Question 1

RISQ Q9.21's guidance on ship's grabs states that a 25% allowance should be added to the calculated grab capacity when estimating cargo weight lifted, because "the surface of the cargo in the grab will be slightly peaked or crowned." Why does this matter for crane SWL compliance, beyond simple weight estimation accuracy?

Accepted Answer

If an operator calculates lifted weight using only the grab's nominal volumetric capacity without the peaking allowance, they will systematically underestimate the actual weight being lifted on every cycle — repeatedly approaching or exceeding the crane's SWL without realising it, since the error is in the same direction (under-counting) every single time, not a random variation that might average out This is a subtle but important distinction: a systematic underestimation bias (every grab cycle slightly heavier than the simple volumetric calculation suggests) is far more dangerous than random measurement noise, because it compounds in the same direction every time rather than cancelling out — exactly the kind of "normalisation of deviance" risk where an operator gets used to a margin that was never actually as safe as assumed.

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."