The future of watertight integrity testing is with continuous monitoring. A lack of proper servicing of seals can lead to deterioration which endanger the lives of the crew, vessel and cargo. The large issue here is that ships are only tested before and after one or perhaps several journeys; yet a leak could occur at any point in between testing and continue unnoticed until the next inspection. A vessel generates its leak sites due to load states, sea states, wind states, and dynamic movement. The severity is amplified within a vessel structure constantly changing by varying sea, wind, load states, cargo types and dynamic stresses. There is a great deal of bending and deformation that naturally occurs in ships during travel. It was found that a comprehensive, autonomous continuous monitoring system for the watertight integrity of a ship’s cargo hatches, weathertight doors and other seals is possible to be developed. One that is capable of automatically detecting emerging leak sites, alerting officers and crew of the location and severity of the leak site and logging all data for future review. The developments in continuous monitoring technology being undertaken by Coltraco Ultrasonics will drive the industry towards ensuring that watertight integrity is never left to chance.
The case study of the Emma Maersk exemplifies the danger of improper servicing. A severe leakage occurred on the container ship in February 2013 when it was loaded with 14,000 containers. The leakage was caused by the mechanical break-down of a stern thruster, creating the shaft tunnel to flood, as well as leading to severe ingress of water in the aft part. This led to flooding of the main engine room. This was caused by non-effective cable penetration sealings: in a sudden blast, four cable penetration sealings in the watertight bulkhead gave way to the water pressure followed by a massive ingress of seawater. Shortly after this, the other three cable penetration sealings also failed, resulting in an even larger ingress of water into the engine room. This led to approximately USD 45 million worth of damages and towage cost .
The NTSB (National Transportation Safety Board) have recently investigated the cause of the 2015 El Faro disaster. SS El Faro was a United States-flagged, combination roll-on/roll-off and lift-on/lift-off cargo ship crewed by U.S. merchant mariners. All 33 crew members tragically died in the sinking, when El Faro sailed from Jacksonville into Hurricane Joaquin, while heading to Puerto Rico. The wreckage was discovered more than 15,000 feet below the sea surface, Northeast of Acklins and Crooked Island, Bahamas. The NTSB have concluded that gaps in safety management contributed to the sinking of the El Faro. One of the significant issues was “poor watertight integrity which allowed seawater into the ship” stating that this accident may have been avoided if “crew had more information about the status of the hatches”. The tragedy of the El Faro has exemplified why it is crucial for the watertight integrity of vessels to be upheld.
To prevent sinking, regulations outline the requirements to ensure watertight integrity checks are done before the vessel sets sail. There is currently no emphasis on periodic watertight integrity checks other than to ensure watertight doors are closed. There are also reasons to believe that this requirement can too be exceeded by implementing the continuous monitoring of watertight compartments such as hatch covers for cargo holds and watertight doors for passenger spaces. This is now made possible by implementing robust ultrasonic transmitters and receivers both inside and outside the monitored compartment respectively. As soon as apertures start to form in the seals of these structures, the ultrasonic signal escapes the compartments and is received by the ultrasonic receiver on the other end. Above a certain threshold, this escaped signal represents the size of the leak that has developed.
Using a portable ultrasonic watertight integrity tester, Coltraco Ultrasonics’ Portascanner® functions on similar principles, detecting the smallest leak size 0.06 mm in diameter which is the most mathematically accurate in the world +/-0.02mm. As an example of how a leak will compromise the stability of a vessel, a leak diameter of one mm under just one metres depth of water below sea level will correspond to a leak of 12,500 millilitres per hour. This means up to 911 cans of soft drinks worth of water in a day. This highlights the importance of watertight integrity.