IALA GUIDELINES ON PLASTIC BUOYS
INTRODUCTION
A survey has been carried out of member authorities who use plastic buoys and replies have been analysed from 14 authorities.
The survey shows that small plastic buoys are used throughout the world but the use of large plastic buoys is still quite limited. The information obtained from the survey indicates that there is no preference for any particular type or design of large plastic buoys and that where authorities use large numbers of small plastic buoys their major advantage is their low initial cost.
The United States Coast Guard(USCG)and Canadian Coast Guard have completed trials to evaluate the performance of several commercially available large plastic buoys(in the Order of 3m diameter)these are manufactured in GRP,rotomoulded polyethylene，elastomer coated foam and all foam. The results from the USCG indicate that the "all foam" buoys they have trialled are particularly effective in sizes upto 1.6m diameter but that steel buoys remain the most cost effective type for buoys of 2.5m diameter or larger. The Canadian Coast Guard are continuing trials with a hybrid buoy consisting of a rotomoulded(foamed wall)thermoplastic superstructure on a steel buoy and also a cross linked polyethylene spar buoy.
Background
Many types of plastic buoys are on the market ranging from small harbour or river markers about 1m diameter, to offshore buoys in the order of 2.5 to 3m diameter and with all-up weights approaching 6 tonnes.
Plastic buoys are suggested to have several advantages over conventional steel buoys including light weight, corrosion resistance and in some cases, low cost. However, these apparent advantages need careful evaluation:
1. Light weight buoys need careful design to avoid having a rapid rolling or pitching motion detraction from their navigational effectiveness in waves or wind.
2. Self coloured plastic materials will almost certainly need painting at some time to maintain their signal colour, to change colour, or in the case of GRP buoys, to maintain the continuity of the gell coat and hence the structural integrity or the laminate. A plastic buoy may retain an acceptable surface finish for up to 10 years in temperate climatic conditions. Tropical ultra violet exposure, will accelerte the ageing process.
3. Experience has shown that plastic materials have no better resistance to marine fouling than other materials and thus must be sufficiently robust to withstand weed being scraped off, or high pressure water jetted, Regularly during the working life of the buoy.
ENG8/5.2/1-Page 2/8-21 Oct. 1997
