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Aug 14, 2021 13:16:18 GMT
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I've bought a little old hydrovane compressor, but I don't know much about it. It's a 3R304E according to the label. It's also apparently for dental work but has a tyre inflate on it (a bonus as mines broke!) It's a cool little thing. I can't find any reference at all to it's existence online though. I've found a few pr303e ones though. They seem to be pretty much the same but don't have the little tank on the side and have a different psi rating. They go to 50psi, this goes to 100psi. I assume the tank on the side is just to catch water/oil? The only thing I know about them is they always pump as no receiver and need to be used with tools that constantly bleed a little air, presumably so it's not fighting itself as it has no cut out for when pressure is reached. So, what tools cannot use with it? If I can't use say a normal blow gun, why can't I just set a constant drain on the air outlet somehow? My plan is to strip it, clean it, replace the filters, paint the motor and try and find out what to do about oil for it, how much etc. Does anyone know anything about these? I'd like to be able to use it to inflate tyres, maybe a bit of blow gun action, maybe a little spraying (the 50psi ones were ment for this, or so I've read, so I assume this will cope with painting small tho us with a gravity fed door shut gun?) Will it run a small air polisher? A small die grinder? I never use much air and never run my compressor for more than 10 mins really, but my old compressor is small, VERY noisy and VERY rubbish. I don't really care if I can't do anything other than pump up tyres with it, I just like it.
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Aug 14, 2021 13:31:57 GMT
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Just seen it says 9/9/59 on the little tank on the side! Older than I thought. No mention of binks either, just bullows.
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Aug 14, 2021 13:40:01 GMT
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Would there be any value in trying to add a receiver and cut off switch to this? Maybe from my old knackered cheapo compressor?
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Aug 14, 2021 20:01:29 GMT
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It's apart. It was manky inside! I've stripped and washed it entirely. It's very well made! I thinknill replace all the o rings while I'm in there. It has some thick felt filters that I'm trying to clean out as I've no idea how I'd sort replacements. Other than the o rings there are only 2 gaskets, one paper, one which was very thin sheet plastic. Odd, not sure how I'll replace that. It's thickness critical as it effects end float on the vanes. I'll sort something though. Once I've got the pieces cleaned up I'll show some pics of how it goes together.
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Ritchie
Club Retro Rides Member
Posts: 764
Club RR Member Number: 12
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Old hydrovane compressor Ritchie
@ritchie
Club Retro Rides Member 12
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Thats very cool, you will be able to get a 1/4 or 1/8" NPT PSV with the correct pressure range for this, I'd drill and tap a thread into lid on the small water trap / receiver on the side of it. Then back it right off, and run the compressor, gradually increasing the tension on the PSV until you reach the 100psi. That should work fine. However it would be better if you could install a cutoff switch aswell. Possibly look for a knackered small compressor on ebay and use the parts? The pressure switch would have to be adjustable though, as most compressors will go to around 120-150PSI.
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Aug 15, 2021 16:57:20 GMT
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Thats very cool, you will be able to get a 1/4 or 1/8" NPT PSV with the correct pressure range for this, I'd drill and tap a thread into lid on the small water trap / receiver on the side of it. Then back it right off, and run the compressor, gradually increasing the tension on the PSV until you reach the 100psi. That should work fine. However it would be better if you could install a cutoff switch aswell. Possibly look for a knackered small compressor on ebay and use the parts? The pressure switch would have to be adjustable though, as most compressors will go to around 120-150PSI. A pressure switch is no use without a reservoir. This is designed to run constantly in use. It doesn't store pressure. Ah, hang on, as I'm writing this I just realised, it would just auto switch off when you stop using air and stay on when you are. Not sure if stop starting all the time will be good for it though. I get what the psv would be but what do the letters actually stand for? Pressure ? Valve I guess? Edit. Safety! Of course.
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Last Edit: Aug 15, 2021 17:02:22 GMT by VW
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jimi
Club Retro Rides Member
Posts: 1,777
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Aug 15, 2021 18:50:50 GMT
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Strictly speaking for that application it would be a PRV (Pressure Relief Valve) it wouldn't be unusual for a pressure vessel to have both fitted, PRV to control the system pressure and PSV as a safety device to prevent the pressure going beyond the SWP of the pressure vessel 🤭
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Last Edit: Aug 15, 2021 18:52:18 GMT by jimi
Black is not a colour ! .... Its the absence of colour
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Aug 15, 2021 19:26:50 GMT
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I think, but am unsure, it may have a safety valve somewhere anyway. There are 3 spring loaded valves in this but I'm not sure what they all do. It may make more sense when I put it all back together. I think some control the oil circulation through the filter, pumped by air pressure.
