‘Open Forum - Question and Answers’ session at the end of the presentation by Martin Wall of ESR Technology and John McCarthy of MAPS Technology
Gus Chown – Bluewater Services. Any plan to deploy that (MAPS-FR technology) subsea?
John McCarthy – MAPS Technology (Presenter). It could be deployed subsea. As I say we’ve worked to a specification that Petrobras gave us and as I say they have particular concerns of the end fittings and just outside the end fittings in the bend stiffener region. That technique could be taken subsea.
Gus Chown – Bluewater Services. So I mean if you had a riser with a lazy S arrangement could you clamp, apply it with an ROV for example?
John McCarthy – MAPS Technology (Presenter). Or another variation of that is a scanning system where you use one probe and you either scan axially or circumferentially.
Gus Chown – Bluewater Services. Ok is there something that could be fitted with transmitters or something like that essentially?
John McCarthy – MAPS Technology (Presenter). Yeah yeah.
Gus Chown – Bluewater Services. Ok thanks.
Alan Smith - DNV. If you were to use this subsea, presumably you’ve got those sensors fitted up pretty closely to that pipe. If you’ve got a situation with marine growth and that kind of thing you’d have to presumably blast all of that off before you could use a system like this wouldn’t you?
John McCarthy – MAPS Technology. Yeah the stand-off or the moving away from the sheath potentially reduces the signal. We’ve gone up to 16 millimetres away from the wires. We’ve not explored any further but ideally you would want to contact at least the outer sheath.
Yannis Savidis – HSE. With the way you cut the wires, does that have any influence in comparison to a real field failure where you might not have a nice clean break of the wire. Does that change the sensitivity of the results or does it actually make it better?
John McCarthy – MAPS Technology. No because in the monitoring application what we’re doing is we’re comparing a sort of a stress state when it was good with a stress state which was bad and they could be days apart or months apart. We’re not looking for the actual separation. It’s not like the acoustic ping. It’s just the fact that the stress has changed. And in the inspection, as I say we weren’t there for the break anyway. Its just we’re picking up the stress change purely by comparing adjacent wires.
Martin Wall – ESR Technology (Presenter). I think Petrobras experience in these deep water risers is if that it is difficult really if the wire breaks - they tend not to have partial wiring breakages because of the high loads as opposed to pipe wall corrosion. (transcription suspect - inaudible due to noise within audio)
John McCarthy – MAPS Technology (Presenter). Certainly something we’ve seen in trials with Petrobras is there was one riser we did some work on which was actually heavily corroded. There wasn’t a polymer sheath between the first and second layers and they have bound up completely. So when you cut the wire the strain gauges saw nothing until you’d relaxed it and reloaded it. Now in that case we were about a metre away from the break and we saw a degradation immediately because there was some movement and then a much bigger signal in terms of the stress change after they’d exercised, if you like broken the corrosion.