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Hydrovane 6PU compressor problems.

Retired UK.

Aluminum
Joined
Feb 16, 2012
Location
Fenay Bridge, Huddersfield, UK.
Hi,

Has any member got one of these Hydrovane compressors and had problems with it? I've just bought mine and feel like I've been conned because when I collected it the seller ran it for me and I watched as air pressure came up to around 110 psi in about five seconds which was most impressive; once it reached this pressure the seller opened the air outlet valve fully venting to atmosphere and I was amazed to see the pressure drop to around 85 psi and hold there so I happily handed over £300 cash; this Hydrovane appeared perfect for me and would replace my extremely noisy 3 hp twin cylinder compressor.

However when I switched the compressor on at home I found if I left the air valve closed the pressure came up correctly to 110 psi then after a few seconds it started to slowly increase until it ran into the red zone on the gauge. I have the correct Hydrovane manual and this states the usual cause of this problem to be the "unloader Valve". I've stripped the valve and initially cleaned the dirty PTFE valve sealing washer and replaced all the associated "O" rings but the problem persisted. I then removed the valve again and made a new valve sealing washer out of Whale Tufnol. The problem still persists so yesterday for the umpteenth time I removed the valve and turned a new valve piston out of meehanite giving tighter tolerances because the original piston is showing signs of wear between valve stem and valve guide bore. Still no luck and it's highly frustrating to watch the pressure gauge needle climb so slowly into the red. I've also serviced the Servo Valve. After ten minutes running the compressor starts to feel quite hot on the vane casing.

After running the compressor for about ten minutes not allowing the pressure to reach the red zone then switching off shortly after oil begins to drip from the bottom flange hole of the motor?

Given the amount of work already carried out on the two valves I think the fault now surely to be elsewhere; although at the moment I feel like I've been mugged I still like this Hydrovane and intend to repair it one way or the other.

Any suggestions please as to what could be wrong with this compressor?

Kind regards, Col.
 
What is downstream of this valve ?

Just a vent ?

is it open and not plugged ?

I just worked on my worthington rotary vane, and the exhaust for the solenoid operated
unloader has a mesh filter/muffler.

Years of oil was in it as a varnish, I used carb cleaner to good effect to wash it.
 
Hi,

Thanks for your reply digger doug which is appreciated. The unloader valve opens directly into the vane unit in fact with the valve removed the vanes can be seen. I also removed and cleaned the Oil return Valve for good measure. After all the work thus far carried out I would expect some kind of result for better or for worse but nothing at all has changed. The manual states that problems with the unloader valve gives symptoms of pressure rising slowly until the safety valve blows and oil and heavy vapour will be blown back through the air intake on stopping the machine? Vapour blows out of the air outlet valve once the compressor has been running for a while. The Servo Valve piston can also stick preventing the unloader valve from closing so I serviced the Servo Valve and it works as it should with its piston nice and free. I gave the compressor an oil change using correct oil and removed the main oil filter to ensure it wasn't blocked.

My Hydrovane is leaking oil from under the motor and this is not mentioned in the manual so I'm wondering if other seals are at fault? I was hoping someone on the forum had suffered the same problem and could state what to look for or what section the fault would be in? I've already spent hours playing around but I think the time has come to pull the compressor apart allowing a full investigation to be carried out? I'm fully retired so can spend more time working on this but it would be nice to know up front what to look out for?

Kind regards, Col.
 
No direct experience with 6PU (run a HV series myself) but these guys are helpful and not silly expensive Air compressor specialist. Sorted out some replacements for obsolete componets on my HV04 very reasonable.

I think the oil reservoir is pressurised to some degree so overpressure will push oil out. May also be a condesation contamination issue if doing short test runs giving th effect of overfilling with oil. Hydrovanes produce a fair bit of condensation when not up to temperature and it pretty much all ends up in the oil. My understanding is that minimum run times on the older types is 15 to 20 minutes to ensure all condensation is driven out.

Got a horrible feeling yours may have been got-at! Must be over 30 years old by now so there has been plenty of opportunity for Bubba & Co to dig in. As I understand it there was a known bodge to the control end of the 6 and 12 PU air ends disabling the proper functioning of the output modulation in lieu of servicing when used in continuous air supply or large reservoir tank applications. The whole point of the output modulation controls being to allow the beast to be used without a tank in intermittant use applications so if you don't need it I guess it makes some sort of sense. A now deceased friend had one that was so operated on and it worked fine for him and the guy he sold it to. No idea what was done as the operation was probably done a couple or three owners previous.

