Tank Roof (design) capability to bear load of new PV VENTS installation 2

[Muhammad Shoaib Anwar]

Hi,

Below mentioned tanks are about 20 years old, previously no PV at roof installed now it is process of installation of PVs but concern about roof is capable to bear PV load or not, below is available information,

Tank # Diameter Height Orientation Type Product Status Roof Type
0001 30.5m 14.63m VERTICAL ABOVEGROUND Petrol/PMG In Service Fixed Roof
0002 24.4m 14.63m VERTICAL ABOVEGROUND Petrol/PMG In Service Fixed Roof

Approx. Weight of PV vents for Tank # T-0001 = 802 kg
Approx. Weight of PV vents for Tank # T-0002 = 660 kg
Since, the nozzles on roof top of each tank are at approximately within 10-15 feet radius from center of roof.

Question is tanks will be able to bear the weight of the said PV Vents during their normal operation or not?

Thanks

 

[JStephen]

Usually, it isn't a problem to support P/V vents. But you do need to check rafter capacity on a fixed roof.
It may be advantageous to locate the vents at the tank center rather than away from the center.
If weight does turn out to be a problem, consider using two smaller vents.
Confirm that size is right for the tank- it may be possible to use smaller vents with a larger emergency vent or some combination like that.

 

[Muhammad Shoaib Anwar]

Dear Mr.Stephen Noted with Thanks,
Shall this query to be tackled by a designer for evaluation and suggestion or process and / or inspection engineer can tackle?

 

[HTURKAK]

Dear Muhammad Shoaib Anwar (Industrial),

The diameter of tanks 30.5 and 24.4 m and fixed roof implies that the roofs are supported cone roofs with rafters supported on girders. The rafters could be supported on girders on columns and with central column. The angular spacings between rafters shall allow to installation of PV nozzle . The nearest two rafters and roof plate shall be checked for the above mentioned extra loads.

 

[IFRs]

Those are very heavy vents, if those weights are for one vent. Definitely should check the structure underneath, in combination with other design loads per API 650.

 

[MJCronin]

The installation of new, very heavy vents makes me think that the tanks are being re-purposed.

Are these tanks being re-used for another, heavier liquid ?

Were the tanks designed to hold a lower SG liquid, but now must store a higher SG liquid (like, say crude oil ?)



MJCronin
Sr. Process Engineer

 

[Dhurjati Sen]

This is a design issue. The load on the tank roof needs to be recalculated before installing PVs.

Spare the poor process and inspection engineers from this ordeal.

DHURJATI SEN
Kolkata, India