Trans RINA, Vol 153, Part A4, Intl J Maritime Eng, Oct-Dec 2011 COATINGS AND PERMANENT MEANS OF ACCESS – THE ANTI-CORROSION
CHALLENGES. (DOI No: 10.3940/rina.ijme.2011.a4.216)
J P Lomas, Amtec Consultants Ltd, UK P D Contraros PDC Maritime SA, UK G Papadakis, AP&A Ltd, UK
SUMMARY
The introduction of new regulations for Means of Access (MA) has led to an increase in the number and complexity of access openings, an increase in the size of the access openings in the ship’s structure, and a stricter maintenance regime which presents new challenges throughout the life of modern vessels. Several of the major issues at the design stage of Permanent Means of Access (PMA); the construction of ships; the application of protective coatings during new building, together with coating maintenance during the service lifetime; problems related to cleaning holds after cargoes have been removed; action by the Butterworth crude oil washing action and the challenges of maintenance in ballast tanks, are discussed in this paper.
1. INTRODUCTION
As part of SOLAS Chapter II-1 Regulation 3-6 and the revised Technical Provisions for means of access for inspection resolution MSC.178(78)
[1] together with
MSC.1/Circ. 1176, new regulations have been introduced to allow close-up surveys, inspection, maintenance and repairs of protective coatings as specified in SOLAS II- 1/3-2.1.1 [2] and MSC.1/Circ. 1333 [3].
This has been
achieved by increasing the number of Permanent Means of Access (PMA) over and above the Means of Access (MA) that were previously required in ships. Ballast tanks and cargo tanks have all had additional PMA structures included in their design since 1st January 2005. Where a permanent means of access may be susceptible to damage during normal cargo loading and unloading operations, or where it is impracticable to fit permanent means of access, the Administration may allow, in lieu thereof, the provision of movable or portable means of access, as specified in the technical provisions.
Whilst the concept of increased PMA has many positive attributes, the practical issues of incorporating these new structures presents many problems throughout the life of the vessels.
2. DESIGN
The new PMA have to remain in place for the lifetime of the vessel and therefore need to be well
designed,
constructed, installed, and maintained. As per SOLAS II-1/3-6-4.1 the ship is to be provided with a “Ship Structural Access Manual” that will include inspections by the crew, the port state control, and class surveyors to maintain serviceability and repair of any substantial damage from corrosion. This is part of the statutory survey of the ship as well as part of the safety construction survey. In addition, a periodic inspection by a competent authorised person from the crew members will be carried out, and the results will be recorded in the
©2011: The Royal Institution of Naval Architects
Ship’s Safety Management System and Ship Structure Access Manual. IACS Recommendation 90 Access Manual offers a detailed description on this issue.
The design of the PMA has thus far proven to be challenging for the designers, builders and the end users. The introduction of the MSC.215(82)
Performance
Standard of Protective Coatings (PSPC) [4] recommends that the coatings of the PMA must provide access for inspection, to the best extent possible, to the parts that are not integral to the ship’s structure, such as rails, independent platforms, ladders, etc. The sections of the PMA that are part of the structural strength element are to be coated to the same standard as the adjacent structures. This has resulted in different parts of the PMA being coated to different standards and in turn, this will affect the longevity of the coatings and the structures.
The addition of such structures into the ballast and cargo tanks can exert significant influence on the flexibility, stresses, strains, and strength of the bulkheads and longitudinal stiffeners to which they are attached. The design of the floors and inner bottom with regard to the regulation manhole openings as specified in SOLAS II-1 Reg. 3-6-5.1 & 3-6-5.2 may also be affected. This can influence and affect the performance of the ship during service.
Oil tankers and product carriers of Panamax size and below, have their double bottoms designed (as in bulk carriers), with double bottom longitudinal girders, with floors arranged between
girders, and ballast lines
arranged along the ship’s length. In this situation, the designer runs
into a problem as to the number and
position of the access manholes to ensure that there is safe access of 800mm x 600mm, (for instance) to both sides of the ballast line within the space formed by the floors and double bottom girders.
The reason is that safe access should be provided in all spaces including those with obstructions, such as ballast lines, to facilitate close-up inspection of
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