[PSUBS-MAILIST] Specifications when ordering shell

Mon Mar 23 11:31:57 EDT 2015

Thanks for the info guys! Made things abit clearer. The company I`ve talked
to is in Germany, and I live in Norway so I can`t go and measure the shell.

This is the tolerances they gave me on a OD1000x1500 shell:

OD +/- 2mm calculated out of >outside circumferential length and real wall
thickness
Ovality max 4 mm, measured at both ends
Straightness 1mm/m max. 3 mm
Length - 0 / + 5 mm

Is the ovality tolerance good enough?

Regards
André

2015-03-23 14:54 GMT+01:00 James Frankland via Personal_Submersibles <
personal_submersibles at psubs.org>:

> 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
>>>>
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>>>>
>>>
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>>
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-- 
Med Vennlig Hilsen / Regards
*André Eriksen*
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