Computer Generated Video of Sinking - https://www.youtube.com/watch?v=FSGeskFzE0s&feature=emb_log
Hi and welcome to Failurology; a podcast about engineering failures. I’m your host, Nicole, and I’m from Calgary, Alberta.
Off the top, I have a couple housekeeping items. Firstly, last week I talked about the International Space Station and how the astronauts only had themselves and the parts they brought with them to fix anything that broke. But what I didn’t mention was that one of the things they brought with them is a 3D printer; which allows them to build replacement parts for many components, greatly expanding their ability to carry out repairs. Thanks to Christopher in Ontario for mentioning this to me.
Second, I thought you guys might want to know more about me or the podcast or my job as a mechanical engineering consultant or maybe you’re looking to get into engineering and have some questions. So I’ll be releasing a Q & A bonus episode in a few weeks. If you have any questions, please send them in. Either on twitter to @failurology or email them to email@example.com.
This week’s engineering failure is the Titanic. I’m sure most of you have seen the movie with Leo Decaprio and Kate Winslet. Spoiler alert, the ship sinks. After the ship sinks, Rose lays on a floating door with Jack in the water “never let go jack”. There was room on that door for two Rose…. Pretty rude if you ask me. The movie was long-winded, so much so that it was 2 VHS tapes, almost as long as the argument on whether Rose should have shared the door.
I’ve always found the tragic story of the Titanic very interesting. I remember being a kid, not really understanding how a piece of ice could sink such a grand ship. I mean, we made ice in the freezer, surely it couldn’t sink a ship. Kid logic, right. But typically, only 10% of the icebergs volume is above the water. So it’s not as simple as the ship bumping into the iceberg and it bobbing out of the way. The iceberg is likely heavier than the ship itself.
I also found the story interesting because everyone was so confident that it was unsinkable. And because of that confidence, decisions were made by the crew that put the ship at risk. It’s not like it even made many trips before it sank. It sank the very first time it crossed the Atlantic.
Although it was built in Belfast, the Titanic started its maiden voyage from Southampton in South East England. From there it stopped in Cherbourg, France and Queenstown, Ireland. Queenstown was renamed Cobh (spelt C-O-B-H) in 1920 and I visited there when I was in Ireland in 2019. While in Cobh we visited a Titanic museum and saw the structure of the original dock that the Titanic passengers used. Due to the time taken to dock in Cobh, the Titanic waited out in the harbor and passengers were ferried to the ship. But still very cool that almost 110 years later, the dock's structure is still there. There’s a picture of the dock on the web page for this episode, if you want to take a look.
Local lore says that a crew member, John Coffey, left the ship when it stopped in Cohb, saving his life. Story goes that he had a premonition of disaster, possibly a fire; but being from Cobh himself, he may have just wanted a free ride home and had never intended to cross the Atlantic on the Titanic.
Looking back, Cobh was my favourite spot we visited in Ireland. And the Titanic factor was a big part of that. The town of Cobh is built into the side of a hill. There are brightly coloured row houses referred to as the deck of cards. And there’s a giant cathedral at the top of the hill. The town is also accessible by Irish Rail, which was fun to travel on. For a town with only 13,000 people, Cobh has a lot of cool things to check out.
Including Spike Island, which is an Irish prison similar to Alcatraz. Don’t worry; it’s not a prison anymore, just a museum. I’ve actually toured several old prisons; they are a fascinating insight into society. Winston Churchill said “The mood and temper of the public in regard to the treatment of crime and criminals is one of the most unfailing tests of the civilization of any country.”
But this episode isn’t about Cobh, or prisons, sorry about the tangent. Because I learned about the Titanic when I was so young, I hadn’t looked at it as an engineering failure until I started this podcast. Researching for these episodes has given me a new perspective on how and why failures happen. On today’s episode, I’m going to do an overview of the ship and its disastrous end, but with an emphasis on the ship's design issues that made it so susceptible to sinking.
The titanic is coming at you soon, but first, the news.
This week in engineering news; 2020 was one of the hottest years on record.
To be fair, the National Oceanic and Atmospheric Administration has ranked 2020 as the second hottest year on record, following 2016. But NASA, the National Aeronautics and Space Administration, analysis ranks 2020 tied with 2016. Either way, this isn’t good news.
2020 started with the Australian bushfires, known as the Black Summer, which actually started in June 2019 and burned until May 2020; resulting in almost 10,000 buildings destroyed and almost 500 deaths. The Western US fires were also especially bad in 2020; the smoke from these often travels north and buries Calgary and the surrounding mountains in a haze of smoke. Millions of hectares of land will be burned around the world in 2020. And that’s just the fires.
