Subsea Safety Signal Tone Separation on Common Umbilical Lines
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Solution Overview
Problem
Existing subsea safety signal systems face challenges in providing fail-safe conditions for subsea installations due to incompatibility with redundant communication and power systems, particularly in avoiding cross-talk between safety and non-safety signals, especially when using modulated formats with substantial bandwidth over common transmission lines.
Innovation Solution
A safety system that uses distinct tones superimposed on communication or power lines, with frequency separation from data signals, allowing for fail-safe valve control without complex coding, ensuring specific signal delivery to each subsea device and maintaining redundancy in power or data communication systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If safety signals are transmitted over common transmission lines using modulated formats with substantial bandwidth, then safety signal transmission capability is improved, but cross-talk between safety and non-safety signals increases
Solution Approach 1:
The transmission system is segmented into distinct frequency bands: safety signals occupy a first frequency band while non-safety data signals occupy a second frequency band. This frequency division allows both signal types to coexist on the same transmission line without cross-talk, resolving the contradiction between reliable safety signal transmission and avoiding interference.
Solution Approach 2:
A frequency separator acts as an intermediary device that receives both safety and non-safety signals from the common transmission line and separates them into their respective frequency bands. This mediator enables safe co-transmission by directing each signal type to its designated processing path, preventing cross-talk while maintaining transmission capability.
2Reliability
If redundant communication links are provided for subsea installations, then system reliability is improved, but complexity of signal management increases
Solution Approach 1:
The common transmission line serves multiple functions simultaneously: it carries both safety signals and non-safety data signals. By making the transmission infrastructure universal and multi-functional, the system achieves redundancy and reliability without requiring separate dedicated lines for each signal type, thereby avoiding increased complexity.
Solution Approach 2:
The system uses frequency as a distinguishing parameter to manage multiple signal types on the same transmission line. Safety signals are assigned to one frequency band while data signals use another, allowing simple frequency-based routing and management without complex signal processing or multiple physical channels.
3Reliability
If safety signals use complex coding formats, then signal specificity to particular installations is improved, but device complexity increases
Solution Approach 1:
Each subsea installation is assigned a specific frequency band or frequency slot within the safety signal band, creating local differentiation. This frequency-based addressing provides signal specificity to particular installations without requiring complex coding schemes, as each installation simply monitors its designated frequency range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable and specific safety signal transmission to subsea devices over common transmission lines, preventing cross-talk and ensuring fail-safe operations even in case of power or communication failures, while maintaining system redundancy.
Implementation Method 1
A safety signal, having a first frequency band, is transmitted over a common transmission line with a data signal, having a second frequency band, wherein the first frequency band is frequency-separated from the second frequency band
Data Source
AI summary
A subsea system comprises a multiplicity of subsea installations (M-1 . . . M-n) and a common transmission line (2a) in an umbilical for the conveyance of power or data communication electrical signals to the subsea installations. The system provides on the common transmission line a plurality of safety signals (T-1 . . . T-n) in the form of tones separate in frequency from each other and the other signals on the line. Each subsea installation is arranged to receive from the common transmission line selectively a respective one of the safety signals for the control of a fail-safe device (9) in the installation.