This 1986 paper by Mr M.R.Williams covering the design of the 5 series and the differences between it and the 6 / 12 PU may be of interest, you will need to cut and past in the browser as it doesn't appear to pharse as a link :- docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1568&context=icec . Or search for The Design of a Small Oil-Flooded Rotary Air Compressor, third result down for me.

As it appears to have some useful information on how the control works etc which may not be in the manual.

The most relevant paragraph appears to be:-

"Controls:-
All Hydrovane compressors, past and present, have had modulating control (i.e. variable output) which has enabled them to run continuously irrespective of air demand. The particular system used has consisted of an intake throttling valve and a servo valve to control its position. A vacuum limiting valve has then usually been necessary to prevent vane instability when running with the intake closed. This system of control causes the off load power to be reduced to about 70 % of full load power, and this figure can be reduced further by decompressing the main casing. However in the case of small compressors, any off load power savings are minimal. Also, market predictions showed that the main demand for small compressors was for receiver mounted automatic stop/start units where there need not be an off load mode. There was therefore a good case for eliminating the somewhat complex and expensive reduced-power unloading system although the specification called for modulating control for stand mounted versions."

Also some intresting plots of oil temperature against run time showing how slow the 6 / 12 PU models are at coming up to stable temperature compared to the later 5 series. Nearly 1/2 hour to 80°C against 10 minutes.

Clive
 
Hi,

WOW Clive; many thanks indeed for posting so much useful and interesting information; I've just read the full details in the link "purdue" and it appears I would possibly benefit by running my Hydrovane up to pressure then opening the air valve venting to atmosphere for an hour to see if this has any effect regarding getting rid of all the condensation the compressor is currently expelling in large amounts? My fingers are crossed that doing this will resolve the problem and if it does I've got a lovely compressor as long as I don't run it for short periods of time? The oil leak seems to only occur when the compressor is turned off after I've run the compressor for a short period of no more than 15 minutes?

I'll also do as you suggest and search for the oil flooded compressors you kindly mention; I need to spend time absorbing all this new information but I'm very pleased I posted about my Hydrovane because I'm sure many other owners must be experiencing similar problems totally in ignorance as I was about the amount of condensation generated? I've cleared a couple of benches today expecting to pull my Hydrovane apart but now I'll give it a good run to really warm it up first; once up to pressure I'll open the air valve and let the compressor run venting to the atmosphere to see what happens; I need to to this otherwise the safety valve will be blowing off with possible overloading? I'll report back with an update tomorrow. The guy who sold me the Hydrovane had been using it on a sand blasting cabinet and it was sold as having a very small oil leak; Thanks again Clive for enlightening me.

Kind regards, Col.
 
Hi Col

The search for The Design of a Small Oil-Flooded Rotary Air Compressor is the same paper as in the "purdue" link. Wasn't sure if the cut & paste would work except on Mac Safari, typical Apple it does some unexpected stuff sometimes not always to the good.

I really would talk to the compressor service guys before you go too far. The Hydrovane nearly bulletproof reputation is justly earned, especially if fed clean oil and filters but ultimately they aren't proof against Bubba & Co. They do have their quirks which can drive you nuts if you don't understand how they work or how the unskilled finger poker can derail things. If the previous owner had it on a small sandblaster it probably was getting run for short periods to get round malfunctions on the controller side.

Clive
 
Hi,

Thanks once again Clive; after posting I realized the link had worked and so only opened up the duplicate after entering the search but better both than nothing; lots of information though. I can play around with the Hydrovane tomorrow and first job will be to run it for an extended period to see what happens before taking it further. If the problem persists I'll contact the compressor guys (Air compressor specialists) for help and information. If it comes to it I don't mind rebuilding my Hydrovane because it's performance is vastly superior to the almost new 3hp twin cylinder compressor I bought; this new 3hp compressor drives me mad with the sheer volume of noise it puts out. I don't think my Hydrovane has "been got at" but time will tell. Due to your information I now know to use my smaller SIP compressor for jobs like tyre inflating and use the Hydrovane for bigger jobs where it will reach proper working temperature to avoid the condensation problem?

