Question 1

RISQ's guidance on crane SWL plates notes that where a crane is rated for both hook and grab operation, "it is usual for the grab operation rating to be 20% less than the hook operation rating." Why would the same crane have a lower safe working load for grab operations than for hook operations?

Accepted Answer

Grab operations introduce additional dynamic loading the hook rating does not account for — grab closing/opening forces, impact loading as the grab strikes the cargo surface, and the additional weight and dynamic behaviour of the grab itself all add stress beyond a simple static suspended load, so the rating is reduced to keep the crane within safe limits under these less predictable, more dynamic conditions A crane operator who treats the hook SWL as the relevant limit while using a grab is working to the wrong number — the dual-rating system exists precisely because grab operations impose genuinely different (and less predictable) dynamic loading than a simple static hook-suspended load, which is why both ratings are required to be separately stated on the crane jib plate.

Question 2

RISQ's hatch cover guidance (Q9.13) explicitly warns that sealing tape and high-expansion foam around hatch cover edges "can accelerate corrosion and give a false sense of security," can be "washed away by heavy seas," and may "prevent water draining from cross joints." Why does RightShip's guidance call this out as a specific risk, rather than treating it as a harmless temporary fix?

Accepted Answer

Tape/foam can visually appear to solve a weathertightness problem while actually doing two things wrong at once — masking a defect that still needs proper repair, and actively trapping moisture against the seal/coaming in a way that accelerates the underlying corrosion it was meant to cover up — so the "fix" can leave the vessel in worse condition than if nothing had been done This is a genuine "looks fixed, isn't fixed, and made it worse" trap worth understanding precisely: a crew member who tapes over a weathertightness defect may feel the problem is addressed, while the trapped moisture against the coaming/seal is actually accelerating the corrosion that caused the leak in the first place. RISQ explicitly distinguishes this from a legitimate additional precaution on an already well-maintained, properly sealing hatch cover.

Question 3

RISQ Q9.10 checks hatch cover panels for misalignment, with guidance noting that "non-central permanent set" of the compressed rubber seal "may indicate misalignment of panel" — i.e. the deflection pattern on the rubber itself is diagnostic. Why is reading the compression pattern on the seal a more reliable misalignment check than simply looking at whether the panel appears level by eye?

Accepted Answer

The rubber seal physically records where and how much compression force it has actually experienced over time — a panel can look visually level while still being subtly misaligned in a way that loads one side of the seal more than the other, and the resulting off-centre compression mark is direct physical evidence of that loading pattern, which a visual "does it look straight" check cannot reveal This is the kind of inspection technique that rewards understanding why a sign means what it means, not just memorising "check for non-central set." The rubber is effectively a passive recording medium for the actual forces it has experienced — which is a more reliable indicator of a subtle structural problem than an eyeball check of whether the panel "looks straight."