Author Topic: Steam Cleaner. Re-Birth of a Karcher MPDS  (Read 17340 times)

Offline awemawson

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Steam Cleaner. Re-Birth of a Karcher MPDS
« on: October 29, 2015, 09:35:18 AM »
When I moved to the farm here eight years ago I needed a stand alone pressure washer - ie independent of electricity or even piped water as at that time I hadn't put services everywhere and yet I was churning up loads of mud with my JCB 3CX. It was of course putting in those needed services  :bang:

Casting around I came across a military version of a Karcher Steam Cleaner. Powered by a diesel engine, and burning diesel to heat its water, it could suck up its water supply from a pond or stream and seemed ideal, if a little large.

When it arrived it turned out that it was an 'MPDS' or Multi-Purpose-Decontamination-System. Intended for field deployment on the German Plains as the Russian hoards swept over using battlefield nuclear weapons, this would hopefully clean up tanks and vehicles as well as personnel.

I managed to find the military instructors guides on the web which I attach to this post

Superb beast driven by a Farymann 6.5 hp diesel engine, one of which I already had on a larger vibrating 'wacker plate' so I knew the engine.


Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #1 on: October 29, 2015, 10:02:53 AM »
Over the years it's given me good service, with the pressure washer bit never letting me down. However the steam side became more and more un-reliable - not firing up on demand. At various times I'd done bits of investigation but never managed to bottom the fault(s) so resolved to have a 'good go' at it.

Problem was that the control box is tightly packed, has numerous relays, and although I have a circuit diagram, relays weren't numbered so it all got a bit confusing. I'd had my suspicions that the 'flame failure' circuit was at the heart of the problem, but it's control box was buried deeply in the main control box, and anyway couldn't easily be tested unless in-situ and connected to it's various peripherals.

I decided to bite the bullet, pull it out, and configure a test rig for it so that I could test it on the bench.
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #2 on: October 29, 2015, 10:11:09 AM »
Pulling the Flame Failure unit out was a bit of a hassle involving taking much of the surrounding controls and indicators off first, so  a very methodical approach was needed if wires weren't to be misplaced.

Eventually it came out
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #3 on: October 29, 2015, 10:25:33 AM »
The first thing I did was a careful visual examination which revealed no obvious issues, then I went through all the components to ensure spares were still available. They were, albeit that that i/c (which is a window discriminator) was being offered on eBay at £75 !!!!

So what does it need to work? Well it wakes up by being supplied with 12v DC. Then it monitors a Cadmium Sulphide photo-cell that is looking into the combustion chamber. It needs to see no light at this stage which is high resistance of over 1 Megohm. If this is the case it turns on the relays controlling the fuel and ignition. Then in the next ten seconds it needs to 'see' light via the CDS cell, represented by a low resistance of about 400 ohms. If this happens then the ignition is cut off, the fuel left on, and it sits in that state until either the flame goes out or the 12v is taken away.

It proved impossible to easily remove the original CDS cell to use it in the test rig as it was hard wired, so I measured it's characteristics and used resistors to emulate it's two states with a toggle switch to select flame or no flame. 12v torch bulbs were wired as the  three outputs (Ignition, Fuel and Fault)
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #4 on: October 29, 2015, 10:38:45 AM »
The mounting of the CDS cell was rather Heath Robinson - it must have been replaced at some time and was a different diameter to the housing, also the housing had to be spaced off the boiler by a pile of washers to allow for various flangy bits. So I re-engineered it all, turning a ptfe collar for the CDS cell and specific spacers to replace the washer pile - sorry no pictures.

Well the test rig worked splendidly. I could not only prove that it went through it's various sequences, but also that it was able to take a reasonable degree of 'tap testing' and voltage variations.

On the face of it slightly disappointing that it wasn't the fault, but in fact actually re-assuring that now I knew positively that it was working and could be eliminated from the diagnosis.
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #5 on: October 29, 2015, 10:56:04 AM »
So now I turned my attention to the ignition side of things. There are two 'spark plug like' electrodes protruding into the flame chamber close to the fuel jet. These are fed by screened EHT leads (military remember so EVERYTHING is screened) emanating from an EHT transformer whose primary is 240v mains. No mains in this device so another unit described on the circuit diagram as a 'transformer' but infact a transformer driven by a transistorised inverter, takes in 12v DC and outputs 240v. Initially I was convinced that the screened leads were 'leaky' as measuring to frame I was getting only about 50 kOhms - then it dawned on me that the EHT transformer secondary was 'centre tap earthed' so I was measuring half the secondary winding resistance  :bang:

So a quick test: I rigged up a lab power supply to the inverter and sure enough nice crisp discharge crackling could be heard (10 kV at 20 mA). I re-terminated the EHT ends as they were rather frayed and put it all back together.
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #6 on: October 29, 2015, 11:19:35 AM »
For the CDS control box to fire up the boiler a few other conditions need to be correct. One is a 'flow switch' needs activating by pulling the trigger on the lance.

