The most important 3 seconds when abandoning ship
Stormy night, alarms blaring and the crew is boarding the lifeboats. This situation is nothing like the training or drills you have encountered in your career. What do I have to do to get the boat in the water and successfully clear the ship? What are the critical actions that can make or break the evacuation?
A 2011 report jointly published by the Norwegian Shipowner's Association and the Norwegian Oil Industry Association investigated the performance of davit launched lifeboats when evacuating into rough seas and gives tremendous insights into what could be expected when launching during a storm.
The section that caught my attention is the one describing the part of the operation when the hooks are released (the "Release Phase"). The report indicates that "the time from initial water contact to release of fall wires is a critical parameter".
So how long do you have to release the hooks when the boat first contacts the water? It really depends on a combination of wave height, wave steepness, the speed at which the boat is lowered, and the part of the wave you hit when you enter the water.
The Norwegian study, which investigated launching into rough seas, reported that attempting to release the hooks 3 seconds after entering the water resulted in a 71% chance of successful release; while attempting to release the hooks 5 seconds after entering the water resulted in a 22% chance of successful release.
Any delays in releasing the hooks will result in shock loading on the falls as the wave literally drops from underneath the boat. If the boat is not released on the next wave, the falls will be subjected to yet another shock load. One too many shock loads will cause something to break.
The Norwegian report indicated "a time to release of 5 seconds is clearly not acceptable since...in roughly 50% of the simulations, wire tensions above breaking load are reported..."
Impact on Training
The Norwegians performed a survey of hook release mechanisms and reported that they were capable of being operated between 1.5 seconds and 4 seconds after the boat entered the water. This is not surprising since many hydrostatic interlocks depend on water pressure to push a diaphragm upwards which in turn moves a mechanical linkage which ultimately unlocks the hook release handle. It is only once the hook release handle is unlocked can the coxswain release the hooks.
Doing the math, if the conditions were the same as those investigated in the Norwegian study, the coxswain must operate the hook release handle the instant that it is unlocked if they have any chance of avoiding a shock load.
So what is the performance like for coxswains who have been trained by launching boats into harbours?
According to training records collected by Virtual Marine from our lifeboat simulators deployed onboard offshore platforms, the average time taken for certified coxswains to release the hooks in their first scenarios is over 7 seconds.
Once the coxswains have been exposed to rough weather conditions in the simulator, however, they develop and perfect techniques to quickly release the hooks and their average time to release the hooks drops to just over 3 seconds. According to the results of the Norwegian study, this 4 second improvement in performance dramatically improves the changes of an evacuation by lifeboat into rough seas.
The ability to improve the performance in rough sea evacuations was a driving force behind the acceptance of simulation in lifeboat training by STCW Flag States and offshore oil & gas regulators. With regulatory approval, lifeboat simulation is rapidly expanding and is becoming the preferred method of increasing training realism to maximize the chances of a successful evacuation.
Virtual Marine has pioneered the use of simulation in lifeboat training. Contact us if you would like to learn more about how simulation has enhanced coxswain training around the world.
Anthony Patterson
President and CEO Virtual Marine