SIO SOLO failure modes

1
SIO SOLO failure modes

• Megan Scanderbeg
• John Gilson
• Scripps Institution of Oceanography

2
Float statistics

• 733 total floats have been deployed by SIO
• 432 are active
• 235 are dead (havent reported a profile for more
  than a year)
• 47 are mia (missing and havent reported a
  profile in less than one year)
• 19 are failed (sending bad messages)

3
Failure modes

• Loss of vacuum inside float 28
• Unknown 26
• Loss of CPU voltage 16
• Float grounds 6.6
• Oil leak 4.7
• Bad CTD 4.3
• Antenna problems 3.0

4
Loss of vacuum inside float (28)

• Problems slow leak resulting in loss of vacuum
• Causes Slow leaks come from water leaking into
  air bladder on outside of float or from air
  leaking through seals
• float slowly sinks over time
• float can still profile and return messages until
  float is too low in water to send messages
• Solutions remove air bladder as on new SOLO II
  and replace old seals with newer ones which have
  mostly erased air leaking as a failure mode
• Currently, difficult to determine how slow
  vacuum loss affects overall float lifetime

5
Loss of CPU voltage (16)

• Problem CPU loses voltage and thus no longer
  functions
• Cause Probably had a bad batch of batteries on
  CPUs that failed after 100 cycles or 3 yrs
• Solutions Doubled batteries on CPU
• Developing new test to check voltage on each
  battery pack on CPU prior to deployment
• Should not be a failure mode in future

6
Float grounds (6.6)

• Problems Float grounds and does not resurface
  again float washes ashore float grounds and
  resurfaces, but does not return any profiles
  after resuming profiling
• Possible cause for not returning profiles after
  resurfacing Problems with software code causing
  float to think it should not send a profile after
  being grounded
• Solution Changed software code
• Problem seems to have mostly disappeared, but not
  convinced code was source of problem
• Hard to predict where floats will go and where
  they might wash ashore or ground and not
  resurface, but keep in mind when planning
  deployments

7
Oil leaks (4.7)

• Problem Oil leaks in external bladders causing
  floats to shoal and not profile down to original
  depth
• Cause Probably a bad batch of bladders
• Solution Still using same bladder company
  appears to be just one bad batch and problem is
  not recurring

8
Antenna problems (3.0)

• Problem Only a very small number of messages
  are being sent during a surface interval. Can
  vary over float lifetime.
• Causes Bad batch of antennas or damage during
  surface interval
• Solution Switched antenna supplier company
  have fewer failures so far
• Pay close attention to messages used to
  create profile

9
Float hard reset

• Problem When measuring P,T,S during drift,
  float resets itself and begins 10 day drift cycle
  over - results in 15-day cycle
• Causes Hard reset occurs when CPU voltage falls
  below threshold value and thus resets itself
• Low voltage could be result of large current draw
  elsewhere or cold water at drifting depth which
  makes it hard for the batteries to work
• Often means float will soon fail
• Currently there is no solution, but small number
  of floats with this problem

10
SOLO-II

• Compact, lightweight, efficient
• No air bladder (removes one source of slow leak
  vacuum failures)
• More efficient reciprocating pump as used in
  Spray glider (55 vs. 40)
• Uses Iridium communications
• saves power from less transmissions
• allows more data to be taken and sent
• Half the batteries of SOLO-I
• Long life (6yrs)
• Can profile to 2000 m anywhere in world
• Prototypes are currently undergoing lab-testing
  with a test deployment in near future

SOLOI SOLO- II
11
SOLO version comparison
SOLO-II internal view, SOLO-I in back
12
Summary Conclusions

• Goal to reduce failure modes so that 90 of
  floats survive 5 yrs
• Reducing/ eliminating slow air leaks with new
  seals and no air bladder on SOLO-II
• Reducing/ eliminating CPU voltage failures with
  larger battery pack and better pre-deployment
  tests
• Reducing/ eliminating oil leaks with better oil
  bladders
• Reducing/ monitoring antenna problems new
  supplier providing better product
• SOLO-II will address many current failure modes,
  but likely will introduce its own, new failure
  modes