MadModder
Gallery, Projects and General => The Design Shop => Topic started by: bry1975 on May 22, 2011, 07:51:54 AM
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Hi,
Any of you chaps into machining Aluminium and Stainless am looking to build a luxury pressure tester.
Any one interested in the machining work or recommend someone suitable?
Kinda after something like below but much better. :D
Thanks in advance.
Bry.
(http://imageshack.us/m/691/2171/125bartester.jpg)
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Better than $3,250 ? :med:
John S.
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Well yer!
I want my next chamber to be able to test comfortably down to 4,900metres so rated to 550 Bar.
Bry
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Some serious pressure there 8000psi plus the safety factor at least 1 1/2 times.
I would be more concerned with the fittings and fixings made or chosen, what threads and materials.
What sizes are we looking at?
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Hi there,
Yes serious pressure my last chamber was ok to about 330-340Bar the gasket would blow at that pressure bolts stretching.
Yes safety factor is important will want 1.5 minimum and limit the hydraulic pump to 500Bar max.
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How are you going to test to your required 550bar if the pump is limited to 500bar ?
J
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I think by the time you get down to 4,900 metres the last thing you will be doing is looking at your watch.
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That was my reaction, John. 3 miles or so down is definitely Davy Jones's locker. I think Bry works on other people's watches, so seems to have been lucky enough to tap into a rich vein of folk with more money than sense!
I'd be tempted toward fraud, sticking with a 330bar chamber and issuing a guarantee that if the watch failed before it reached 4,900 metres, it would be replaced. Claims should be infrequent.
And
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Hi there,
I'd limit the hydraulic pump to 500 or 550Bar as the machine only needs to test down to 4,900metres maximum.
Just thought I'd build a pressure tester at the moment as no one else offers a pressure chamber for testing the Latest Rolex Deepsea marvel of Swiss engineering:-
Great article:-
http://www.allankuefer.com/en-rolex-deep-sea-v-series-review.html
Looks a lovely watch not that I can afford a Rolex these days! :(
(http://www.allankuefer.com/images/rolex-deep-sea-review-02.jpg)
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I have to ask this... what the hell for?... given that he only way this could ever be exposed to pressures even a small fraction of that are on a very very long line?
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:D Because I'm slightly mad etc etc.
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I suspect the reason for the seemingly massive depth is because the "static pressure" a watch is rated to seriously under-rates dynamic pressure? e.g. my Sekonda manual says that a 30 metre "water resistant" watch is basically only safe in a shower - you're not to wear it in the bath, or when swimming. 50 metre resistance means it'll still work in the bath/swimming pool, and 100 metre resistance means you can dive into said swimming pool (but not from the high board) - and scuba diving is out of the question.
Given that sort of scale, if a real diver wanted to wear a watch at 2000ft down, having a 4900 metre rated watch is probably just about right...
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are you saying these are a new watch out? if so WHY would an owner give one to you for reepair do they not have a good warantey I know the likes of tag do and if I get them repaird by a non agent I loose the cover, second what happens if it fails at that presure WHO pays because all you would have is bent metal parts.
Peter
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So basically the rating ie either a lie or a con?... or both? :bugeye:
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:D
IMO most dive watches are over built anyway so a 600m Seiko dive watch would most likely pass 1000metres. 2000ft is only about 600 odd metres, a 1220 Rolex sub would be fine for 600metres depth static or dynamic.
The movement is removed when tested to serious depth, worse thing can happen would be that the glass cracked or the case flooded meaning the case would have to be disassembled dried out and reassembled gaskets changed etc etc.
I thought the machine would be a cool bit of kit to have etc etc.
Most of my work is for watches passed warranty etc etc.
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So basically the rating ie either a lie or a con?... or both? :bugeye:
No, but you could say it was misleading.... a 30 metre watch would presumably pass a 30 metre static test (i.e. using a chamber, like the ones shown on this thread); but if you dived into a swimming pool with it, it's quite possible that the dynamic pressure (i.e. the instant pressure as it hits the water) could be significantly higher than the 30 mtr pressure.
As an example; consider when you drop something. It accelerates at 1G; but when it hits the floor; depending on how much the floor & obect deform, it could be decelerating at a rate in excess of 1000G, which is why so much stuff breaks when you drop it.
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Some people actually say 30m means the watch is tested at 1metres depth for 30mins.
I will google the rating.
Regs
Bry
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According to a Google the record for a free scuba dive is 330 metres or 1,000 odd feet.
After that you are in hard suits so a mickey mouse watch will work.
So one has to ask Why ?
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Yep your correct deepest with a metal suit is something like 701Metres.
It's purely marketing with Rolex and IWCs some of the liquid filled watches can pass way beyond 5,000metres.
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Might have a job for you Bry a 1974 Seiko orange face automatic unworking.
