[PSUBS-MAILIST] Specifications when ordering shell

Mon Mar 23 09:54:19 EDT 2015

Thanks for the clarification Steve.
Regards
James

On 23 March 2015 at 12:18, Stephen Fordyce via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi guys,
> The material certificate thing is all about quality control and
> traceability of exactly what is the composition of the elements in
> it.  Ie. when the steel gets smelted and poured into a block (or whatever)
> at the mill, that particular batch gets analysed for exact percentages
> of all elements, and all parts poured from that batch are given the "heat
> number" of the batch.  Since the certificate is meant to trace back to the
> original steel mill, it's often called a "Mill Certificate".
>
> Each time the steel goes through a process (ie. rolling into sheet, the
> sheet formed into pipe or endcaps) there is a chance the traceabilty to the
> original analysed composition could be lost, if the material gets mixed up
> - and there are varying levels of quality control that make sure of this,
> and these are reflected in different types of material certificates.
>
> The EN 3.1 cert is pretty high end (ie. good enough for the SS304/316
> cryogenic liquid ethane pressure vessels I'm currently involved with at
> work) and typical for most industrial applications at least.  I've not come
> across requirements for 3.2 (which is even more stringent), and we
> frequently work with lesser requirements than 3.1.
> Here's a good explanation of the difference:
> http://www.classicfilters.com/blog/materialcertificates/
>
> Tracing the material back to the mill is supposed to be important in case
> there is a failure in another part in the same batch, so it can prevent
> other failures.  I've always thought the whole certificate/traceability
> thing was just a PITA and that so long as you get steel or parts from
> reputable suppliers who's QC practises you trust, then that's just as
> effective.  Especially when you're building a big system with hundreds of
> welded parts.
>
> Cheers,
> Steve
> (Among other things - mechanical engineer in Melbourne, Australia)
>
> On Mon, Mar 23, 2015 at 10:55 PM, James Frankland via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>> Hi Andre,
>>
>> I was in this position some years ago.  Not knowing what to specify on
>> the order.
>>
>> I believe the EN number is a certificate of the material quality.  Mine
>> was done to EN10204.3.1.B but i never specified it.  I just asked for the
>> material type.
>>
>> So just ask for your dimensions of shell, material, percentage of round,
>> bevel, weld.
>>
>>
>> Example.
>>
>> Shell.  P355 Steel.  10mm Thick.
>>
>> OD 1000mm x 2000mm length.
>> Shell to be within +\- 3mm on diameter.
>> Welded seam.
>> 35 degree external bevel with 2mm nose.
>>
>>
>> Something like that should do it.  They will send you a quote and should
>> tell you what material grade it what code they will be working to.
>>
>>
>> Make sure you specify clearly the tolerance of roundness you want and say
>> your not paying for it if its not right.  They will probably need to
>> re-roll the cylinder.
>>
>> Ideally go to the factory with a wooden template and measure the cylinder
>> before you accept it.
>>
>> Get the bevel put on, it will save you pain.  But. don't bother with grit
>> blasting, you need to paint it straight away after that or it will start to
>> oxidise again.  By the time you've finished your hull, it will be all rusty
>> again.  Grit blast when you've finished working on the hull.
>>
>> Someone else may have some other suggestions.  Comments.
>>
>> Hope this helps.
>>
>> Kind Regards
>> James
>>
>>
>>
>> On 21 March 2015 at 22:30, André Eriksen <personal_submersibles at psubs.org
>> > wrote:
>>
>>> Hi,
>>>
>>> I`m in the process of ordering the shell and tower for my submarine.
>>> What specification should I ask for? (Europe)
>>>
>>>  I asked for EN10204 with 3.1 Sertificate (Not 100% sure of this, but
>>> this is what I got when I ordered the endcaps from another company. 3.2
>>> Sertificate was a bit too expensive)
>>> Told them I had no special requirements for the plates and needed no
>>> edge preperation.
>>>
>>> *They replied*: "this is not the normal enquiry type, but we will not
>>> ask any longer" (?)
>>> And said the plates was going to be EN10028-3 with certificate 3.2.
>>>
>>> I want to keep the cost down, but should I ask that they grit blast the
>>> shell after rolling?
>>> Also I didn`t ask for bevel on the edges. Again to keep cost down. But
>>> maybe I should, to spare me the extra work?
>>>
>>> May I ask what you tell your supplier when ordrering?
>>>
>>>
>>> -André
>>>
>>> _______________________________________________
>>> Personal_Submersibles mailing list
>>> Personal_Submersibles at psubs.org
>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>
>>>
>>
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>
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