can the roof plates be fixed to the structure in api 650 tanks? 1

[DIP91]

God day, I have a question for the forum:
I want to guarantee an internal pressure in an API tank of 200 mmH2o, but this is almost 4 times higher than the pressure exerted by the roof plates and all the accessories.
can i fix the roof plates to the tank structure?

 

[HTURKAK]

API 650 does not encourage that and for frangible roofs , forbidden..


But for APPENDIX F tanks yes. The relevant para. copy and pasted.

 

[DIP91]

HTURKAK, thank you for your reply

 

[JStephen]

Generally, that pressure would be resisted by the plate itself, and by the top angle area acting as a compression ring. So you don't need to attach the plate to the structure to resist the uplift. Refer to Annex F.

 

[DIP91]

JStephen Thank you for your response.
The issue is as follows:
The tank I am talking about will be a tank used to dehydrate the crude oil, and in addition, we want to recover the gas that is managed to separate. The pressure exerted by the roof plates and the fittings attached to the plates is 51.5 Kgf/ m^2. Therefore, the pressure I need internally is 3.8 times higher.
We agree that the ceiling tiles alone resist this value.
But API 2000 for the VPV setting in 3.6.2.5 suggests that excessive uplift and bending of the roof plates should be avoided, as long as the tank is not covered by annex F.
Is there anything written that tells me when there is excessive uplift, or simply if I use annex F is it necessary to fix the roof plates to the structure?
I will be very grateful for your collaboration

 

[JStephen]

If it's a new tank being built, then design and build it per Annex F for the appropriate design and operating pressures.
If it's an existing tank, then you are looking at a Change of Service as indicated in API-653, and the tank needs to be evaluated for the proposed pressure.
This may also involve checking anchorage, overturn, combined wind/pressure, top angle detailing, roof nozzle detailing, etc.