EN 13480 external hydro test pressure

[rachwill]

As EN 13480 is a harmonised standard it's no surprise that the hydro test pressure is as per the PED (i.e. 1.43xPs or 1.25x(ftest/f)xPs). However, the piping I'm currently concerned with is SEP in the PED (<DN25) AND it's pressurised externally.

Where ASME B31.3 points to ASME VIII Div1 UG28 for thickness (and ASME VIII Div1 has no specific rules for pressure testing externally (Interpretation VIII-82-57) and simply points to U-2(g)), it does at least give guidance on externally pressured piping in 345.2.4: "Piping subject to external pressure shall be tested at an internal gage pressure 1.5 times the external differential pressure, but not less than 105 kPa (15 psi)." Interesting that it's an internal test.

Any thoughts on what the hydro test requirements should be for EN 13480 application on 12mm x 0.7mm SS304 tubing with an external design pressure 5.5MPa? Am I stuck with 1.43xPs?

 

[XL83NL]

Based on your description you either have
- an insert device like a thermowell or
- or a jacket to provide the external pressure which would then be considered a piece of pipe

Can you shed some light (like a sketch) on your exact application? Given it is SEP you may have to come up with your set of rules for this specific issue, and in doubt, check this with your notified body. Using para 345.2.4 for your situation should be enough I believe - any nobo would appreciate your effort on this.

 

[rachwill]

Thanks XL83NL.

This affects several items of equipment I'm looking at with different tube sizes (all <1" so SEP) and different materials, however the application is basically the same: a coil of tubing with water internally at <6bar (though for worst case design purposes and largest differential it's assumed to be empty and at atmospheric pressure) and gas externally at up to 55bar. The tubing will be inside a large Ø pressure chamber (which effectively acts as the 'jacket').

If I used ASME B31.3 (and therefore 345.2.4) then it's all fairly clear. However, ASME B31.3 points out to ASME VIII Div1 for thickness calc and the tubes fail on min thickness (I'm not able to change the tubing...a long story). That's why I'd like to use EN 13480 which allows a much higher external pressure for the same tube (and uses essentially the same calc as EN 13445 and PD 5500). Neither of the European Piping or PV codes have anything explicit to say about external hydro test and I'd hate to be stuck with a test pressure of 1.43xPs as our test pot isn't rated high enough. None of the 3rd party rule sets covering my application (LR, DNV, ABS) have anything to say about external hydro test pressure either and I'm wondering if justification for a test pressure lower than 1.43xPs can be reasonably made given that this is driven by the EN codes' harmonisation with PED but the tubing in my application is SEP.

PD5500 (not a harmonised standard) would allow a test pressure of 1.25xPs (modified by strength reduction for op temp higher than test temp), and calculation yields the same allowable external pressure as EN 13480 and EN 13445, though again it is not explicit about external hydro test pressure. Also PD5500 is aimed at fusion welded unfired PVs, and not piping.

Would it be SEP to use a proper piping code i.e. EN 13480 for the calc on max external pressure, but an external hydro test pressure of 1.25xPs. I guess in the absence of clear guidance from any of the literature I'm at the mercy of 3rd party approvals Engineer and whether they accept the justification or not. From experience though where no clear statement is available within recognised codes and standards, the 3rd parties all fall back on the old "test pressure should be 1.5xPs"

 

[XL83NL]

I wouldnt be too concerned. Sure, you need to make sure your design is correct and properly tested, but for SEP there are no requirements. So

Would it be SEP to use a proper piping code i.e. EN 13480 for the calc on max external pressure, but an external hydro test pressure of 1.25xPs.

would surely be enough.

However, since your tubing will be inside a large ø pressure chamber, shouldnt it be cosnidered as part of that piece of pressure equipment?