The watertightness of a ship’s bulkheads, and Multiple Cable Transits (MCTs) are crucial to making sure a vessel stays afloat, while the weathertightness of its hatches ensures that its cargo is protected, and that any water ingress can be contained. International Association of Classification Societies Mandate Z28 provides requirements on surveying MCTs for all vessels contracted for construction after 1st July 2021. This mandates that:
“All transits are to be examined to confirm their satisfactory condition and the Register is to be reviewed to confirm it is being maintained” (4.1.1)
Z28 dictates this must be by a surveyor or firm approved as a service supplier. Additionally:
“The owner is to maintain the Register to record any disruption (repair, modification or opening out and closing) to a cable transit” (2.2.1)
This was a result of recognising MCTs as a key failure point in ships which had dramatic consequences in collisions and incidents where the watertightness of these MCTs was relied upon.
For example, the grounding of HMS Nottingham in the Tasman Sea in 2002, which nearly resulted in her loss, was dramatically exacerbated by flooding “occurring above free flooded compartments from water passing through cable glands” [Board of Inquiry Report]. Resultingly, the report concluded that “Fixed hatch waterwalls profile sealing arrangements were inadequate – all leaked following free flooding of compartments below”. It called for a feasibility study into “conducting post upkeep compartment pressure/vacuum testing”, to prevent recurrence. This incident necessitated GBP 39 million in total repairs and refurbishment costs, which would likely have been dramatically less had this flooding been contained by the cable glands and watertight hatches as they were intended to.
Similarly, in 2008 the FV Alaska Ranger was lost in the Bering Sea with multiple fatalities after it sank after losing a rudder. Crucially, this flooding was only sufficient to cause the ship’s total loss because of a failure of watertight structures. The NTSB report put this down to one of three potential factors – an open bulkhead, a failed watertight seal, or failure of watertightness of cable glands in the bulkhead. 2 of these 3 causes would have been detected and prevented had the crew been equipped with an ultrasonic integrity tester. Following this, US Coast Guard Marine Safety Alert 1-08 listed as its first recommendation:
“Ensure all watertight decks and bulkheads are inspected periodically to verify that there are no unprotected openings or improper penetrations that will allow progressive flooding.”
In both of these incidents, a failure of a watertight compartment occurred which, due to the assumption of watertightness, had drastic consequences for the ship and crew. The missing link in preventing these incidents was a system to easily verify and assure watertightness.
The integrity of a watertight structure is critical – bulkheads and cable transits must operate as intended into to allow for compartmentalisation in the event of water ingress. The maritime environment is prone to corrosion and deterioration of the seals in watertight hatches and cable transits. Therefore, watertightness monitoring must be conducted regularly using a reliable and simple means. Ultrasonic watertightness verification remains the single best method to achieve this, and its ease-of-use allows crews to periodically test all watertight and weathertight structures to maximise safety and detect failures at the earliest possible opportunity.
Ultrasonic watertight integrity verification offers a solution for loss-prevention and cargo security. Wet cargo, which is often caused by a failure of weathertight and watertight seals in cargo bays, is the second most common type of claim on bulk carriers, and the costliest, accounting for nearly half of the costs of claims. Water ingress into sensitive cargoes like grain can destroy the cargo, with dramatic results. Overwhelmingly, leaking hatch covers are the most common cause for this, in both numerical and monetary terms.
This provides a second pillar to support the necessity of ultrasonic testing. While water ingress putting a ship at the risk of loss is rare, water ingress through supposedly weathertight structures is common and can have significant implications. The failure of a weathertight hatch may occur because of the failure of an inexpensive seal which is easily and cheaply replaced. The issue is locating the instances of seal failure or lack of integrity across numerous such parts installed on a vessel.
Conventional methods of measuring weathertight integrity such as the Chalk Test and the Hose Test, are outdated and have significant shortfalls in accuracy and reliability. The Chalk Test assesses the compression of the door seal rather than watertightness, and it is easy to overlook small leaks or damage which may affect the overall watertightness of a hatch. It also cannot be used on structures like MCT’s. The Hose Test relies on large amounts of water to be sprayed to check for leaks, which can potentially damage machinery, electronics and dry cargo. By posing a threat to the vessel it aims to protect, it is an undesirable method to measure watertightness.
In contrast, ultrasonic integrity monitoring allows for the most efficient way to ensure maritime safety and minimise the risk of loss, with no damage. The Portascanner® WATERTIGHT PLUS is a global market leader in ultrasonic integrity testing.
Its ease-of-use, requiring a single operator with no modification to the watertight structure, allows it to be quickly and regularly utilised to prevent water ingress. Portascanner® WATERTIGHT PLUS is:
- Handheld
- Portable
- Efficient – requires just a single operator
- Fast and reliable – detect leaks as small as 0.06mm in diameter.
It can operate as either a watertight or weathertight integrity testing device.
This allows for faster detection of shortfalls in watertight integrity, meaning less risk is assumed by the vessel, both in terms of cargo damage and the threat of sinking. Ultrasonic testing is clean, providing no threat of contamination to sensitive cargoes, and actively reducing this threat by facilitating more regular watertightness testing. Ultimately, ultrasonic testing represents the best solution to ensure marine safety, minimise cargo damage, and optimise the safe operation of a ship at sea.