The flow switch is mounted in a dual purpose housing (it has the main pressure switch in it as well) but this flow switch has a magnetic shuttle that is pressed 'left' by a weak bronze spring, and 'right' by the water impinging on it. The magnet operates a reed switch in an external brass tube.

I had tried operating it by pressing it 'right' - there is a filter plug that can be removed and an allen key would just reach round the corner and press it - sure enough operated according to my meter. However measuring is real operating conditions it didn't work - all very odd  :scratch:

Next I made a bit of an error  :bang:

I decided to unscrew the plug that gives access to the bronze spring and magnetic shuttle. It went ok until, having difficulty getting the shuttle out, I turned the water on. Of course - obvious realy- the shuttle shot out like a bullet from a gun  :(

I  eventually found it after a bit of searching, but now I didn't know which way it was supposed to face.
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #7 on: October 29, 2015, 11:42:55 AM »
Now initially I had though that the large end should face the incoming water, but then I noticed the 'screwdriver slot' in that end - this could only be accessed from the right. Both ends of the shuttle had turned down sections that nicely matched the spring diameter so no help there  :bang:

I put it in 'screw driver slot right' - tested it with the allen key trick through the filter plug - which worked - and then tried it under operating conditions. No go, still not closing the reed switch.

Well - nothing to lose I pulled it apart again this time putting a rag over the opening to catch the shuttle  :ddb: then re-assembled it 'screwdriver slot left'.

 :clap: :clap: Hey it now works  :bugeye: :bugeye:

Now the magnet is very weak and various descriptions of other Karcher pressure washers say to change the magnet annually. So I've ordered another one. BUT - it begs the question - was it in wrong to begin with. The only other explanation I can come up with is that I did ease a few slight burrs on the shuttle - was it perhaps jamming. Anyway at this stage she fires up on demand.

Just two more issues to resolve:

 Firstly there is a two way fuse box that seems to be described as a 'continental type' holding the style of car fuses that are pointed and sit between springy brass leafs with location holes. One way was weak in the springyness department and I'd temporarily wired it out. Someone had packed the other way with a screw to give it more oomph but it needs changing. (The holder on the left is an 'indicating' ie has a neon across it - 2A mains fuse for the inverter circuit)

Secondly there is a persistent diesel leak with diesel running out of the vortex chamber of the main blower fan - not healthy :bugeye:
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #8 on: October 29, 2015, 11:50:17 AM »
After much searching I managed to locate an exact replica of the two way fuse box - at one point I'd thought I'd have to use 'in line' fuse holders as space is very tight, but this turned up.

Joy when it arrived - EXACTLY the same size even down to hole mountings - joy was soon dashed when I took it off the vacuum packing and found it cracked  :bang:
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #9 on: October 29, 2015, 12:02:47 PM »
Never mind - the seller seems to have loads and is posting another one, having first unpacked it to check it hasn't suffered the same fate !

So on to the diesel leak:

Close examination revealed that the diesel was coming out of the rear of the injector pump so I rather expected major mechanical issues with the pump itself. It looks almost identical to a standard oil boiler injector pump, just not quite the same  :(

Then is occurred to me - in the book of words for this machine I have a parts list where all the parts have NATO stock numbers - Google the NSN ! This not only told me it was a SUNTEC pump, but one was for sale in the USA on eBay !

However it also allowed me to identify the model and get the makers literature. This showed me that there was an oil seal on the drive shaft, that is in a chamber that is filled by the oil retuning to the tank. Hence not huge pressure. It also allowed me to locate the very same exact seal on eBay in Germany - it's a bit of an odd size - 8mm shaft but 26mm outer diameter.

Seal duly ordered and arrived this morning
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #10 on: October 29, 2015, 12:08:12 PM »
So I whipped the pump off, revealed the seal, undid a circlip, used a rather crude method of removing the seal (how else??) popped the new seal in and she works a treat. No more dripping diesel.

It turned out that the entire inner lip of the lip seal had come detached from the body and indeed remained on the shaft when I took the rest off - never seen one so bad before !
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #11 on: October 29, 2015, 12:11:10 PM »
So just that fuse holder to sort, and probably a bit of wiring tidying up and she should be good for another 8 years  :clap: :clap:
Andrew Mawson
East Sussex

Offline hermetic

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #12 on: October 29, 2015, 12:47:05 PM »
And better than it has been for a long time, good work Andrew!
Phil
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline Pete.

