Practicality of Polyethylene Buoys

Polyethylene buoys have been used as maritime Aids to Navigation (AtoN) for almost thirty years. Their steel equivalent was limited in both its weight and size, making them an extremely difficult product to transport, position and manoeuvre safely. There was also a growing need for buoys that were larger in size to increase their visibility on the water and aid mariners in their journey.

Whilst steel buoys have a longer lifespan; the initial cost is some 150% more than polyethylene. Steel buoys also need annual maintenance as opposed to polyethylene which only needs to be serviced every two years. Polyethylene buoys are sustainable and can be recycled and repurposed after their service life.

Why is polyethylene used to make buoys?

Polyethylene is available in different forms and is one of the most common plastics used today. It is lightweight, strong and versatile. In the manufacture of marine buoys, linear low-density polyethylene resin (LLDPE) is used and specifically designed for rotational moulding applications.

LLDPE has higher tensile strength and exhibits greater impact and puncture resistance compared to some other plastics. It offers high environmental stress cracking resistance (ESCR), toughness, flexibility and at end of life, is recyclable.

Why do we only use virgin, UV stabilised polyethylene to
manufacture our buoys?

Marine buoys are faced with some of the harshest environmental conditions. The effects of icing, cyclonic winds, salt spray, prolonged UV exposure and tropical humidity can quickly deteriorate poor-quality plastics.

The UV stabilised virgin polyethylene we source at Sealite contains coloured pigments that permeate all the way through the material. This gives our buoys unmatched durability, colour vibrancy and additional protection from the long-term effects of the sun’s ultraviolet rays. And, unlike steel buoys, our polyethylene buoys never require painting.

What gives our large ocean buoys their outstanding strength and durability?

The float section of our ocean buoys contains a concrete ballast to aid its stability.

They incorporate:
• Two large lifting and mooring points, and are
• Interconnected by 316-grade stainless steel tie bars

This is particularly important when buoys are facing turbulent conditions or during deployment and retrieval. This is when the buoy is under additional mooring load and the addition of these features provides greater buoy strength and durability on the water.

In addition, the float section is filled with closed-cell polyurethane foam as standard to:
• Increase the wall strength in the event of vessel impact
• Provide excellent buoyancy
• Act as a water restrictive barrier

Clever design principles

Manufacturing as modular pieces makes buoys spanning up to three metres in width possible. Dependent on size and design, they typically comprise the float and tower and incorporate additional float collars and spacers to increase the buoy’s overall height and diameter. The use of these same design principles for smaller ocean buoys means that components can be consolidated into shipping containers, offering a more economical option for many customers.

In addition, their modular design offers full interchangeability of components to simplify repair or to make changes to buoy configuration.

Reduced weight, reduced operating cost

The significant size and weight advantages of using polyethylene buoys over steel buoys means:
• Smaller cranes can be utilised
• Smaller cranes, allow for more buoys to be deployed at once, or
• Smaller ships can be utilised
• Smaller ships require less maintenance crew

All these factors attribute to a lower operational cost for the authority over the product service life of twenty years.

Maintenance advantages

The greatest cost of steel buoys is their requirement for ongoing maintenance. Polyethylene buoys can be maintained on station, pressure cleaned onboard the maintenance vessel and returned to their position on the water all on the same day. Steel buoys require repainting onshore every five years before being redeployed, which is both time consuming and costly.

Complete packaged solution

In addition to buoy selection, the Sealite team can utilise our proprietary Seamoor™ Mooring Calculator to match synthetic mooring, chain and a cast iron sinker taking into consideration the water depth, watch circle, wind speed and current. In addition, adding a solar marine lantern will provide a solution for both day and night time navigational safety.

Learn more

Sealite offers an extensive range of marine buoys for all sorts of marine applications. From small marker buoys to large ocean buoys, we have you covered. Sealite navigation buoy products are manufactured on-site, available in a wide range of configurations and sizes and can be economically shipped worldwide.

Visit our marine buoy product page to find out more, or contact our team directly to discuss your requirements.