August 7, 2015

Japanese Submarines – Critical operational life and hull cutting issues

"In 1994 the RAN Magnetic Treatment Facility (MTF) was commissioned into service following the successful deperm [demagnetising] of the Oberon Submarine HMAS Orion. Since then the MTF has been used to successfully deperm several other classes of vessels including a Collins Class submarine, ANZAC Frigate, Fremantle class Patrol boat and a decommissioned Hydrographic ship." (Description above "Executive Summary" page 1. Photo courtesy Page 3 http://dspace.dsto.defence.gov.au/dspace/bitstream/1947/4085/1/DSTO-TR-1340%20PR.pdf)
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In comments below http://gentleseas.blogspot.com.au/2015/08/australias-naval-shipbuilding-blueprint.html “S” (and comment at August 8, 2015 at 7:47 PM for answeres to 2.1 and 2.2has provided very interesting views on Japanese-Australia submarine issues. This is concerning the Soryu and Collins.

The actual submarine designs that are being proposed for SEA 1000 will be significantly different from current subs - but discussion has more substance when on the basis of current subs. The Japanese proposal, which will likely win the SEA 1000 CEP, is likely to be an evolution of the Soryu.

One concern is that the operational period of postwar Japanese submarines, including the Soryu is significantly shorter than the 30 year average for submarines designed in Europe or the US.

I have clarified the English in S’s responses and hope this clarification is faithful to his intended meaning. On August 5, 2015 S indicated:

That he thought that having set views on average years of operation of a submarine without considering the rate of operation is “meaningless.”

“Submarine hull will experience physical, chemical and chemical-physical degradations such as fatigue, corrosion and stress-corrosion cracking. Also, mechanical parts such as diesel engines, batteries systems and AIP systems will deteriorate. These degradations will come up only under actual operational conditions. For example, if there is no repeated surfacing-submerging, the fatigue of the hull caused by repeated application and release of external stress is not experienced.

It is said that the rate of operation of the Soryu submarine is 80%. As operational period of Soryu is 24 years, actual operation period becomes ca. 19 years (= 24 years x 0.8). In the case of the Collins submarine, the rate of operation is obviously lower than that of the Soryu. For the Collins’ 60% operational rate over a 30 year operational period, the actual operational period becomes 18 years (= 30 years x 0.6) which is nearly same as that of Soryu.

[Best to consider the] increase in numbers of submarines [and] also improvements in the rate of operation.”

On August 6 I asked S five questions – and below each I have provided S’s responses, also provided on August 6. I have added follow-up questions in bolded italics.

1. Why is the "operational period of Soryu 24 years"?

S answered “Submarine operational periods used to be as short as 18 years, and JMSDF [Japanese Navy] was criticized. Also National Defense Program Outline FY 2011 decided to increase number of submarine to 24 including 2 training submarines.”

The previous JMSDF requirement and orbat was 16 submarines. Japanese perceptions of an increased threat from China (and perhaps some US persuasion) has resulted in the revision upwards to 24 subs.

2. Why not 30 years like Germany, France and almost all other submarine builders?

S answered “Submarine building span in Japan is in line with Long-term or Mid-term Defense Buildup Plan and technology innovation.”

So are the following factors important in the number of years of operational life for a Japanese submarine?:

2.1  Is there a need for continuous build by KHI/MHI?
 (The pattern of launching and commissioning one submarine per year appears to be very important. Continuous build would keep the workers (eg. welders) busy and would make budgeting more certain for the JMD and KHI-MHI.)

S answered "I think that the continuous building system is an implicit requirement to achieve and maintain a higher performance [capability] of the Japanese submarine force [and individual subs]. One of the most important technologies is hull welding. Welders must be continuously engaged in welding to maintain their welding skill and qualifications, especially for gas tungsten arc welding (GATW). Other technicians, including inspectors, must maintain skills and qualifications. Inspectors are required to have the highest skill." 