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #13 on: October 29, 2015, 01:58:40 PM »
Noice work :beer:

Offline mattinker

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #14 on: October 29, 2015, 03:36:39 PM »
So, this is what you've been up to recently nice to see
 you've been having fun!

Regards, Matthew

Offline Kjelle

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #15 on: October 30, 2015, 02:25:58 PM »
It's alwas fun, and educating, to read about your projects... It's not often I can contribute to what you are doing, but now, for once... The fuse, ceramic body with pointy ends, are called "Bosch" type in the automotive world. Quite common in German cars up to the late 70's-early 80's. Renowned for oxidizing between the ends and the holder, causing problems... Nope, I don't miss'em!

Kjelle

Offline jcs0001

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #16 on: October 30, 2015, 03:19:27 PM »
Andrew

Interesting project and nicely documented.

John.

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #17 on: October 31, 2015, 09:40:40 AM »
Thanks chaps for the kind words.

That replacement two way fuseholder arrived this morning, so I've fitted it and sorted out one or two other little issues.

I noticed that there was no stopper for the filling orifice for the high pressure water pump - no idea whether it had always been missing or if it's a recent loss, but I made another out of a bit of stainless bar - also no idea what the original design was but I'm sure that this will fit the bill.

I replaced the engine air filter, as I happened to have one in stock, and ordered up an oil filter. When it arrives I'll drain and flush the oil through with a new fill using the old filter, then replace filter and oil again - it only holds 1 litre so no great volume. I'll also drain and refill the high pressure water pump oil at the same time.

I've also at some time to replace the fine brass gauze that stops muck entering the diesel pick up pipe. There is a standard Jerry Can built into a holder in the main frame, and it has two 10mm brass pipes dipping in, that were originally protected by a wrapping of gauze soldered on forming a filter. Over the years the ends of the pipes have bashed their way through the  gauze making it useless. I have a bit somewhere and when it turns up I'll effect a repair.

Meanwhile I gave it a good testing blasting away the moss that was growing on the ramp that leads up to my loading dock - it had got so bad that the forklift would sometimes slide down with locked wheels!

I burnt about 10 litres of diesel in 2 hours - I was 'steaming' rather than just using pressure really just to test the machine. Apparently it generates 390,000 BTU  or 114 kW of heat  :bugeye:
Andrew Mawson
East Sussex

Offline Spurry

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #18 on: October 31, 2015, 01:10:55 PM »
Yet another superb job  :thumbup:
Pete

Offline sparky961

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #19 on: October 31, 2015, 01:52:22 PM »
Gotta say, I'm a bit jealous of your troubleshooting prowess.  I have a lot of the knowledge required to figure out problems like that but end up frustrated at the lack of information usually available.  I've also made mistaken educated guesses in the past as to how many volts to apply to what and where, resulting in the release of the "magic smoke".

Sounds like you have a very robust unit there, and under your care it will likely outlast you.  Nice to see that some things are still made to be fixed and to last.

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #20 on: November 04, 2015, 10:55:02 AM »
The secret Sparky is to spend a life time with not quite enough finances to do what you want without doing it yourself - they say that necessity is the mother of invention  :lol:

Now having this machine reliably working again is proving SO useful - I've just started working on my ancient Thwaites 2 ton swivel dumper. I've had it  nine years, and even when I got it the forward cylinder has been reluctant to fire up when cold. In all that time it's never come to the top of the list to be worked on, but now it's got so bad something has to be done.

It's a Petter PH2 engine with electric start. Years back I've proved diesel is getting to the forward injector, and even swapped the injectors to see if any difference, so I strongly suspect poor compression, either worn bore or burnt valves.

So back to the steam cleaner - I hate working on oily grubby engines (which is probably why I've put this off for so long   :clap: - you could barely see the fins on the front cylinder barrel it was so gunged up - but 3 minutes with the steam cleaner and it's quite nice   :ddb: Mind you it takes paint off as well.
« Last Edit: November 04, 2015, 11:32:50 AM by awemawson »
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #21 on: November 04, 2015, 11:31:18 AM »
The other day the new oil filter arrived for the Steam Cleaner, so I flushed it with new oil - twice actually as a lot a gunge came out, then drained it again and refilled with clean oil and the new filter. I also drained and re-filled the high pressure water pump as it takes the same oil, and re-greased it's sliding bits. So it's now had a full in depth service which is re-assuring for it's future longevity.

