Cargo access sealing system condition can be easily checked without interfering with other shipboard activities using MacGREGOR's new type-approved Sherlog ultrasonic testing system

Type approval from Lloyd's Register has been gained for MacGREGOR's new Sherlog ultrasonic testing system for checking the tightness of key cargo access equipment, notably the seals of hatch covers and RoRo equipment such as bow doors, stern doors, side doors, inner doors and ramps, and ramp covers.

"Testing is clean and easy, and unlike hose testing, for example doesn't interfere with other shipboard operations during the short and busy time that a vessel is in port, and tightness testing can be performed even with the hold already loaded," says Esa Wendelin, maintenance manager in MacGREGOR's Hatch Cover division. Sherlog can also be used to test bulkheads or any openings on board which need to be sealed for example, doors into refrigerated provisions stores and machinery spaces, and windows.

An accurate and reliable tool, Sherlog was introduced by MacGREGOR to allow users to locate and assess a leak site swiftly and without guesswork. MacGREGOR has applied ultrasonics for hatch cover tightness testing for over 10 years, and participated in the development of the technology for marine use.

Integrated data-logger

A unique feature of the Sherlog system is its integrated data-logger. Data can be downloaded to a PC/laptop for subsequent use as a periodic survey information source and can easily be forwarded by e-mail. Hatch cover leakage data, for example, can be downloaded for easy reporting and safe logging as required by IACS UR Z17 and classification societies.

The Sherlog system comprises two equipment elements: a portable ultrasonic multi-transmitter and a compact hand-held detector. In checking hatch cover tightness, the multi-transmitter is placed in the cargo hold in a central position, where it produces a uniformly distributed omni-directional sound field throughout the hold space. On deck, the hand-held detector is used to measure any sound energy leaking through the hatch cover seals, both around the hatch coaming and along panel joints.

Transmitter sound is produced in a narrow frequency band and the detector is tuned to filter out just this band. So the inspector, wearing a headphone and reading a digital display, is not hampered by surrounding noise and can positively detect any leak greater than 0 dB. The detector logs the recorded dB values in its memory, which can then be downloaded.

As well as supporting MacGREGOR inspectors in their work, Sherlog is a valuable tool for surveyors, shipyards, shipowners and operators, charterers, and P&I clubs. MacGREGOR which already has some 30 certificated inspectors worldwide trained for tightness testing and reporting in accordance with UR Z17 offers training for other Sherlog users.

Following Sherlog's type approval, MacGREGOR sought a global Class Service Supplier certificate from Det Norske Veritas, fulfilling the requirements of UR Z17 for ultrasonic tightness testing of hatch covers. It was anticipated that certification would be issued by the end of September 2001.

Sherlog system merits:

• no risk of damage to cargo in the hold, unlike hose testing
• reliable in most weather conditions, even below 0°C
• no water hoses involved, and no interference with other shipboard activities
• operators can ascertain cargo access sealing system condition at any time
• easy and tamper-proof logging of sealing system condition
• PC connectivity for data transfer to PC/laptop
• can be used as a periodic survey information source
• clean (produces no waste), safe and quick (no extra preparations)
• one-man operation.