In addition, 2020 saw over 100 named tropical cyclone systems. There were so many tropical storms that the National Weather Service used the entire list and had to carry over the Greek alphabet for naming the storms.
The 2020 global sea surface temperature was 0.76 degrees Celsius higher than the 20th century average. Record high sea-surface temperatures were observed across parts of the Atlantic, Indian and Pacific oceans. And the northern hemisphere saw the fourth smallest annual snow cover since 1967.
The world’s seven warmest years have all occurred since 2014, ten of the warmest years have occurred since 2005, and 2020 is the 44th consecutive year with global land and sea temperatures above the 20th century average.
This news article is perhaps more science based than specifically engineering. But engineering is an integral component to improving our current climate crisis. From designing new systems and techniques, improving those designs to make them more compact and affordable, helping clients make more energy conscious decisions either by showing them possible operational savings, marketing benefits or government incentives, even selecting low flow plumbing fixtures are some of the ways engineers can make a difference.
Global warming is real my friends. And slowing it down, starts with us; and by holding our governments and corporations accountable, we can start to see real change. Maybe in addition to slowing down climate change, we can start to reverse some of its effects. All is not lost, yet, we can do this.
There are several articles on 2020 being the hottest year on record, but to read the one I enjoyed check out the episode page, link in show notes.
Now on to this week’s engineering failure; the Titanic, the unsinkable ship that sank on its maiden voyage. She struck an iceberg at 11:40pm on April 14th, 1912 and sank 2 hours and 40 minutes later, 600km southeast of Newfoundland, with over 1500 souls still on board. There were only 705 survivors. This story is unbelievably tragic and completely preventable. And while it shouldn’t have happened, there is a silver lining or two, but I’ll get to that a bit later.
A White Star Line Olympic Class Ocean liner with 11 decks, the ship was 269m long, 28m wide, and 53m tall from the keel to the top of the funnels. At the time, the Titanic was the largest moving object ever built; displacing 52,000 tons. Even though it was the largest ship at the time, it would be dwarfed by today’s modern cruise ships.
It had a first class dining saloon, swimming pool, and four elevators. I know it was 1912, but only four? Could you imagine waiting for those things? Second class on the Titanic was so nice, it was comparable to first class on other ships.
The ship had 24 double ended boilers, which are two boilers back to back, allowing the back walls to be removed to conserve some weight, as well as 5 single ended boilers. They served two steam engines for each of the wing propellers, as well as a low pressure turbine for the centre propeller. The steam engines were 20m long, weighing 720 tonnes each. The power plant was capable of producing more power than a typical city power station at the time.
The ship had a cruising speed of 21 knots, or 39km/h and a max speed of 23 knots or 43km/h
The Titanic took over 26 months to build. Completion was delayed due to last-minute owner changes to provide additional shelter to first class passengers. Had it finished earlier, it might have missed the iceberg. During construction of the Titanic, 246 injuries were recorded including severed arms or crushed legs from falling pieces of steel. Nine people died during the construction
The ship’s structure is made up of 2000 hull plates; each 2m by 9m weighing 2.5-3 tonnes. Since welding was in its infancy in the early 1900s, the hull plates were held together using over 3 million rivets, weighing over 1200 tons themselves. They were installed by hydraulic machines or hammered in by hand.
The centre anchor weighed 15 tonnes and was 5.5m long. At the time and for several years later, it was the world’s largest anchor made by hand. It was cast in a bed of sand and clay.
22 tonnes of soap and tallow, which is animal fat, were spread on the slipway to lubricate the ships passage into the River Lagan. The slipway is still there today. The shipyard in Belfast has been turned into a museum.
As I mentioned earlier, the ship started its voyage in Southampton, England and made two stops before heading across the Atlantic to New York.
There were 2,225 people on board; 324 in first class, 284 in second class, 709 in third class, and 908 crew. The Titanic could carry almost 2500 passengers, but considering the lack of lifeboats, it’s a good thing it was under capacity for this trip. Speaking of lifeboats, there were only 20 on board, which were enough for 1,178 people; about half of the people on board. I will circle back to the lifeboats shortly.
In the two hours before the iceberg collision, two nearby ships sent messages to the Titanic to warn of ice fields, but the message was never delivered to the bridge and Captain Edward Smith maintained 22 knots full steam ahead.
In addition, the ocean was unusually calm that night making little water breaking at an iceberg’s base harder to see. And of course, the crow’s nest binoculars were missing.
By the time the iceberg was spotted, they were only about 400 meters away. The Bridge ordered the ship to turn to port (or left), but it was too close to avoid collision.
Many experts believe that the titanic would have survived if it had hit the iceberg head on, as it would have likely only damaged the two forward compartments. The ship was designed to remain afloat with up to four compartments flooded.
