There are various types of subsea umbilicals, including for remote operated vehicles (ROVs), communications, control of and supply of chemicals to subsea production systems, and supply of power to subsea processing systems. This article discusses the last two types. ROV umbilicals are discussed in a separate article.
An electrohydraulic subsea control umbilical tyically supplies electrical power and multiplexed signal, hydraulics, and chemicals to one or more subsea control modules (SCMs) controlling subsea christmas trees and/or other elements of a subsea production system; and signals from subsea instrumentation back to the control center.
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A direct hydraulic control umbilical provides direct hydraulic control of each valve on a subsea christmas tree, through a bundle of tubes from the topsides hydraulic power unit (HPU) to the subsea tree. No electrical power or signal is required. Actuation of valves is by the supply of hydraulic power to the relevant tube. This is accomplished by opening the relevant valve on the manifold located on the topsided HPU. This type of umbilical is limited to subsea production systems with short offsets to the host and few trees.
An electric power umbilical supplies the large amounts of power (up to 100KV) required to operate subsea boosting and processing systems. They may or may not include wires for multiplexed control systems and instrumentation, and tubes for hydraulics and chemical injection.
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Umbilicals may be classified by the materials used for the tubes, i.e. steel-tube thermoplastic.
Umbilicals or portions of umbilicals may be classified by whether the riser portion is supported for the full length (static)or is suspended in the water column from a floating structure (dynamic)
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Umbilicals are typically terminated subsea by an umbilical termination assembly (UTA), which allows for the distribution of hydraulics, chemicals, and electrical signal and power through flying leads connecting the UTA to the subsea production system.