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Offshore Pipeline
 
Submarine pipelines are pipelines installed under water that are resting on seabed. Submarine pipelines can be divided into three different groups.
·         offshore pipelines
·         coastal submarine pipelines
·         deepwater pipelines.
In general, the low and uniform resistivity of seawater simplifies the operation of cathodic protection systems for submarine pipelines. The current demand in different seawater locations varies upon temperature, salinity, and depth. For the majority of situations, the critical factor is water temperature.
Sacrificial anodes in bracelet shapes are the most preferable type of cathodic protection application for offshore pipelines. These sacrificial anodes are typically applied as “bracelets” and are installed at certain intervals along a new line. The standard materials for bracelet anodes are Aluminum-zinc-indium; however, zinc anodes are also used occasionally.
The use of zinc bracelet anodes is not recommended at applications where the pipeline surface can reach temperatures higher than 50C. For elevated pipeline temperatures, we recommend using sled anodes, or anode beds, which are placed alongside the pipeline and are connected with a cable. It is also recommended to apply thermo-insulation inside the anodes using adhesive glue.
To achieve an electrical connection a copper cable is earthed and is thermo welded between the insert steel and the pipeline.
In order to provide adequate cathodic protection of the pipelines, sufficient direct current must be supplied on the external pipe surface, so that the steel-to-electrolyte potential is reduced to values at which external corrosion occurs at a minimal rate.
Cathodic protection is used in combination with a suitable coating system to protect the external surfaces of steel pipelines against corrosion.
Short pipelines can be protected by anodes installed at each end. This type of installation is typical for inter-platform pipelines, at which the anodes for the pipeline can be attached to the platform, if the pipeline is electrically connected to it. 
Design parameters
The design of a pipeline CP system shall be based on
·         detailed information on the pipeline
·         environmental conditions
·         burial status
·         the design life of the system
·         information on existing pipelines
·         information on existing CP systems
·         availability of electrical power, electrical isolating devices, electrical bonds
·         applicable local legislation
·         construction dates, start-up date
·         pipe, fittings, J-tubes, risers, clamps and other appurtenances
·         performance data on CP systems in the same environment
 To achieve the maximum protection the field should be examined to identify features such as:
·         protective current requirements to meet applicable criteria;
·         electrical resistivity of the electrolyte, including seasonal changes if relevant
·         pipe burial depth (if buried) and identification of exposed span lengths and locations
·         water temperature at the seabed
·         oxygen concentration at the seabed
·         water flowrate at the seabed, including seasonal changes if relevant
·         seabed topography.
 

Bracelet Anodes

 

Alloy Specifications

 
The bracelet anodes are available in a variety of sizes ranging from 3” to 48” in pipe diameter, from 100mm to 1000mm in length, and from 20mm to 250mm in thickness.
Bracelet anodes are designed with a utilization factor higher than 0.80, and are based on ISO, NACE, and DNV standards.
The electrical connection between the anodes and the pipeline is achieved by using a bonding wire, which can be attached by thermite welding or by pin brazing.
Epoxy coating is applied to the interior of the anodes with a minimum thickness of 100 microns, and in accordance with client requirements.
Neoprene sheets used to enhance friction between the pipe coating and the anodes are fixed by appropriate adhesion methods on the underneath side of the pipeline at steel loop locations.
For pipelines with elevated temperatures, thermo insulation inside the anodes is suggested to reduce the temperature in order to increase the electrochemical performance of the bracelet anodes.
At SYNCOR, we have the capability to manufacture anodes of different shapes and sizes to allow for easy installation, and to reduce damages when the anodes pass over a stinger as the pipeline leaves the lay barge.
All bracelet anodes are designed and manufactured based on client specifications.
Bracelet Anode type
BTB - Tapered, Bolted half shell bracelet anode
SHB - Square, hinged and bolted half shell bracelet anode
BSB - Square bolted half shell bracelet anode
 
 
 
BSG - Bracelet anode, segment
BHB - Bracelet anode, hinged and bolted segment bracelet anode
BTW - Bracelet anode, tapered welded
 
 
 
BTH - Bracelet anode, tapered, hinged and bolted half shell bracelet anode
BSH - Bracelet anode, square hinged and bolted half shell bracelet anode
BSW - Bracelet anode, square welded half shell bracelet anode 
 
 
 
 
 
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