Pin Hole Leaks

[runner42]

Hi all,

I am having problems sealing my boiler to pass the pressure test of 2 X WP of 160 psi. Although I can get the pressure to this value it quickly drops off due to pin hole leaks that I thought I had corrected by soldering with acid core soft silver solder over the pin hole. This is putting a thin veneer over the pin hole with more solder over the adjacent area than the area needing it, so it obviously a useless repair method. What is the recommended method of repairing these type of pin holes?

I was thinking that I could attempt to close the pin hole mechanically with a say centre punch before soldering.

Brian 

[Boadicea]

runner, tell us a little more information. Are we talking just one leak or lots and in what type/size of boiler?
Is this a used or new boiler?
Are pinholes in the material (copper?) or in the solder joints?

[ejparrott]

New 3.5" Doris boiler, thread in the boiler section.

[Deleted]

Hi Brian ,

Must make sure that these are just occassional pinholes and not signs of bigger areas of poor silver solder penetration .

If ok then two traditional methods of sealing small pin holes :

(1) Caulking with a small round nose punch . Don't punch directly on the pinhole centre . Work your way around pinhole a very short distance from centre . Best put boiler on a pile of old sacks or something similar when doing this .

(2) Drilling out pin hole , tapping a thread and inserting a tightly fitting bit of threaded PB rod . Works well but very hazardous to do because of risk of broken taps . Must have a good depth of threads .

Best find out what methods are acceptable for boiler test first though .

MichaelW .

[Shawki Shlemon]

Brian , my first question is has the boiler inspector seen it , if so what did he suggest ? If not talk to the boiler inspector before doing anything that may get you in trouble . This is common , it depends on where they are , how many , how big are these holes and how quick you loose pressure . I personally don't like using soft solder at all ( I must admit over 30 years ago when I started the hobby I did use it on couple boilers but after I saw what can happen if over used , I never used it again ) . To seal the pin holes the solder has to flow through the hole , a layer of solder on top will not fix the problem . A weeping stay may be fixed by sharp strike on the stay while still soft but a pin hole is different , the hammer will not cure it in my opinion . Can you remove all soft solder and clean the boiler properly . after doing that mark all the leaks and talk to your boiler inspector and work with his advice .

[cupalloys]

Hi Brian,
The main consideration for the repair of pinhole leaks is heating technique or poor joint design.

To prevent the build up of thermal stresses (and further leaks!)keep them to a minimum. Your choice of solder seeks to do this. However if you apply heat locally on the leak, the large thermal mass of the highly conductive copper can drag the heat away and the joint does not attain soldering temperature. The solder would not penetrate the pinhole. Apply heat such that all the surrounding area is about 250 deg C. Use a burner that produces a flame for general heating and not a focused flame.

The flux in the cored silver-tin solder is very active but has a very short life. It is very easy to overheat the flux such that it stops working = no joint or repair. This type of liquid flux (unlike powder flux) offers no guide as to joint temperature. A conventional low temperature silver solder (55%) is often easier to use with greater chance of success.

Preplace the cored solder over the pinholes and heat but don't heat the solder directly.

I have tried to condense a reply that would rival "war and Peace" as reading matter. If you require more information talk to us at Harrogate on Friday/Saturday or ring 01909 547248 and leave a landline number on which I can contact you.

Regards

Keith

[Deleted]

I agree entirely with Shawki Shlemon's views on soft solder .

Probably not be nescessary for your boiler but just mention that with Oxy Acetylene and a competent user small areas of bad seams can often be reworked locally without damaging rest of boiler .

[jma1009]

hi brian,
sorry to hear of your woes.
as always Shawki's advice is excellent.
get all the fittings and bolts cured of leaks and pump up again and see where other leaks might be in the silver soldered seams, and submit to your boiler inspector as Shawki suggests. it is a pity you jumped in with your low temp solder - i would not have done this. leaks on the foundation ring are im afraid indicative of a bad joint and poor penetration of the silver solder. grooving out with a dremel and use of oxy acetylene to re- silver solder (use easyflo 2 as you can get it 'down under') may be the only option.
cheers,
julian

[runner42]

Thanks to all for your replies.

Hi Shawki, I used the acid core soft silver solder because it was presented in a thread on this forum as the way to go. The rationale being the likelihood of precipitating further leaks if using high temperature silver solder and the fact that the longitudinal stays were fitted and further silver soldering would have annealed them. Also a highly experienced SASMEE member recommended it's use. I would have preferred to use silver solder because the flux used does a better job and provides an indication of reaching the correct temperature. The pinholes would be permanently corrected.

No I haven't spoken to the boiler inspector, he would want to see the leaks and that would require a pressure test to be performed, I am trying to get to the position where the boiler can be pressure tested successfully.

Hi Michaelw, the pin holes are not at plague proportions, one in the foundation ring, one in the transition of the barrel to the outer wrapper and another somewhere in the firebox tubeplate. The first two not being present at the same time. Thankyou for the details on mechanical closure methods.   

Hi Keith, thanks for the offer of further dialogue, but being in Australia makes that more difficult. Your details on the limitations of the flux in the acid core silver solder has been borne out by my attempts to effect a permanent repair. As I stated earlier I would have preferred to use silver solder. Having used only one type in the construction, BOC ProSilver 45T then a 55% silver solder may be the way to go.

Hi Julian, the pinhole in the foundation ring is due to not having enough or proper copper gap fillers at the back of the foundation ring. Michaelw's second method appears to the solution.

Brian

[gingerneer]

Hi Brian

I have used a high wicking Loctite 290 i think, to cure weeps on studs and non structural pin holes. Get the loco hot first them the vacuum from the boiler cooling down should suck the stuff deep into the pin hole or weep.

Hope you get it sorted.

Will

[runner42]

Hi Will,

your use of Loctite has been suggested by others and it appears to be a rather benign method of achieving a leak proof status, something to consider if all else fails. However, I would like to continue with a repair method that is not a palliative measure but permanent. There seems to be equal numbers advocating a low temperature hard silver solder and those advocating persevering with the acid core soft silver solder. The former will require the use of oxy-propane or oxy-acetylene gas which I don't have. At the moment the jury is still out.

Brian

PS I was using water to do the pressure test to detect leaks it provided a somewhat optimistic view of what was actually the situation, I thought I had a couple of areas that need attention. However I decided to change to air pressure under water and this really showed up a dire situation even with a fairly low pressure of 15 psi. I have about 10 areas where the air bubbles were leaking. Water travels and gives you a false indication of where the problem lies and doesn't appear as bad as escaping air. Air pin points where the problem lies.