Nozzle flange thickness

[Syahar1975]

Dear experts,

If many of our nozzle flange thickness is less than the code, do we need to replace the flange ?

The tanks is single wall tank and design pressure is 130 mmBar.

The flange is 150# class,

The product storage in the tank is water in some tanks and crude oil in other tanks.

In my opinion we do not to replace the flange. But we can ask tank designer to check if the flange still OK or not.

I do understand the code for flange does not accept minus tolerance. But I believe the tank designer reserve the right to decide based on their calculation.

Your comments and advise is highly appreciated.

 

[geesamand]

If it's a flat face flange, I don't see anything wrong with proceeding to calculate as you propose.

If it's a raised face flange, I don't see much opportunity to reduce thickness as so much stress comes from the gasket / bolt offset.

 

[Duwe6]

If the mating pipe flange is indeed Class 150, it is raised-face [Cl. 125 for FF flanges], and the faster, cheaper solution ti to replace the tank's flange with a 150 slip-on or weldneck. Bolting a standard class 150 to a thin FF will most likely cause a leak, and *will* distort the thin flat flange. Change it out and bring it up to API Code.

 

[Syahar1975]

Good morning Gents,

The RSFO flanges are 150# class and our piping flanges connected to this nozzle also RFSO same class.

We are not decided yet to replace but I strongly request for tank designer calculation for this issue.

 

[11echo]

Are these API-650, or API 12B or 12D tanks? ...And under 10,000 BBL.s? IF so the tank wall thickness is about 1/8" + or -, and 3/16" at 10,000 BBL.s! Whether or not a flange is RF or FF is immaterial, as long as the flanges meet ASME B16.5 requirements. They far exceed what the tank is made of! PS ...you won't have any CI - cast iron flanges on any tank! Cast iron is far to brittle! You may have cast iron components or other "soft metals" exterior of the tank (like aluminum mushroom cap pressure/vacuum regular) which will require a flat faced flange on the tank to deal with them, but that's it!

 

[Syahar1975]

Good morning 11echo,

This is API 650 tank. We did check by UT several times involving 3rd party as well. The result is yes our flanges thickness mostly less than ASME B16.5 requirement.

My understanding ASME B16.5 does not allow minus tolerance.

If we have to replace all this "minus" flange it would be a night mare since hydrotest, painting and piping connection have been completed.

Yes this should have been caught when the flanges material arrived in the fabrication shop before fabrication and before shipped out to site.

There must be a way to check whether these "minus" flanges are still OK for 130 mm Bar design pressure. We did pneumatic test till 200 mmBar and did not found any problem on these flanges.