https://www.youtube.com/watch?v=c3cqr0AHIjU
I had posted this video earlier of the Double decker from MAS to Bangalore. It illustrated many points I had made in my post. I had talked about 60kg/m rails IR uses and also how the rails have to be degassed at Bhilai or else hydrogen embrittlement weakens the rail and this was the cause of the Khanna accident in 1998. But this video also highlights another important factor. So I come back to this video. The video shows the derailment at 7:35 at Chitteri of the Muzzafarpur-Yeshwantpur express. I have seen this derailment too traveling on the Shatabdi soon after. I dug out the CRS report on the derailment and it highlights several problems with the MAS-Katpadi section. These problems will have to be addressed system wide in the quest for higher speeds. The reason here was failure of the rail welds. IR uses two systems of welds, Alumino Thermic (AT) and Flash Butt welding, (FBW) which is a superior process and does not need any filler material. It seems that Chitteri-Mahendrawadi-Katpadi has had many problems with the track. The tracks no doubt are 60kg/m the highest density rails IR uses( the linked article explicitly says so), but the concrete sleepers are 20 years old and the welds are AT. Because of shorter sections of track due to degassing issues as explained above, the number of welds will increase and this then causes issues like the Chitteri accident. So steel plants like Bhilai have to start manufacturing rails in longer lengths and mechanisms developed to transport these rails to the work site. Here is the CRS report of the Chitteri accident:
http://timesofindia.indiatimes.com/city ... 181019.cms
Welding
in situ is done in numerous ways, but more or less (AT) and (FBW) are the preferred ways. Due to the time block constraints on busy sections like MAS-Jolarpet etc, AT is preferred. Usually the welding can be done with a 55 min time block. In AT, a mixture of Aluminum and Ferric oxides is prepared. This usually has the trade name thermite. The ends of the rail are coated with kerosene, and brushed with wire brushes to remove, grease and dust. Then the ends are pre-heated by an acetlyne torch. The thermite mixture is introduced and lit with a Magnesium strip. A violent exothermic reaction ensues and the metal melts, filler is also added. Then after the weld cools, excess metal is ground off and the collar of the weld painted with some anti-corrosive paint, since this degrades due to the
sewage from the open toilets on IR. This could have been a factor in the Chitteri accident, among others.
Flash Butt welding is accomplished by arcing between the two ends of the rail. The ends are held together and electricity is passed between the two ends between 400-500 volts at 30,000-80,000 amps. One has to be careful that there is no short circuit and the arc does not go dead. The heat of the arcing causes metal to melt. Essentially that is the basic idea, there are details. Flash butt welding can be made an automated operation and in fact IR has flash butt welding equipment supplied by Plasser which you might observe hard at work across the IR system. Here is what to look for:
http://www.plassertheurer.com/pdf/aktue ... 2en_04.pdf
So there is a balance between longer rail segments, transportation of such rail segments and effective degassing. Thus even the issue of
higher speeds as opposed to high speed rail( which is a harder problem to solve) is much more complicated, it is also a metallurgical problem that has to be addressed as seen by the example of the Khanna and Chitteri accidents. Too long and you cannot degass effectively and/or transport, short then but many welds and other problems arise. I see many are posting thoughtless comments without any engineering or material science thought going into these posts. One gets the impression from these posts that it is as easy as taking a school atlas and connecting two cities with a ruler and the problem is solved or 4 power point bullet points and ergo we have HSR, better management, better implementation, write to Prabhu and wave Alladin's lamp.
Question For Arshyam or any other IR cognoscenti, I am definitely not one: Are all the rail welds on Class A lines of the Flash Butt weld type? If the answer is yes, there you go why MAS-SBC is a Class B line.
Theo-Fidel and Singha: Here is something for the two of you. As you may know TBM Godavari ( Bangalore Metro)drilling a 973m tunnel from Sampige Road to Majestic got stuck after a drive of only 350m. The company used Indian operators with minimum or zilch experience who destroyed the cutter head. They encountered granite with a crush strength of about 200MPascals and essentially the operator has to maintain the optimal pressure, neither too much and certainly not too little. Thus the operator has to carefully monitor this crush pressure as they go along, and also the preliminary geotechnical survey must reveal the type of rock, crush strength etc and this engineering analysis must go into the choice of TBM type, slurry, Earth pressure balance machine whatever, the nature of stuff above also matters, if there are houses, dwellings etc . as sinkholes may develop if the wrong choice of machine is made. Unfortunately with the limited experience they destroyed the heads and distorted it, or poor geotechnical survey or a combination of everything, who knows, jugaad all the time. The pictures that have emerged from the damaged head are mind boggling. Cutter heads missing from the drum and what not. For a long time Pradeep Singh Khairola, IAS who heads Bangalore Metro Rail Corporation (BMRC) and the press officers suppressed this news and released all sorts of rosy predictions as to when the project will be complete. Eventually they had to admit that the TBM was stuck in the middle. It cannot back out as it has already placed tunnel rings behind it and the hole behind is now smaller. Thus the only way out is to dig a shaft, get a new cutter head (8-10 crores), attach it, fill the hole and move forward. The new head was ordered from Italy and took a long while to come. Then the shaft was dug, and the clowns as usual never, never learn. They again went and told the press that in a month the TBM would start again. Unfortunately they forgot one thing,
the monsoons. Now the shaft is filled up with water, supposedly the pumps cannot keep up and it is next to impossible to bring the entire damaged cutter head assembly up and lower the new one and get it moving. So now they say 2 months before they can get it done. In the meantime when Modi had a Skype type of interview with Khairola, he assured Modi that things were on track and the entire Phase 1 of Bangalore Metro would be operational by March 2016. This is clear prevarication and was obviously a canard to anyone who had a rudimentary understanding of where the project is currently. This is too ambitious. At current tunneling rates, my prediction is March 2018. After the tunneling is over, they have taken a year to install the tracks( by the way they are using Flash butt welding on Bangalore Metro) and signalling and communication equipment, plus the obligatory CRS inspection. My prediction of March 2018 is also sanguine. It may very well be close to the end of 2018. You are going have this problem x10,000 tunneling in the ghats for HSR. The sad thing is they are repeating this problem with Phase 2. Instead of learning from their mistakes and concentrating and awarding contracts for the underground sections first, they are focusing on the overground section. It is the UG sections that take time esp. with Bangalore where there are differences in the geological formations and strata as one goes from say North to South. There is one saving grace though, the land above where the TBM failed is vacant land, free from dwellings, thus a shaft could be dug. The only restriction is, that it is near the IR tracks into Yeshwantpur. Since they have encountered granite( as can be seen in the pictures of the shaft) IR has only allowed blasting on a very limited scale. The shaft fortunately has been dug completely. But why bring out newsletters with misleading information and give fake dates to the PM, the Press?
contractors put in their prequalifications. A large majority also appeared to have been fabricated though our team of 2 reviewers did not have time to figure it all out. We were under a 6 month deadline.
welding...