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taz24
28-10-2006, 01:34 PM
A while back I was involved in the installation and subsequent service maintenance of a large supermarket. The site was problematic from the start. There were too many complications to mention but one of the main faults that developed was that the brazing rods used were found to be porous. We had numerous gas leaks mainly caused by the extra low temp sub cooled R22 liquid. We started to find untraceable gas leaks in the armaflex that we then eventually found to be the joints that were all weeping. Oil was present but each leak was too small to detect. We worked it out to be loosing about 60 to 100kg of gas a year. The combined plant held about 800kg of gas in three mixed temp packs.<O:p</O:p
We removed a joint and it was sent away for testing and found that the silfoss brazing rod was substandard. The whole batch was. We used best part of 100kg of the stuff on the install and then we spent the next ten years mopping up the oil and adding gas. Fortunately all that has now been replaced for localised packs spread across the store.<O:p</O:p
<O:p</O:p
Has anyone else had similar problems with brazing rod?
<O:p</O:pCheers taz. <O:p</O:p

monkey spanners
28-10-2006, 05:49 PM
I went to fix a leak on a suction/liquid line heat exchanger that i though had been silver soldered. Out with the oxy kit, only to find it was plumbing solder when the previously good suction joint dripped onto the floor:mad: I now had two soft solder joints to try and silver solder over:mad: :mad: This is when you realise why the senior engineer who had found the leak in the first place claimed he couldn't fix it with his turbo torch (didn't try) :mad: :mad: :mad:

Fools rush in .....

Cheers Jon

old gas bottle
28-10-2006, 08:12 PM
just a thought, maybe the nitro pressure was to high when brazing or no purge point, other way is to much oxygen in the flame/too hot, never heard of porous rods,had crap ones,but then again every days a learning day.

taz24
29-10-2006, 12:32 AM
It was one of those sites that everything was wrong. The joints took about 4 years to reveal itself properly. I had not thought of the N2 but all though I can't account for all the install team I installed quite a bit of the ring main so can confidently say that the install was OK.
Lots of things were wrong on the site though. The LT side had subcooled liquid at 0c which caused all the heat exchangers to fail and leak gas. They ether leaked out and we had a big liquid leak or they leaked internaly to suction and we then had liquid in the comps. We had to systematicaly replace the heat exchangers for straight pipe. Every liquid mag valve in the HT cases had to be wrapped in plastic because they were under the evap and the defrost water would fail them. The LT liquid mag valves had to be removed to less than 1 ft before the TEV because the subcooled liquid was hamering the valves and spliting the flarenut off. There was a list as long as your arm with the defects of the system but the bad joints was one we had no control over.

Cheers taz.

al
29-10-2006, 12:57 AM
Funnily enough one site we had very bad hammering on was due to using 240v valves when only 210/220 was available.

Al

old gas bottle
29-10-2006, 08:34 AM
just one of those job,s "eh"

Handyman-1
29-10-2006, 09:06 AM
We removed a joint and it was sent away for testing and found that the silfoss brazing rod was substandard.
<O:p</O:pCheers taz. <O:p</O:p

Substandard materials could be easily pointed as the culprit but have you also check on the welder/technician that worked on the joints?

The work method should be thoroughly checked before ruling that the substandard materials was the main reason.

taz24
29-10-2006, 08:38 PM
Substandard materials could be easily pointed as the culprit but have you also check on the welder/technician that worked on the joints?

The work method should be thoroughly checked before ruling that the substandard materials was the main reason.

I agree that could be a posibility but the instal team were all experienced and the whole store was defect. If the install team were at fault then there would be other stores that they moved onto or previously had been on would also be of the same substandard and that was not the case. When the rod was inspected in a laboratry they found that the rod was without one of the main components that made it what it should of been. It was actualy pourous at the molecular level.

Cheers taz.

taz24
29-10-2006, 08:43 PM
Substandard materials could be easily pointed as the culprit but have you also check on the welder/technician that worked on the joints?

The work method should be thoroughly checked before ruling that the substandard materials was the main reason.


A full and intensive post mortem was carried out because of this as you could imagine. Money was involved and it was decided by expert metalolagists that the rod was at fault. the descision was made at a much higher level than us at the coal face. The store ran on for about 12 years before it was refitted.

