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  1. #41
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    Quote Originally Posted by JST View Post
    The horsehockey ain't where you think it is.....

    That 85% is perfectly possible. What you have is an effect of improving the power factor of the motor. Motors at full load can get to 0.6 to 0.7 PF without trouble. That leaves a considerable range for improvement.
    Yazz.. "in theory". And you can usually accomplish as much of it as is worth the bother of chasing at all with less than $25 worth of PF correction capacitance, bought wisely too.

    Except that it is only at its best behaviour in a narrow range of operation.

    It isn't that the Ronk goods violate any Laws of Physics.

    It's the economics as fit but a rather narrow niche, even that not perfectly, and for the size and type of load the OP has?

    Probably "nowhere even CLOSE".

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    Ja, it is the long way around the barn, in some ways. For a constant load pump motor a half mile from anywhere out in a field, it's a very decent solution, though.

    A BFH is not a solution to a stuck jam jar lid either, but that does not make it universally useless.

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    Quote Originally Posted by JST View Post
    Ja, it is the long way around the barn, in some ways. For a constant load pump motor a half mile from anywhere out in a field, it's a very decent solution, though.
    So is a single-phase motor if the service is single-phase. Hardly any shortage of them.

    I mean - it is an ignorant PUMP, not an ancient steam railway system synchronous master time clock nor a polyphase warship gun-turret director.

    Same again with filling SCUBA bottles.

    They don't know or care their compressor used a motor that matched the available utility service - or one that did NOT match kludged to run with several thousand dollars worth of third-party "converter".

    A BFH is not a solution to a stuck jam jar lid either, but that does not make it universally useless.
    But THIS case is not even BFBI vs "finesse".

    It is obstinately trying to bend a problem into a solution when the choice was wrong for the tasking from the outset.

    All this kit does is make an existing mistake into a more complicated and expensive mistake.

    Brand-new 15 HP single-phase motors are about a thousand bucks and up. I'd oversize it if it were my rice-bowl.

    I'd also reduce the outlay by peddling the surplus 15 HP 3-Phase motor. Should make some wiser Pilgrim a right decent RPC idler!



    What d'you suppose a for-sure 15 HP capable Ronk static converter that can for-sure manage a compresser's usual curse - VERY frequent starting loads, year-in, year-out - sells for? And how kindly can a "static" of any race treat a motor in such service?

    A spend at multiple the price of a better choice of motor might be the case?

    Why wuddja?

    Turn one bad judgement call into a second, compounded, error by classing it as a "technical issue" and pissing money in its general direction?

    The only "physics" that have a chance at alleviating poor judgment are more recently called "laxatives".

    Even if the partaker learneth NOT, he's at least a tad less full of complicated s**t!


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    Quote Originally Posted by thermite View Post
    So is a single-phase motor if the service is single-phase. Hardly any shortage of them.

    I mean - it is an ignorant PUMP, not an ancient steam railway system synchronous master time clock nor a polyphase warship gun-turret director.

    Same again with filling SCUBA bottles.

    ......
    50HP single phase irrigation pump motors can be a bit thin on the ground...... Baldor stocks up to 15 HP......

    I mean, YOU can GET them, but........

    Large Horsepower Single Phase Motors Up to 100 Horsepower!

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    Quote Originally Posted by JST View Post
    50HP single phase irrigation pump motors can be a bit thin on the ground...... Baldor stocks up to 15 HP......
    Baldor ain't ABB's only motor brand. ABB ain't the world's only motor-maker.

    But how did we go from 15 HP to 50 HP anyway?

    You itching to try a static converter on fifty hoss?

    Good luck with that!

    Last edited by thermite; 03-25-2020 at 06:46 AM.

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    Quote Originally Posted by JST View Post
    The horsehockey ain't where you think it is.....

    That 85% is perfectly possible. What you have is an effect of improving the power factor of the motor. Motors at full load can get to 0.6 to 0.7 PF without trouble. That leaves a considerable range for improvement.

    Stepping aside slightly, a "PFC" motor (which is an induction type not too different from a standard induction motor), can have its start/run capacitor selected by trying several and choosing the one that provides the least input current under load. They can approach a PF of 1.0 under load, with the right capacitor.

    The motor with the add-a-phase or similar can also get nicely up in PF, and that is where that 85% of normal current comes into the picture. I'd not expect a PF of 1.0, but it can be better than 0.7.

    You are of course correct that the "in-phase" current, the current corresponding to power, has to be there. The trick is that the out-of-phase current is reduced, which reduces the total current input.
    Yup, and the synchronous motors can be purchased with .8 or 1.0 PFC as well.
    I read that these (the 1.0 version) are used on constant large loads like blowers (in steel mills) to make power for the fan, but to also correct the power factor of the entire plant.

