Permanent attachment clause 5.8.1.1 in API 650

[Syahar1975]

Dear expert,

We are constructing a tanks with group V material with over flow nozzle.

API 650 5.8.1.1. states permanent attachments above the maximum liquid level are not permanent attachment. Since the tanks have an over flow nozzle so the maximum liquid level will not reach above the over flow nozzle.

Clause 7.2.3.6 also state all permanent attachments on the shell must be either MPI'ed or PT'ed.

We have rafter clips with a pad plates welded to the shell above over flow nozzle.

In my opinion this rafter clip's pad plates not need to be MPI'ed nor PT'ed.

Syah

 

[IFRs]

The standard does not define "maximum liquid level", but I would use Design Liquid Level H as defined in 5.6.3.2 and say that these rafter pads do not need the NDE in 7.2.3.6 if they are above the liqud level. The tank name plate should clearly state the design liquid level.

 

[Dhurjati Sen]

Dear Syahar1975,

How much resources would be saved if these are NOT PT'ed? Imagine there is a failure during operation in one of these joints. The tank has to emptied and other precautions need to be taken before a hot job permit is issued.

Check the code again. Does it allow any welding on the shell above the overflow nozzle? Definitely, it is not a good engineering practice.

Regards.

DHURJATI SEN
Kolkata, India

 

[Syahar1975]

Dear All,

Thanks for the response.

Yes, there will be a lot of saving since there are a lot of attachments (inside and out side the tank) which is above the design liquid level.

Syah