I would certainly look in to the tensile strengths of materials most notably the fixings and bump up the thread size accordingly.
Also have doubts anything off the shelf to connect the pump to would handle it. ie have sheared off the shelf steel 1/8"BSP hydraulic fittings rated at 10000psi at only 6300psi. Even filled with water and pumping in oil, it still goes smack.
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Hi chaps,
With the pump I used in the past the hydraulic hose is very thin like less than 10mm diameter, I will speak to the firms that produce the 10,000psi hand pumps and get advice from them and with regards the chamber fasteners I will be looking at using Grade 12.9 diameter M16 and probably 6 of them for plenty of overbuild.
Bry
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550 bar isn't ridiculously high pressure, but a bolted joint will need some serious pre-load to work well.
Materials - should be fairly strong, but not at the expense of toughness; fatigue is always your worst enemy - Low alloy steels are quite common, also some stainless steels. Soluble oil/water makes a good test fluid - it's kind on pump seals, and has anti-corrosion properties (can smell a bit if left to stand and the bug killers get used up).
Clamps or a threaded barrel are common instead of bolts for the closure at higher pressures, also sealing on the bore rather than the end of the chamber will be more forgiving. There are several detail options. An O ring (with suitable back-up ring) can be made to work, there are other options, though more costly.
Fluid connection - stainless capillary tubing is probably simplest at very high pressures, there are compression fittings available, or it can be brazed.
Standard design formlae aren't used at higher pressures - stresses are nothing like uniform through the vessel wall. There are a few design codes that are applicable. Use a minimum design factor of 2 x MAWP, testing should be to roughly 1.5 x MAWP.
May sound 'soft' but you should draw up an inspection schedule for such a chamber as it sounds like it will be pressure cycled regularly. I haven't looked for viewing ports at that pressure for a hwhile, they should be available in saphire.
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I have thought about having the whole chamber face covered with gasket sheet probably better than just relying on an o ring in a groove.
Thanks David.
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So basically the rating ie either a lie or a con?... or both? :bugeye:
No, but you could say it was misleading.... a 30 metre watch would presumably pass a 30 metre static test (i.e. using a chamber, like the ones shown on this thread); but if you dived into a swimming pool with it, it's quite possible that the dynamic pressure (i.e. the instant pressure as it hits the water) could be significantly higher than the 30 mtr pressure.
As an example; consider when you drop something. It accelerates at 1G; but when it hits the floor; depending on how much the floor & obect deform, it could be decelerating at a rate in excess of 1000G, which is why so much stuff breaks when you drop it.
misleading = lying
if its a divers watch & you cannot dive in it to its rated depth it is not fit for puropse.... so still a con :headbang:
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Conventional gaskets are a big ask at 550 bar. The more gasket area, the tighter the bolts have to be so that pressure in the gasket material remains greater than in the fluid.
O rings can work successfully to a few thousand bar - if the detail of the joint is right (but don't expect to re-use them many times). Typically you need line contact (lens rings, cone rings etc) and a fair bit of pre-load, or some kind of pressure activated seal (Bridgman, O ring, wave ring, Grayloc).
For simplicity, a plug which protrudes into the end of the bore with a groove round it for an O ring and a back-up ring is probably the way to go. Within reason you don't need to worry too much about bolt stretch as the plug can move axially a bit and the O ring will still seal.
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Thanks David,
Some interesting information there.
Bry
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I should also have mentioned - within the EU such a chamber would fall under the scope of the Pressure Equipment Directive.
Fortunately when the working fluid is a liquid that is neither explosive, flammable, toxic nor oxidising; then the chamber would fall into the 'Sound Engineering Practice' catageory as long as
Working pressure < 1000 bar
Working pressure x volume < 10000 bar.litres
(full description is slightly more complex)
It therefore MUST NOT be CE marked, there is no requirement to involve a Notified Body in reviewing the design or inspecting the finished item.
The 'manufacturer' is held liable under the Pressure Equipment Directive, so anybody with any experience of pressure systems would probably want to know the categorisation of the chamber and see some design calculations, or know which code it is design to meet, before they would undertake producing such an item.
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Thanks David.
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Bry - I've asked a company that does a lot of high pressure work about this. The company is Stansted Fluid Power, based in Essex. Their Sales Director is optimistic that they could offer something straightforward that would meet your needs.
To give a quote they'd need to know required internal diameter, if a window is required and any other features needed. It wouldn't be cheap, but they would try to base it on their standard designs of lab pressure chambers, so hopefully very little design effort. It wouldn't have a bolted closure.
For PED purposes they would need to be clear what the working fluid is (simpler if just a liquid, gas over liquid may lead to complication depending on volume).
If you want to follow up, I'll pm the contact details.
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Thanks David.
Probably be to expensive for my pockets but will certainly contact them for advice.
Bry