![]() Marine breakaway coupling which allows for emergency disconnection of the pipeline to prevent rupture of hoses/hawser and subsequent oil spills.Floating hose strings which connect the buoy to the tanker.and can take the form of a Chinese lantern, lazy-s, lazy wave or steep-s The configuration varies on depth, sea state, buoy motions, etc. Flexible subsea hoses also referred to as Risers which connects the PLEM to the Buoy.The basic product transfer system components are: ![]() This system transfers products from the tanker to the PLEM located on the seabed. The heart of each SPM is the product transfer system. Chain stoppers (connects the chains to the buoy)įigure 2: SPM (Turntable) being towed into positionįigure 3: SPM CALM Buoy system configuration 1.1.3 Product Transfer System.Anchor chain (systems with six or eight anchor chains are the most common).Anchors (piles- or gravity anchors connects the mooring chain to the seabed).Figure 3 illustrates the CALM Buoy type concept. The vast majority of Marine Terminals installed since the mid-1990s have been CALM Buoys. The primary benefit of a CALM Buoy over a SALM Buoy is ease of maintenance. The SALM system is similar, except that the SALM is anchored by a single anchor leg. CALM holds the buoy in place by anchor chain that extends in catenaries to anchor points some distance from the buoy. ![]() The two main types of mooring configurations for SPMs are Catenary Anchor Leg Mooring (CALM) and Single Anchor Leg Mooring (SALM). The type of anchoring system is greatly dependent on local soil conditions and may consist of ships-, rig-, piles- or gravity anchors. Figure 2 illustrates a Turntable type SPM system during installation. The size of the buoy is a function of the counter buoyancy needed to hold the anchor chains in position, and the chains are a function of the environmental conditions and the vessel size. SPM mooring concepts are distinguished in Table 1. The type of bearing used and the split between the rotating and geostatic parts determine the concept of the buoy. The moored tanker can freely weathervane around the buoy and find a stable position due to this arrangement. These two sections are linked by a roller bearing, referred to as the Main Bearing. The body has a rotating part above water level connected to the offloading/loading tanker. The buoy body is held in place by means of static legs attached to the seabed underneath the surface. The SPM system consists of four main components:įigure 1: SPM system including moored vessel and connected floating hoses 1.1.1 Buoy Body ![]() Refer to Figure 1 illustrating a vessel moored to an SPM system. The buoy contains a swivel that provides the fluid transfer path between the geostatic part and the rotating part of the buoy. The fluid transfer system includes submarine hoses between the pipeline end manifold (PLEM) on the seabed and the buoy and floating hoses between the buoy and the tanker. The vessel will approach the buoy with its bow into the dominant environment, thus maximising control while minimising the need for tug assistance.Ī tug is required at all times during mooring and offloading to maintain the nominal amount of tension on the mooring hawsers to prevent collision of the tanker with the buoy and assist with the weather vane of the vessel. As the vessel in its stationary state is always positioned head-on into the winds/currents direction, the total force is less than would be experienced by a vessel on a fixed mooring which is not always head-on into the prevailing conditions. The vessel always takes the most favourable position in relation to the combination of wind, current and wave and is free to align itself with the prevailing environmental forces at the time. The tanker is moored at the bow by means of one or two hawsers to the buoy. ( See our full detailed article on SPM CALM Systems)Īn SPM is a loading buoy anchored offshore that serves as a mooring point as well as an interconnection for tankers loading or offloading liquid products. Permanently moored vessels are excluded from the scope.
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