Kind regards, Col.
 
I have an old Hydrovane 120 cfm unit that was getting oil in the air stream when I bought it. I had the local agents (Compair) service it and replace various O rings, seals etc - total cost $1400 IIRC. That fixed all those issues. The unloader valve on mine works as it should so I'm no help there.

Biggest issue with mine in the end was the previous owner - how often have we heard that! The idiot was a sand blaster so he sand blasted the unit including the gauge faces to a nice frosted finish, which was bad enough, but he also got a lot of crud in the electric motor. One day a chunk of it came loose and there was a big flash/bang as the magic smoke escaped. There goes another $1200 for the rewind of a 25HP motor..... which of course was a very odd frame size so couldn't be simply replaced.

Now it's all clean, shielded to stay that way, and way oversize for my needs as I'm doing little blasting nowadays. I have 2 small compressors I use for the fiddly jobs.

PDW
 
Hi,

Thanks for your reply PDW. Some people should be banned for life from even going near a machine let alone messing around with a machine but I like many others have made lots of silly mistakes during the learning curve so I'd better not throw stones. Your story though is so common; Clive also mentioned that my Hydrovane might have been got at and of course he could be correct. I wonder how many machines worldwide have been stripped by novice owners to end up being scrapped?

I'll run my Hydrovane for an hour this morning just to double check that the fault isn't something like condensation and if the fault persists I'll contact the compressor guys. Typical isn't it that I have this Hydrovane problem and post about it on an American forum to receive a reply kindly suggesting I contact Hydrovane specialists in Derbyshire about 50 miles from home; such is life but I'm grateful for the information and I'll be buying spares from them shortly.

The unloader valve is a critical part of any Hydrovane and although I've done so much work regarding this valve it's possible it still could be at fault? I was thinking about it last night and find it most strange that the unloader valve piston has a flat bottomed straight sided wide groove rather like a piston ring groove but a standard type "O" ring is installed? There could well be a logical reason for this but my engineering background is screaming at me that this groove should be rounded and a much closer fit to the "O" ring? I can't help but think possibly a sleeve type seal should be fitted in this groove? Anyway I'll run the compressor shortly then later today I'll contact the compressor guys in Derbyshire because I doubt running the compressor for an hour will sort out the problem; my guardian angel sadly died many years ago so my luck means I'm in for some work and expense?

Out of interest; this Hydrovane 6PU is a substantial bit of kit; not a big footprint but heavy and solid being manufactured of a time when such machines were made up to a specification not down to a price. It has a top quality Brook motor installed and I should know because I worked at Brook Motor's headquarters here in Huddersfield for 24 years before retirement; being in distribution (No 5 Despatch) I've despatched thousands of motors to Hydrovane in Redditch; unfortunately no Brook Motor is now manufactured here in the UK they are manufactured abroad and shipped in; Brook UK is now simply a distribution for imported motors and I've not been back to the factory since leaving in 2000; what a shame one of our top companies has ended up like this? This Hydrovane at 1.5hp is light years ahead of my much newer 3hp twin cylinder compressor. I bought the 3hp to power a brand new soda/hard media blaster Bron kindly bought me for Christmas which I used to blast a lathe (not the machined ways etc) and also a bandsaw; the 3hp did the job but was deafening and running flat out all the time trying to cope with the demands of the blaster struggling to maintain 30psi; it did the job but was incredibly slow. Now at 1.5hp the Hydrovane vents openly to the atmosphere putting out a constant 80psi and I can stand besides the Hydrovane in comfort not needing ear defenders. There are at least a couple of these 6PU's on eBay and they appear to attract bids up to half what paid for mine but if I can get my Hydrovane sorted I'll not begrudge the money in fact I'll sell the 3hp compressor because I will still have the smaller SIP compressor for light duty. It will all come right in the end but I'm finding it a challenge at the moment.

Kind regards, Col.
 
Im sure theres a local comp air or similar dealer near to you. Hydrovanes need the proper parts and regular servicing. The oils expensive, but its gotta be the right stuff to avoid issues. looked after there great and like you found out nothing like as noisy as a piston lump either!

The only people i know that get issues with them are the ones that don't service them correctly!
 
