Incident Report
Subject: Atmospheric Storage Tank Gassing - Roof Sinking Potential
Date
of first enquiry: 08/05/04
Initial enquiry / comment.
Can anyone help out with a response to the following
question. I would appreciate you 'RESPOND TO ALL' to share the learning.
Members
I would like to run a question about running down low RVP (light) condensate/crude
into floating roof tanks. Thus we have a liquid with what appears to be a
potentially lower specific gravity than documented (like the Bermuda triangle'
effect with gassified sea water unable to sustain buoyancy of vessels on the
surface) .
I am trying to gather together 'real' events where light material (high gas
content) entering a floating roof tank has led to for example seal leakage,
roof tilt/sink, fires etc.
Any world-wide incident reports where light material entering the tank has
led to such scenarios is what I am after.
Perhaps there are case histories within our JOIFF group network.
Responses:
Date |
Detail |
Documents |
11/08/2004 |
Infrequently, we do have to slop
off-spec LPG from the unit into crude storage tanks. To avoid gassing
up the tank, the receiving crude tank must have a minimum pre-determined
amount of crude (100 kb) before we allow LPG to be rundown . In addition
we re-circulate the bottom portion of the tank content during the whole
duration when the slopped LPG is being rundown.
This procedure was put in after we experienced oil-on-roof during un-controlled
slopping of LPG/light ends. Since establishing this procedure no such
recurrence .
Our refinery also has pigging operations for our product shipments
through marine. We use 100 psig Nitrogen pressure to propel the pigs.
We have had incidents whereby tank roof seal had been damaged by the
high pressure Nitrogen bypassing the pigs due to out-of-roundness of
the pigs. Couple of times we had oil go above the floating roof due
to same reason. Since replacing the typical spherical pigs with Bi-directional
compressible discs, we have overcome this problem. |
|
