Hatch cover testing: ultrasonics, hose test or chalk?

Wet cargo claims are large, slow and difficult to defend. The test that would have prevented one costs a fraction of the deductible - but only if it is the kind of test that tells you where the water is getting in, rather than simply that it did.

Three methods, answering three different questions

The chalk test

Chalk on the compression bar, close the cover, open it, look at the packing. It tells you whether the cover is making contact and roughly how evenly.

What it does not tell you is whether the seal is tight. Contact is necessary but nowhere near sufficient - a cover can mark chalk beautifully along its whole length and still leak, because compression is not the same as sealing. Useful for setting up and adjusting a cover. Not a tightness test, and it should never be recorded as one.

The hose test

Water at pressure along the joint, someone inside looking for ingress. It is a genuine tightness test and it has the great advantage of being obvious.

The disadvantages are real. It needs the hold empty, it needs someone inside, it puts water into a cargo space you may then have to dry, and it is frequently prohibited or impractical in freezing conditions. Most importantly, it tells you water got in somewhere - the person inside sees the consequence, not the path. Finding the actual point can take considerably longer than the test.

Ultrasonic testing

A transmitter inside the closed hold, a receiver outside, and an operator working along the joint. Sound leaks where water would. The reading rises at the point of the gap.

How an ultrasonic tightness test works

• No water into the hold, so it works on a loaded or a dry-prepared vessel and in freezing conditions.
• One operator, outside, rather than a team including someone in the hold.
• Locates the path rather than confirming the symptom.
• Produces a number, which can be recorded, compared between inspections and put in front of a surveyor or a charterer.

Video · Coltraco UltrasonicsPortascanner WATERTIGHT PRO - How to Use

What actually leaks

Rarely the middle of a panel. In practice the recurring culprits are:

• Cross joints - where two panels meet, and where wear and misalignment concentrate.
• Compression bar condition - corroded, bent or previously repaired bars that no longer present a clean line to the packing.
• Packing that has taken a set - rubber that has compressed permanently and no longer springs back.
• Drainage channels that are blocked, so water that the seal was never meant to hold back is standing against it.
• Cleats and securing devices that are not pulling the panel down evenly.

All of those are cheap to fix and expensive to discover through a cargo claim. That asymmetry is the entire economic case for testing.

When to test

The obvious answer is before loading a moisture-sensitive cargo. The more useful answer is also:

• After any hatch cover repair or panel work - a repair can easily leave the cover worse aligned than before.
• Before a charterer's or a surveyor's inspection, so you find it first.
• Periodically as a baseline, so deterioration shows as a trend rather than as a claim.

The documentation argument

Worth stating separately, because it is often the thing that actually pays for the instrument. A dated, recorded tightness reading taken before loading is evidence. It changes the conversation in a wet-cargo dispute from an argument about probability into an argument about a measurement - and it is far cheaper to hold that evidence than to construct a defence without it.