The steam hose is rather cumbersome to wrap up after use - it's 3/8" bore two wire DN10 hydraulic hose rated at 490 BAR and 150 deg C with an outer diameter of 3/4", so although it bends OK, it doesn't twist at all and fights you when trying to coil it. So I've decided to make a reel for it, and fit quick release fittings on the ends, which will also act as swivels.

Proper high pressure high temperature steam reels are available, but at enormous expense - over £200 for one whose reel diameter is large enough for the minimum bend radius of the hose  :bugeye: so I've bought these redundant fire hose reels off ebay and will modify them - one for the feed water (may not need modifying), one for the high pressure, and the other can be a 'shelf spare'

At £20 each I reckoned that they were worth a punt  :lol:
Andrew Mawson
East Sussex

Offline nrml

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #22 on: November 04, 2015, 03:58:20 PM »
Yet another great thread :thumbup:! The only problem with reading your threads is that I always end up thinking 'I'd like to have one of those..... Would be very handy.' I end up wasting a few hours on ebay before reality eventually kicks in and I realise I couldn't use whatever I was searching for to a fraction of it's potential either for lack of knowledge how to or lack of playtime :hammer:.

The thread that got me sidetracked the most was your wire EDM restoration project. I actually ended up bidding on one before I came to my senses and realised I would spend a few years learning how to use it. Luckily I didn't win it.

Looking forward to your next project.

Offline Pete W.

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #23 on: November 05, 2015, 07:06:20 AM »

SNIP!!

.... so I've bought these redundant fire hose reels off ebay and will modify them - one for the feed water (may not need modifying), one for the high pressure, and the other can be a 'shelf spare'

At £20 each I reckoned that they were worth a punt  :lol:

So, Andrew, all you need now is a spare reel on which to store the redundant fire hose when it's replaced by the steam hose!!!!    :lol:   :lol:   :lol: 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #24 on: November 07, 2015, 10:45:01 AM »
Well I reckon that I now know what happened to the original stopper for the pump oil reservoir - it popped it's cork  :bugeye: I noticed the other day that my nice new stainless stopper had raised until it was resting on the O ring seal. If it had been lighter it would have gone the way of the previous one. Presumably there is back pressure when the pump is running, and the only vent is via the filler.

I ordered a commercial 3/8 BSP filler / breather unit and drilled and tapped my stopper to take it - hopefully now it will remain in place.
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #25 on: April 07, 2020, 04:37:58 AM »
The last few times I've used the Karcher MPDS I've had an annoying water leak from down low, apparently from the water inlet arrangement,  certainly not high pressure as in pumped water. So the unit has been in the workshop for a few weeks waiting for me to get round to finding the problem.

So first thing this morning I at last gave it a good going over, and what did I find - a pin prick hole in a 1/4" male / male elbow. A quick look through the bits box failed to find one so a repair was called for !

A quick clean up in the cabinet grit blaster of course made the hole bigger, and I decided that a nice blob of SIF Bronze brazing rod would cure the problem and if I ended up filling the elbow with bronze it would be easy to drill it out again.

The surface tension of the bronze was in fact sufficient for it not to wick inside, and it's all now back together with Loctite 542 sealant curing as I type - perhaps now it can be evicted from the workshop to gain a bit more space !
Andrew Mawson
East Sussex

Offline Sea.dog

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #26 on: April 07, 2020, 05:57:22 AM »
I'm not sure I'd call that a pin-prick.

The elbow has definitely seen better days judging by the thread on one side  :D

Offline AdeV

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #27 on: April 08, 2020, 03:54:31 AM »
I'm not sure I'd call that a pin-prick.

Exactly what I was going to say!  :lol:

Makes you wonder - why do they make plumbing parts out of stuff that goes rusty in contact with water?  :loco:
Cheers!
Ade.
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Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #28 on: April 08, 2020, 06:57:09 AM »
In fairness it was probably galvanised when installed - but that was quite possibly 40 years ago !

This unit is a survivor from the early Cold War when 'limited battlefield nuclear weapons' were in vogue, and was intended to decontaminate vehicles in the field.

So it was probably retired from active service around 1980 but made quite a while before then.

But you are right - bronze would have been a better choice.
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #29 on: April 08, 2020, 06:59:16 AM »
I'm not sure I'd call that a pin-prick.

