Bolt on vessel/piping legs, do they need welding to code?

[cjaseng84]

Hi All,

I'm new here and new to PED. The summary of this question is: I have a vessel I'm designing that has some tapped pads welded to the side to allow some legs to be bolted on. I have to jump through hoops to get stuff welded to code, i.e. do an individual drawing for each part, have each part made at a machine shop and then sent to our specialist fabricator who can weld it to EN15614 for us.

It'll be much easier for me to do one general fab drawing and have one of our generic fabricators make the legs up for us (they're good welders just not necessarily to code).

Mining down a bit more into the design...it is not technically a vessel and can be considered Pipework at Category 3 as it does not retain pressure, it's only pressurised when fluid is moving through it. Therefore technically the legs will also be considered Pipe supports and will also act as anchor points.

So the big question is, do these bolt on legs need welding to code?

Thanks

 

[XL83NL]

Trying to figure out your situation. What do you mean when you say the vessel legs can be considered pipe work category 3?

 

[cjaseng84]

The vessel can be considered pipework. Our NOBO have confirmed that.

 

[XL83NL]

Ok, so it’s not a vessel then. Don’t see how that matters. But if it’s cat. III, then it doesn’t matter if it’s pressurized or not; it’s regarded as a pressure retaining item under the PED. Period. Has to meet the ESRs then.

Do you have a sketch? I’m confused about the problem here.

 

[cjaseng84]

I'm happy to class it as pipework, I believe it conforms to the PED Article 2 Definition section 3 of piping. I'm not happy to post sketches at this stage due to NDA's etc. Imagine a pipe with plates welded on, the plates have 4 tapped holes to bolt legs onto. i.e. the legs are separate items bolted onto the pipework. Technically speaking I suspect they could be considered pipe supports. The legs themselves require welding on them. My query is do the legs/supports need to be welded to code?

 

[XL83NL]

Probably not, though there's a section under EN 13480 (one of the appendices) that has specific requirements for pipe supports and fabrication thereof. Is EN 13480 your design code, or something else (e.g. ASME B31.3)?

 

[cjaseng84]

We're using 13480, I have tried to read through the pipe support section but it's a bit unclear for the fabrication of pipe supports. I'll have another read through it and see what our NOBO has to say as well.

Thanks for your help

 

[XL83NL]

Refer to, amongst others, normative appendix N of EN 13480.

 

[cjaseng84]

Thanks for the pointer, can quite clearly see now it'll need welding to code...that's annoying!

 

[DekDee]

A bit of a worry if you have something that has absolutely nothing to do with pressure (bolt on legs) being governed by the PED !!!

 

[cjaseng84]

I assume they make you do it for pipe supports as they are subject to thrust loads, if the supports fail technically the pipe could then fail. Personally though, I think simply being welded by an EN 9606-1 qualified welder should be enough for supports.

 

[XL83NL]

DekDee, I agree.

 

[KevinNZ]

For our projects we would treat the supports that are not welded to the pipe/vessel as structural steel and design and fabricate This steel to the local structural steel code. This code does require welder qualifications and weld QA but this is less that the pipe/vessel codes.

 

[cjaseng84]

From what I can understand, EN 13480-3 13.1.2 describes how to classify the support i.e. S1, S2 or S3. Being my supports are rigid anchors on a Category 3 pipe they are classed as S3. Annex N dictates that S3 supports must be welded to 15614-1.