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60007 (4498) Sir Nigel Gresley Overhaul

Discussion in 'Steam Traction' started by No.7, Mar 25, 2016.

  1. osprey

    osprey Well-Known Member

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    What a luxurious workshop...
     
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  2. 2392

    2392 Member

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    Looking at 4498's move to Crewe. It's a case of "full circle" as when the A4 Society [or what ever they were called back then] bought the loco, they had her overhauled under contract there.
     
    Last edited: Nov 1, 2021
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  3. guycarr360

    guycarr360 Well-Known Member

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  4. osprey

    osprey Well-Known Member

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  5. guycarr360

    guycarr360 Well-Known Member

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  6. guycarr360

    guycarr360 Well-Known Member

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    Picture here shows the successful pressure test on the last of the three main steam pipes, now signed off, they will be fitted in the smokebox later this week after which the front can be reassembled for the last time before the return to traffic.

    265032191_2178654378940777_569734370383530443_n.jpg
     
  7. osprey

    osprey Well-Known Member

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    Thanks for the update much appreciated...
     
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  8. guycarr360

    guycarr360 Well-Known Member

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  9. mike1522

    mike1522 Long Time Member Friend

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    Thanks for sharing. 2022 should be good!
     
  10. Mandator

    Mandator Part of the furniture

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    Wouldn't want to be the person wear the orange hi-vis if the pipe blew!

    Sent from my SM-J330FN using Tapatalk
     
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  11. Richard Roper

    Richard Roper Well-Known Member

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    I was thinking exactly the same thing...

    Richard.
     
  12. Enterprise

    Enterprise Part of the furniture

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    It's not a steam test.
     
  13. osprey

    osprey Well-Known Member

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    An hydraulic test ..it seems to me? A hydraulic pipe burst can still cause death..
     
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  14. Steve

    Steve Resident of Nat Pres Friend

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    There should be no air trapped in the pipes so very little energy and very little water ejected, if any. That’s the whole purpose of a hydraulic test; it should be safe.
     
  15. guycarr360

    guycarr360 Well-Known Member

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    I am quite sure these guys know what they are doing, and if any danger or problems could ensue, the pipes would be taken to a "expert", for testing and certification. With LSL's help, they have excellent workshop and backup facilities, part of the reason for the move.
     
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  16. osprey

    osprey Well-Known Member

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    You seem to be confusing the issue. An air lock which I think are referring too, you seem to state that it affects the energy?
     
  17. Jamessquared

    Jamessquared Nat Pres stalwart

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    Yes. AIUI, in the limiting cases at either end: If the system was perfectly full of water with no air at all, then if there was a sudden rupture, the water inside would go from high pressure to ambient with a negligible change on volume, so no real impact or release of energy (released as e.g. a jet of fast-moving water).

    At the other end, if the system was full of air at high pressure with no water, a rupture would be catastrophic as there would be a huge increase in volume as the air pressure went from high to ambient.

    In the middle, with a hydraulic test but with an air lock that has trapped some air, a rupture would still be damaging as the volume of trapped air would expand and either directly vent, or (depending where the rupture was), force out a jet of high pressure water until the pressure had dissipated.

    Tom
     
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  18. 242A1

    242A1 Well-Known Member

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    Liquids are usually thought of as being incompressible. They can be compressed but it takes a great deal of energy and you achieve very little compression so for all intents and purposes they are considered incompressible.

    So with a hydrostatic test the smallest defect has a noticeable effect on the pressure reading, first pit to pass the failure post on a tube for example; this is assuming that the vessel that you are testing can be viewed as being essentially rigid for the purpose of the test. The problem arises when this is not the case.

    Having a 4" or larger SAE300 flanged hose tail launch itself out of an industrial rubber hose while an assembly is under a 30 bar test is not the same as testing a steel main steam pipe. The hose can stretch, the length can extend under test for metres, the bore expands too, the products of some manufacturers are very poor in this regard. Other manufactures can produce a product which is close to indestructible, if you are producing hoses to convey hydrogen cyanide for example, these have a very high safety factor and samples of a batch are destructively tested under independent observation. But sometimes the test pressures reached are so high that the destruction point is not reached and the test is concluded. Just too much pressure trying to escape confinement from a vessel which is not rigid.

    So if your vessel under test can be viewed as rigid you should be safe with an elastic vessel you need to be more careful.
     
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  19. Steve

    Steve Resident of Nat Pres Friend

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    I don't think I'm confused. I've carried out plenty of hydraulic tests in my time. The whole principle is to eliminate the air and reduce the potential energy to a negligible amount. You can tell if there is air in the vessel when you pump it up.
     
  20. osprey

    osprey Well-Known Member

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    Car brakes for instance I get that. I too have carried out hydraulic tests on occasions. Having a gas/air in a system will give you a false impression. No criticism by the way, just observation...I don't consider myself infallible by all means..
     

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