I was looking for the most developments on the discontinuation of LPS lamps, and while reading a thread about it on here, this idea crossed my mind.

There have been discussions on the (theoretical) possibility of acquiring the LPS lamp production equipment to keep said production alive, a project that would prove... um... challenging let's say. It's not my goal to bring that discussion back to life, but I wonder if it would be feasible to REBUILD low pressure sodium lamps?

It's my understanding that turning raw materials into low pressure sodium lamps is a very difficult process. What if most of the steps are done in the first place? Unseal, remove the spent electrodes, put new ones in, re-seal. Probably still quite a challenge, yes. But would it be doable?

Isn't the electrode sealing one of the most complex so one of the most expensive part of LPS fabrication? Because when "rebuilding", you made it even more complex by working with aged tube material, plus the section where the protective layers is compromised is spreading, allowing more glass damage from the sodium...
The materials alone are rarely the expensive thing with lamps (well, there are some exceptions like the large XBO or so, but that are really exceptions), what makes it expensive is the processing. And that is not that much where the materials are rather homogenous (like drawing a tube), but mainly where dissimilar materials have to meet (like the seal and surrounding area - and that is, what you would have to mess with).
So the used SOX may serve as a material source, we won't be talking about lamp rebuild (like "replace electrodes in a 55W SOX"), but rather about lamp fabrication (like "make a 35W SOX using materials salvaged from a 55W SOX" or so, as e.g. part of the arctube would have to be cut out to get clean tubing to form the new seal; plus you would likely need many materials new, like the fill fas, sodium, getters,...).

The impossibility of it has been fully covered by James on here before, but to prove the point, even the Chinese have given up on making them now!, 1 because there’s just no market for them, and 2 the difficulties in making them! 
You’re theory is indeed interesting though, but how would you ‘unshape’ the bottom of the outer glass, (and it’s stem), too get its discharge tube out?

The basic problem with LPS production is that it cannot feasibly be done on a low-volume basis. You have to make millions of them a year (and sell them) for it to be financially viable. The equipment is incredibly specialised and so are the skills required. The people are key if you ever want to end up with a usable lamp. The other problem is the glass. Arc tube glass is made from a ply tubing that is not used anywhere else in the world for any other purpose, and maybe Max or James will correct me if I'm wrong, isn't easily (if it can be done at all) re-workable. So you have to have the glass furnaces running 24/7 for years at a time, they can't simply be shut down and restarted. And then there are the incredibly skilled workers who produce that, who along with the production line workers, have all dissipated to the four winds and (hopefully, anyway) found other jobs.

It would really be wonderful if it could be done, as James can do for things like mercury lamps, but sadly I doubt it will ever happen 

Just to make things extra clear, I'm talking very specifically about "fixing" existing, spent lamps, not making brand new ones from scratch.


What I have in mind is something similar to a CRT rebuilding facility. I'm not directly comparing CRTs and LPS lamps, but it's possible to replace the cathodes of a CRT with relatively simple glasswork equipment. With LPS lamps I would imagine something along the lines of this:


After removing the cap, the glass would be cut exactly where the seal is, and the outer bulb end heated then stretched (basically the opposite of the initial shaping process) so that the discharge tube can be extracted. Then a similar cutting process would be repeated for each of the discharge tube ends. And after that, if one can successfully make brand new electrode assemblies (electrode + glass-sleeved leads + stem), then the parts can be "reassembled", after making sure the existing ones are physically and chemically intact. But it would be interesting to know if the discharge tube glass can be reworked. I have a hard time imagining how it couldn't (not even just "very difficult"), but if so, I'd certainly be curious to know why!


So what I'm imagining is almost more an "artisanal" process rather than an actual mass-volume industry. But maybe this entire thought process of mine screams naivety... 

That's understood, Vince. But specifically with regard to the arc tube, it is a very specialised 2-ply glass - normal soda-lime but with a thin flashing of borate sodium-resistant glass. I may be wrong, but I really don't think it would be re-workable. The pip at the bend is where the sodium dose is introduced, and there are various heat treatments involved in the finishing processes. The electrode construction is rather intricate as well.

I can recommend a book called Lamps and Lighting which goes into detail about the construction of many types of lamp, including LPS.

Here’s a thought?, I wonder if any of the tubes from the old SOs ever got melted down to make new ones?
It’s ironic to think if they would have stuck to the SO design, then ‘fixing’ the old ones would have been less hassle! 

That's the thing, Rich - I don't know whether it would have been possible 

As I understand it from the explanation given by James a couple of years or so ago, production of the glass tubing was a very specialised thing, and the finished product had to be transported from the glassworks to the factory in heated trucks and kept at a specific temperature in heated storage rooms until it was ready to be used.

