Boiler Barrel Patch Repairs

Then I'm afraid your boiler inspector has misinterpreted the regulations and recommendations. Which means that your repairs, while perfectly acceptable and arguably more through are also more time consuming than they need to be and therefore expensive. It is a myth.

My dear friend who used to run the boilershop at bridgnorth has just done a lovely patch on an eastern region loco.

As a boilersmith I constantly argue these points with inspectors who can provide no proof that patch repairs are unacceptable.

No one needs an excuse to make a locomotive overhaul more expensive.

 

Stages in replacing the lower throatplate of 2968's firebox. This particular patch passed the NDT testing, but it was decided to replace it anyway.

 

From a position of ignorance, may I ask: is the boiler inspector quoting regulations, or what his employer is prepared to insure?
Pat

 

There’s a lot of judgement in this one (isn’t that always the case with boilers?!)

I can see merits on both sides. But the angle grinder and welder does remove existing cracks, so I can see why an inspector might prefer that route.

 

A boiler inspector will always prefer new material, in fact I would suggest they would prefer a new boiler every time. They are in the business of diminishing risk.

Most boiler inspectors spend their time in industry on modern packet boilers where welding is the norm and need educating on our locomotive boilers which are 19th century technology.

Welded repairs and patch repairs are both acceptable. All boilers crack, all new material will crack. the need to remove all cracking all of the time is uneconomic.

What will we do if patching is banned and in ten years time that nice new welded insert is cracked?

I know many people of a certain generation say 'mechanics don't fix cars anymore they're just fitters swapping old bits for new.'

So what would happen if a Morris Minor developed a fault and no new parts are on the shelf? Do we scrap it and buy another?

For anybody that is interested I have attached the Heritage Railway Association Guidance Notes on Boiler Platework. These are part of the accepted code of practice, and section 9 covers BOTH welded inserts and traditional Patches. All guidance notes are available from the HRA website if anyone is foolish enough to want to fix boilers.

Regards
Matt Jervis
Left Handed Boilersmith.

 

There are no specific regulations other than the Pressure Systems Regulations 2000 and that is silent on the subject. The Pressure Equipment (Safety) Regulations 2016 deals with putting on the market new boilers and requires their design to be certified by an approved body. What an inspector (Competent Person) will accept is entirely up to him/his employer.

 

Often the left hand doesn't know what the right hand is doing and educating ones inspector is part of the process

 

" Boiler inspectors...........would prefer a new boiler every time" effectively what can well happen on the Continent. The maintenance regime for a boiler in Germany is that
you periodically cut an oval out of the boiler shell and if the piece fails examination and testing you have a new boiler.

This I would submit is over simplified and the very different practice here - I do wonder if the detailed regulations there actually require a new boiler there long before one is
beyond repair - leads to a much better understanding of boilers but does require boiler makers and inspectors of a a decidedly high calibre for high order workmanship, real
craftsmanship, perception, integrity and in the end being prepared to take reponsability.

 

Interesting photos, thank you.

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Isn't this only giving half of the story? What happens if the oval piece 'passes' the inspection? Is it them 'Simply' (although obviously to required standards) welded back in and the boiler put back into service? How big is the oval section? Is the intention to actually get some sort of an otherwise inaccessible access hole into the boiler? Can any-one clarify please?

 

Must admit I was struggling with that notion too. I can't see what advantage cutting a piece of material out really gives you - OK, you could get callipers round to measure thickness, but it still only tells you about the thickness of that specific bit of metal, and leave you with another assurance problem of how to certify the repair of the hole you have just cut! My understanding (open to correction) is that the materials testing of boilers in this country would be a combination of ultrasonic for thickness measurement, in numerous places, coupled with a visual inspection to look for surface defects - both of which are non destructive.

Tom

 

Isn't it in "Railway Adventure" that Tom Rolt tells the story about the boiler inspector that drills a hole in the bottom of the boiler barrel of the Old Lady. Finds that the plate is OK and they put a screw in the hole. When the boiler a few years later is sent away for overhaul they find that this was about the only spot that was thick enough...

 

Quite correct

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Drilling and plugging was a fairly 'standard' method prior to the 'invention' of ultrasonic, the other method was hammering and listening to the 'echo', for want of a better word. During the'60's in Essex a Fowler Showmans Road Locomotive was re-boxed, being sold about 10 years later, not long afterward the new owner had a inspectors plug blow out of the backhead. By this time inspectors were using portable ultrasonics, which revealed a similar story to Tom Rolts.

 

When I was the Grunt with the Grinder cleaning the patches for pre survey testing on Balmoral I came across several 'bolts. relics of surveys in days past

 

With lap joints where there was a possibility of grooving on the water side it was a common practice to cut a slot part way through the plate to act as a tell-tale. If grooving occurred there would be a slight escape of water before plate thickness became critical.

 

I quite agree it seems to me an improbable way to do things.

 

Does that not just apply to single lap jointed boiler barrels where they are not truly circular in cross section but try to assume circularity each time they are pressurized? My old Marshall had a single lap barrel and my first boiler inspector (an ex Cunard Chief) insisted on either me drilling holes through the joint or having it tested ultrasonically for cracking. This was in the mid 70's before inspectors had their own pocket-sized thickness meters etc and one had to arrange (and pay extra) for specialists to bring in something the size of a large microwave oven on a handcart! Having already drilled holes in the bottom of the barrel to establish thickness I didn't fancy drilling any across the joint so chose the latter. Apparently a single lapped vertical boiler on a steam crane had gone 'pop' a few years before and had made all similar construction suspect. Strangely over the next 30+ years that I had the engine the seam was never tested again.
Cheers,
Ray.

 

Tried to describe this issue on single lap joints in some more detail a few years ago.
https://www.national-preservation.c...oposed-new-builds.1002976/page-2#post-1924263
#27 and following replies.
The lesson learned, is that the single lap joint is not intrinsically dangerous. But you really have to know what to look out for to determine if it is safe or not.
And this knowledge is almost totally gone today.