Hi everyone, I would like to share some notes and questions regarding road tanker filling of a tank farm holding flammable liquids.
Some questions were made for the way large tanks are filled
from tanker, as part of the Control of Major Accident Hazards (COMAH)
Regulations.
Like my other posts, questions here can be asked for any
generic process plants.
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| Photograph 1: Liquid Storage Tank |
Bund in a tank farm:
1.
Can you share the bund of a tanker offloading
point with the same one from a tank farm?
(1)
Usually they are linked to a fire pit, that is
brick lined
(2)
Where foam is poured inside of it (This is the American
approach, not common in the UK)
(3)
Usually need bund and sump (for rain water)
(4)
Are the drains channelled into interceptor
tanks?
(5)
Can sloping be used to remove pool under tank? –
usual for butane tanks
(6)
Could you direct spills into another area, for
burning, where fire engulfment is less?
Tank farm protection:
2.
Are the support legs of the tanks fire
protected? – e.g. with Intumescent coating?
(1)
As the coating heats up, it swells, which chars
and creates an insulating layer
(2)
This is ok against pool fires, BUT NOT for jet
fires, as it blows off the char in
(3)
Usually the legs are over coated, (thin or thick)
(4)
But char on a thin film (structure) is soft
& may not be able to handle, 37 kW/m2 of heat
(5)
Note that steel usually has a critical
temperature of ~650 to 720°C
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| Photograph 2: Generic storage tank with pipes |
Tanker filling transfer pump system:
3.
Is tanker being filled with own tanker pump or will it use the facility's pump system?
(1)
Usually design transfer system around the tanker
(2)
Tankers can have different pumps and systems –
e.g. small or large pumps
(3)
Are the road tanker or tank rated for pressure, maximum
of the transfer pump?
(4)
Have maloperations been accounted for? E.g.
deadheading of pump?
(5)
Usually tanker have a compressor system with air
for transfer rather than pumping.
(6)
Usually in COMAH sites, it is the sites in
control of the pump and transferring, rather than the driver, e.g. pump,
transfer hose coupling, connections, etc
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| Figure 1: Road Tanker Zoning (As per HSG176 guidelines) |
Preventing tanker movement during filling:
4.
What are the safety systems to prevent tanker filling
failures? E.g. tank movement during filling
(1)
Can the ramp (tanker inlet point) be wet? If in
a slope for tanker to park on?
(2)
Has ice and snow been accounted for at the
tanker filling point?
(3)
Battery powder interlocking to keys and brakes –
to prevent movement of tanker
(4)
CCTV, with permanent staff – usually credited in
a LOPA study
(5)
HSE guidelines usually has 3 types of tanker
filling set ups,
i. Standard
set up with little to no protection
ii. Mid
range – 1 method in which the driver is protected
iii. Above
average – multiple methods to protect tanker filling, e.g. movement detectors
protection to trip transfer if road tanker is moved – HOWEVER this gives a lot
of false positives
(6)
Types of protection
i. Wheel
protection, to prevent drive away
ii. Battery
interlocks
iii. Barriers
iv. Remove
keys/cables
v. Break
away couplings
vi. Automated
trip valves
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| Photograph 3: Tanker Filling, connections |
5.
Could short pneumatic coupling connections be
used, to prevent tanker movement?
(1)
For example, a 1.5 metre hose, that could be
stretched out, linked to trip system
(2)
Can it work for a manifold system, with multiple
connections at distances away?
(3)
Would you need multiple specifications for these
hoses for different types of tankers?
(4)
Where would it connect on the tanker? Rear or
the centre?
(5)
Also account for different specs on the outlet
on the vehicle
(6)
Would it require regular inspection?
(7) Could the hose easily melt if it were ignited somehow?
Thank you for reading, please comment, like and subscribe to
this blog
Hope you have enjoyed reading this
Chiraq
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