storage tank construction
Post on 21-May-2017
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Tank Types
• Coned Roof
• Internal/Covered Floaters
• External/Open Top Floaters
Cone Roof Tanks
Cone Roof Tanks
Normally contain high flash-point liquids
Cone Roof Tanks
Cone roof tanks have a vapor space between the liquid level and the roof.
Cone Roof Tanks
At the time of ignition if the vapor space between the liquid surface is in the flammable range, a vapor air explosion will occur.
Cone Roof Tanks
Cone roof tanks are equipped with a pressure/vacuum relief device to adjust the internal pressure so that it is nearly equal to the external atmospheric pressure
Pressure/Vacuum Vent
Pressure/Vacuum Vent
As liquid enters the internal space, the pressure created by the compressing vapor is vented to the atmosphere or directed to a vapor recovery system.
Pressure/Vacuum Vent
When the product in the tank is discharged, the pressure/vacuum vent allows air to enter the tank, preventing damage that may be caused by the negative pressure.
Pressure/Vacuum Vent
Roof To Shell Seam
The roof to shell weld on cone roof tanks are only welded on one side.
Roof To Shell Seam
This weak seam provides a point of failure during the case of a vapor air explosion. It prevents tank failure at the base of the tank.
Roof To Shell Seam
Weak Seam
Roof To Shell Seam
Incidents Involving Coned Roof Tanks
• Pressure/Vacuum vent fires
• Fish mouthed fires
• Full surface fires
• Manifold fires
• Dike fires
Open Top Floaters
Open Top Floaters
Open Top Floaters
The floating roof eliminates the vapor space above the liquid.
Open Top Floaters
Open top, or external floaters, are designed with a stiffening ring (commonly known as a wind girder) to add support due to the absence of a roof.
Wind Girder
Roof Seals
• Provide spacing to allow for the roof to travel up and down on the product without touching the tank wall.
• Provide a barrier between the fuel surface and the atmosphere.
Roof Seals
Roof Seals
Incidents Involving Open Top Floaters
• Seal fires
• Full surface fires
• Dike fires
• Manifold fires
Internal Floating Roof Tanks
Same basic design as the open top floater but it also utilizes a fixed roof.
Internal Floating Roof Tanks
Internal Floating Roof Tanks
Internal Floating Roof Tanks
Internal floating roof tanks can be identified and distinguished from the cone roof tank and
the open top floater by the characteristic “eyebrow” vents at the top of the tank shell.
Internal Floating Roof Tanks
Eyebrow Vent
Incidents Involving Internal Floaters
• Vent fires
• Fish mouthed fires
• Full surface fires
• Dike fires
• Manifold fires
Causes Of Ignition
• Lightening strikes
• Hot work on live tanks
• Flare stack fall-out
• Over heat or failure of mixers
• Over-fill with remote ignition sources
• Floating roof contact with tank shell
Reducing The Risk Of Ignition• Secondary seals for high vapor
pressure products.
• Fire retardant rimseal materials.
• Independent high level alarms.
• Linear heat detection in the rimseal.
• Wind girders with handrails, to facilitate inspection of seal areas, and foam application to the seal area.
• System maintenance
Costs Associated With Tank Fires
• Denver International Airport Tank Farm, USA. Fuel pump failure. - 32,000,000
• Marine Terminal, Naples Italy.
Tank overfill. - $42,000,000
• Refinery Tank Farm, Milford Haven, U.K. Exposed oil on the roof. - $11,100,000
• Tank Farm, Newark, N.J. USA,
Overfill - $ 35,000,000
• Tank Farm, Romeoville, Illinois, USA
Lightning strike. - $8,000,000
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