Weld dye testing a new narrowboat shell.

[Gybe Ho]

In one narrowboat vLog I follow the build of the shell was videoed. When the hull was finished but before painting the diesel tank was pressure tested with a foaming gunk squirted over all the weld seams. That made sense. What surprised me was how the rest of the hull welds were tested, white foam was applied along all welds on one side then on the reverse side a purple dye was used. The idea here is that after 24 hours any pin prick hole in a weld would allow the purple dye to migrate through the faulty weld and discolored white foam would reveal a problem.

 

Is this common practice?

[Alan de Enfield]

3 minutes ago, Gybe Ho said:

When the hull was finished but before painting the diesel tank was pressure tested

 

That is a standard RCR / RCD requirement and must then be marked with the tank volume, the test pressure, the date, and the authorised testers ID number.

[Tony Brooks]

8 hours ago, Alan de Enfield said:

 

That is a standard RCR / RCD requirement and must then be marked with the tank volume, the test pressure, the date, and the authorised testers ID number.

 

I think that he was talking about hull welds, not the tank.

 

9 hours ago, Gybe Ho said:

What surprised me was how the rest of the hull welds were tested, white foam was applied along all welds on one side then on the reverse side a purple dye was used. The idea here is that after 24 hours any pin prick hole in a weld would allow the purple dye to migrate through the faulty weld and discolored white foam would reveal a problem.

 

Is this common practice?

 

It is a perfectly standard non-destructive testing procedure as far as industry is concerned, and one budget hull builder told me that is how they tested their hulls, but I have yet to be convinced that it is common practice in canal boat building. It is however, a good way of doing it and probably cheaper than on site X-Ray testing.

 

Another similar method squirts a liquid that glows in ultraviolet light along the weld and use an ultraviolet light on the other side to look for glowing penetrant.

 

The same method can be used to detect cracks and pinholes in cylinder head or block faces, cylinder liners as well, I expect. In that case, after allowing the penetrant to penetrate, you clean it off and spray the white stuff (developer) or shine the ultraviolet light onto the suspect surface.

Edited March 15, 2025 by Tony Brooks

[john.k]

machine done welds sometimes get long cracks in them .........small cracks in hand welds are of little consequence ,unless its a tank .........normally with tanks there will always be pinholes you have to fix up ,but not 3 ft long cracks............you are also likely to get laminations in low grade steel sheet ....often called floor plates  .............for something like boiler fabrication ,you use a higher grade thats already checked for faults.

Last job I did ,was on a 5000 sq metre floor crude oil tank .........the main contractor was CBE (Chicago Bridge) .........they would do one shift welding with machines,two shifts arc gouging faults ..........the tank was like 3 months behind ,and the crowd I was working for couldnt get access of a weekend ,as they were supposed to .........20-30 men on weekend rates doing nothing.............when youd come up to the tank,you could hear the hissing of arc gouging from 400 metres away.............the boss idiot son was running the job,and hes --if you tell the old man ,youre gone......the job started out bad with drug testing on the first day ,17 of our  20 guys failing drug testing.........including the boss s son.

[Gybe Ho]

39 minutes ago, john.k said:

you are also likely to get laminations in low grade steel sheet ....often called floor plates  .............for something like boiler fabrication ,you use a higher grade thats already checked for faults.

 

 

The hull I viewed during the week had Tata steel production labels still attached, I could see where the welder had scraped back the label to weld in a roof rib. I hope that indicates the shell fabricator sources decent steel. The steel plate amounts to 20% to 25% of the cost of a shell.

 

The fuel tank is formed in the stern of the hull, plenty of chances for this to go wrong e.g. canal water ingress, diesel leak into the canal or the bilges. The mandatory RCR pressure test should cover this risk.

 

2 hours ago, Tony Brooks said:

nd one budget hull builder told me that is how they tested their hulls, but I have yet to be convinced that it is common practice in canal boat building

 

 

I got the same impression this week when talking to the boss of a shell fabricator this past week, they have done dye weld testing before and will do it if I stipulate it. Not sure whether to demand every weld is tested of just below waterline welds.

 

I wonder how much epoxy filler is used in a typical shell before final painting. 

[Tonka]

21 minutes ago, Gybe Ho said:

 

The hull I viewed during the week had Tata steel production labels still attached, I could see where the welder had scraped back the label to weld in a roof rib. I hope that indicates the shell fabricator sources decent steel. The steel plate amounts to 20% to 25% of the cost of a shell.

 

The fuel tank is formed in the stern of the hull, plenty of chances for this to go wrong e.g. canal water ingress, diesel leak into the canal or the bilges. The mandatory RCR pressure test should cover this risk.

 

 

I got the same impression this week when talking to the boss of a shell fabricator this past week, they have done dye weld testing before and will do it if I stipulate it. Not sure whether to demand every weld is tested of just below waterline welds.

 

I wonder how much epoxy filler is used in a typical shell before final painting. 

