Ultrasonic Hatch cover testing
Ultrasonic testing of hatch covers and seals is a quick and accurate way of carrying out leakage tests in a non-destructive way.
Testing does not involve water jets of mess, but can identify the position of leaks, and can confirm effectiveness of repairs.
The protection of cargo by a properly sealed hatch cover is vital, and proving the efficiency of the seal arrangements is usually a condition of continuing P&I cover.
Traditionally, seals could be tested using a water jet, but this requires acces to the underside of the seal to be useful. Another test was a "chalk transfer test" which relied on a layer of chalk being applied to the sealing bar and then after closing and then re-opening the hatch, assessing where there may be areas where the seal was not properly made (and hence may leak).
Modern methods now available include the use of a sound source, placed within a closed hold, and a tuned and calibrate sensor that can be moved around the outside of the seal.
In effect, the machine listend for sound leakage and quantifies the size of any leak on its display. Such equipment is expensive and requires a trained operator.
We have a Hatch cover testing machine, made by Coltraco, designed around Ultrasonic sound generating and receiving equipment and approved by Class. It comes with headphones to allow its use in noisy environments, and gives a reading that can be compared with the "open hatch" reading to quantify the leakage if any is found.
In the pictures below, a sound cource is placed beneath a circular hatch, and after the hatch is sealed, measurements of the integrity and efficiency of the seal are taken.
The pictures below show the sound source attached by its magnetic base, within a temporary opening on a ship, and then the photo at the bottom, shows the effectiveness of the seal of the temporary closing plate being tested. - this one failed.
It would of course have been better if the nuts had been on and tightened, this was just a demonstration test.
The results from the meter pinpoint the locations of leaks, and after repairs, the test can be repeated to confirm the integrity of the repair, or otherwise.