Hatch cover order from Korea includes complete steel structures
Sherlog ultrasonic tightness testing tool receives type approval
Cargo access sealing system condition can be easily checked without interfering with other shipboard activities using MacGREGOR new type-approved Sherlog ultrasonic testing system
MacGREGOR new Sherlog ultrasonic testing system for checking the tightness of key cargo access equipment has been certified as type approved by Lloyd Register. The Sherlog type-approval certificate was issued on April 30.
The Sherlog equipment can be used to test 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 doesnt interfere with other shipboard operations during the short and busy time that a vessel is in port, says Esa Wendelin, maintenance manager in MacGREGOR Hatch Cover Division. The Sherlog can also be used to test bulkheads or any openings on board which need to be sealed, such as doors into refrigerated provisions stores and machinery spaces, and windows.
A unique feature of the Sherlog system is its integrated data-logger. Data can be downloaded to a PC, for subsequent use as as a periodic survey information source for example, and can easily be forwarded by 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.
Sherlog is an accurate and reliable tool and was introduced by MacGREGOR to allow users to locate and assess a leak site swiftly and without guesswork. MacGREGOR has used ultrasonic technology for hatch cover tightness testing for over 10 years, and participated in the development of this technology for marine use.
Testing made simple
The Sherlog system comprises two pieces of equipment: a portable ultrasonic multi-transmitter and a compact hand-held detector. When used to check hatch cover tightness, for example, 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.
The 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 MacGREGOR inspectors, the equipment is ideally suited for use by surveyors, shipyards, shipowners and operators, charterers, and P&I clubs. MacGREGOR offers training in ultrasonic tightness testing for Sherlog users. MacGREGOR already has some 30 certificated inspectors worldwide who are trained for tightness testing and reporting in accordance with UR Z17.
Sherlog system merits:
Following Sherlog type approval, MacGREGOR is in the process of obtaining a global Class Service Supplier certificate from Det Norske Veritas, fulfilling the requirements of UR Z17 for ultrasonic tightness testing of hatch covers. It is anticipated that the certificate will be issued by the end of June 2001 at the latest.
Checks pay off
An Oslo-based dry cargo shipper reports that, following a significant case of cargo damage in 1990, it became obvious that around 70 per cent of all reported damage to its cargo was water related (mainly water ingress via the hatch covers). Traditional hose tests carried out on a regular basis led to a noticeable but not spectacular fall in reported damage. But since the company first used an ultrasonic-based leak detector in 1994, reported water ingress on sea-going tonnage dropped to almost zero (there was only one case last year).
All dry cargo ships calling at the shipper home port are now inspected with the system, even if they call twice or more in a week, and pre-inspections are carried out in ports such as Rotterdam, Antwerp and Amsterdam. The ultrasonic technique, says the company, is extremely reliable, ergonomic and seems to be foolproof.
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