Successful pullback tests would prove the robot could be retrieved from the site without having to undergo the expensive task of depressurising parts of a site, digging down and cutting out sections of pipework. Utilising a gearbox mounted outside of the launch vessel which is connected to the Umbilical Management System (UMS), the aim was to pull the robot back in a series of tests, increasing in difficulty and risk.
Preliminary tests were done, pulling back in a straight line over a distance of roughly 2 metres, this proved that the robot would indeed pullback without the UMS or the robot being damaged by the forces created within the system. This was tested further by sending GRAID beyond a T-junction and up to 12 metres within the test rig framework. Again there was no visible damage done to either the robot system or the tether back to the UMS, but it did show how much effort on the winch was needed!
The final tests were to recover the robot from around a bend, something that will mean more stresses upon the system. This test presented additional risks, with no control over the position of the robot in the pipework, increased friction forces, breaking the UMS or snapping the tether before we had retrieved the robot. None of these issues were thankfully realised and the robot successfully made it around the bend and back to the Launch Vessel without damage.
Taking this to the next level, the Synthotech team decided to raise the robots centre of gravity; fitting the full 900mm NDT arm to the robot. This would mean a greater potential to topple the robot through the bend however, again the robot and UMS system didn’t fail and the robot was safely recovered without damage.
Having managed to pull back the robot several times through the two days of testing, the UMS and GRAID robot is now undergoing analysis to determine what, if any mechanical damage was done during the pullback tests.