The ROKN’s submarine plans has hit a bit of a snag when it was discovered that its latest submarine, the ROKS Son Wonil, is noisier (about 40 decibels higher) than expected, making it easier to detect by enemy vessels. The problem has been traced to the screw shaft, and as a result the Son Wonil will be going back to the Hyundai shipyard, where it was built, to have the shaft replaced. In addition its AIP (Air Indepedent Propulsion)unit, which increases its underwater endurance, seems to be not functioning properly and the sub is reported to heel over 40 degrees during cruising.
Interestingly, HDW, the German company that designed the sub, put down USD 5 million of its own money and pledged to solve the problems in one year, before the sub’s commissioning last year. Each of the three initial boats cost USD 350 million and the ROKN is looking to buying six more.
On the other side of the world, Greece is having problems with its own HDW designed sub which is the same class as the Son Wonil. In this case, the Greeks have refused to take delivery of the sub and there are apparently “diplomatic tensions” between Germany and Greece.
24 Comments
That’s what happens when you buy a design instead of doing the actual work yourself. Now, I guess we’ll have lots of HHI “high grade” patch work made to make this sub sooo much better than the original design.
Will be interesting to see how this develops, but I guess “someone” will make sure we never hear how this story ends.
Pilsan, Korea!
“noisier(about 40decibels higher) than expected”
This is incredible. The faulty shaft alone cannot produce that much extra noise. If the shaft is really defective, it is bent(more than 0.05″TIR) or it is running at or near the critical speed. In either case the shaft would also vibrate abnormally.
“the sub is reported to heel over 40 degrees during crusing.”
These two problems must be caused by faulty designs rather than faulty manufacturing.
Sounds like expensive German cars that are unreliable.
Various random Internet sites describe 40 decibels as a quiet conversation, a quiet residential area at night, a quiet office, or a fridge. (I guess that’s from the outside. From the inside it would be really loud what with all the gasping and screaming.)
#3,
Sounds like second-hand British subs. LOL
#4
It’s 40 decibels louder than expected, not 40 decibels total. That could be a very significant amount of noise since the decibel scale is logarithmic: 40 decibels is ten times more intense than 30 decibels and sounds twice as loud and 80 decibels is 1 million times more intense than 10 decibels and sounds 64 times as loud. A typical conversation is at about 60db, but exposure to 85db for a whole day (the sound of a bulldozer idling) can potentially damage your hearing. Imagine how noisy it would be inside the submarine if the expected noise was 60 or 70 decibels? Exposure to 110 db results in permanent hearing damage in less than two minutes.
They should’a bought Kilo SSs.
Perhaps some second-hand subs from Murmansk would be a better choice ?
#6,
Thanks for the explanation. The sites I’d quickly looked at don’t explain it as well as you did. Because the extra noise seemed so low (a quiet conversation), I figured that 40 decibels over what they’d planned for was a problem but not a super serious one. I was wrong.
Actually, Korea came close to inducting Kilos into its fleet during the mid 90s. According to a book authored by a DSME VP, who was also the captain of the first ROK sub, the Russians offered the Kilo class subs to the ROK as part of its repayment for its debt. The author reportedly inspected the subs and informed the ROKN CNO that he shouldn’t accept the offer giving the reason that the equipment on the subs were “a generation behind.”
http://www.cbs.co.kr/Nocut/Show.asp?IDX=754467
The unusual high level of noise is most likely to be caused by cavitation which can be seen in pumps, water turbines and ship screws. The screw of the sub must have been designed by an inexperienced engineer. It has been my experience as an industrial pump engineer that it is almost always impossible to lower noise levels by more than 2 decibels by improving existing machines. Even if the screw is replaced with a new one, I don’t think it is possible to lower the noise level by as much as 40 decibels. In order to mitigate cavitation(therefore to lower noise levels), the sub must reduce cruising speeds(by lowering the shaft RPM) or must cruise under deep sea where water pressure is a lot higher.
#11,
Yes, noise does not travel as fast underwater as on the surface, and even less so deep underwater.
Hey natto, you in the pump business too? Have you ever attended Weftec here in the states?
Regarding the ROKN submarine, I think the problem is probably not caused by design but rather more likely a QC issue with the machining at the Korean end. The problems listed sounds like an shaft that was not balanced properly and that is rubbing up against the mechanical seal causing excessive vibration.
No, Jing, do your web searching. There were problems with the 214-class submarine before the design was initiated in Korea.
