Shell manhole nech thickness table 5.4a note b

[Jagmtr]

Dear all,

I have one issue in my api 650 storage tank. Due to oversight i have not considered note b in table 5.4a for shell manhole thickness.
I have chosen less thickness than the minimum requirement & mistake come to know when hydro test has been done.
Please give me suggestions for following points:-

1. Is this possible that we can modify the neck thickness or provide other means without replacing manhole ( as per code acceptance)?
2. If we will have to replace the manhole then can we perform box type local hydro test of nozzle only instead of again performing full hydro test? (as per code acceptance)

It will be very helpful if i get any guidelines that needed urgently.

Thank you in advance for support.

 

[mk3223]

Just for reference, IMO,
- Communicate the issue with the Owner and Tank Inspector ASAP for the possible solution
- Calculate the actual neck thickness of the manhole per actual design condition, i.e. actual liquid height, density, P&T, etc., and compare it with the API-650 Table
- Consider the option for additional reinforced pad around the Manhole, if accepted

 

[Jagmtr]

Thanks mk3223 for your kind response.
We have motor sprit tank dia 34 m & 16 m height. Manhole neck ID is 750 mm. Manhole neck, manhole flange, RF pad material is same as we have for shell plate ( it is IS2062grB equipment to SA36)
Shell bottom corse thk is 25 mm which is more than required thk 22 mm & RF pad thk is also 25mm. Other RF pad diamentions are as per code requirements.
when i calculate the manhole nech thk with the same concept that we apply for shell thk calculation, it equal to = (shell bottom corse thk/ shell dia) * manhole dia = 0.6 mm.
As per table 5.4a(without considering note b), manhole neck thk is 11 mm while we have provided 14mm.