UNEXPLODED ORDNANCE - Wind Energy Network

SPONSORS OF Unexploded Ordnance
If you then have two conical charges
directionally opposed to each other where
they are mounted in-line on either side of
the UXO you create a ‘collision’ charge
effect this is where you have two explosively
formed jets meeting at approx 18,000m/s
any explosive compounds in between will
have the best chance to sympathetically
detonate/produce a reliable detonation
pressure shockwave and if not the whole
UXO will be destroyed into very small pieces
due to the effect of the collision charge.
Blast Design use plastic explosives in
the shaped charges along with an EBW
(Exploding Bridgewire) Firing System
to initiate the charges, this requires an
all fire current in excess of 3,000volts
and 1,000amps, which ensures a safe
environment for initiation.
Operational Planning
Once the donar charges and firing
system is agreed along with the data
collected from the ‘as found’ survey,
the Environmental Impact Study, Risk
Assessment and Operational Procedures
are put together along with operational
meetings with key personnel is carried out.
Mitigation method
The mitigation method is then agreed
based on the NEQ of the UXO –
distances, mitigation methods etc. This
would include a seabed anchored PAM
system (Passive Acoustic Monitor), this
will pick up the vocalisations of marine
mammals which will track them from/to
the target or danger area.
A decision is then made as to what
deterrent mitigation systems to use,
namely seal/dolphin/whale scarers that
emit various frequencies of noise which
is uncomfortable to each type of marine
mammal.
A pressure pulse scarer for fish is then
used, as they are not affected by the
acoustic deterrents but need a small
explosion producing a pressure pulse to
scare them away. Again Blast Design
have designed their own ‘pressure pulse’
grenade for this purpose which after the pin
is pulled out and deployed in the water, it
sinks and initiates 4 tiny explosions.
PAM system
The PAM system operates full time while
on UXO site – the acoustic scrammers are
put on within 30min of detonation and the
fish and the fish pressure pulse grenades
are fired 2 minutes before detonation.
They also have a minimum of one
MMO (Marine Mammal Observer) and
one PAM technician out on every UXO
operation. All members of the vessel are
potential MMO’s on every trip – it is all the
responsibility of al personnel to look out for
marine mammals.
Mobilisation
All explosives related equipment is tested,
checked and mobilised.
The vessel selected is chartered along
with all appropriate equipment. Use of
robotics and not divers is preferred.
On Site/Disposal
• The PAM system is deployed
• Full time MMO’s are in place –
consideration is to time of year/species
present etc), Scrammers are also
placed
• The donar shaped charges are laid on
the sea bed and firing cables run out
to safe firing distances
• All local shipping, DSVs, MVs,
coastguard, Navy etc. are informed
and given an approx initiation time
Procedural stages
• The seal, whale, dolphin acoustic
scarers are turned on, for approx
20-30 mins
• Once all systems are in place the
MMO’s give an agreed firing the
go-ahead
• Activation of overpressure blast
monitor
• Set off fish pressure pulse scarers and
fire the shot
Successful detonations are identified by
the effects on the surface and also the
sound/effect on the bottom of the vessel –
an inspection is then made by ROV.
Findings would be...
• A crater on the seabed
• Very small pieces of UXO lying on the
seabed
Any pieces bigger than a large paint tin are
recovered and an ‘as left’ survey is carried
out and full report is written up.
Blast Design
www.blast.co.uk
Ed’s note – this is an abridged version.
We recommend you visit Blast Design’s
microsite held within our supply chain
register by scanning the QR code below
or clicking on the pink flash in the online
magazine.
Click to view more info
www.windenergynetwork.co.uk
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