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RE: [PSUBS-MAILIST] Hydrogen Build-up



Hydrogen and submarines, several observations

 

It use to be general practice to allow a small percentage of hydrogen to build up within the submarine’s hull while charging batteries along side the pier with hatches open.  Some one would light a match to “flash-off” the accumulated gas and the problem went away.  A fast, hot rush of momentary fire would flash through the boat burning off the hydrogen supposedly without causing harm.  While the web site referenced previously stated 4% was explosive, I have previously seen the number 3% quoted as a teen while experimenting with splitting water into hydrogen and oxygen with a battery.  At that time, I confirmed by experimentation that small quantities of 3% hydrogen and air mixture would explode with a nice loud snap from a spark.  Back to subs, I believe it was the diesel boat USS Guittaro charging batteries along side the pier and the “flash-off” caused severe burns to personnel and started a fire.  This method of charging was no longer allowed after this accident.  More recently the USS Barbel, one of our last diesel boats had a battery fire from a hydrogen accumulation that was severe enough to result in her decommissioning.

 

The older Johnson Sea Link battery pods had a patented vent system for their lead acid batteries that were kept at ambient sea pressure.  The battery pods were rectangular in form and covered by a clear, dished plastic cover.  The battery air space was filled with oil and capped with vented closures.  The pods were also filled with oil.  At the apex of the dished cover was a one way valve to allow gasses to vent off but salt water could not enter.  I don’t know if they are still using this technique.

 

Other research and commercial subs use battery pods similar to the K-350.  The intent with many of these were so that the battery banks could be quickly slid out and exchanged to get the boat back in the water where it made it’s money.  It also allowed the batteries to be charged outside the pods so that hydrogen accumulation was not an issue.

 

The old Tekna scooters original charged the batteries in the housing without venting.  Early on in the first units, there were some housing explosions so several round disk hydrogen catalytic converters were placed inside the housing.  After a few more explosions, a large belt of hydrogen absorbent material was placed in the housing.  More explosions (the belt’s effectiveness was negated with exposure to water) and the scooter design was modified so the nose was removable for charging.

 

Personal experiences with hydrogen explosions related to batteries involve two incidents that occurred due to different reasons.  The old Ikelite high-powered NiCad Modular light (about the size of an old 1 pound coffee can) would allow charging in the casing when the lens was removed.  After a charge, I replaced the lens and snapped it down with the restraining straps.  Had to check for leaks in a void that was being filled below a bunk on a square rigger.  As I looked under the bunk, switched on the light, and an immense explosion took place.  I flew back, my right hand in great pain, people screaming at me as to what happened but I couldn’t hear them as I was momentarily deafened.  Initially I thought there was an explosion in the void but upon inspecting the light, found the lens blown off and cracked along with the restraining straps bent straight out.  After talking with the engineers at Ikelite, determined that there was a hydrogen explosion, they replaced the lens and straps, and the light worked for many years after (only with battery packs charged outside of the housing though J ). 

 

The second incident occurred early in the dive year off of Block Island in 165 ft. of water while making the first dive of the year on the wreck of the sub USS Bass (SS-164).  I was first down the line to tie in the anchor as I had the most experience on the wreck.  The bottom water temperature was in the mid-30’s and the water was pretty murky.  I now had two Modular Ikelites, one mounted to each side of my helmet, with new high powered 50 W. PAR bulbs.  The bulbs were over-rated as to what Ikelite provided and would drain the battery pack in just over 20 minutes so I didn’t turn on the lights until I almost ran into the side of the wreck.  A shotgun went off on the right side of my head and I noticed that the light dimmed out to a brown color but continued operating for some time…figured the light imploded.  I completed the 35 minute bottom-time dive, an hour of deco (this was before tech diving with mixed gas and O2 decos), and had a look at the light on the surface.  Found the light partially full of water, the lens cracked, and once again the restraining straps bent outward…thus not an implosion but another explosion.  In discussion with our team’s electronics expert from Philips Electronics, we learned that with a rapid discharge of a battery under cold conditions, hydrogen is given off.  Couldn’t have been much hydrogen as the light was just being turned on (had been charged outside of the housing) and a spark from the switch must have occurred.  Batteries were heavily rinsed in fresh water, lens replaced, and restraining straps bent back into shape.  The light continued in service for a few more years, the battery pack didn’t hold quite the same charge, and the Modular lights were removed from the helmet and back to being hand-held (didn’t need anymore gun shots by my head).

 

MORAL OF ALL THIS…I WILL NOT CHARGE BATTERIES IN THE SUB!  Maybe in the pods since they are designed to deal with an explosion