The fixed and non-portable internal panelling and flooring commonly fitted to Inland Waterways vessels means that more often than not the internal construction cannot be inspected as part of a survey. Even without leaks, all hulls, but especially steel hulls, will sweat internally leading to corrosion. Other issues are internal water in flat bilges areas which cannot be removed by bilge pumps. Bilge water which may be trapped where it is constrained by sub-division and frames may lie unseen. Internal ballast should be removeable and placed on battens or frames. However, ballast, often in the form of paving slabs or engineering bricks, may lie directly in contact with the hull platework.
All of these issues need to be determined. Therefore, if a surveyor cannot conduct a survey properly and, therefore, professionally, due to lack of access then the surveyor should either refuse to survey the vessel, or at least ensure that the instructing client is aware that there were circumstances that made a thorough inspection impossible at time of survey. Consequently, the integrity of the hull structure could not be determined and therefore they are receiving a partial and largely meaningless survey report, which once again may not be accepted by insurers.
By analysing the existing rules and interpreting the details, all vessels (sea going and inland waterways), should comply with the rules applied by the Classification Societies, CE Compliance (RCD ISO 12215) and the MCA. These are the standards to which the vessels should have been originally constructed to, and this should be determined by the surveyor to enable assessment of suitability of and any subsequent deterioration of the structure.
The Canal Boat Builders’ Association (CBA) Code of Practice for steel inland waterways craft and narrowboat construction includes vessels up to 20 feet constructed of 3mm steel plate. All vessels to be constructed to RCD Cat D (IAW ISO 12215). Under RCD and now RCR, preferred Classification Society rules are those that are principally intended for use with pleasure craft, e.g.: - Germanisher Lloyd Pleasure Craft Rules (2004).
- American Bureau of Shipping Guide for Offshore Racing Yacht (1994).
- American Bureau of Shipping Guide for Motor Pleasure Yachts (2000).
The information required to make a safe judgment on the acceptable parameters of loss of thickness when conducting a survey of a steel inland waterways craft is available to all. Levels of diminution requiring replacement/repair are variously considered to be a loss of
approximately 15-25% of the original plate thickness. The surveyor must use all the information gleaned from the vessel’s original build specification concerning plate thicknesses together with his/her visual observations and experience. But in general, a loss in excess of 20% of original thickness will be deemed the point at which steel plate is replaced.
In order to inspect a hull once removed from the water, it should be pressure washed and cleaned of any marine growth as previously stated. This will allow an initial, thorough visual inspection of the hull plating which, depending on the type and thickness of the hull coatings, may include the welding. The visual inspection is primarily to look for evidence of buckling or distortion and the identification of any suspect areas that might require
further investigation using hammer soundings and ultimately thickness measurement. Even if the coatings have not been removed or if due to their nature i.e. epoxy coatings, where it would be inappropriate to remove them, their condition and suitability should be recorded.
Ultrasonic Thickness Measurements taken during survey are only an indication of the overall thickness and level of steel loss (diminution). Thin areas of plate may be discovered but equally where readings were not taken, such areas may be missed. Unfortunately, without removing all the paint coatings a full detailed inspection would never be possible. If the hull is found to have a high level of surface corrosion the hull will require to be blasted off back to bare metal.
Internally the surveyor should insist on a level of access to check the condition of the hull plating and structure. The internal areas where the highest levels of corrosion are likely are those that are least accessible for maintenance. In this instance the surveyor’s terms and conditions, circumstances and limitations of survey should include a disclaimer for all the areas that could not be inspected to his/her satisfaction.
Modern Multi Echo Ultrasonic thickness measurement meters can cope with some surface coatings providing they are smooth and dense but ultimately grinding back to smooth metal will generally produce more reliable results. This limitation also needs to be explained to the commissioning client and the potential risks arising out of not having the coatings removed should also be included in the disclaimers contained within the surveyor’s terms and conditions and limitations of survey.
110 | ISSUE 111 | MAR 2025 | THE REPORT
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