It may have been possible, but I just don't know, we will have to wait for James, who was involved in SOX production, to tell us.

By the way, we have one of the 60W "Bamboo" SO/H lamps we got from James lit at the moment   

Another thing I always wondered about, let’s say that the IR coating would have been invented in the 30s, would the SO design have stayed with us, and would it have worked the same in the Dewar jackets?? 

I can only agree that 2-ply glass would at the very least be quite difficult to rework! I guess the dissimilar coefficients of expansion of the two sorts of glass is the biggest obstacle here.


On the hand, if it's been worked once, it should (in theory) be possible to rework such glass, even if it is incredibly hard. But then I guess from our perspective it's as if it really were impossible.


Maybe this is something worth experimenting with! Say take a broken lamp, extract the two straight sections of the discharge tube, and try different procedures on short sections, even if just for the sake of science.

[...]

As I understand it from the explanation given by James a couple of years or so ago, production of the glass tubing was a very specialised thing, and the finished product had to be transported from the glassworks to the factory in heated trucks and kept at a specific temperature in heated storage rooms until it was ready to be used.

[...]

Would this imply that some kind of change takes place during the cooldown that then makes the glass impossible to rework? I guess it's possible. 

Would this imply that some kind of change takes place during the cooldown that then makes the glass impossible to rework? I guess it's possible. 

I just don't know, that's why I would want to see an answer from an acknowledged expert like James, who actually worked in SOX production, to say one way or the other. I'm not trying to throw water on the fire here,  I would love it to be possible, but it's just something I doubt, somehow 

China has been producing Sox lamps, and further improved the basic raw materials and production process of Sox in June 2018 to make its service life fully meet Philips standards. But the production plant is mainly OEM. The factory enjoys a high reputation in China, Japan, South Korea and Taiwan. Its direct business is mainly for special testing equipment companies and terminal testing equipment users. The export business is not well-known, and the products are exported by China's domestic foreign trade companies and some old lighting companies.

It's embarrassing to know which companies in the world are purchasing products from production plants. Factories want to contact these companies, but many people think our production plants are liars

 

I can only agree that 2-ply glass would at the very least be quite difficult to rework! I guess the dissimilar coefficients of expansion of the two sorts of glass is the biggest obstacle here.


On the hand, if it's been worked once, it should (in theory) be possible to rework such glass, even if it is incredibly hard. But then I guess from our perspective it's as if it really were impossible.


Maybe this is something worth experimenting with! Say take a broken lamp, extract the two straight sections of the discharge tube, and try different procedures on short sections, even if just for the sake of science.

Would this imply that some kind of change takes place during the cooldown that then makes the glass impossible to rework? I guess it's possible. 

Could certainly be something to play around with if someone has the skill and equipment for glasswork. Full disclosure I have absolutely no knowledge or expertise in this area, I’ve never made a lamp in my life. That said, I have some things to consider in no particular order:

- sourcing electrodes and or doping material for them. Possibly re-doping electrodes still in good condition, I know nothing about this…
- sourcing getter material and activation equipment
- would the indium coating suffer damage from atmosphere exposure?
- cleaning garbage from the electrodes out of the arc tube

I’m thinking that unless you are able to re-use the electrodes somehow, it’s likely moot. My unqualified understanding tells me the electrode connection through the glass is one of the most complex parts of the SOX lamp that uses multiple types of materials assembled in a very specific and intentional way. If the outer and inner tubes can be cut, the arc tube cleaned and the electrodes cleaned and re-doped, then everything reworked, filled, getter’d, and annealed, It just might work?

China has been producing Sox lamps, and further improved the basic raw materials and production process of Sox in June 2018 to make its service life fully meet Philips standards. But the production plant is mainly OEM. The factory enjoys a high reputation in China, Japan, South Korea and Taiwan. Its direct business is mainly for special testing equipment companies and terminal testing equipment users. The export business is not well-known, and the products are exported by China's domestic foreign trade companies and some old lighting companies.

It's embarrassing to know which companies in the world are purchasing products from production plants. Factories want to contact these companies, but many people think our production plants are liars

 

well I hope your company gains the traction it needs to convince the world. because it would be awesome to maintain my SOX fixtures without having to have a stock of lamps in my basement!

I wonder if they sell them in single quantities to individuals. I found Chinese made SOX lamps for sale on business to business bulk sale sites like Alibaba but I haven't been able to find them on Aliexpress, which is the sister site for more direct to consumer sales.