2.2 I have a theory that the reason the Yield Strength of the pressure hull steel is very high (at NS110 = HY156 see Submarine Pressure Hull Table) is due to deep diving needs. So does deep diving put greater stress on the pressure hull – leading to more rapid degradation – resulting in shorter operational life?

S answered: "[The relationship] between operational life and hull strength is not clear, because operational life of Uzushio class submarine [see SS-566] with NS63 hull was 18 years."

"I think Australia should not persist [with] NS110 technology [use Japanese NS110 grade steel for the] following reasons: 


1) this technology including GTAW technology is one of most important technology which Japan cannot share with other countries (eg. Germany does not share its non-magnetic hull steel, except with Italy [the joint builder of the 212]), 

2) maintenance of this technology is very difficult [particularly cutting and welding], 

3) new steel which Japan will propose may be more suitable for Australia than NS110."

"I think that Collins class with single hull made of BIS 812 EMA [see Submarine Pressure Hull Table] is out of date in terms of magnetism. As the Ni content (1.28wt%) of BIS 812 EMA is very low [1], this steel is magnetic. So a weak point of the Collins class is a more detectable hull than more modern submarines (which have a low magnetic single hull or low magnetic double hull (low/non-magnetic outer hull and magnetic inner pressure hull)). [On BIS 812 EMA's Ni content see page 11 and much detail on BIS 812 EMA's magnetic properties in that document - including pages 24-25. Many references to magnetism and submarines here.  So development of welding user friendly steel with higher Ni and Cr contents improving magnetism and low-temperature properties is a better option."

3. What happens if Australia needs to lift availability of its Japanese built submarine to 80% in time of strategic need?

S answered “I think that Australia may reduce defense cost as a result of reduction in number of submarines.”

4. What happens if Australia wants to cut the NS110 pressure hull and reweld it to do major maintenance work (including large parts replacement on the propulsion system) or major emergency repairs?

S answered along the lines: Hull cutting significantly weakens the pressure hull thus limiting diving depth. [JDS Asashio (see SS-589 converted to testbed submarine TSS-3601 preceded Oyashio Class has an NS110 and NS80 pressure hull like Soryu Class) required hull-cutting for the experimental fitting of the large Stirling AIP system. After this hull-cutting the submerged depth of Asashio was limited.]

5. Can this pressure hull cutting-rewelding work be done in Australia?

[see S's answers to 2.2 above] “Aside” [this depends?] “whether JMSDF agrees NS110 technology transfer or not, advise from Japan is required, because Japan has an experience of hull-cutting of [the NS110 and NS80 pressure hull for the] “Asashio”.

S made the observation "I think there are four options for Australia's of next submarine: 1) modified SS29 [or 29SS see see Table at bottom of] type of Japan, 2) modified SS29 type with new steel hull, 3) Type 216, 4) Conventional "Shortfin" Barracuda."

Thankyou S.

Please connect with previous Submarine Matters articles, including:



Pete

9 comments:

Anonymous said...

Hi Pete

Question “Was the previous requirement for 16 or 18 submarines?”
16 submarines, according to JMSDF

Question 2.1 “Is there a need for continuous build by KHI/MHI?”
I think that continuous building system is implicit requirement to achieve and maintain high performance of Japanese submarine. One of the most important technologies is hull welding. Welder must be continuously engaged in welding to maintain welding skill and qualification, especially for gas tungsten arc welding (GATW). Other technician including inspectors must maintain skill and qualification. Inspectors are requires to have highest skill.

Question 2.2 “So does deep diving put greater stress on the pressure hull – leading to more rapid degradation – resulting in shorter operational life?”
Relation between operation life and hull strength is not clear, because operation life of Uzushio class submarine with NS63 hull was 18 years.

I think Australia should not persist NS110 technology by following reasons: 1) this technology including GTAW technology is one of most important technology which Japan cannot share with other county (Germany does not share non-magnetic hull, except Italy), 2) maintenance of this technology is very difficult, 3) new steel which Japan will propose may be suit to Australia than NS110.

