NAXYS - SUBSEA MONITORING SYSTEM

NCM⁴ offers a new concept for monitoring of subsea machinery and processes.

On land and offshore topside, monitoring of machinery and processes is used extensively. For subsea installations the philosophy of minimizing monitoring and run to failure has been justified by the fact that instrumentation requires structural interface/cabling and generally increases the complexity and thus also the failure modes of the various subsea modules.

The concept of NCM⁴  is to monitor large subsea structures using distant positioned sensors. This is obtainable by analysing the acoustic emissions in the vicinity of the structure. Whether a bearing damage, valve defect or oil/gas leakage to the environment arises, a change in the acoustic picture will result and immediately be observed by NCM⁴.

The 4D reflects the system’s ability to focus its sensing capabilities in space in addition to trending over time, thus providing resolution in 4 dimensions. The NCM⁴ consists of two main sub-systems, the Acoustic Module and the Diagnostics System.

Acoustic Module (NAMM) - Naxys Acoustic Monitoring Module

The Acoustic Module is centrally placed on the structure to be monitored, normally as a single unit. The NAMM contains various active and passive acoustic sensor arrays and an electronics container in a robust framework.

The communication and power connector is placed on a pigtail hose accessible for ROV. 

Diagnostics System (NADS)

The diagnostics system is integrated into the NAMM.  The NADS continuously receives acoustical raw data and carries out data analysis applicable for leakage, vibration and condition monitoring.  Using virtual sound tubes, the monitoring of the subsea structure is organized into spatial sectors for each of which data analysis is carried out.

If components of the analysed data exceed a downloadable alarm threshold, the NADS will respond with an alarm when requested by the control system over e.g.  Modbus interface.  For optimum interpretation of the acoustical data, it is advantageous for the NADS to have access run time parameters, like choke and valve operations, over the same  interface. 

The run time parameters are input to adaptive filters that adapt to the normal noise level. Upon an alarm event, the NADS triggers upload of snapshot raw-data from the NAMM to the top side command, control, and data presentation and storage module (CCDS).

The software in NADS runs on a dedicated Digital Signal Processor (DSP). The system supports future e-fields and can be connected to Naxys’ inhouse diagnostic center which is connected to the operators e-field centre.