Single point mooring (SPM) buoy systems are used to keep a vessel stationed at a fixed location. They serve an integral purpose in offsite machining, and there are many configurations and designs depending on their use.

Follow our guide below to these buoy systems, how they work and their benefits.

SPM | Single Point Mooring Benefits

What is Single Point Mooring Buoy (SPM)?

Mooring systems are designed to keep a floating offshore structure in the a position, and this is true of SPM as well. SPM is usually necessary when the tanker isn’t near a specific facility for loading or unloading cargo or cannot come into a shore-facility.

It is also an option for when a vessel desires to save money and fuel by not coming into port. Waiting to dock in port, pay fees and submit to checks and regulations can eat up a lot of time and effort. This is especially detrimental when a vessel is working within a tight window to transfer products, complete jobs or undergo mission.

That’s why SPM’s are often the preferred alternative to docking at the shore. Instead, when a vessel needs to moor to a designated point for services such as unloading cargo or receive machining, it’s attached to a single point mooring system for quick access.

Single Point Mooring Buoys are known as Single point buoys, mooring buoys, single point mooring among other industry names. There are also several types of configurations such as Single Point Mooring Towers, Spars, and Catenary Anchor Leg Mooring (CALM), among others.

Vessel Access for Machining | Single Point Mooring Buoy

Benefits of Using a SPM

SPM is incredibly useful and accessible to almost every large vessel on the water. The are some of the key benefits to using an SPM for transferring products or parts of the vessel machined:

  • An SPM can handle extra large vessels with ease, as well as small
  • Large quantities of product can be transferred easily
  • Vessel doesn’t have to make port. saving fuel and time

How Does a Mooring Buoy Work?

While there are several generic and highly specialized mooring buoy systems on the market, they have the same basic construction. Each part of the system has a specific function and three main parts:

  • Mooring and Anchor System: The entire single point mooring buoy is securely fastened to the seabed using a combination of anchors and anchor chains.  This system is constructed with a little flexibility so that the buoy can move with waves, current and sway with tanker ships without causing too much wear and tear. The anchor chains attach to the sea floor and lead to the anchor point. Chains and chain stoppers then connect the anchor point to the buoy.
  • Buoy Body: This is the visible part of the SPM and it floats above the water, connecting to the tanker via a rotating piece.
    • The rotating piece is especially important, as it allows the tanker to drift in the current or navigate wind and waves without having to remain at a stationary point. Without this, there’s a greater chance that the ship could break the buoy chains or damage either the buoy, the tanker or both. A tanker or ship is often moored with a hawser arrangement (nylon or polyester ropes on a hook.)
  • Product Transfer System: The SPM also includes a product transfer mechanism, depending on the specific purpose of the buoy. For example, oil tankers can transfer liquid products like gas or oil via a system of pipes and hoses along the seabed that are connected to a larger pipeline.

Buoy-Laying Vessel | What is a Single Point Mooring Buoy | Cutting Edge

Our Preferred SPM: CALM Buoys

At Cutting Edge, our team uses Catenary Anchor Leg, or (CALM) buoys. This type of buoy is the industry preferred version since the mid 1990’s, because of ease of access and maintenance of the buoy. This creates a safer device overall!

The SPM CALM has a rotating head that has a turntable on a roller bearing. The innovation in the rotating head makes it so that when the subsea pipeline is connected to the hull in the case of product transfer, a product swivel in the main bearing allows the product to still transfer while the moored vessel drifts in the water. The turntable simply rotates along the floating hoses, preventing pinching or obstruction of product flow.

The CALM buoy is utilized in both in deep water and nearshore, reducing reliance on extensive infrastructure such as jetties, ports or marine loading arms.

Product transfer and oil extraction are just some of the marine services that Cutting Edge offers. In addition, Cutting Edge performs CNC shafting, propeller maintenance and large-machine maintenance onboard large vessels, offshore rigs and more.

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