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Research & engineering support
to the SSN Kursk salvage project
The Krylov Institute and the national
submarine construction
From the very day of its foundation as
the first model tank in Russia in 1894, the Krylov Shipbuilding Research
Institute became the focal point of scientific developments and unique
experimental facilities for all major disciplines associated with naval
shipbuilding.
The following milestones of the Russian submarine development history
may demonstrate the role and the significance of the Krylov Institute:
- All submarine designs ever considered in the country, which by today
number over 300, have been tested in towing tanks, cavitation tunnels,
acoustic, magnetic, and nuclear and radiation experimental facilities
of the Krylov Institute. The Institute has developed all engineering
regulatory documents (guidelines, norms, design rules, manuals, etc.)
on performance, seakeeping, manoeuvrability, structural strength,
signature control, nuclear and radiation safety. The Institute designs
propellers, hydroacoustic tiles, resilient mounts, degaussing systems,
etc.
- It was at the Institute (at that time the Experimental Tank) that
they worked on the first national submarine design, the Delfin. That
project was carried out by a team under I.G.Boubnov, the Senior Assistant
to the Tank Superintendent and later the Head of the Naval Ship Drawing
Shop of the Baltic Shipyard. The first national nuclear submarine
project (Pr.627) has also originated within the Institute since it
was commenced under V.N.Peregoudov, then the Deputy Director for Research
at the Institute and later the chief designer of that submarine and
the head of a newly established submarine design bureau known today
as Malakhit.
- Nowadays, aiming at establishing closer relations between researches
and seamen who operate their developments, the Krylov Institute has
revived a long-standing Russian tradition of patronage. The Institute
has become the patron of the SSN Gepard of the Guards, the
250th nuclear submarine that happened to be the first nuclear boat
of the Russian Navy commissioned in the third millennium.
Krylov Institute contributions to the
SSN KURSK salvage project
The recovery of the sunken SSN Kursk
was a unique project because of the huge weight of the submarine and
of the fact that she carried a nuclear power plant and combat missiles.
The operation was also complicated by unfavourable wave and wind conditions
at the accident site.
Specialists of the Krylov Institute carried
out research and engineering work in support of the project design that
has required resolving a number of intricate technical and engineering
challenges involved in every step of the unique operation.
The Krylov Institute has within extremely
short deadlines generated computer models describing the mechanics of
interactions in multi-stage power systems. Based on numerical simulations,
they have found the safety-optimum way to grip the submarine through
special holes cut in the pressure hull, and designed optimised shapes
of both the grippers and the gripping holes.
In order to derive information necessary
for generating computer models of the submarine and of the salvage barge
properly representing the realistic conditions, the Institute had to
apply special procedures and to perform comprehensive model tests in
the Wind Tunnel, the Rotating-arm, the Seakeeping and the Manoeuvrability-&-Seakeeping
Basins.
All final decisions eventually implemented
in this international project by Mammoet were taken only after experimental
validation of strength margins available in every major component of
the system: the submarine hull, the gripper, the strand bundle and various
in-between parts. Such a laboratory validation exercise has become possible
only thanks to unique experimental facilities of the Krylov Institute.
The Krylov Institute has also provided
radiation monitoring at the SSN Kursk accident site and
in the immediate vicinities of the submarine hull. Those measurements
taken by staff members of the Institute enabled to assess the status
of the nuclear power plant, to evaluate the radiation situation and
to estimate potential effects upon the environment and the safety of
the job.
The achieved unprecedented scale and speed
of introducing innovative engineering developments into practice have
ensured a high level of safety of the whole salvage operation.
Krylov Institute work on dynamics and
hydrodynamics
The Krylov Institute has under a vary
tight schedule performed extensive experimental and numerical exercises
in order to develop and justify measures aimed at failure-safe execution
of every step of the submarine salvage operation.
Dynamic processes associated with the
lifting of the real submarine were investigated with the help of the
most advanced numerical and physical modelling techniques. That has
enabled to account for both the design features of the salvage system
components and the sophisticated nature of their hydrodynamic and mechanical
interactions among themselves and with the environment.
In order to derive information necessary
for generating computer models of the submarine and of the salvage barge
properly representing the realistic conditions, the Institute performed
comprehensive model tests in the Wind Tunnel, the Rotating-arm, the
Seakeeping and the Manoeuvrability-&-Seakeeping Basins. The models
were tested both separately (to describe submarine separation from the
seafloor and lifting towards the surface while the distance to the barge
is still big) and together, i.e. under conditions representing submarine
to barge mating, haulage and docking phases. In some cases it was necessary
to devise special testing procedures in order to reflect the specifics
of the involved objects (e.g., the effects of pneumatic motion compensators
mounted on the barge) and processes (submarine break-out of the seafloor
soil, mating with the salvage barge, etc.).
The unique engineering complex consisting
of the submarine, the barge, the lifting strands attached to 26 jacks
and compensators has required generating special computer models describing
the interactions of these components that had been never before used
in any research associated with marine operations.
Experimental and numerical methods served
to predict environmental forces on the submarine and on the barge, including
rough sea and wind effects, loads on grippers and strands, motions of
heave compensator pistons, and other dynamic parameters associated with
system deployment, gripper positioning, submarine separation from the
seabed, lifting and transportation to the docking site.
