Case Study:
Acoustek™ Pipeline Blockage Detection System

Acoustek™ Pipeline Blockage Detection System

iNPIPE PRODUCTS™ was approached by a North Sea Operator who required assistance with validating their Gas Import / Export SSIV [Subsea Isolation Valve] closes within 60 seconds and meets their pipelines Performance Standard document.

The SSIV forms part of the ESD [Emergency Shut Down] System on the pipeline and as such is classified as safety critical equipment and is subject to regular testing to meet the criteria set out in the Performance Standard document. The SSIV was situated subsea at the base of the riser in 136m water depth and is around 338m along the pipeline length. The SSIV acts as a secondary isolation against hydrocarbon release in an emergency event, but the valve has no position indication feedback to DCS [Distributed Control Systems] meaning an accurate closure time cannot be confirmed by closing the valve alone.

Prior to utilsing Acoustek™ gas gun equipment, the closure time has been inferred from hydraulic feedback, but this method does not confirm the status of the closed valve nor closure time without the requirement of venting the riser. Venting the gas from the pipeline riser is a costly option and a process that brings its own set of risks to the platform operator, platform, and environment.

Acoustek™ Technical Information

  • Acoustic–based blockage detection for gas pipelines
  • Gas gun used to inject pressure pulse into line
  • Return signal from line monitored
  • Return time used to fix locations of obstructions
  • Able to detect partial or full blockages
  • Range up to 10km, dependent online conditions
  • Can be used in pressures up to 5,000 psi

Pipeline Details

Parameter Detail
Pipeline Nominal Size 6"
Pipeline Material API 5L X52
Pipeline Length 338m (to SSIV), 5km to Receiving Platform
Production Product Gas
Production Rate 0 m³/day (during survey)
Operating pressure 22 barg (during survey)
Pipeline Temperature 14.4 ºC

The Acoustek™ connection point selected was a 2” instrument tapping located topsides.

Pipeline Feature Details

Feature Distance (m) * Comments
PI-11036 0.00 Connection point
XSV 11020 2.47 6" Isolation point
XSV 11027 7.04 4" Isolation point
Top of Riser 30.41
Bottom of Riser 226.41
End of Pipeline Spool 326.41
End of SSIV Spool/XSV 11043 338.73 SSIV position
Receiving Platform 5,391.90

*From connection point

 

Following a review of the project details and discussions with the Client, iNPIPE PRODUCTS™ mobilised a Field Engineer to visit the site with iNPIPE PRODUCTS™ Acoustek™ gas gun equipment, all of which can be deployed within 24 hours in emergency.

 

The Acoustek™ gas gun uses acoustic reflectometry to detect blockages or partial blockages in gas pipelines. In essence, an acoustic pulse is generated by a small pressure pulse generated in the gas column. This pulse travels along the pipeline and as it passes locations where there is a change in acoustic impedance it generates a reflection, which then travels back along the pipeline to the injection point, where it is detected and recorded.

 

This scope of work was conducted by the iNPIPE PRODUCTS™ Field Engineer, supported by the Control Room, Area Authority and was completed within a single shift.

 

The acoustic data was processed by aligning each shot and as the ‘Timed’ case was identical to the ‘Closed’ case, the valve is confirmed as closed by the time the pulse reaches it in the timed case. This transit time is <1 second, indicating that the valve is closed at 41 seconds (worst case) after the command was issued. If the valve was still partially open at this point, one would see a reflection at lower amplitude than the fully closed case and therefore a conclusion can be made with absolute confidence that the SSIV meets HSE guidelines.

 

Figure 6 provides corroboration of the technique, showing a reflection consistently detected in the ‘Open’ case at approximately 31.5 seconds. The initial pulse being at 1.5 seconds, this corresponds to a feature at 30 seconds round trip time. Based on the speed-of-sound this will be at a distance of approximately 5.4 km, consistent with the distance to the Receiving platform.

Fig 1 – Acoustek Shots – SSIV Closed
Fig 2 – Acoustek Shots – SSIV Open
Fig 3 – Acoustek Shots 40 Seconds After ‘Close’ Command
Fig 4 – Comparison of Shots
Figure 5 – Detail Comparison at 1st Echo
Figure 6 – Open Detail

 

Project Site Photos

Acoustek gas gun

  • Easy to use and install
  • Supplied and operated by  iNPIPE PRODUCTS™ Field Engineer

 

Acoustek software

  • Easy to follow instructions
  • Easy to mobilise
  • Supplied and operated by  iNPIPE PRODUCTS™ Field Engineer

 

Single gas bottle and regulator  – supplied by site