Or they just stick Tata stickers on an old piece of steel

 

Hopefully they weld it better then the new Scottish ferry which has taken 7 years to build and only started operating in January. Now out of service due to a crack letting in water

You do know that Tata have closed their blast furnaces so cannot produce the top grade steel anymore in this country. It will be a few years before their electric arc furnaces come on line and they can only produce recycled steel

Edited March 15, 2025 by Tonka
Spelling

[Tony Brooks]

40 minutes ago, Gybe Ho said:

I wonder how much epoxy filler is used in a typical shell before final painting. 

 

At least epoxy is better than polyester (body) filler that some have claimed has been found filling poor welds below the waterline.

[Stilllearning]

3 hours ago, Tony Brooks said:

 

I think that he was talking about hull welds, not the tank.

 

 

It is a perfectly standard non-destructive testing procedure as far as industry is concerned, and one budget hull builder told me that is how they tested their hulls, but I have yet to be convinced that it is common practice in canal boat building. It is however, a good way of doing it and probably cheaper than on site X-Ray testing.

 

Another similar method squirts a liquid that glows in ultraviolet light along the weld and use an ultraviolet light on the other side to look for glowing penetrant.

 

The same method can be used to detect cracks and pinholes in cylinder head or block faces, cylinder liners as well, I expect. In that case, after allowing the penetrant to penetrate, you clean it off and spray the white stuff (developer) or shine the ultraviolet light onto the suspect surface.

Foam and dye testing was how we did it in the yard I worked in.

[john.k]

Dye penetrant testing is pretty standard in welding....even in non critical welding, it gives a simple visible check on the welds............more critical work uses X rays ,but costing around $1000 per image ,its not used unless required.

[David Schweizer]

57 minutes ago, Tonka said:

Or they just stick Tata stickers on an old piece of steel

 

Hopefully they weld it better then the new Scottish ferry which has taken 7 years to build and only started operating in January. Now out of service due to a crack letting in water

You do know that Tata have closed their blast furnaces so cannot produce the top grade steel anymore in this country. It will be a few years before their electric arc furnaces come on line and they can only produce recycled steel

 

Is that actually correct? When I was at College we studied both Blast Furnaces and Electric Arc Furnaces as a means to manufacture Steel. I have no recollection of being told that Electric Arc Furnaces were only able to use re-cycled steel, but the process using ore was more complicated and time consuming when using raw Iron Ore. Producing steel by using only Electric Arc may make it a sound commercial option, but not an impossible one, as is now being suggested.

 

 

Edited March 15, 2025 by David Schweizer

[Tony Brooks]

7 minutes ago, David Schweizer said:

 

Is that actually correct? When I was at College we studied both Blast Furnaces and Electric Arc Furnaces as a means to manufacture Steel. I have no recollection of being told that Electric Arc Furnaces were only able to use re-cycled steel, but the process using ore was more complicated and time consuming when using raw Iron Ore. Producing steel by using only Electric Arc may make it a sound commercial option, but not an impossible one, as is now being suggested.

 

 

 

I do wonder how any furnace using recycled steel deals with the alloys and contaminates that may be in the recycling feed. After a number of recyclings and adding alloys, it seems to me that the "new" steel could end up as an unpredictable mix with unpredictable properties. i.e. fine for fence posts, but not for stressed or special purpose panels

[Alan de Enfield]

5 minutes ago, Tony Brooks said:

 

I do wonder how any furnace using recycled steel deals with the alloys and contaminates that may be in the recycling feed. After a number of recyclings and adding alloys, it seems to me that the "new" steel could end up as an unpredictable mix with unpredictable properties. i.e. fine for fence posts, skips on muddy ditches but not for stressed or special purpose panels

 

🤣

[cuthound]

When I worked in the critical power and cooling industry the welds on chilled water pipework was tested using magnetic particle inspection, where a penetrating liquid containing magnetic particles is painted over the welds and the pattern of the magnetic particles inspected. A faulty weld stops them from lying parallel to each other.

 

Cheap, effective and widely used to test critical welds in industry.

[Tonka]

1 hour ago, David Schweizer said:

 

Is that actually correct? When I was at College we studied both Blast Furnaces and Electric Arc Furnaces as a means to manufacture Steel. I have no recollection of being told that Electric Arc Furnaces were only able to use re-cycled steel, but the process using ore was more complicated and time consuming when using raw Iron Ore. Producing steel by using only Electric Arc may make it a sound commercial option, but not an impossible one, as is now being suggested.

 

 

Well the BBC News and the shop stewards were saying that when TATA were proposing to close the furnaces at Port Talbot 

[john.k]

All of Trumps 25 new steel works are remelt using scrap ........it costs a few million to set up a remelt as opposed to a billion for a blast furnace ........a number of Indians have been selling the Australian Labor government here a pack of lies about reducing iron ore with hydrogen ....green hydrogen. steel works ........anyhoo,Labor has finally realized the Indians are grifting money from suckers ,and taken over the seriously detoriated blast furnaces ...and the $2 billion debt .

[blackrose]

The dye penetrant used is typically lower viscosity than water, so it finds any defects as it's drawn in by capillary action.

Edited March 15, 2025 by blackrose