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Testing Gauge glasses

Discussion in 'Locomotive M.I.C.' started by dhic001, Sep 27, 2008.

  1. dhic001

    dhic001 New Member

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    I've been looking at pictures of various locomotive cabs, and I've noticed something that I hadn't come across on a boiler before. Some of the locos, (particularly obvious on a Castle see http://www.brwcomputing.co.uk/images2/5043_cab_pn_v.jpg ) have the two cocks from the boiler linked together with a single lever, with the drain cock being left independant.

    I'm well used to boiler gauge glasses, but always with three independant cocks. My question is, how do you properly test a gauge glass when the two cocks on the boiler are linked? Normally in testing a gauge glass, the steam cock would be closed off, and the water one blown through using the drain cock, and vis-versa. If the two cocks are linked, how does one do this?

    Ideas anyone?
    Thanks,
    Daniel
     
  2. Kerosene Castle

    Kerosene Castle New Member

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    The quick way is to just open the blow-through, and close it again once the glass has drained of water. Good for scaring kids is that one.

    In any case, closing the shut off cocks and opening the blow-through will still drain the glass, however it can be sluggish at times, so you may need to just lightly tap the shut-off lever upwards, in order to speed things up.
     
  3. Steve

    Steve Part of the furniture Friend

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    Coupled top & bottom cocks are quite common on ex main line locos. They were pretty standard fittings on GW, LMS (Stanier) and BR standard locos. The method of testing is covered in the Black Book. Basically, shut the coupled cocks, open the drain, open the coupled cocks and shut the drain. Water level should disappear then reappear.
     
  4. Sugar Palm 60526

    Sugar Palm 60526 New Member

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    It's important to change the glasses regularly, for new ones, usually at boiler washout and to rod out the connections from gauge frame back into the boiler at the same time.
     
  5. dhic001

    dhic001 New Member

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    Ok, thanks for that guys. It seems that marine practice (which I am used to) is a bit different from railway practice. We generally wouldn't replace the gauge glasses so regularly, usually just at survey time, and we always test the cocks independantly, which means that rodding through the fittings only occurs if there is a blockage, which is unusual. That said, we all use boiler treatment, as we run closed cycle systems, so we don't have much corrosion or scale to contend with.
    Thanks again,
    Daniel
     
  6. Ivatt

    Ivatt New Member

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    Having linked cocks has a particular advantage when a glass breaks on you. In that hot fog that surrounds you, it is far easier to find that big handle than two individual handles which are arguably a tad closer to the gauge frame itself.
     
  7. Steve

    Steve Part of the furniture Friend

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    At Middleton we have a Danish loco that has the top and bottom cocks coupled. Not only that but they are coupled to a shaft which extends to the drivers position where the operating handle is. If a glass blows it is very easy to turn it off without going anywhere near it. It's such a good idea I'm surprised that it didn't see more widespread use. One of the two experiences I've had of a glass blowing was on this loco and it was very easy to sort out. The other was on the K1 and it was a case of jacket over the gauge glass and fumble for the valves. The exploding glass on the Danish loco actually broke the toughened protector glass!
     
  8. odc

    odc New Member

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    This still misses the original point of the post. How do you test the top and bottom valave are working properly indepentantly. On the FR we are encorages to blow through each cock seperatly as the is supposed to blow out any rubish in them. Haveing both shut of and opening the drain just proves the drain works and gives you a fresh reading.
     
  9. baldric

    baldric New Member

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    Testing a glass is reasonably easy, when you open then close the blow-down if the water does not re-appear fairly quickly then one of the water-ways is blocked in some way, normally there would be some form of bounce. When slowly opening the frame with the drain open you would expect to see steam in the glass turning to water, thus indicating the top is not blocked. It is also worth remebering that normally when an engine is moving you would expect to see the level changing, if it stops moving there is probably a blockage.

    While it is easier to fully test a glass with seperate cocks it seems better in my view to have a single lever for the reasons others have already stated.
     
  10. Avonside1563

    Avonside1563 Member

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    Seems a bit excessive to change the glasses every washout which would mean new glasses on average every 14 steam days! We only change them at annuals if required, some of our locos have kept the same glasses right through a 10 year ticket!

    Don't think there is anything laid down for frequency of change, just inspection. But happy to be corrected!

    The ORR publication states that inspections should include :

    "(i) gauge glasses for signs of pitting, wastage of ends, flaws or streaks - if these are found,
    the glass should be replaced;"
     
  11. Steve

    Steve Part of the furniture Friend

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    Depends on how long you go between washouts! It is OTT to change them at every washout but you really should examine them and this can only be done by removing them. Whether you put them back with new rubbers if Ok or change them as a preventative maintenance requirement is down to the guy in charge. It takes away the decision making/subjective opinion if you always change them. The 'Railways' used to change them routinely, I doubt that 'Industry' did and probably still doesn't in many cases. NCB Examinations of Mechanical Plant required that they were stripped, cleaned and examined at 3 monthly intervals but there was no specific requirement to change the glasses.
     
  12. Avonside1563

    Avonside1563 Member

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    Absolutely they should be examined regularly, and very true it depends on how long between washouts, but unless your on Porta treatment it would be normal to washout on 14 days or there abouts. Our's do get inspected regularly but only changed as required, not on a fixed period. Can't be too bad as we have only had 2 go in 40 years. (Hastely touches nearest available wood! :-$ )
     
  13. mick wilson

    mick wilson New Member

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    Which raises the debate on frequency of washouts and the positive effects of water treatment in its various guises.
     
  14. howardw-s

    howardw-s New Member

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    With reverse osmosis of a lot of the water, careful monitoring of boiler water quality and metering of chemicals into the water from the water columns rather than 'chucking a bit in' the K&ESR achieves 26 days between washouts.
     
  15. Steve

    Steve Part of the furniture Friend

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    If you get your water treatment spot on the only need for washouts is due to the need to internally examine the boiler. Industrial boilers with treated water on closed systems don't get washouts. They don't generally need them.
    At Middleton with softened treated water and blowing down to maintain TDS we go 30 days in steam, which can be a full year if we have 4 locos available.
     
  16. olly5764

    olly5764 Member

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    I don't know about ten years without changing a guage glass, it would not be the first time that I have had to change one on a loco standing in a station. Not had one go on the road...yet!
     
  17. burnettsj

    burnettsj New Member

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    Even in my limited footplate work - I have had to change two gauge glasses.

    It all really comes down to the amount of time the engine is in stam and the gauge frame blown down.

    I suspect that on some railways, the engines run less miles in ten years than some engines do on one.
     
  18. aldfort

    aldfort Part of the furniture

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    I was looking at some gauge glasses we'd changed out the other day. They do get wasted on the bottom end (by blowing down too often perhaps?) Whatever we change them out regularly.
     
  19. Fireman Dave

    Fireman Dave New Member

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    Easy. With the cocks open drain the glass, then close the drain. As long as water returns to the original level quickly and remains stable all is well. If the water rises slowly then the bottom port is blocked. If the level rises quickly to the top of the glass then slowly falls to the original level the top port is blocked.
     

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