Slow steaming has earned its place as a very commonly used term in the current shipping industry. It is a strategy that shipping companies have on the top of their priority list, and it affects the entire industry, right from the cargo owners to the global supply chain.
Something happened in the year 2008, that made the entire world think again. Being the major industry that drives the world economy, shipping was supposed to be the pioneer in the thinking process. There was a heavy downturn in the global economy that resulted in reduction in the demand of transportation capacity. Freight rates fell. The worse was still to come. In the years prior to 2008, there was a shipping boom. Order books were full and new ships were on the production line. By the time the record-high deliveries were made, recession hit the industry and new ships were rendered useless. Projects still under development were cancelled. Number of ships sailing the oceans considerably reduced. Idle ships were not the only trouble. There was more.
The global financial crisis triggered the rise in fuel costs. Higher fuel costs in the time of crisis means diminishing profits and soaring losses for the shipping companies. Operation costs shot up. In short, world trade languished.
The major issue that hit the shipping companies was high fuel costs. The only way to tackle the issue was to reduce the consumption of fuel in ships. For that, engines would have to be run on power ranges below their normal operating range. As a result, the speed at which the ships had to sail, were to come down by a few knots.
You can look at it from the other perspective too. In ships, the power consumed is proportional to the cube of velocity of the ship. So a minute change in a ship's speed can affect the power and fuel consumption to a large extent. (See Figure 1)
|Fig. 1: Correlation between ship speed, required engine power and fuel consumption|
(Image Courtesy: Wartsila Technical Journal, 2010)
Maersk Line, the world's leading container shipping company used this property of ships to survive through the recession. They reduced their speeds from 27 to 22 knots, that is, a 19% reduction in speed. That reduced the hourly main engine fuel consumption to 58%. In some cases, further reduction of speeds to 18 knots reduced the fuel oil consumption to 75%. Engines were operating at about 40% of their rated capacities, fuel costs were saved, and Slow Steaming Strategy was born.
The Domino Effect
The strategy triggered a chain of other factors as soon as it was adopted by Maersk Line. One ton reduction in fuel consumption reduced the carbon dioxide emissions by three tons. Consumption of engine cylinder oil was also reduced nearly by the same percentage, which reduced solid particle emissions.
But the pioneers had to convince two different sectors which were an integral part of shipping. One, the engine manufacturers, who believed that their engines were not designed to operate efficiently at only 40% of load capacity. Two, their customers, for whom the time of delivery was about to be affected due to slow steaming.
In 2008, Maersk approached engine manufacturers MAN Diesel and Wartsila to research the effects of engine operations below their design load level (MCR). In late 2008 and early 2009, both the companies published letters of No Objection for low load operations. However, it required extensive maintenance and inspection of machineries onboard.
The other issue with slow steaming was longer time of deliveries, which customers felt, would slacken the global supply chain. Maersk convinced the customers that slow steaming would delay the deliveries, but it would provide more guarantee for safe delivery of goods. This was also offset by another issue. If you remember, due to the recession, more ships remained idle than those which sailed. This was a perfect chance for ship owners to increase their fleet. More ships, low speed, guaranteed safety of goods. And they made a revolutionary strategy out of the global recession.
Propeller and Engine Efficiency
Marine propellers are designed for an optimum RPM for maximum propulsion efficiency. Slow steaming when incorporated in existing ships, would reduce the RPM levels, therefore decreasing the efficiency of the propeller. Thus it is natural that when the entire main engine and propulsion system is operating at low load levels, the overall system is no longer an optimised one. So the marine engineers and engine builders were initially reluctant to embrace the concept. However, when Wartsila investigated into the matter, what they reported, pushed slow steaming strategy even further. In their reports, they published that their engines could efficiently operate even at low loads up to 10% MCR. It was also discovered that the loss in propeller efficiency was actually offset by the cost savings due to reduced levels of fuel consumption. Some ships also got their propellers replaced to sync with the low load levels. Wartsila and MAN Diesel upgraded their engines to specially designed slow steaming kits. Ships in which, replacements were not done, the engines were to be kept efficient with rigorous maintenance of the main engine and machineries like turbochargers, boilers and blower systems.
Due to low load operation, combustion of fuel in the cylinders is insufficient, resulting in poor atomisation and deposition of soot layer within the cylinder. Regular maintenance is required. Marine engineers are required to clean the cylinder linings before the engines are again fired to full load.
During slow steaming operation, the engine temperatures are generally lower than what it is designed for optimum performance. As a result, corrosive vapours condense, corroding the interiors. Again, maintenance is the key.
Other than the major factors which require regular maintenance for efficient performance, there are few which might affect the performance due to slow steaming practices. In low load operating conditions, the propeller is subjected to low RPM, which increases the probability of propeller blade fouling. Hull fouling probabilities also increase, which require periodic underwater surveys and cleaning.
Solutions and Acceptance of the Strategy
Inspite of a few issues that popped up during the development of this strategy, it proved to be an overall economic boon to the industry, going by the fuel cost savings. Carbon dioxide emission levels came down, ships that were idle joined the fleet and brought in more revenue even in the years of recession thanks to slow steaming strategy. World's leading manufacturers Wartsila and MAN Diesel joined the initiative and upgraded their engines with special kits designed for slow steaming. Following the success of Maersk Line due to this concept, other shipping companies have adopted the same strategy for efficient shipping. Initially tried on only container ships, now the strategy is being successfully applied to bulkers. That is quite an evidence of the fact that the domino effect is still on.LSD
Article By: Soumya Chakraborty
2) Slow Steaming - A viable option? (By Wartsila)
3) Slow Steaming practices in the global shipping industry. (By MAN Diesel)