At 12:20am, about 40 minutes after the collision with the iceberg, a distress signal reached the Carpathia and it headed immediately for the Titanic, but was 3 hours away and didn’t make it in time to save everyone. There were other ships in the area, but they either couldn’t be reached or in the case of the Californian their wireless was turned off for the night (I’m sure there was some logic for this, but I don’t see what it is). The Californian was only 37km away from the Titanic, close enough to see it, but claimed they thought it was too small to actually be the Titanic. History might have been different if the Californian had realized they were looking at the sinking Titanic and were able to save more passengers. The Californian and its captain, Stanley Lord, were heavily ridiculed for not assisting in the rescue. Lord became a bit of a scapegoat for the Titanic disaster.
The Titanic’s hull was divided into sixteen large watertight compartments. After the ship sideswiped the iceberg, almost 100m of the hull was damaged from six slits below the waterline. The openings impacted six of the compartments on the starboard side. As soon as the damage was realized, the compartments were sealed.
But, there was a huge oversight in the design of the compartments. The walls separating them were not full height and were only watertight horizontally. In fact, the compartment walls were only a meter or two above the waterline. The designers of the ship had only guaranteed that it would remain horizontal if four of the sixteen compartments were compromised.
As the six compartments filled with water, the bow became heavier and heavier and pulled below the waterline, allowing the ship to take on more water, overflowing into neighboring bulkheads. The overflowing of the bulkheads happened roughly twenty minutes after the ship hit the iceberg. Twenty. Minutes. Once the bow pitched, water started to enter through the anchor chain holes. The bow became so heavy that the stern of the ship lifted out of the water and the ship was almost at 45 degrees. Eventually, the weight of the bow ripped the ship in half, and the bow sank to the bottom in roughly 6 minutes; the stern sank shortly after. The Titanic currently lays on the ocean floor, roughly 3,800m below the surface.
National Geographic and James Cameron’s team made a really good computer generated video of how the Titanic sank if you want to check it out. There’s a link on the episode webpage, to the video as well as an image of the Titanic on the bottom of the ocean.
Several experts who have studied the disaster have concluded that the bulkheads not only contributed to the sinking of the ship, but they made it sink faster because it weighed down the bow and the ship no longer remained horizontal, causing it to take on more and more water. This took away precious time for other ships to reach the Titanic and assist in the rescue. Some estimates are that the ship could have remained afloat for another 6 hrs. if that had happened, the Carpathia would have reached it in time to rescue most, if not all, of the people on board.
In 1991 a scientific expedition discovered a Frisbee-sized piece of the hull on the ocean floor; it was 25mm thick with three 30mm diameter rivet holes. Extensive research on this tiny piece of metal has uncovered additional clues to the cause of the rapid sinking.
The steel and wrought iron rivets that made up the Titanic’s hull failed due to brittle fracture; which occurs without plastic deformation. Three factors contribute to brittle failure; low temperature, high impact loading, and high sulphur content. All three were present when the Titanic hit the iceberg.
The retrieved hull piece had jagged, sharp edges, like broken china and showed no signs of bending. Typically, ship steel is higher quality and would show signs of bending rather than breaking.
Similar damage was found on the Titanic’s sister ship, the Olympic, after it was broadsided by a British cruiser 7 months before the Titanic sank.
Scientists also did what is called a Charpy test on a piece of steel from the Titanic, using a piece of modern high quality steel as a control. The test strikes the metal sample, held against a steel backing, with a 30kg pendulum on a 75cm long arm. Prior to the test, both samples were placed in a bath of alcohol at -1 degree Celsius to simulate the actual conditions at the time the Titanic sank. When the control sample was struck, the pendulum stopped with a thud and the sample bent into a V shape. When the Titanic sample was struck, the pendulum barely slowed and the sample broke into two pieces with jagged edges. There is a picture of the samples on the episode webpage.
Microstructural analysis also confirmed a brittle fracture of the steel. The test showed the titanic steel contained high levels of oxygen and sulphur, implying a semi-kilned low carbon steel. High oxygen content indicates an increase in ductile to brittle transition temperature; which in the case of the titanic was 25-35C. Modern steel typically needs to be at -60C before it transitions to brittle steel. The high sulphur content also contributed to the brittleness of the steel. The sulfur combines with the magnesium in the steel to form strings of magnesium sulphide, acting as highways for cracks to spread. Early 1900s ships had high sulphur content, but the Titanic’s sulphur content was even high for the times.