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    Quote Originally Posted by digger doug View Post
    Yup, and the synchronous motors can be purchased with .8 or 1.0 PFC as well.
    I read that these (the 1.0 version) are used on constant large loads like blowers (in steel mills) to make power for the fan, but to also correct the power factor of the entire plant.
    Assuredly. And they "rotate" do they not?

    Cheatin' izzat?

    Poor iggerant souls don't even know about Ronk?


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    You don't even need to buy them with a particular power factor, synchronous motors can have the PF adjusted by changing the excitation, the current in the field coils.

    But that is a different issue. Not exactly the market the Add-a-phase was made to handle. (and, the Add-a-Phase is not your uncle Billy's static converter, either)

    Thermite is correct that it would be a lot simpler to use a single phase motor FOR THAT PARTICULAR SCUBA PUMP. Tha 15 HP is available, perhaps not cheaply, but then, the fancy-ass transformer based converter is not cheap either. Nor small and light.

    The idea of running the pump with a lowish cost static converter box, and changing the pulley to reduce the load has a lot to recommend it. That seems like the simplest way to deal with it, actually.

    If it is super important to get the faster fill from full power, then pop for a single phase motor and be done with it.

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    Quote Originally Posted by JST View Post
    You don't even need to buy them with a particular power factor, synchronous motors can have the PF adjusted by changing the excitation, the current in the field coils.

    But that is a different issue. Not exactly the market the Add-a-phase was made to handle. (and, the Add-a-Phase is not your uncle Billy's static converter, either)

    Thermite is correct that it would be a lot simpler to use a single phase motor FOR THAT PARTICULAR SCUBA PUMP. Tha 15 HP is available, perhaps not cheaply, but then, the fancy-ass transformer based converter is not cheap either. Nor small and light.

    The idea of running the pump with a lowish cost static converter box, and changing the pulley to reduce the load has a lot to recommend it. That seems like the simplest way to deal with it, actually.

    If it is super important to get the faster fill from full power, then pop for a single phase motor and be done with it.
    Just remember the inrush current on this will be sizeable. I bare minium for 15 hp at 240 volts would be around a 60 amp service for it. If the
    compressor is hard starting I think 100 amp service would not be out of line.

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    Quote Originally Posted by JST View Post
    If it is super important to get the faster fill from full power, then pop for a single phase motor and be done with it.
    Or put a 20 hp 3 phase motor on it, derating it 75% gives you the full 15 hp.

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    Many ways to skin that octopus.

    If using the pulley trick, make sure the lube will still be OK. That size may be pumped lube, splash lube may not work as well at a slower speed.

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    Quote Originally Posted by JST View Post
    (..the Add-a-Phase is not your uncle Billy's static converter, either)
    Surely. Nor priced like one. Hence the puzzlement over why not an RPC or single-phase - if only on lower cost.

    If it is super important to get the faster fill from full power, then pop for a single phase motor and be done with it.
    "Fast" fill is seldom an easy goal on tanks. They heat-up. Bigtime! Yah have to go at a measured pace and/or pause and let them cool. Can't cheaply "rush" the physics on that.

    Usual approach is to manifold a LOT of them, then one or two full-time guys can be steady rotating them on and off the teat, staggered fill.

    That's how yah make USE of a larger compressor to get good thoughput. Mind - it wants a large inventory of tanks. Read "money".

    ISTR the TO&E load was 1500 ea. 7 cu meter O2 cylinders @ around a hundred bucks, each, GI cost, for a field-mobile Oxygen Generating unit, Korean or 'Nam wars. We HAD far more. Those are about double or more a SCUBA tank volume. Also cheaper, AFAIK. Good SCUBA tanks are relatively high-tech compared to welding tanks.

    Compressor at the head end was 100 HP. Final pump, LOX to gas, was only FIVE HP, and we could manifold 20 or so active "pigtails" for cylinder attach at a go, each of two A2 plants, 24 hrs by 6 days a week.

    Even so they finished-up too hot for comfortable touch, what with ambient temps generally around 100 F, daytime, not a whole lot less at night down near sea-level as Long Binh was..

    "One wonders" if the OP even has the tankage inventory and labour force to make best USE of a 15 HP rig?

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    LWs has a manifold appears to be about 25 bottles on each side.

    I noticed the operator using a handheld temp gun, he indicated
    that yes, you've got to watch things.

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    Quote Originally Posted by digger doug View Post
    LWs has a manifold appears to be about 25 bottles on each side.

    I noticed the operator using a handheld temp gun, he indicated
    that yes, you've got to watch things.
    First took command of the 518th I asked my grizzled old Sergeant why the built-in manifold down one whole side of our Acetylene plant was valved-off and had wooden bungs driven into each fitting, sawn off, flush.

    "Every one of these Acetylene plants that has blown-up so far was charging off this side. They never could figure out WHY, so just issued orders to disable it and use the other side, only."