Cheers taz.

winfred.dela
30-10-2006, 02:32 AM
Hello taz,

Thanks for the added info.

Regards,
Winfredy :)

Below 0
31-10-2006, 09:15 AM
Hi, had the same experience a number of years back and the fault was traced to being insuficient silver content in the brazing rods.Like you taz we had to slowly replace joints as the leaks became big enough to detect.

chillyhamster
01-11-2006, 11:20 PM
Porus joints are normaly caused by engineers using a flamethrower to heat (do not let rod material "boil") the joint in a misguided effort to speed up the process (pipe strangler on job and knock), Even, gentle heat, enough to allow the rod to flow into the joint will produce a full and proper leaktight joint.

sumant mathure
21-10-2007, 07:02 PM
Hi, Many times Copper-phos alloys are blamed for such defects, but if you see metallurgical reason it is very clear why it is so... Phosphorous, normally 7% works as a flux forming pentoxide also as fluidity to copper by forming copper phosphoide. hence when ever there is Joint gap more than 0.1mm on diameter in copper phos joints, there is always gas formation which is during brazing. This entraped gas gives porosity in joints there by weakening it.

Sumant Mathure, Brazingconsumable

WINJA
20-11-2007, 08:48 AM
I have come across faulty rods before ,but Ive also had a situation where the enviroment was causing dodgy welds, it was grit in the air from concrete cutting and sand

750 Valve
27-11-2007, 11:17 AM
Wow taz, never heard of it before, you live and learn.

I have had bungs left in copper pipe from manufacturing, and holes in copper pipe from manufacturers name stamped in there but this is crazy.

I bet you all got hauled over the coals before they worked out what it was...

Did they want warranty on gas for the 12 years?

taz24
27-11-2007, 01:47 PM
Wow taz,

I bet you all got hauled over the coals before they worked out what it was...

Did they want warranty on gas for the 12 years?



The company that did the install carried out the maintenance for the store for the 12 years or so after the build to the subsiquent refit (full cost contract so all costs were included).
I was involved in the initial install and was personaly responsible for the store for all the years after and through the refit.

A lot of desciesions were made that were way above my pay grade :)
From my point of view it was very intresting.
I got to see the whole process from start to finish and I was the person who cut out the faulty joint samples that were removed for testing.

No real difference was noted from my point of view.
The system was a subcooled R22 ring-main system and there were lots of other problems that were associated with the design.

The subcoold liquid if alowed to warm up in a line (say when the case was on defrost or down to temp) caused expansion and hydrolocking of pipes.
We had to systematicaly remove all the heat exchangers in the cases because of this (they ruptured and leaked).

The thing that I was led to believe was the main problem was the combination of the R22 refrigerant that was subcooled down to 0 degC.
This large multi pack ring main system was new in design and I think it was somewhat experimental as well.

It was one of the very first UK installs to incorporate the Copeland discuss compressor.
Old and reliable technology now but a prooving ground for the store.
We went through countless disc valve sets and the cylinder heads were off all the time.
Copeland upgraded the ring valve to the type they use now on the back of that trial.
Even the alarm system was new.

At the time a new company called ELM were produceing pack and case controllers controlled from a master controller. Old technology now but quite inovative in its concept back in the late 80's.
Now ELM has long since gone and the company that installed it has been bought out by its main rival / competitor.

For me it was day to day work and because we were kept in the loop very exiting.

Nobody acctualy got blamed from the design failures and no one person was held to account for the joints.

It was all done over a 2 or 3 year period and it was 17 years ago when it happend.
People move on and companies buy out other companies.
All the old plant and pipe work was scrapped about 2003 so its all gone now.

Cheers taz.

750 Valve
28-11-2007, 11:47 AM
Mate with the majors over here someone would have been hung out to dry over it, thats the diff from what i hear about the two countries and fridge work, you guys are amicable, our customers are absolute asswipes and will ALWAYS finger point and want something for free.

PaulZ
28-11-2007, 12:04 PM
You got that right 750 Valve, some of them will take every chance they can to screw you.
Paul