Hi,

Thanks adama for your reply and totally agree with you. I've just emailed the compressor people in Derbyshire asking for help and advice. I've also asked if this compressor is really suited to my needs and would I possibly be better off trading up to a much newer Hydrovane given the time it takes for my compressor to reach full working temperature; I might be able to trade in my Hydrovane so I await their reply. In the meantime I'll pop into the garage and switch the compressor on and let it run to warm it up.

I bought 5L of Vane 2000 oil rom Cages in Dewsbury who also supplied the o rings; now Clive has kindly informed me of the compressor specialists I don't mind starting over and buying correct parts from them. So far though I would have thought the work thus far carried out would have an impact but it hasn't in the least?

I'm certainly not bored.

An update. I've now run the Hydrovane for well over an hour only to find the air pressure still climbs slowly into the red zone; not really a wasted effort because I've established it isn't over-heating and not dropping oil in use.

One idea has sprung to mind if this job starts to become too silly or expensive. The two concerns are the small oil leak and the air pressure creeping into the red zone at around 150psi? The oil leak is very small and can be easily controlled by keeping a check on the oil level which isn't difficult. The air pressure is more serious because 150psi can prove very dangerous indeed especially if the safety valve doesn't operate. I could add another but remote safety valve but set this valve to blow off at 115 psi; this would allow the compressor to run unstressed whilst still affording full 110 psi which can then be stepped down by a pressure regulator for individual tools? Just an idea and the cost would be minimal with simple installation? Ideally I'll repair the compressor.

Kind regards, Col.
 
Last edited:
Sorry to derail, but very much looking forward to see if you find a solution for your problem. I have a Hydrovane 5 pump myself that awaits to be put into service, bought it used from ebay. Only paid £60 and when it came home I was somehow disappointed. The machine looked like it's been doing 8 hour a day shifts. All gaskets cooked etc. However, I managed to came across a genuine top up kit and when I opened up the machine for overhauling, I was amazed to see the vanes/rotor/stator were absolutely pristine. Now it's all back together, just needs a motor and needless to say I'm anxious to see it running as I've never actually had it on. I hope I won't be coming here with the same issue as you.

In contrast, I also took a chance on a for spare and repair Mattei AC3 (4Kw, c/a 15cfm FAD). It was a 2009 machine, it came to me seized and turned out to be a broken vane wedged (at full speed apparently) right in between the rotor and stator. Complete mess, I figured I needed at least the vanes and another rotor so ended up in my scrap box, but not before firing a few emails to the UK Mattei distributor. The machine was just out of warranty and this was definitely a manufacturing defect. The person I bought it from had a service contract with a compressor specialist in the area (which I've also spoken to), so it definitely wasn't a lack of service. Moreover, it turned out the original pump had been already replaced under warranty 2 years before, which makes this pump only 2 years old! One thing I noticed is the contact surfaces of the stator and vanes weren't anywhere near as smooth overall as my Hydrovane. In the end I gave up as it was probably too much to expect some sort if good will gesture. I'd hate to be the original owner though. Mattei and Hydrovane have a similar price range and I can't speak for the newer Hydrovane but from what I've seen Mattei is definitely not up to its price tag.
 
Hi,

Thanks for your reply Miller13. One thing is becoming clear to me and that is if these Hydrovane's are looked after they simply live forever running 24/7 year in year out. Good luck with your Hydrovane 5 venture and I hope you can get hold of the correct motor at not too high a cost. I'll be interested to learn how you get on with yours in due course. What a sad story though about your Mattei and it's not even got any age on it so it failed quickly; for the first pump to fail was bad enough but a two year old pump to fail begs the question as to how poor your Mattei compressor was in the first place? My Hydrovane is ancient compared to your Mattei but still performing very well; too well in fact I can't keep the air pressure down?

I'm still awaiting reply to my email I sent to Air compressor specialists which I look forward to; I've never been one to bodge so I think the only way forward for me is to do the repair using correct OEM parts; I just hope I don't need to take out a mortgage? It was interesting though this morning having my Hydrovane singing away on the bench for over an hour without it missing a beat doing its job in pushing lots of air out without it rattling the whole bungalow with noise.

I'm pretty sure there must be plenty of other Hydrovane owners wanting a quick cheap fix to get their compressor in order.

Kind regards, Col.
 
