Pressure-Compensated Proximity Sensor for Subsea Shaft Monitoring
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Solution Overview
Problem
In subsea fluid extraction wells, existing sensor assemblies struggle to accurately monitor the health of rotating equipment like subsea pumps and motor shafts due to harsh environmental conditions and indirect monitoring methods, leading to delayed detection of equipment issues.
Innovation Solution
The development of pressure-compensated proximity sensor assemblies that can directly detect the position of a rotating shaft without physical contact, using RF radiation, light, or other energy types, and are designed to withstand high pressures and be flexible and adjustable for various configurations, allowing for precise monitoring of dynamic and static parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If indirect monitoring methods (accelerometers on motor case) are used, then the sensor assembly can be installed without direct shaft access, but the measurement precision and diagnostic accuracy deteriorate
Solution Approach 1:
The patent replaces indirect mechanical monitoring (accelerometers on motor case) with direct non-contact electromagnetic sensing (eddy current sensors). The eddy current sensor uses electromagnetic fields to directly measure shaft position and vibration without mechanical contact, eliminating the signal attenuation problem where small shaft variations are lost in the heavier motor case mass.
Solution Approach 2:
The patent introduces an electromagnetic field as an intermediary between the sensor and the rotating shaft. The eddy current sensor generates an electromagnetic field that interacts with the conductive shaft surface, allowing direct measurement of shaft parameters without physical contact or mechanical coupling to the motor case.
2Measurement precision
If direct shaft monitoring is implemented, then measurement precision improves, but device complexity and installation difficulty increase
Solution Approach 1:
The patent employs a flexible bellows structure that allows the sensor probe to extend and retract, accommodating shaft movement and installation variations. This flexible element simplifies installation by allowing the sensor to be positioned close to the shaft without rigid mechanical constraints, reducing overall system complexity while maintaining direct measurement capability.
Solution Approach 2:
The patent creates a dynamic mounting system where the sensor probe can move with the shaft through the flexible bellows connection. This dynamic arrangement allows the sensor to maintain optimal positioning relative to the rotating shaft while simplifying the mounting structure, avoiding complex rigid positioning mechanisms.
3Measurement precision
If proximity to shaft is increased for better signal, then measurement precision improves, but reliability deteriorates due to contact and wear
Solution Approach 1:
The patent replaces mechanical contact-based sensing with non-contact electromagnetic sensing. The eddy current sensor measures shaft position and vibration through electromagnetic field interaction with the shaft surface, eliminating mechanical wear and contact-related reliability issues while maintaining high measurement precision through direct shaft proximity.
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
These sensor assemblies provide accurate and timely monitoring of subsea rotating equipment health, enabling early detection of issues and reducing the risk of equipment failure by directly measuring vibrational parameters and eccentricity, thus improving maintenance schedules and preventing production halts.
Implementation Method 1
proximity sensors typically actively emit RF (radio-frequency) radiation, light, sound, or other types of energy, and detect changes in the electromagnetic field or return signal
Implementation Method 2
proximity sensors typically actively emit RF (radio-frequency) radiation, light, sound, or other types of energy
Implementation Method 3
mounting an end of a sensor housing connected to the proximity sensor tip assembly to a wall of the device housing, the sensor housing defining a fluid reservoir containing a substantially incompressible fluid therein that is in fluid communication with the interior portions of the proximity sensor tip assembly
Data Source
AI summary
Sensor assemblies and methods of assembling and using the sensor assemblies are provided for monitoring operational characteristics of subsea rotating devices such as subsea motors and pumps. Pressure-compensated proximity sensor tip assemblies configured to withstand subsea pressures are mounted adjacent a subsea rotating shaft for directly monitoring a position of the rotating shaft during dynamic operation thereof. An end of a sensor housing opposite a sensor tip assembly is mounted to a wall of the device housing. The sensor housing defines a fluid reservoir containing a substantially incompressible fluid therein that is in fluid communication with the interior portions of the proximity sensor tip assembly. A length of the sensor housing is adjusted to accommodate a distance between the wall of the device housing and the rotating shaft.