Hatch covers are essential to a ship’s cargo containment system. They are designed to protect the cargo from damage and prevent water from entering the ship’s holds. However, if the hatch covers are not properly maintained and tested, they can fail, resulting in severe consequences.
A Swedish P&I’s Monthly Safety Scenario involving leaking hatch covers recommended the use of ultrasonic instrumentation for hatch cover testing as a preventative measure.
The Incident:
The vessel was loaded up with wire coils. When loading was complete the crew taped across the transverse beams of all the cargo holds with Ram-Nek. During the vessel’s transit it sailed through heavy weather that lasted for about two days. During this time the vessel was pitching and rolling and the cargo hatches were covered in water.
While discharging in port it was found that the steel coils in the top tiers were corroded. The steel coils below the centreline and folding seams were the most affected. A surveyor in attendance observed that the cargo hatch covers were not in good condition. The greatest amount of rusted coils were in holds 1 and 3.
Investigation Results:
- The water integrity of the cargo hatch covers were tested with an ultrasonic device which detected significant defects to the sealing arrangements.
- The gaskets were in poor condition and the hatch covers tested positive for chloride which indicates that salt water has leaked.
- The non-return valves for the drain channel were also in a poor condition as they were clogged and the ball inside was not moving.
- The transverse packing on the hatch covers was leaking, there were some cracked corners and leaking side joints. The surveyor also found a number of leaking ventilation covers.
What caused the damage?
The cargo hatches were in a poor condition, which caused seawater to enter the cargo holds. The gaskets were also in poor condition and the cleats could not be tightened beyond hand tightening.
Recommendations:
- It’s strongly recommended to do an ultrasonic test instead of a hose test for testing the cargo hatch covers.
- Coltraco Solution: Portascanner® WATERTIGHT – most mathematically accurate handheld watertight integrity test indicator available – ABS Type Approved & RINA – click here for details
- The cargo hatch covers and other essential equipment should be inspected at continuous intervals. It is especially important that non-return valves for the coamings are inspected.
- Coltraco Solution: Permascanner® HI-LIFE & Permascanner® DYNAMIC – semi-fixed and fixed watertight integrity continuous monitoring systems to test hatch-cover seals while at sea – not just when alongside – to test the dynamic stresses of sea, weather and load states.
- These jobs should be included in the PMS (Planned Maintenance System).
- The PMS should also be inspected during internal audits and it should be logged if specific jobs have not been completed.
Original source: The Swedish P&I Club
Article published by MFAME
Emphasis (yellow highlighted) and bold “Coltraco Solution” added by Coltraco Ultrasonics
Ultrasonic Watertightness Testing
Ultrasonic watertightness testing is one of the most effective ways to ensure safety at sea and assess the weathertight integrity of your vessel without causing any damage. In simple terms, this technology works by using the behaviour of sound at boundaries between different materials. Sound travels easily through the air, but when it hits a solid material, most of it is reflected or absorbed, with very little passing through. Typically, this can be a problem for ultrasound-based technology. In this case, it helps us detect even the smallest leaks in solid seals with great accuracy.
Ultrasonic hatch cover testing is clean and poses not threat of contamination to sensitive cargoes. Instead, it actively contributes to reducing the risk of contamination by facilitating regular integrity testing. Ultrasonic watertightness testing is the best solution to ensure marine safety, minimise cargo damage, and optimise the safe operation of a ship at sea. While the chalk test lacks quantitative data, ultrasonic testing allows for precise identification and quantification of leak points. This enables you to undertake timely maintenance and repair actions to maintain watertight integrity and prevent potential hazards or losses.
