Difference between revisions of "Umbilicals"
Phil Collins (talk | contribs) |
Phil Collins (talk | contribs) |
||
| Line 52: | Line 52: | ||
Kvaerner bundles umbilicals slightly differently than other bundlers: | Kvaerner bundles umbilicals slightly differently than other bundlers: | ||
*the pitch of the helical wind is about 2% rather than the usual 6-7% | *the pitch of the helical wind is about 2% rather than the usual 6-7% | ||
*the tubes and cables are held in a matrix made up of reeled elements which lock together as they are | *the tubes and cables are held in a matrix made up of reeled elements which lock together as they are bundled into the umbilical | ||
*carbon rods may be included in umbilicals designed for very deep water, to provide axial stiffness without adding significant weight | *carbon rods may be included in umbilicals designed for very deep water, to provide axial stiffness without adding significant weight | ||
Revision as of 21:18, 16 October 2013
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.
What is a subsea production umbilical?
An umbilical is a bundle of tubes and cables that
- provides hydraulic power to subsea control systems
- provides electric power and signal to subsea control systems
- delivers chemicals for subsea injection at the subsea christmas tree or downhole
- can provide bulk methanol
- can provide gas for gas lift
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.
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.
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)
Steel Tube Electrohydraulic Umbilical
Simple, static umbilical- few wells, shallow to medium depths
Media:SimpleEHUmbilical.png
(Click on link to see full-screen version of image)
A simple electrohydraulic (EH) umbilical will have the following components:
- steel tubes to deliver chemicals and hydraulic power to the subsea production system. There may be one or more backup tubes for use in case of tube failure. Tubes may be sheathed in LDPE to achieve the proper cross-sectional geometry.
- one or more electric cables (usually quads of 4 to 10 square mm)to deliver power and multiplexed signal to the subsea control system, and to carry instrumentation signals back to the surface control station.
- fillers to help create the proper cross-sectional geometry.
- tape which is wrapped around the elements as they are bundled and twisted into an umbilical. This holds the entire assembly together until it is passed through the extrusion head to receive its HDPE sheathe.
- HDPE Sheathe
Complex, dynamic umbilical- deepwater, multiple wells or drill centers
(Click on link to see larger image). A larger, more complex EH umbilical may have additional features:
- cables will be armored for dynamic applications, at least in the dynamic zone above the touchdown point
- steel tubes may be sheathed for wear protection where they are in contact with other steel tubes in the dynamic zone
- steel rods or cable may be added to achieve the correct weight-to-diameter ratio to avoid clashing in the dynamic zone with other risers hung off nearby
- armor may be added for weight-to-diameter ratio, tensile strength and crush-resistance during installation (above right cross-section)
Special case- Kvaerner
Kvaerner bundles umbilicals slightly differently than other bundlers:
- the pitch of the helical wind is about 2% rather than the usual 6-7%
- the tubes and cables are held in a matrix made up of reeled elements which lock together as they are bundled into the umbilical
- carbon rods may be included in umbilicals designed for very deep water, to provide axial stiffness without adding significant weight
my header 4 == 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.