The elbow has definitely seen better days judging by the thread on one side  :D

It got bigger as I poked it  :clap:

Andrew Mawson
East Sussex

Offline aeromad11

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #30 on: August 20, 2021, 01:55:45 PM »
Thanks for the great pics and info on the Karcher MPDS! I recently picked up an LMDS which is very similar to the MPDS. I am having similar issues with the burner and ignitor.
 Due to congestion in the control panel, I am looking for a  user/parts/service manual to make troubleshooting easier. I did see the training pdf which was very helpful but doesn't quite answer all of my questions. One question I had was in reference to the knob on the flow /pressure safety block, I'm not quite sure what the function of the knob is. Possibly a lockout when pulled and a bypass when pushed? Do you by any chance have any manuals? If so, could you share or refer me to a source? Thanks in advance.

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #31 on: August 20, 2021, 05:12:01 PM »
All the documentation that I have is attached to the first post in this thread, and I donít think mine has the knob that you are referring to.

Can you please post a few detailed photos of your unit?


Thanks
Andrew Mawson
East Sussex

Offline aeromad11

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #32 on: August 21, 2021, 07:46:41 AM »
I will upload some pics later today. The safety block I was referring to is the same as the valve in your pic  "Water-Flow-Sensor-Housing.jpg". It has a pull-up position that latches, and a push-in position that is momentary.
   I spoke with Karcher and they are trying to get me technical 
manuals. Thanks

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #33 on: December 12, 2021, 11:27:16 AM »
I recently wanted to bring the Karcher out of storage to steam off the considerable hard grease build up on my newly acquired JCB 3CX. I knew it needed a new battery but also that there was a pressure feedback issue from the HP side back to the feed water so it would need a bit of fettling.

After jumping through a whole load of hoops to extract the battery and fit a replacement (covered on the JCB thread here, post #82 https://www.madmodder.net/index.php/topic,13429.75.html) and coming then to the back feeding issue I realised that the pump needed a full strip down and rebuild.

First issue was access - all the bits are at floor level - solved by putting it on the forks of the JCB and raising to a convenient height.

I could then start removing bits to examine the water valves. It's a twin cylinder pump, each having an inlet and exhaust valve but with some complicated plumbing between them to form other functions.

The valve are a plain flat disks pressed onto raised seats by a weak spring, the seats appear to be stainless steel inserts pressed into the brass casting.


So lets start pulling it apart . . . .
« Last Edit: December 12, 2021, 12:12:51 PM by awemawson »
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #34 on: December 12, 2021, 12:00:21 PM »
Now looking at the valve seats it was obvious that they need some form of re-finishing. I went through several ideas - perhaps a custom HSS cutter hand driven - maybe a spigot of suitable size with silicon carbide paper glued on - maybe a standard 'spot face cutter' ?

All these ways of doing it would leave debris in the pump bore that would be pretty impossible to remove, so I discounted them all in favour of a total strip down so that proper cleaning could be applied as the final stage before re-assembly.

So today the strip down began. The construction really only allows the brass casting that comprises the bore and valves to be withdrawn leaving the pistons attached to the crank, crank case and electric clutch unit. Not sure how easy it's going to be to get the pistons back in those bores. No rings, just VERY precise fits, with packing glands to keep the water and grease inside.

Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #35 on: December 12, 2021, 12:10:53 PM »
I then decided to give the casting a thorough de-grease, using Toluene (as I happen to have a few gallons of it)

It was at this stage I discovered two things:

A/ Toluene dissolves the paint - no big issue - happy to lose  the paint.

B/ More seriously - the bores of the cylinders are not machined brass as I had thought, but are brass at the outer end with a very thick sleeve of some composite material for the majority of their length.

Quickly stopping the use of the toluene in case it affects this composite material adversely, I had intended to blow off the casting with compressed air . . .

. . . oh no chum . . .your compressor has packed up  :bang:

It was at this point I decided to call it a day - I do have a reserve compressor that I can bring into service but really DIDN'T want the distraction !
Andrew Mawson
East Sussex

Offline philf

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #36 on: December 12, 2021, 05:32:00 PM »
I had intended to blow off the casting with compressed air . . .

. . . oh no chum . . .your compressor has packed up  :bang:

It was at this point I decided to call it a day - I do have a reserve compressor that I can bring into service but really DIDN'T want the distraction !

"There's a hole in my bucket dear Liza"
Phil Fern
Location: Marple, Cheshire

Offline modeng200023

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #37 on: December 13, 2021, 03:09:51 AM »
It couldn't happen to a nicer person!! Perhaps you should use your 'spare time' to write a book about your experiences with your collection of equipment going wrong just when you need it.
John

Offline RussellT

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #38 on: December 13, 2021, 05:46:00 AM »
Now looking at the valve seats it was obvious that they need some form of re-finishing. I went through several ideas - perhaps a custom HSS cutter hand driven - maybe a spigot of suitable size with silicon carbide paper glued on - maybe a standard 'spot face cutter' ?

