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Flanges? BS EN1092

Flanges? BS EN1092

Flanges? BS EN1092

(OP)
Hello - I am after some help.....

We have a customer that has requested a replacement vessel for one we previously supplied a few years ago.  At that time the vessel used BS4504 PN16 flanges for nozzle connections.  However the new BSEN1092:2002 has superceded BS4504, and these PN16 rated flanges have a reduced PT rating meaning I am unable to supply a design that would suit the required connection dimensions and the pressure/temp rating - am I correct in thinking this, or have I overlooked something??

Flange material is ASTM A182 F316L. Pressure 10 Bar.G. Temperature 200degC.  Design is CAT III to the PED meaning third party appraisal by Lloyds.

Regards,
Lee

RE: Flanges? BS EN1092

There was a common mistake when users applied BS4504 flanges, the pressure ratings of 16 bar for a pn16 flange was only good for carbon steel at room temperatures.

Take a look at Table 3 of EN1092-1 for the flange type, you might find that a PN16 flange is dimensionally identical to a PN40 flange, for a type 11 flange (weld neck) this is true upto and including DN40.

Also, take a look at Table 20, you'll see that grade F316 is group 2C2 while grade F316L is group 2C3. At 200 deg c this means grade F316 has a maximum design pressure of 10.6 bar, higher than the 8.5 bar for group 2C3. This is useful if you can get dual certified material, you get the mechanical properties of grade F316 and the chemical properties of grade F316L.

Table ZA.1 shows how the flanges comply with the PED.

Hope this is useful.

RE: Flanges? BS EN1092

(OP)
Hi Fawkes,

Thanks for your response - the dual rating aspect is something that would be useful, and I'd never considered.

The flanges are DN100 - so the PN40 rating does not apply unfortuately.

I asked our flange suppliers and they told me that the flanges are still marked with BS4504 anyway and that if we wanted flanges to EN1092-1 then it would cost us more and take longer to get!!  Also, PD5500:2006 section 3.8.1 b) states that flanges must comply with an appropriate Bristish Standard, BS1560 / BS4504 / BS EN 1092 - I thought 1092 replaced BS4504 from 2002??

The other thing that puzzles me is that the material group 13E0 seems to be a 316L equivalent (1.4404), but flanges made from this group have much higher PT ratings than the ASTM equivalent - am I missing something here??  If not, then I'd just ensure that we purchase and use flanges of this group when we design the vessel - but the design code would need to be PD5500 and not our usual ASME.

Lee



RE: Flanges? BS EN1092

EN specs do provide higher allowable pressures than ASTM  specs and you can quite often get flanges that are certified to both.

I've checked on the BSI website and BS4504 is withdrawn but we still get asked for Table 10 flanges, some people just don't keep up to date, I wonder what they'll think when they find out about the new fangled automobile thingywink

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