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Hatch cover ultrasonic tightness testing
One of the possible applications of testing with ultrasounds consists of tightness testing of non-pressurised vessels. A cargo hold of a ship is generally a non-pressurised vessel. This technology allows tightness testing of hatch covers, watertight doors, ventilators,… Generation of a distinctive ultrasonic signal is done by using a transmitter (SDT 200mW for small compartments and SDT 8 MS for larger compartments) which is placed inside the compartment to be tested.
Ultrasounds passing through sealing arrangements, cracks, holes etc. can easily be picked up and measured by an SDT Sherlog ultrasonic receiver equipped with a handy flexible sensor.
Basic principles to be observed when carrying out tightness tests of hatch covers with Class Type Approved ultrasonic testing material:
Advantages
Testing hatch covers, or other cargo access equipment such as bow-doors, visors, ramps, etc., with ultrasonic testing gear offers the surveyor or inspector several advantages. The most important benefits of using ultrasonic testing material are:
- Reliable, Non-destructive, repeatable testing method.
- Allows detection of areas where lack of compression exists with pin-point accuracy (no time consuming investigation needed for finding the leaks, as the leak can be pin-pointed local repairs might be sufficient and adequate,….).
- Gives indication about compression.
- Allows quick and easy testing, without assistance from ship’s crew (except for supervision and safety aspects).
- Can be used in holds loaded with water susceptible cargo.
- Can be carried out irrespective of weather conditions.
- Can be used for weathertightness and air/gas tightness testing purposes.
- Allows to identify leaks without the use of a transmitter, on condition that the compartment tested for leaks is pressurised (air escaping through small openings, cracks etc… will cause disturbance of molecules/friction which creates ultrasounds that can be detected).
Who can use it?
Class Type approved equipment can be used by classification societies (or qualified operators/service suppliers), surveyors, ship’s crew, repair yards in order to determine areas where lack of compression exists.