Tap reseating tool?

equipment going wrong just when you need it.

Yes, I find that stuff seldom goes wrong when it's sitting on the shelf. :D

Russell

Common sense is unfortunately not as common as its name suggests.

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #39 on: December 13, 2021, 06:29:21 AM »
Your'e right there Russell!

So first thing I gave the Hydrovane another chance, but no it wasn't having it. Pumps up to about 50 PSI then struggles to get any further. So the reserve Hydrovane was brought out to play. First one is single phase, second one is 3 phase, but both have been connected previously where the compressors live (my Portakabin) so the wiring and plumbing was straightforward. Reserve plumbed in, plugged in, powered up, and brought my compressed air network rapidly to the 100 psi that it's regulated at.

OK time to go searching spot face cutters. (I knew that I had a box of them stored unused for years), and sure enough not only did I find them, but measurement show that they were tolerably flat across the cutting edges and  there was one of just about exactly the right 20 mm diameter. But there were no arbors. OK have to make an arbor, but it would be an oddity, as the drive is 8 mm square with rounded corners, but I'd need to make a guide bush to ride in the 14 mm through bore of the valve to keep concentricity.

I think I've come to the conclusion that I may as well turn up an arbor to take washer shaped discs of silicon carbide paper that has a spigot smaller than the 14 mm through bore but riding is a 14 mm bush in that bore. This way the cutting isn't taking place at the edge of the paper but in the middle. Also depending on how hard the valve seats are I can make as many silicon carbide washers as I like (I have a 'washer punch' that cuts i/d and o/d simultaneously dependant on which punches you assemble)

. . . enough excitement . . coffee time . . . :coffee:

Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #40 on: December 13, 2021, 11:06:36 AM »
This afternoon, having first performed a bubble / leak detector test on the mornings air plumbing (all OK  :thumbup:) I started on the valve grinding / lapping / recutting gizmo.

First I tested that cutting silicon carbide paper with the washer maker was practical - it is ! My 20 mm washer cutter is producing 21 mm washers so I had to go down a size.

Then I turned a 20 mm bar end down to 19 mm to clear the threads on the valve block, with a 6 mm spigot to locate the washer of  wet and dry paper. I drilled and tapped the spigot M4, and made a 14 mm o/d 6mm i/d collar that slid onto the spigot to pinch the silicon carbide paper, and also form the guide bush in the through bore for the valves. This bush is retained by a cap socket screw and washer.

First tentative tests show that it seems to work quite well but I've run out of time and now need to do other things. The results in the picture are literally 5 turns of the tool lightly pressing it into place by hand.
Andrew Mawson
East Sussex

Offline tom osselton

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #41 on: December 13, 2021, 03:10:59 PM »
Not bad!

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #42 on: December 14, 2021, 10:30:32 AM »
This morning I had a lapping session - firstly on the four valve seats that are fixed in the pump casting. They have come out OK'ish but there is still pitting apparent. I may have  a further go at them tomorrow if I wake up full of enthusiasm !

Then I moved on to the disk valve face seals that press onto the valve seats by way of a weak spring. The first water inlet valve did have a distinctive shaped bit worn out of it which took quite a bit of work to bring up to a fair surface, but the other three weren't too bad - minor pitting.

There is a ball valve built into the casting of the pump, that apparently returns the output of one cylinder to the input side to halve the pumped volume when producing dry steam - I assume that the boiler cannot cope vaporising the full 1450 litres per hour that the pump produces and this seemingly reduces the flow to 740 litres per hour. Burner output is 420,000 kJ so some mathematically gifted person can no doubt confirm that!

I could find absolutely no way of removing the ball element, which has one quadrant as a plain sphere, two quadrants with a through drilling at 90 degrees the 4th quadrant being apparently not involved. This of course could be another path by which high pressure water is playing havoc with the input, so I wanted to examine the valve seat - sadly not possible.

I've decided to remove and blank off the twiddly bits that allow sucking in of chemical agents, and dosing with softening chemicals for the time being, I can easily add them back if and when I find I've solved the problem that I'm chasing and I don't want the complications that they add to the party.

Going through all my documentation for the hundredth time I've come across a drawing that implies that the pump may actually be a 'displacement pump'. This means no super tight cylinder fits, just tight packing to keep the water in. This technique is sometimes used with single acting hydraulic cylinders where the rod acts as the piston and the oil just displaces it.