I think that Collins class with single hull made of BIS 812 EMA is out of date in terms of magnetism. As Ni content (1.28wt%) of BIS 812 EMA is very low [1], this steel is magnetic. So Collins class has weak point to be more detectable than other modern submarine which has low magnetic single hull and low magnetic double hull (low/non-magnetic outer hull and magnetic inner pressure hull). So development of welding friendly steel with higher Ni and Cr contents improving magnetism and low-temperature property is better option.

I think there four option of next submarine: 1) modified SS29 type of Japan, 2) modified SS29 type with new steel hull, 3) Type 216, 4) Conventional Barracuda.

http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAAahUKEwjHscX0jJnHAhXBXaYKHbDTAS4&url=http%3A%2F%2Fdspace.dsto.defence.gov.au%2Fdspace%2Fbitstream%2F1947%2F3309%2F1%2FDSTO-RR-0014%2520PR.pdf&ei=NMLFVcfHDcG7mQWwp4fwAg&usg=AFQjCNFNg5lB3A6W0LyaK4SRFp5l20IX4g&bvm=bv.99804247,d.dGY
Page 4, Table 1 ” Chemical compositions of ship plate steels, wt%”

Regards
S

Peter Coates said...

Hi S

Thanks for all your comments. You'll notice that I have also placed your 2.1 and 2.2 comments in the text.

I have also located open source DSTO documents on Ni percentage and magnetic properties - now in the text. Also on "deperming" demagnetising - see Oberon photo.

Before I saw your comments I too came to the conclusion that the problems of working with NS110 in Australia and Japan's need to maintain security made using a different steel (probably lower in NS/HY value) a good approach.

I'm wondering how the operational life of the Oyashios is being extended? Structural changes?

Regards

Pete

Anonymous said...

Hi Pete

Question “I'm wondering how the operational life of the Oyashios is being extended? Structural changes?”

As budget of the life extension of the Oyashio is included total budget of repair of JMSDF, the extension measures are unknown. So, I show my idea on the life extension measures as follows:
1) Non-destructive inspections of whole hull (pressure and non-pressure hulls) and repair of detected damages will be performed. If serious damages such as pitting or stress corrosion cracking are found, submerge depth may be limited after repair. I do not think that there is structural change like hull-cutting except these cases. But, these non-destructive inspections are cumbersome, time-consuming and very expensive.
2) Exchange of sound reflection rubber on the hull.
3) Exchange and repair of aged parts inside submarine.

According to JMSDF, batteries and hydroplanes are exchanged for the submarines---perhaps for Soryu and Oyashio.

Regards
S

Peter Coates said...

Hi S [at August 9, 2015 at 10:11 PM]

Thankyou for your views on Oyashio Class operational life extension measures.

I didn't understand the meaning of "batteries and hydroplanes are exchanged for the submarines---perhaps for Soryu and Oyashio.".

Does that mean that all Oyashios with standard lead acid batteries (LABs) and the first 10 Soryus (that have LABs) will be receiving new LABs. This is noting that LABs "wear out" (become too inefficient after several hundred uses/cycles).

Do hydroplanes suffer metal fatigue (degredation)?

Regards

Pete

Anonymous said...

Hi Pete

I will answer for your question and introduce idea of knock-down production in Australia.

Question “Does that mean that all Oyashios with standard lead acid batteries (LABs) and the first 10 Soryus (that have LABs) will be receiving new LABs. This is noting that LABs "wear out" (become too inefficient after several hundred uses/cycles).”

Performance of submarine must be maintained by batteries exchange, because batteries show performance degradation and capacity reduction by using, like those of automobile. Batteries are checked by capacity testing at every 6 months after submarine commission or batteries exchange, managed and exchanged at periodic inspection of submarine. One or two submarine batteries are exchanged every year. Annual batteries cost and exchange cost per submarine is around 1.5 billion yen and 270 million yen, respectively.

Question “Do hydroplanes suffer metal fatigue (degradation)?”

No they do not suffer metal fatigue. The aim of hydroplane exchange is improvement of motion performance in water.

