier letters of the alphabet..."

At one time I was heavily involved with supplying and servicing Hydrovane compressors, perhaops my knowledge is somewhat dated but if I can help with information let me know. One question Andrew, does your machine still pass the threepenny bit test?

Jerry


Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #14 on: February 18, 2017, 06:39:33 AM »
Not actually tried the vibration test Jerry, but I do have a couple of bank bags full of uncirculated threepenny bits  :ddb:


One thing I could do with sourcing is a service manual for this compressor - I'm not sure of it's exact model - I suspect that it's a '15' - certainly the bits from a '15' service kit fitted ok.

Despite searching the interweb no downloads appeared :(
Andrew Mawson
East Sussex

Offline JerryNotts

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Re: Boom - or the Power of Compressed Air !
« Reply #15 on: February 20, 2017, 03:37:59 AM »
Andrew, I don't remember what the service sheets said but one of the features of the genuine Hydrovane was simpicity of servicing. As long as you use the correct oil the separator works well enough.
I am sure that if you have had it long enough you will be well aware of the main wear points at the end faces and you probably keep spare gaskets so that you can take up this wear. Sourcing these gaskets was the problem that most customers had.
The point of the 3d is to check for out-of-balance due to blocking of the vane cooling slots. If you have the rotor out it's worth checking for this. If you find blockages then you should clear them. A quick blow through with compressed air should be enough. While you are at it check that the oil hasn't gone gummy.

Hope this helps.
Jerry  :coffee:

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #16 on: February 20, 2017, 04:19:50 AM »
Jerry,

I confess that I've had it for ten years, it's been on 24/7, but not heavily loaded, and I only changed the oil and filters for the first time last week  :palm:

It was 'refurbished' when I bought it, and I'm sure that the oil and filters were new then, and it had been given a quick blow over with blue paint, and new labels. The foam inlet filter, surprisingly, was clean as a whistle, but the screw in one was a bit manky.

I've never dismantled it other than the filter and oil change last week  :bugeye:
Andrew Mawson
East Sussex

Offline DMIOM

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Re: Boom - or the Power of Compressed Air !
« Reply #17 on: February 20, 2017, 06:55:11 AM »
....... One thing I could do with sourcing is a service manual for this compressor - I'm not sure of it's exact model - I suspect that it's a '15' - certainly the bits from a '15' service kit fitted ok.  Despite searching the interweb no downloads appeared :(

Andrew,

If I can 'volunteer' another member, I seem to recall that John Doubleboost has a similar compressor, and he recorded an overhaul for one of his video programmes.

Dave

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #18 on: February 20, 2017, 07:32:13 AM »
Dave yes I remembered that and watched it again before I did mine. But that is only an 'oil change and filter change' - I was hoping for something a bit more 'internal' technically  :scratch:
Andrew Mawson
East Sussex

Offline JerryNotts

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Re: Boom - or the Power of Compressed Air !
« Reply #19 on: February 20, 2017, 10:47:00 AM »
Andrew this might be in the realm of teaching my grandmother, ... but just in case look at the UK Hydrovane site which has an animation showing the principle of operation.
What's not apparent though is that the vanes are not solid (unless they have sneakily changed the design from my time...). Their construction is the reason they were so proud of their product.

Each vane has holes which run radially through. As the rotation occurs things happen as you will appreciate, driven by the differential air pressure. Those holes conttribute to lightness, thus lower rotating mass and providing cooling due to the pumping action as the vanes move in and out.

The whole mechanism is ingenious and simple. You only need to keep tabs on the oil and occasionally on the end float. I don't recall the end float which we tried to maintain. That's where the different gasket thicknesses come in.  The threepenny bit test is a rough and ready way to check for wear. By standing the coin on its edge on top of the motor connector box ( flat surface) in line with the axis of rotation you can see if the balance has been affected. If the coin topples over then investigate further.

Jerry

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #20 on: February 20, 2017, 11:34:41 AM »
Thanks Jerry,

Demonstrably they  are a very reliable robust design as evidenced by my neglect of mine  :bugeye:

I previously had an old 23 hydrovane that also gave good service for many years.
Andrew Mawson
East Sussex

Offline mechman48

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Re: Boom - or the Power of Compressed Air !
« Reply #21 on: March 15, 2017, 12:35:16 PM »
....... One thing I could do with sourcing is a service manual for this compressor - I'm not sure of it's exact model - I suspect that it's a '15' - certainly the bits from a '15' service kit fitted ok.  Despite searching the interweb no downloads appeared :(

Andrew,

If I can 'volunteer' another member, I seem to recall that John Doubleboost has a similar compressor, and he recorded an overhaul for one of his video programmes.

Dave

Doubleboost  has a similar one &  he's video'd  a Sunday night nightcap episode on carrying out a service on it, I watched it. Go onto his you tube web site & click on videos heading, you'll see all his videos, so far he's  up to the 166th episode, can't remember what episode # though .

George.
George.


Always look on the bright side of life, & remember.. KISS..' Keep It Simple Stupid'

Offline awemawson

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Re: Boom - or the Power of Compressed Air !
« Reply #22 on: March 15, 2017, 01:07:32 PM »
George, look further up the thread and you'll see we've discussed it already, but thank you anyway  :thumbup:
Andrew Mawson
East Sussex