“Mins”, I’m curious. Wasn’t Hyundai suddenly awarded with building contracts for this when they lacked the experience that Daewoo had acquired through the years? I seem to remember a conversation I had with a German fellow regarding such a while back. He basically said Hyundai had to learn what Daewoo already knew since Hyundai did not have the knowledge base for this type of work. I am not sure I remember this conversation correctly though. I talk to too many people maybe.
Yes, forgive my hindsight mins; the German fellow I talked to did say such, in fact he went on to wonder if Roh’s administration awarded this to Hyundai, in thanks for their support in the NK/SK relations arena (Kumgang-san).
There was also some speculation about the design intentionally being not as good as it could be.
Also, “Jing”, please don’t take my comment above as being anything less than a friendly rejoinder; I did not mean to be nasty to you so I’m sorry if it read that way.
After reviewing Elgin’s link I am 100 % sure this is a design flaw. They will have to redesign the screw(propeller) and/or the shape of the sub hull close to the screw. To perfect the new designs, they will have to experiment on a trial-error basis and it will take a long time.
#13 Jing, the excessive shaft vibration resulting from cavitation would also cause the mechanical seal failure and therefore water leakage.
#15.
Actually the selection was done during the Kim Dae-jung administration. As you commented, there was a bit of controversy when HHI was selected to build the subs, considering that DSME was Korea’s “submarine house” and HHI at that time had no experience in building subs.
Three years after the selection, the BAI reported that there were “irregularities” in the evaluation process that resulted in the selection of HHI.
http://news.naver.com/main/rea.....0000201491
That wasn’t the only unusual selection process for defence equipment during the DJ administration. Remember the FX project? During the first round evaluation the Rafale came out on top, but after a second round evaluation that considered “political factors”, the F-15K was selected as Korea’s next fighter.
Hey Mins, thanks for keeping up with the defense-related stories!
The problems that the South have appear to be very similar to the problems the Greeks had with the Type 214–the sub would roll excessively on the surface, propellers are noisy, etc. (http://www.strategypage.com/htmw/htsub/articles/20061211.aspx). Ironically, the Germans don’t appear to have the same problem with their Type 212s (the 214 is the export version of the 212). I seem to recall that the Greek and possibly the Korean versions had some design modifications that could have been the source of some of the problems.
This does not seem to be an issue with this being Hyundai’s first foray into submarine construction, although that is a good place to look first. Germany built Greece’s first Type 214 and it had all the problems that are arising now with the Korean one. This may be more of an issue with a new submarine design more than anything. I haven’t heard if Greece managed to eliminate or reduce some of the problems in subsequent submarines.
Designs get modified, though, as problems are identified. The first of anything as complex as a warship or submarine usually has a number of problems that get fixed in the next hull.
by the way, why was Kim Dae Jung so intent on sinking Dae Woo?
and helping out Hyundai?
why did one of the Hyundai sons commit suicide, by jumping out of the building?
#12
“Yes, noise does not travel as fast underwater as on the surface, and even less so deep underwater.”
you are wrong
the deeper the water level is, the faster sound travels
#11 is saying that the sub may produce lower noise at deeper levels because he has asserted that the probable cause of the noise is cavitation.
at deeper levels, pressure is higher
higher pressure -> less probability of cavitation
Mins,
How ironic. IMO, the ROKN doesn’t need anything better than the Kilo; if it’s good enough to sneak op on the Kitty Hawk (twice, at least), then it’s good enough.
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Someguy,
#20 is correct about the speed of sound in water; travels ~8x faster in water than air. Any diver can tell you this.
What is the mission of these submarines? How long has the ROK Navy had submarines and what role do they expect their submarines to accomplish in the event of a war with North Korea?
Welcome to the club of the “listing german subs”. There is a problem in its design, which cause most of the problems. The second Greek U214 (Pipinos)seems to have the same problems with the first (Papanikolis), as its testing should have been finished by now.
Unfortunately, these problems cannot be solved, unless the subs will be cut.
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“Yes, noise does not travel as fast underwater as on the surface, and even less so deep underwater.”
you are wrong
the deeper the water level is, the faster sound travels
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exactly. In the water the noise ‘moves’ faster as the density of the water is higher than the air.
Hello there! Are there any articles (in Korea) concerning these problems and especially the overheeling?
If someone comes from Korea and knows something more please post a link (and maybe a … short translation!)