Recently Professor Hidemichi Katsumata shows knock-down production of the Super Soryu submarine. In this production, expert team of KHI or MHI as field superintendent visits ASC, and guide Aussies about welding and assembling of steels or materials from Japan.

Regards
S

Anonymous said...

Hi Pete

In “Batteries are checked by capacity testing at every 6 months after submarine commission or batteries”, I forgot “for 3 years”. So, “Batteries are checked by capacity testing at every 6 months for 3 years after submarine commission or batteries” is correct expression.

Regards
S

Peter Coates said...

Hi S

Thankyou for the informationa at August 12, 2015 at 1:04 AM and August 12, 2015 at 1:48 AM. I will use it for a future article.

Regarding "Recently Professor Hidemichi Katsumata shows knock-down production of the Super Soryu submarine. In this production, expert team of KHI or MHI as field superintendent visits ASC, and guide Aussies about welding and assembling of steels or materials from Japan."

Do you mean Professor Hidemichi Katsumata, KHI and MHI will visit ASC-Adelaide soon? Will Professor Katsumata, KHI and MHI propose that Japan build prefabricated parts - then send them to ASC in kit form - for submarine assembly in Australia?

Regards

Pete

Anonymous said...

Hi Pete

(1) Opinions of Professor Katsumata and a member of MOD (Ministry of Defense, Japan)
It is story of the assumption in the case of Japan has been selected in the competitive evaluation process. It is Professor Katsumata’s personal opinion. Professor Katsumata is specialist on defense issues and currently works for Advanced Research Institute for the Sciences and Humanities, Nihon University.

According to Professor Katsumata, a member of MOD said “We cannot export high strength steels N110 and NS90 as well as NS80. We heard that the needed submerged depth of Australia’s next submarine is as half as that of Soryu. Then, NS63 (YS(yield strength)=630MPa) or N70(690MPa) is enough.”

(2) My comment
There are significant communication gap between MOD and Australia on submarine information and recognition of situation. MOD should understand that Collins hull steel is stronger (BIS812EMA, YS=700MPa) than NS63 or NS70 and that China’s 980 steel is equivalent to NS80. Also Australia should communicate Japan properly. I have got a prejudice that RAN does not collect well information on Japanese submarines. If I am wrong, I will apologize.

Regards
S

Peter Coates said...

Hi S

Re (1) It is very useful to have experts, like Professor Katsumata, who can talk with knowledge and authority about such important issues.

For Australia it is important that the future Australian submarine steel has all the qualities that are currently important to their mission and can be anticipated to meet mission requirements in future. The ability of Australian shipyards to cut and reweld pressure hulls for scheduled maintenance and emergency repairs is important.

(2) "Also Australia should communicate Japan properly. I have got a prejudice that RAN does not collect well information on Japanese submarines. If I am wrong, I will apologize." The significant communication gap between Japan's MOD and Australia is regrettable but perhaps inevitable.

(a) Australia procrastinated by not starting a submarine selection process at the best time - which was five years ago. Australia's delay is now making it ask for new submarine proposals very quickly.

(b) Japan is being asked to present submarine proposals quickly - when Japan is very inexperienced as a weapon seller.

(c) However this is what weapons sellers have to do. But it takes decades for large weapons companies to learn how to find out what customers really-really want.

(d) If Australia presented a Tender Process with definite questions (for definite answers) it may have been easier for Japan to answer. But the immeasurable Alliance criteria is in Japan's favour.

(e) the bigger and more expensive the weapons the more political (and indefinite) is the selection process. In this CEP the US has asked Japan to sell the submarines and asked Australia to buy Japanese submarines.

(f) This CEP is so political that Abbott is closely involved with the CEP as is new, inexperienced, Defence Minister Andrews. Abe and Nakatani are also inexperienced in weapons selling.

(g) Australia's weapons selection organisation (DMO) has just been dissolved - leading to more confusion.

All this means you are not wrong. Politics makes processes inefficient but politics is essential in our democracies.

If Japan can sell weapons to Australia, with all these problems, Japan will be well prepared to sell to any democracy in the future :)

Regards

Pete