And then there were the rivets that held the hull plates together. Similar to the steel, the rivets also failed due to brittle fracture. As the iceberg swiped the side of the ship, the rivets sheared off in areas of impact, opening up seams in the ship's hull. As water flooded into the ship, this placed additional stress on the already brittle and strained rivets and began to elongate or shear them, opening up additional seams, allowing more water into the ship.
The ship was only as strong as its weakest parts.
Following the sinking of the Titanic, White Star Line made some design changes to their ships. They wrapped the double wall ship bottoms, made by taking two plates of steel and spacing them 1.5m apart, up the sides of the hull. This would prevent damage to the watertight compartments in the event of a minor collision. They also raised the walls separating the watertight compartments preventing water from spilling over into neighboring compartments.
As I mentioned earlier, there were only 20 lifeboats on board; enough to 1,178 people. There was room on the deck for twice as many. The original designer had allowed for two rows of lifeboats, but the second row was removed shortly before the voyage to make the deck more aesthetically pleasing. Even though the ship only had enough lifeboats for half the occupants, it actually exceeded the outdated British Board of trade regulations in place at the time by 10%.
In addition, the crew, unaware that the davit arms used to lower the lifeboats had been tested in Belfast, thought a full lifeboat would be too heavy for the davit arms to lower it safely into the water. The lifeboat drill scheduled for earlier that day had also been cancelled. As a result, most lifeboats left under capacity; specifically, Lifeboat 7, which had capacity for 65 people, left with only 27. In the end, only 705 people were rescued by lifeboat.
Those in lifeboats, afraid of being swamped by passengers in the water, delayed in returning to pick up survivors; causing many to die of exposure, rather than drowning.
The majority of the fatalities were crew and third class passengers. Due to the captain’s failure to sound a general alarm, many third class passengers failed to realize the situation until it was too late, or it simply took too long to navigate from lower levels to the top deck before most of the lifeboats were launched. Yes you heard that right, the captain did not sound a general alarm, not just a delay in the alarm, didn’t do it at all.
Ship safety has since been corrected with the creation of the SOLAS Treaty, SOLAS being an acronym for Safety of Life At Sea. The first version, passed in 1914, required adequate lifeboats for every person on board, that lifeboat drills be carried out for every voyage and that ships maintain a 24hr radio watch. The current version is SOLAS 1974 with later amendments. It covers construction, fire protection, life saving appliances, radio communications, navigation, cargo compliance, safety measures including in polar waters, and verification of compliance. With respect to the watertight compartments, they outline requirements for quantity and spacing, integrity and bilge pumping arrangements, with the highest requirements for passenger ships.
Around the same time, the International Ice Patrol organization was established to monitor and break up icebergs in the Atlantic and Arctic Oceans and provide iceberg warnings to the maritime community. Today the Ice patrol has expanded to include contributions from 17 countries. While it started out with a fleet of ships to navigate the ice fields and warn nearby watercraft, now they use search and rescue aircraft.
The titanic was seen underwater for the first time on Sept 1, 1985 using a submersible sled with a remote control camera that relayed an image to a monitor. The bow was recognizable, but the stern was severely damaged. It’s believed the stern imploded as it sank due to water pressure in that section, which still had air inside.
So there you have it, the tragic sinking of the Titanic. It was equal parts design issues, material flaws and overconfidence that caused the grandest ship of it’s time that sink on its maiden voyage. Now 1912 was a long time ago, and we have learned a lot since then. I don’t know exactly how much of the design issues were negligence or just unknowns at the time. But one thing’s for sure, we certainly have made a lot of improvements about safety at sea since then. Does that mean accidents don’t happen, of course not. For one thing, the sea isn’t always our friend and sometimes even the best laid plans can go awry. But we also tend to become complacent as time goes on. And that’s part of why I chose this failure. Even though its over 100 years, the tragedy of the Titanic still shapes marine engineering to this day and it’s important we don’t lose sight of what we’ve learned. 1500 people did not die in vain.
There was an article a couple years ago about a project to build a Titanic replica and follow the route from Southampton to New York. Except with adequate lifeboats and modern navigation and radar equipment. I think this is a weird, and crazy and fantastic project. I would definitely be interested in touring the ship at the dock. But would I take the voyage across the Atlantic? I don’t know. What are the odds it would sink twice? What would you do? Would you take the risk?
Check out the podcast page, link in show notes, for photos and sources from this week’s episode. If you’re enjoying what you’re hearing, please rate, review and subscribe to failurology, so more people can find it. And if you want to chat with me, or send me questions for the Q&A bonus episode, my twitter handle is @failurology or you can email me at firstname.lastname@example.org.
Thanks everyone for listening. And tune in next week to hear about the Flint water crisis; the story of a struggling Michigan city with contaminated drinking water. But more on that next week. Bye everyone, talk soon!