Failed 47mm evacuated tube

[Rtrak]

I installed a 20 tube (47mm) Navitron panel at my house in Portugal just over a year ago. Due to the orientation of the house, the panel is located at ground level but is well protected to prevent accidental damage.  I noticed the other day that one of the tubes was discoloured. On closer examination I noticed that this tube (one of the central ones) is warm where its brothers are cold hence I assume it has failed. There are no visible signs of damage, I guess it's just one of those things.  Is it better to remove the offending tube and heatpipe or should I leave it insitu? I assume that I'll only need to replace the evacuated tube and not the heatpipe, god only knows how I'll get a tube out here!

[MR GUS]

Woah! ..I 'm a tad concerned at the set up being within gravel pinging level of vehicles, or footfall throwing up debris, dust etc, ..can you raise it up at all?
Anything that rolls or blows down that incline may have already inadvertently messed up a tube.., how damaging would a loose plastic bag be melting on the hot tubes etc!? 

would only take a kid & a rock a matter of seconds to destroy your work & water supply.

..gives me the jitters, is there no way a raised rack could be incorporated into this?

[grevls]

I would recommend leaving the tube in until a replacement can be fitted. It will still be assisting with your water heating just not at it's full potential.

If it is discoloured it will have failed and most likely have a tiny crack in it somewhere. Has the bottom turned a cloudy white colour?

[Ivan]

There's always a reason for failure, although sometimes the damage is done during installation and not obvious until moisture in the air gets inside the tube and reacts with the selective coating (which can take several months to occur in a dry environment). Quite often it's because the vacuum seal on the bottom of the tube is knocked off during installation. Alternatively, if you have the older style jubilee clips to retain the base of the tube, it can be due to over-tightening (circular crack underneath the jubilee clip).

[Rtrak]

Thanks for the input everyone, I'll leave the tube in place until I source a new tube, strangely enough, over here they exclusively use flat panels which is a nuisance.  I may be able to get one (not Navitron) from a supplier in Spain, I'm waiting for them to get back to me. The height of the panel is ideal at its current level (possible to thermosyphon and pipe length of maximum 2 metres to cylinder) and the tubes always remain cold (except the warm failed one). There are no kids or other sources of annoyance here to damage the tubes, I'm putting the failure down to experience, maybe if it was one of the end ones (first fitted) I'd accept I could have damaged it in installation and yes, the frame is perfectly level! Sincere thanks for your responses. I'm encouraged to post regarding solar pumping from one of my water mines now!

[Wyleu]

Them is pretty tough,
I've kicked a football repeatedly at the centre of an array with no ill effects.

[Iain]

WHY?
Iain

[clivejo]

I guess when you run out of burning £20 notes for heat, kicking a football against a solar array is the next best thing! 

[Rtrak]

Maybe I didn't read the installation guide correctly, I've got myself a football and I'll kick it against the panel repeatedly edly edly edly for a while to see if I can make any more tubes fail before ordering replacements!

[biff]

  ,
      i say ,,take it easy old man,read the small writing on the installation sheet.
          it says among other things,that needlessly and recklessly kicking a football up against the solar tubes for purposes other than scientific research will invalidate the warranty and land the owner with a fine of 100,000 euros to be paid in cash to the head office in donegal who are the only persons qualified to apply scientific research to naviton tubes.this of course is perfectly understandable since we here in donegal are all off to croker to play dublin in the all ireland football semifinal.(on BBC 2) to jim and the gang,,all the best.
                                                                                               from biff,margaret,dsl and nat

[martin]

Why? - what a strange question!  - The experiment was carried out during the early days of the forum as a response to the "how tough are the tubes?" questions.........

Which boils down to the fact they're "tough as old boots", and once mounted will cope with most things normally encountered (and the odd flying football)

[desperate]

I agree with Martin, they are tough, I dropped one once and it was fine. one of the 60 on our roof has gone soft, I can't get close enough to be sure, but I think as Ivan says, the seal has cracked due to frost over the winter freezing water in the retainer cap.

Desp

[Rtrak]

I bought 3 replacement tubes from Navitron (reckoning that more may fail in the future and thinking that 3 could be taped together easily / stably for transport).  A member of the UK Expats Portugal forum very kindly collected the tubes from Oakham and dropped them off to me here in central Portugal.  I had the faulty tube replaced in minutes, when I removed the failed tube,  there was a small crack in it, strangely enough on the lower side of the panel near the top, maybe I did it when using the brushcutter.  Incidentally when I took the old tube to the recycling centre I threw it into the glass skip, a drop of about 3 metres, it broke a few bottles that were in the container but remained intact, much to the amusement of the attendant who thought it was a florescent tube!