What's the functionality difference between a psv and a prv?, mechanically speaking The psv I've been looking at is just a plunger with a spring that lifts at a certain pressure. Is a prv different?
It only needs a constant bleed, I can always just crack the water trap valve open 😉. At least I'd never have to worry about draining it!
I've been thinking about if it will need a regulator or not too, but they never use them. If I have a bleed valve in the system anyway I can just open that more until only the pressure I want is at the tool.
But I think I'm trying to get it to do things it's not designed for. I'll just use it and see how it goes. It's more just fun and cool than a compressor I'm trying to get to do all I need.
As far as the prv valve goes, can that just be a screw valve you open as much as you want? An adjustable vent to atmosphere. That's easy to do. The gauge on the front will show the psi at the tool as the whole system.is always at the same pressure.
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Last Edit: Aug 15, 2021 19:28:40 GMT by VW
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Aug 15, 2021 19:34:56 GMT
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Found a good explanation of the difference tameson.co.uk/relief-valve-vs-safety-valve.htmlSeems I could use a prv as the regulator then, will let me alter working pressure, provide the constant bleed it needs, and I'll rely on the internal safety valve if it has one. If it doesn't, maybe the badly cracked air line will act as a safety valve instead 😂 Only kidding, if it has no safety valve, I'll fit one. But I'd be surprised if it doesn't have one!
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Aug 15, 2021 19:36:34 GMT
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Right, a psv is £8, prv vary from £100-£800!!!!
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Aug 15, 2021 19:52:12 GMT
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I guess constant bleed air tools just always pass a small amount of air, so any way I introduce a constant leak will be fine. If that leak is adjustable, I can also control pressure at the tool.
Ok, decided, unless anyone has a better idea, I'm just going to make a fitting that takes an old carb air screw with a taper to give adjustable bleeding.
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jimi
Club Retro Rides Member
Posts: 1,777
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Aug 15, 2021 20:27:50 GMT
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Black is not a colour ! .... Its the absence of colour
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Aug 15, 2021 21:00:17 GMT
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jimi
Club Retro Rides Member
Posts: 1,777
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Aug 15, 2021 21:08:22 GMT
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Ooops never noticed that, sorry. Try this one Linky
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Black is not a colour ! .... Its the absence of colour
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Aug 15, 2021 22:15:35 GMT
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Ooops never noticed that, sorry. Try this one LinkyIf it actually bleeds the excess off rather than just restricting flow then yes, that will do. I bet it's just a spring loaded screw valve though, with a gauge. I don't need the gauge. The proper prv's I've been looking at ramp up and down with very controlled rates rather than just opening and bleeding. That's why they are so expensive. I've seen others like than one you link that have 2 knobs, one to set the flow pressure and one as a safety valve too. No one want to actually tell you exactly what they do and how they achieve it though. I have a lathe, maybe making a decent valve would be a nice little project.
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jimi
Club Retro Rides Member
Posts: 1,777
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Aug 15, 2021 22:47:44 GMT
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I have a similar one on my blast cabinet to keep the blast pressure down to 60 psi (my compressor is set to 100 psi) from what I remember it uses springs and a diaphragm to regulate the pressure. I don't remember hearing it bleeding air off, but it certainly supplies enough air at 60psi to run my bead blast cabinet. Mine is a Parker one that I "acquired" from a previous employment.
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Black is not a colour ! .... Its the absence of colour
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Aug 16, 2021 22:41:24 GMT
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Browsing completed listings on ebay and I found this! Same 100psi version as mine, with the same catch tank. Pressure gauge is on the receiver though, but shows this pump is ok being used with a receiver. Or at least devilbiss thought so!
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Aug 20, 2021 10:56:41 GMT
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It's back together. All seals replaced, filters cleaned, fresh oil and a repaint if the motor in crackle black. 're greased the motor bearings too. It runs well. It only made 60psi before blowing off the safety valve. It made 80psi before I took it apart, but was getting noise. The spring on the safety valve looks to have been cut so I spaced it back out untill it cut in at about 85psi. It all seems happy like this. It's perfect for tyres, blow guns, and spraying. It won't run air tools though. I didn't think it would though. I never use any anyway. I'm curious though, so I think I'm going to see if I can adjust the cut if switch on my old noisy sip to work at 80psi, then see what happens if I link this up to a receiver. I think its 25l. I don't think it will really have much benefit but I'll dig it up and see.
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