Based on examinations of numerous weather
options, lifting jack and heave compensator operation modalities, and
other submarine lifting parameters, they have evaluated the safety of
each operation phase and formulated recommendations on the execution
of those phases. For the sake of such safety assessments, it was necessary
to evolve dedicated safety criteria related to strength and design features
of the salvage complex. Those criteria were successfully applied both
at the research stage and in the course of the real operation. Among
those purpose-developed safety criteria, one of the key ones was the
criterion that accounted for the dynamics of the heave compensator pistons
designed to reduce strand and submarine hull loads in waves and due
to dynamic effects associated with the submarine break-out from the
soil.
The performed investigations have shown
that the Sea State and the wave propagation direction sizeably affected
the loads on system components, their motion parameters and eventually
the safety of the operation. A very significant aspect of successful
execution of the job was also the procedure of the salvage operation.
Violating any of the weather restrictions formulated by the Krylov Institute
for every step of the operation could have resulted in an accident.
Those restrictions and limitations were formulated on the ground of
the results of the above-mentioned tests and simulations specifically
for each phase of the salvage operation.
Considering the thus elaborated recommendations,
the Institute has confirmed the possibility of performing all preparatory
steps, including strand pre-tension, submarine separation from the seafloor
and lifting in waves of Sea State 4 inclusively. For the subsequent
mating and haulage phases it was possible to allow a wider range of
wave conditions up to Sea State 5 provided the salvage barge kept close
enough to head seas.
All recommendations and their justifications
were co-ordinated with the SSN Kursk salvage project designer
Mammoet, with the Rubin submarine design
bureau and with the relevant experts of the Navy. After that, they were
handed over to the salvage team as manuals and instructions on submarine
lifting and transportation. The Mammoet company has used
those recommendations as the basis for their safety plans for all phases
of the operation.
Krylov Institute work associated with
the mechanical strength
The SSN Kursk salvage operation
safety largely depended on the sufficiency of the strength of all components
of the lifting system and of the submarine hull. In order to resolve
problems associated with this aspect, the Krylov Institute has already
at an early stage of the project development made a complex of theoretical
numerical studies on the mechanics of gripper/hull interactions and
on the submarine hull strength under different gripping options. The
outcomes of those investigations enabled to formulate guidelines on
more rational configurations of the gripping holes and on modifications
of some gripper parts in order to achieve more favourable conditions
for interactions between the grippers and the hull.
Considering the uniqueness of the operation,
the Krylov Institute has initiated an experimental validation programme
for all suggested engineering solutions. For that purpose, the Rubin
design bureau has on the basis of computations and the Institute's configuration
of the system designed test structures that included all principal components:
a piece of the hull from a submarine similar to Kursk, the gripper the
strands and the associated in-between parts.
The hull structures fabricated at the
Sevmashpredprijatie shipyard and the actual grippers
delivered by Mammoet were tested using unique machines
under the greatest static and cyclic loads anticipated for the lifting
operation. In order to establish the real safety margins, the structures
were tested till failure. Analyses of the obtained results enabled to
formulate requirements to allowable conditions for the execution of
the intended operation in terms of Sea States and the minimum number
of the grippers.
Test results have also demonstrated the
need to additionally reinforce the salvage barge hull in way of the
strand holes and to change the original collapsible plastic shoes of
the grippe clamps for new ones made of perforated soft steel.
It was also at the Institute's site that
they have practically tried the new technology suggested for cutting
the gripping holes and removing obstructing details of the submarine
hull.
Altogether, the performed work has made
it possible to finalise design solutions and to validate the safety
of the salvage operation under the guidelines formulated by the Krylov
Institute.
Krylov Institute work on radiation measurements
and assessments
The Krylov Institute started working on
radiation measurements and assessments already two weeks after the submarine
was lost, i.e. in late August 2000. In September, the Institute took
an active part in two voyages to the accident site in order to clarify
the actual radiation/ecological situation in the Barents Sea and to
assess the status of the reactors and their shielding. As a result of
a large series of measurements using submerged gamma spectrometers and
hydro-physical instrumentation deployed primarily around the submarine
site both from surface ships and deepwater submersibles, they obtained
information showing that no radionuclides had reached out from the submarine
hull into the environment. The measured data proved that the reactors
were in a favourable condition and the radiation situation in the area
was normal.
The Institute has provided methodological
and instrumental support to all radiation-related activities throughout
all preparation and execution phases of the salvage operation. They
have considered various radiation scenarios, formulated guidelines on
measurement techniques and work programmes. The Krylov Institute has
upgraded the available instrumentation for radiation and ecological
monitoring and generated specifications for instrumentation necessary
to ensure reliable radiation monitoring of the nuclear submarine salvage
operation.
In summer - autumn 2001 the Institute's
staff took radiation measurements during four voyages to the site made
at different phases of the SSN Kursk lifting, transportation
and docking operations.
The performed comprehensive measurements
taken in those voyages and directly on the submarine hull from the
Giant-4 salvage barge have demonstrated the absence of any increases
above the normal radiation background. That has allowed concluding that
neither the SSN Kursk salvage operation nor the accident with the submarine
had inflicted any damage to the environment and the personnel involved
in the job.
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