Development of an underwater riser inspection robot

Abstract

Purpose

The purpose of this paper is to describe a new multi‐sensor robotic system designed for riser, mooring lines and umbilical cables in situ underwater inspection. Due to the aggressive operation environment, such structures are susceptible to a broad spectrum of failure causes, such as aging, mechanical, chemical and thermal loads, hydrodynamic stresses, vortex‐induced vibrations and installation or fabrication non‐conformities. Current inspection methods present major risks and inefficiencies, especially as deeper fields are being reached for exploitation.

Design/methodology/approach

The SIRIS (In Situ Riser Inspection Robotic System) is designed to reconstruct the actual riser profile and perform non‐destructive tests. The robot is propelled by thrusters to scroll by the outside of the catenary riser. Mechanical, electronic hardware, image acquisition and software/firmware design are described here.

Findings

Simulated data from an inertial measurement unit is fused with depth sensor measurements, using a Kalman filter to reconstruct the riser profile, with small localization errors. Laboratory and sheltered waters tests were successfully executed to assess robot subsystems' performance: imaging, leakage, displacement and easiness of operation.

Research limitations/implications

The robot prototype is designed to operate down to 250 m deep, although the final goal is reaching 3,000 m. Tests offshore, in a real oil production platform, have not been performed up to this moment. In the present version, the robot must be coupled to the riser with the aid of a scuba diver.

Practical implications

The robot is expected to allow non‐destructive testing in risers that cannot be performed nowadays with the existing tools. The inspecting procedure is easy to operate and does imply any kind of production stopping. More accurate assessment of the riser structural condition can allow extending its life span, thus avoiding early decommissioning.

Social implications

Better assessment of actual riser facilities status will have great impact on reducing the chance of oil spill episodes and serious environment damage.

Originality/value

The design, construction and evaluation of a robotic tool for non‐destructive riser inspection has been described. A few similar robots exist in literature but none of them is able to reconstruct the actual riser profile.

Citation

Santos, M.F., Brito, M.O., Neves, C. and Menegaldo, L.L. (2013), "Development of an underwater riser inspection robot", Industrial Robot, Vol. 40 No. 4, pp. 402-411. https://doi.org/10.1108/01439911311320895