Miller13

The 5 or V series use a standard size motor so its not too difficult to find a replacement if you have the dimensions. Guy down my way used to, maybe still does, do single phase conversions to the 501 & 502 models using Teco motors. The aforementioned compressor specialists also do a similar service. If yours is the small air end used on the 501 / 502 it appears that the only specification difference is in motor speed with the 501 running at 1450 rpm for 4.2 cfm at 10 bar whilst the 502 runs at 2850 rpm for 7.9 cfm at 10 bar. Not quite that simple. Although the basic units are the same there are a few other differences and simply over-speeding a stock 501 will shorten the air end life. The small 5 series air ends have no adjustments for wear so its even more important to service them as anything much beyond simple seal or gasket failures are effectively fatal.

Clive
 
For the record whilst i would love a hydrovane there’s just no way i would want to own a second hand one, just too many unknowns. I would not touch the clones either, have never heard of a good one.

As to service, IMHO vane pumps and screws generally show way less wear and tear when they have been in a high demand environment. Its were they never get to temp and the oil gets damp that the problems - wear starts big time!

Some point a hydrovane is on the shopping list though. Currently i ownly have a industrial - clean room grade oil less 1hp compressor. This is not to be confused with your typical big box variety but is of French origin, truly brilliant quiet pump and incredibly clean air, but just not enough for what my true needs are some days. Wil keep it though as zero risk of oil contamination comes in real handy on optical stuff, saves buying nitrogen :-)
 
Hi,

I would always go for a four pole motor rather than a two pole motor where possible Clive; much less stress?

I'd love a new Hydrovane adama but for my limited use it doesn't justify the expense so I'm playing around with my second hand Hydrovane in fact it might have had many owners during it's life to date? There is no doubt that running an Hydrovane continuously is much better for it giving greater reliability rather than many stop starts which just gums up the works. Your 1hp compressor sounds to be top quality but as you say rather small for general duties. My Hydrovane is only 1.5hp but puts out lots of air at a very steady pressure unlike my 3hp piston compressor sitting on a 50L receiver; when the receiver is fully up to pressure it is fine but once demand drops the pressure then the motor works flat out trying to keep up and it usually fails even with a spray gun being used. I've not tried the Hydrovane yet but so far even though it is faulty I like my Hydrovane.

No reply yet to my email which I sent to the Air Compressor Specialists this morning (compressorman) he must be busy?

I'm considering turning my Hydrovane into a restoration project; it would be interesting to find what ails it?

Kind regards, Col.
 
Hi,

Thanks for your reply Miller13. One thing is becoming clear to me and that is if these Hydrovane's are looked after they simply live forever running 24/7 year in year out.

Mine has 27000 hours on its hour meter. The service tech said I should get it serviced - basically an oil & filter change - every 2000 hours, and if looked after, I would likely see 100K hours.

Hah. I doubt I'll use it 2000 hours in the remainder of my lifetime. Nice to know that they're built to last, though. Mine is now right up to scratch so I don't anticipate any further problems. Unless I'm running the blast cabinet, it doesn't get fired up, though. Gets expensive running a 25HP motor even if you're not using the full capacity.

PDW
 
@Col
Well, the sad story is the original owner really. He pretty much had to take the full brunt of the loss. It was sold to me on a 'spares or repairs' basis. It wasn't really my claim to make towards Mattei UK, but I did it with full permission and support of the original owner. It's not all bad though, I've kept all the ancillaries including the 200l tank. The Mattei pump doesn't have an oil radiator like our Hydrovanes, the pump and motor sit inside a 'tunnel' and being cooled by a fan attached to the end of the motor. I can attach same fan to my Hydrovane motor, which will provide extra cooling for the pump.

Original old stock top up kits do come on ebay from time to time and they're usually cheaper than aftermarket ones. Over the last year or so I've seen Compair branded kits for about a dozen models by now.

@Clive
Thank you for the tips, the trouble with these compressors is the motor has to have both feet and B5 flange. Very rarely I have come across second hand motors with both, and the odd Hydrovane branded motor makes some £80 to £100 posted. Not worth it, I have a motor shop near me and can get one brand new for a little more than that.

