Knowledgeable Steel Boiler Inspector Wanted

[domo1977]

Hi All
Would anybody be able to put me in touch with a club boiler inspector who knows his stuff with regard to steel boilers. I'm in the process of building a 7.25 gauge Bulleid Pacific and I need to spec up and make a boiler - in steel due to the size. For simplicity I am going for a Briggs which I wish to design and manufacture myself. Before I get shot down I am aware of the rules and regulations and 1) I am a mechanical engineer so competent to design 2) I served a traditional apprenticeship and although not coded am a compentent welder prepared to make test pieces (which is accepted by the rules).
I therefore ask if anybody knowws of a boiler inspector who has followed this approach recently?

Many thanks

Dom

[ejparrott]

What part of the world are you in?

I'm one of the Rugby boiler inspectors, currently designing the steel boiler for my manning wardle, and I've a thread going in this section about calculations if its any help to you. I also have one going about currently used boiler materials.

[domo1977]

Hi thanks for the reply; I've been following your threads with much interest and they've been very helpful as there is not much other practical info around for steel boilers.
I'm not tooooo far away from you as I'm down in Banbury.

In detail I plan to make a Briggs Boiler as it is simple to design, and has less welds than any other type reducing the chance of a cockup. I will follow the Australian Codes for Briggs boilers for all design and material specs as this seems like the best practice for this type of boiler.

I had planned to keep to about 200bar.litre limit, but reviewing the 'Examination and Testing of Model Steam Boilers 2008' it looks like I could go up to 500bar.litre without trouble providing the design calculations show it is good - is this true as I thought the PED required a lot more substantiation for boilers over 200bar.litre?

With reference to the 'Examination and Testing of Model Steam Boilers 2008' page 16 it states that I only need to identify and furnish mill certs for the plates and tubes used for construction. There is no mention of welding rods or stay/bush material. Obviously they have to be fit for purpose but not traceable; is this true?

I'm particularly interested in how many test pieces I will need to prepare and how they will be tested. As the boiler is a briggs I guess its only really going to be a fillet weld between plates of the various thicknesses that I'm going to use?
what about stays and bosses, do I have to do test pieces for them too or are they done by analogy to the main structural welds?

Sorry for all the questions - happy to talk offline if easier

Dom

[ejparrott]

I'm glad they've been of some use, its what I was hoping when I started them!

You are correct that the blue book makes no mention of welding rods, however the Australian code does. I would say, keep certs, better to have them than not. I will add it to the questions I want to ask. It doesn't actually say anything about certs for stays, bushes and domes either in my opinion.

Under the current regs, 500bar.litre is the limit, article 3.2, although article 3.3 says up to 1100 provided the insurers are notified, which I thought they were anyway! Anyway, non of our boiler come near 500 so I don't worry! I'm not sure what the new proposals say. ~I did read the info that came with the notice of the NAME meeting, but I wasn't able to attend, and I won't get my feedback until Sunday.

Page 16 again covers the weld specimens, and it doesn't actually make specific requirements...again, I'll ask for clarification from the insurers when I speak to them. I presume you'll still use rolled tubes?

I will ask the questions of WM tomorrow, but they may say I need to speak to someone else, but when I have the answers to yours and my questions, I'll be posting the results, because I believe they are of interest to many people, and are not publicised enough.

cheers

[domo1977]

EJ,
glad you arrived at the same conclusions as me wrt the blue book and material traceability. Am I right that for us non commercial home boiler makers that the blue book is the only code we have to comply with and the PED (or PER or what they are called) applies to comercial boiler makers only? as the two do contradict each other a bit.

I will definately only be specing up seamless tube probably ASTM A106B as this seems most available.

I look forward to hearing the results of your progress with WM as I'm sure will others - I think that plenty of people are forced down the mega expensive copper route because of the lack of decent information on steel boiler making.

Dom

[ejparrott]

Spoke to WM...didn't get the answers I wanted.....BUT! he has given me a name and number to call at RSA which is brilliant. Previous investigations with RSA failed to find the right person to talk to, but now I have that name, I'll compose an email and send it off, so it might be another week before we have the answers, but we'll have them!

[fostergp6nhp]

IIRC the welding rods for boilers are 'Low Hydrogen' which compared to mild steel rods are a pig to use.

[weldsol]

You should be looking at E7018 type electrodes such as Murex Fortrex 7018 or ESAB OK 48.00
You want to go for vac pack as the coating on these electrodes are hydroscopic if not purchased in vac pack then you should be looking at baking them @450c for one hour prior to use (see makers recommendations)

Paul

[domo1977]

Yep definately plan to use low hydrogen rods from a vac-pack as the wifes oven doesn't get that hot
They are a bit harder to use but as always plenty of practice and good preparation can overcome that. I'm also planning on using a DC welder for the job which is less prone to sticking than AC.

Talking of sticking rods; my old welding instructor used to shout 'Indians' at full volume across the workshop any time someone had a rod stick on account of the fact that usually the rod came out of the holder and was left sticking out of the job so it looked like it had been shot with an arrow!!! ;D

[parker3]

The use of DC current with low hydrogen electrodes is, in theory, the best method.
but could I make a suggestion that they are use with an AC current and not DC.
DC would be great except that it has the problem known as "Arc Blow" when welding .This can occur at the end of butt welds, inside corners or any joint which is adjacent to a mass of metal.
"Arc Blow" is a condition where the DC current produces a magnetic field round the arc and tends to attract the arc away from the joint being welded, in the worst scenario to splatter weld metal any were but the joint being welded.
With an AC current this magnetic field is not present due to one half of the cycle canceling out the other.
This does however create an other problem. That of extinguishing the Arc at every half cycle of the welding current and restarting it again.( the hydrogen content of the coating helps the restart).

Use of low hydrogen electrodes requires a higher OCV (open circuit voltage) than normal mild steel electrodes, between 60 -100V, in order to make welding more easy to weld with.
Most "home" welding sets are below this voltage, which is why many people have problems using them, starting being one.

From a metallurgy point they should always be used warm to ensure that the hydrogen content of the weld metal deposited is as specified on the box. (Hydrogen tends to reduce the tensile strength).

Sorry if this is long winded but to point out that its not always the electrodes or operator that is at fault but the equipment used.