## F.6.1 - calculate the Minimum Roof Thick required for Internal Pressure (t)

## F.6.1 - calculate the Minimum Roof Thick required for Internal Pressure (t)

(OP)

In F.6.1, to calculate the Minimum Roof Thick required for Internal Pressure (t), you required to estimate the P = Internal Design Pressure – Effect of Nominal Roof Dead Load.

- How to estimate the Effect of Nominal Roof Dead Load?

- I presumed that the (Internal Design Pressure) mentioned-above is the MIN(PF.4.1 , PF.4.2, Preset Design Internal Pressure, 18KPa as per 5.2.1.c), am I correct?

Mohd Yaseen

- How to estimate the Effect of Nominal Roof Dead Load?

- I presumed that the (Internal Design Pressure) mentioned-above is the MIN(PF.4.1 , PF.4.2, Preset Design Internal Pressure, 18KPa as per 5.2.1.c), am I correct?

Mohd Yaseen

## RE: F.6.1 - calculate the Minimum Roof Thick required for Internal Pressure (t)

- The nominal roof dead load is roof plate wt for unit area.. Suppose that the roof plate 8 mm, and the unit is kPa,

nominal roof dead load = 8mm * 7.85 kgf/m2/mm=62.8 kgf/m2 =kgf/m2 *=0.00980 =0.61 kPa

- The Internal Design Pressure

SHALL BEstudied and decided by an experienced process engineer..## RE: F.6.1 - calculate the Minimum Roof Thick required for Internal Pressure (t)

Design pressure is always specified by the Purchaser. The value in 5.2.1.c is the maximum pressure permitted by the API 650 design code, but the requested design pressure is very rarely even close to this value. The most common design pressure for API 650 tanks is 0.0 kPa/psi (also called atmospheric).

## RE: F.6.1 - calculate the Minimum Roof Thick required for Internal Pressure (t)

Thanks for your inputs.

Now Dead load issue is clear.

Dear Geoff13;

about Internal Pressure; agree with you 18 Kpa is normally didn't reached & is considerably large compare to the OP of the ATM Tanks, however, my question is mainly focusing on PF.4.1/PF.4.2 compare to the Preset Design Internal Pressure?

Mohd Yaseen

## RE: F.6.1 - calculate the Minimum Roof Thick required for Internal Pressure (t)

You would start with an initial roof-shell junction detail, and then calculate it's maximum permitted pressure per F4.1. If it's less than the required internal design pressure then strengthen the detail by using larger members or a different detail. Repeat until an acceptable roof-shell junction detail is found.

Next you would assume an unanchored tank, and then calculate the maximum permitted pressure as limited by shell uplift per F4.2. If it's less than the the required internal design pressure then make the tank heavier or anchor it. That decision is a cost issue. Since both can be expensive it may be worth pointing this out to the Owner to see if they can reduced their required internal design pressure and save some money.

The Code rules don't alter or limit the internal design pressure specified by the Owner. They only determine if the chosen tank details meet or exceed that internal design pressure.

## RE: F.6.1 - calculate the Minimum Roof Thick required for Internal Pressure (t)