    Our one eventually caught afire from a failed carbide pellet feed hopper valve, but the man who saved it was the only notable injury -all his hair and eyebrows burnt-off when he went right into the fireball with big-old iron-wheeled ex USAF crash krew "purple K" extinguisher .. and a fire axe to bust the thick "sight" glass. Hung a Bronze Star on him for that. Kinda-shudda had a "V" device, but fire wasn't considered a combat hostile.

    The A2 oxygen plants were generally a lot safer.

    Only death I was aware of, an earlier deployment, four years in the Korean War.

    Seems they had sited the plant on gravel (10" concrete pads for our ones.. you'll see why..)

    Over time, spilt lube oil and stray Diesel from the slightly up-hill 100 KVA gen sets that powered the plant had soaked the soil and gravel under the plant.

    A tech was UNDER the 40-foot trailer all this plumbing lived in, blowing-down crude LOX to clear the distillation column for maintenance.

    LOX, boiled at once to relatively high-purity O2 vapour hit the oils, the whole gravel bed detonated like a massive shotgun shell - converting him to a resemblance to needled steak.

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    Evidently LOx spilled on asphalt will detonate quite nicely with very little provocation.

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    Jim, your pm box is full. but maybe that's the way you like it

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    Quote Originally Posted by thermite View Post
    ....
    "Fast" fill is seldom an easy goal on tanks. They heat-up. Bigtime! Yah have to go at a measured pace and/or pause and let them cool. Can't cheaply "rush" the physics on that.
    Usual approach is to manifold a LOT of them, then one or two full-time guys can be steady rotating them on and off the teat, staggered fill.
    That's how yah make USE of a larger compressor to get good thoughput. Mind - it wants a large inventory of tanks. Read "money".

    .........
    Whatever.....

    The OP has the thing, and it does what it does at the full 15 HP. I don't know much about filling scuba tanks and admit it cheerfully.

    But I DO know that with a smaller pulley and slower compressor, it will fill tanks , or do whatever he wants done, slower than as-designed with the full-sized pulley and 3 phase.

    So if the SCFM is important, it's got less if modified that way.

    Simple as that.

    BTW.... did nobody ever put an "intercooler" type device on the filling systems?

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    Quote Originally Posted by JST View Post
    BTW.... did nobody ever put an "intercooler" type device on the filling systems?
    Uhh.. on the "system" of course. 40-ton Worthington reefer as well.

    You thot Jacques Costeau (L'Air Liquide, Paris.. also Saigon.. and Hanoi for the 3 ton per day French plants), or our Air Products 1, 2, and 5 tonners (USAF, DELON-500M) were amateurs? Jacques pioneered SCUBA, BTW. Off the back of money and technology - and skilled staff to do as he asked - of the family industrial gas bizness.



    In 'nam the ambient temps were high so we dug a well and ran water over our air-to-air intercoolers, each of first 3 stages. (50 PSIG, 250 PSIG, 1500 PSIG) The fourth stage - 3600 PSIG - was technically an after-cooler, not an intercooler.

    But on the last few feet of fill system, other end of the distillation process?

    No.

    We were in 100-plus F ambient, the gas off the LOX converter pump was cold - it was when the pressure climbed inside the tank we had to go slow.

    Nothing to gain by chilling the tanks in refrigerated glycol or such as I've used in Wine shops - Australia, IIRC? - to fast-chill Champagne.

    There was only so much O2 coming down the pipe.

    Yah just put more OF the tanks on the teats in parallel and the heat rise rate vs what was being shed back to the air around the tank became manageable.

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    Quote Originally Posted by thermite View Post
    Jacques pioneered SCUBA, BTW. ....
    Not according to my source. He claimed that jacque was a jonny come lately at this stuff. The source
    was the late Oliver Welles, who pioneered cave diving (and SEMs) as a young man. He always said
    cousteu got credit for a lot of things that others did first.

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    Quote Originally Posted by jim rozen View Post
    Not according to my source. He claimed that jacque was a jonny come lately at this stuff. The source
    was the late Oliver Welles, who pioneered cave diving (and SEMs) as a young man. He always said
    cousteu got credit for a lot of things that others did first.
    EVERYTHING has some amount of prior-art. Wikipedia cover it for anyone who didn't know your man, Welles.

    Closest "root" for modern practice was probably set down by Benoît Rouquayrol, then improved around 1864 when he teamed with Auguste Denayrouze.

    Le Prieur's further work, 1920's, was still reliant on a manually-set regulator.

    Cousteau had the "need", knew what was lacking, enlisted a specialist Engineer at L'Aire Liquide to actually sort it out and build it:

    Emile Gagnan - Wikipedia

    The 1942 Cousteau & Gagnan regulator re-engineering was significant in adding automatic demand adjustment, which made "modern" Aqualung/SCUBA development feasible.

    ISTR he said he had borrowed some ideas from a Citroen automobile - the War Two "wood gas" regulator! He explained it rather casually in his book - just the concept and goal - not a lot of detail as to the "how". That was probably because Emile had done the "heavy lifting".


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