Mine is a stock 5 air end indeed and I am planning to put a 2800rpm single phase motor in there. What you say troubles me a bit and would very much appreciate if you can elaborate on it. I was speaking to a CompAir technician and he said the first production run had identical air ends for 5 and 15. Afterwards, they modified the oil cooling to the 15 (he didn't get into specifics, perhaps in the form of an extended radiator?). The thing is, I need a minimum of 9-10CFM at 7 bar and I will have to overdrive it, even with running the risk of shortening its life span. Otherwise it's no use to me.
 
Miller13

Was around 5 or 6 years back when I talked to the local (ish) guy who was doing single phase conversions on the 501/502 Hydrovanes so I can't guarantee to recall exactly what was said. He had just retired from a compressor supply and service place and was one of their trained Hydrovane specialists so presumably would have known what he was talking about. I was buying some used control gear to convert a 504 from a dedicated semi computerised control set up (huge box on the side) to normal receiver mount configuration for a friend who'd got it cheap so was more making conversation than being particularly interested in the 501/502 detail differences. Bog standard receiver mount 502 was doing just fine for me.

He said he used Teco motors because they were a decent motor and could supply the flange & foot mount combination off the shelf at a sensible price. He had just done either a 501 or 502 receiver mount conversion and had the other size air end up on the bench waiting to be done. Naturally I said the air ends looked the same so was the only difference between a 501 and 502 motor speed. He said that although a 501 air end would happily run faster it wouldn't last as long as proper 502 air end as there are some other differences. As I recall it he said the proper conversion was perfectly practical but it wasn't worth the effort and not financially viable for him. I presume doing the job properly involves some component changes which add up to more than the selling price difference between a 501 and 502. As I recall things he was selling conversions with a fully overhauled and serviced air end at around £450 to £650.

Of course life reduction has to be taken in context with the expected 100,000 hr "if you look after it" service life. I did look at one "502" which turned out to be a 501 with 2,800 rpm motor. The seller claimed to have been using for a couple of years in full time industrial use. Their story was that they bought the 501 used, needed more air after a couple of years and had a suitable motor about the place for a cheap upgrade. Couple of years down the line they needed still more air and upgraded to a 504. Air tools in fabrication shop mostly. No reason to disbelieve them. Saw a factory 502 for a few pounds less on same trip which I bought.

Clive
 
Hi,

25hp is a big compressor PDW and many of these won't be found in home workshops; it must be excellent though to have 120cfm on hand especially for sand blasting but rather over the top for inflating the odd car tyre? As you say though it should last you out without trouble if given little use but it will still require servicing once a year?

Fortunately you bought your compressor knowing it to be for spares Miller13 so it was a bit of a gamble; sometimes these gambles pay off because many machines are sold by owners who have little knowledge of how they work so a small easy repair could possibly end up with a good machine for little cost? The ancillaries as you say will possibly come in useful and an Hydrovane pump added to your 200L tank would give a nice compressor? My Hydrovane doesn't have an oil cooler installed although the stand appears to be drilled for one? There are lots of service kits on eBay for Hydrovane's but so far not for the 6PU?

I've just been into the garage and switched on the Hydrovane; I was very surprised to watch as the pressure quickly came up to 110 psi and hold there for quite a while; I thought the problem had finally disappeared but then it took around three minutes for the gauge to reach 125 psi? As previously stated I made a new Tufnol unloader valve seat washer and also turned a new unloader valve piston; it might be that these two are settling in and if so then perhaps new OEM valve washer and piston might fully cure the problem? It's frustrating to be so near and yet so far. The oil drip now appears to be coming from one of the big nuts at the base of the pump unit under the motor; I'll have a look at these next; something has changed though because the oil leak was coming out of the motor flange hole before I did anything.

I would like a reliable source of Hydrovane spares because I've still not received a reply to the email I sent yesterday morning; I know the average home workshop guy isn't of much interest to bigger companies who want to sell a new expensive compressor rather than a handful of low cost spares; I can see the merit in this but it doesn't help me; I might as well buy a new Hydrovane through eBay if this is the amount of back up I can expect when I need help and spares?

I'll have a look at the two big nuts this afternoon because so far I haven't touched them and they are easy to access before ripping the compressor apart in fact I'm loathe to take this compressor apart given the spares back up support; for my use I could as stated install a remote blow off valve to control excess air pressure.

Kind regards, Col.
 








 
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