I am fairly sure that the hydraulic accumulator that cushions pump pulses needs re-charging but I have no idea how to test it. The system operates (in theory) at 60 bar - does this mean that the compressed nitrogen in the accumulator should be at 60 bar ? If anyone is skilled in this direction please shout out.


Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #43 on: December 15, 2021, 06:14:16 AM »
I did in fact sneak out again last night and have another go at the valve seats - they are not perfect but will have to do - I'll see if they give issues when re-commissioning.

It occurred to me that it would be sensible to test the safety blow off valve before putting everything back together, so I rigged up my 'PRC1' test pump that goes up to 60 bar. Oops - the valve doesn't open at any pressure that I can give it - actually a bit more than 60 Bar according to the gauge  :bugeye:

So I dismantled it for examination. It's a fairly conventional spring loaded face seal valve that probably would work very nicely were it not totally encrusted in lime scale. Now the book says that the safety or Pressure Relief valve should blow a bit when the pump starts - obviously it hasn't been doing this - is THIS our smoking gun ?

So a good soaking in citric acid and a clean up later it was restored to better health. I've set it to a conservative 40 Bar as it can easily be adjusted when things are back together and running.

I will also test the pressure switch that disconnects the electric clutch driving the pump before powering up. As I mentioned in an earlier posting I've never been happy that it's trigger point is correctly set, and with the PRC1 (which I'd forgotten that I had !!!) I can test it, but a job for another day.
Andrew Mawson
East Sussex

Offline hermetic

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #44 on: December 16, 2021, 04:46:51 AM »
after all this tension build up, only a video of you in a Santa outfit cleaning the JCB with the steam cleaner is going to assuage the yearning! I look forward to it!
Phil
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #45 on: December 16, 2021, 07:25:33 AM »
Don't hold to many hopes Phil !

This morning I set up to check the pressure switch that controls the stopping and starting of the pump via an electric clutch.

AS I think that I mentioned before this has given me trouble in the past. A vertical threaded rod is one end of a piston exposed to water pressure, and it carries a 'spool' that rises up and down with changing water pressure. Into the space in the centre of the spool is the operating leaf of a microswitch. But this isn't 'just' a microswitch in the ordinary sense, it has two stable states. Flick the leaf upwards and it toggles into the off state, and flick it downwards and it changes to the on state to start the pump.

When I got the machine the spool was broken, and actually consisted of two 'top hat nylon washers' of the type often used to insulate things passing through panels. This almost certainly wasn't original, and it's been guesswork getting the design of one right. The set point can easily be adjusted by nuts above and below the spool, bit it always seems that if the high pressure limit is set right it fails to turn back on when the pressure drops.

Today I've made yet another spool of slightly narrower centre section and although it is working it's upper pressure is somewhat lower than i'd intended -  but it is switching reasonably reliably so good during the pump recommissioning phase so I'll leave it as it is for now.

To connect the test pump I needed to adapt from 1/2" BSP to the karcher pipes of 18mm x 1.5mm pitch and the only thing that I had to hand was the pressure relief valve, so it got pressed into service !

Next step - reassemble the pump!

Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #46 on: December 16, 2021, 10:46:48 AM »
So - how did it go?

Well, like the Curates Egg, it's 'good in parts'

Putting it back together I was concerned that lining up the two pistons and bores might have been an issue, so initially I put the packing glands on the pistons to leave less to align. This was a mistake! Once I put the pump casting back on it's studs it proved impossible to start the threads that pull the packing glands into the cylinders. So the pump casting had to be removed, glands loosely screwed in, then the casting put back and bolted to the crankcase. After that it was just a case of putting all the gubbins back on facing in the right directions!

Starting up, the engine leapt into life, and the pump started pumping - no high pressure back feed to the water inlet, so that at least is cured. However the pressure switch is again playing up. It started switching the clutch off at about 15 bar - I did tweak the spool nuts but I couldn't get it to be consistent in where it switched off the clutch.

Pump is producing pressure up to whatever I set the relief valve to (yes I tweaked that as well!) it's just that bally pressure switch  :bang:

The hot water side is working, producing boiling water with no problem - the flame failure circuit is a bit iffy - probably needs the window on its cadmium sulphide cell cleaning.

I am very tempted to design a replacement pressure switch arrangement if I can find anything suitable - stuff in this pressure range tends to get a bit pricey. I suspect that the current piston mechanism and it's seals are perhaps getting a bit tired and not responding as fast as they should. Remember, it's always been temperamental.
 
Andrew Mawson
East Sussex

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #47 on: December 18, 2021, 06:45:44 AM »
I have tracked down a 60 bar adjustable pressure switch - actually 0 - 220 bar - (eBay £15) which has a 1/4 BSPT male thread so my intention today was to remove the original pressure switch from its mounting flange, and make up a matching thick flange and gasket to mount the new switch.

. . . best laid plans of men and mice . . . ! Having removed the original switch it became apparent that it's mounting flange would leave far too narrow a 'land' to satisfactorily seal against 900 psi. The original switch seals not by the flange but by a series of O rings in its bore. Rather than commit myself to endless blown gaskets another solution was needed - a bit of lateral thinking called for.

Well, it matters not a jot WHERE in the pressure system the switch lives - were I to re-install the original to 'seal the hole' and find a suitable pipe joint to insert an adaptor then all will be well with the world . . maybe !

It turns out that the flexible hydraulic hose feeding the original switch housing has enough room round it to be a suitable candidate, and this means that the wiring should even just about reach.

So the hunt is on for an M18 x 1.5 mm pitch Male / Female cone tee fitting with a 1/4"BSPT female branch. I very much doubt that they exist but I'm sure something can be made !

(amusingly I noticed that the cast body of the original pressure switch has it's alloy composition cast into it!)


« Last Edit: December 18, 2021, 08:09:56 AM by awemawson »
Andrew Mawson
East Sussex

Offline vintageandclassicrepairs

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #48 on: December 19, 2021, 05:09:09 PM »
Hi Andrew,
Time to make some more swarf  :dremel:

John

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #49 on: December 20, 2021, 03:20:50 AM »
Iím waiting on delivery of the pressure switch which probably wonít be until after Christmas now John.
Andrew Mawson
East Sussex

Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #50 on: January 18, 2022, 09:22:14 AM »
Things have gone rather quiet on this repair until recently.

The pressure switch that I ordered failed to arrive. Tracking information said that it had been 'damaged in transit' but I didn't receive that information for a very long time. The seller did the decent thing and posted me a replacement that arrived in the New Year. But I found that unlike the description it was NOT a normally closed contact that opens on pressure rise (thus disengaging the electric clutch) but a normally open one.

Searching the web I failed to find an adjustable pressure switch centred on 60 BAR / 900 psi, suitable for water and at a reasonable price, so I decided that the obvious thing to do is insert a relay to reverse the sense of the switch.

To this end I ordered up a standard 12 volt car type relay and socket.

Meanwhile I had already made up an adaptor for the plumbing that actually proved to be far simpler than I'd imagined. The hose fittings on the Karcher are threaded 18 mm x 1.5 mm pitch (spark plug thread!!) and eBay provided me with male to male 1/2" BSP to 18 mm x 1.5 mm male adaptor fittings with a 60 degree cone. This allowed me to assemble a 1/2" BSP brass Tee fitting with the adaptors in the straight through positions and the branch on the Tee adapted with a 1/2" Hex blanking plug that I drilled and taped 1/8" BSPT to suit the pressure switch. I've sealed all the threads with Loctite hydraulic thread sealant.

Yesterday the relay and it's socket arrived so time to get serious, but frankly it's so bally cold outside it's really not sensible to be playing with water so it's going to have to wait a bit longer !

Andrew Mawson
East Sussex

Offline vtsteam

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #51 on: January 18, 2022, 12:12:44 PM »
Yes the cold.......!  Gettiing a relay to reverse the pressure switch's NO to NC is just the sort of cob I would do!  :thumbup:
I love it when a Plan B comes together!
Steve
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Offline WeldingRod

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #52 on: January 24, 2022, 04:17:04 PM »
At least you resisted the urge to open it up and change the internals ;-)

Sent from my SM-G715A using Tapatalk


Offline awemawson

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Re: Steam Cleaner. Re-Birth of a Karcher MPDS
« Reply #53 on: January 24, 2022, 04:49:42 PM »
Iíve fitted the new pressure switch and managed to house the relay in the main control box AND by carefully pulling the cable from the original switch through the corrugated trunking and coiling it up in the box have left it so that reverting to the original configuration is pretty easy should someone want to do so.

It turned out that it was not possible to fit the new switch where I had intended. The Tee fitting needed to be rotated to screw into the original casting and there wasnít room so Iíve relocated it to the pressure manifold on the pump itself.

Switch and relay work just as they should, and adjusting the set point is just a case of twiddling an Allen key in the switch.

So itís all back together and working. For what I need itís rather overkill and I have my eye open for what may turn up. Sadly most steam cleaners seem to be very plastic and not very durable.
Andrew Mawson
East Sussex