EXPLORATION • DRILLING • FIELD SERVICES


ig operations have numerous challenges. Accidental release of gases, operating in extreme environments or when being towed during a heavy sea state are just a few. A common and often-overlooked concern among the above, is the assurance of enclosure integrity against gas or water ingress. Gases and excessive water entering into open enclosures, are a recipe for disaster. With likely outcomes being power outages, engines over revving, fi re, explosion, intoxication and potential stability concerns. Whenever drilling or when under way to the next destination, exterior doors and hatches should remain shut and eff ectively sealed from the elements, with an internal positive pressure present to prevent gas or water ingress. Similarly, below the waterline


R


hydraulically operated watertight doors should be permanently closed to function as a safety barrier, preventing water ingress from one compartment to another during an accident or fl ooding. When enclosures are shut, daylight, noise and smells should never be sensed. Yet wear and tear, poor maintenance, paint and the environment can all contribute to seal integrity losses. Invariably, the hardening of neoprene seals becomes commonplace and an indentation of the enclosure becomes permanent, causing a signifi cant portion of the seal’s surface contact area to become ineff ective against gas or water ingress. Using the services of a Class-registered,


third-party inspector, one can actively fi nd leaking sites to assist the Rig Maintenance Supervisor (RMS) enclosure and maintenance compliance needs, using high-frequency emission ultrasounds. T e acoustic leak detection method generates


THE SOUND OF SUCCESS


frequency emissions greater than human audible hearing range, over 20MHz.


THE IDEAL SOLUTION Purposely designed to ensure enclosure compliance, professional equipment such as the ABS Class-approved Cygnus Hatch Sure provides the safe and direct means of closure integrity assurance, in a timely manner and with pin-point accuracy. T is non-invasive method does not


disrupt rig operations and can be performed at any time of day, in any conditions. Mounted on a tripod behind a closed door or beneath a hatch cover, a high- frequency transmitter inundates the enclosed space with ultrasound. After heterodyning (the process where the high- frequency sounds are modulated in real time for listening), the inspector – wearing a set of headphones – scans the other side of the shut enclosure with the ultrasound probe, tracing around the enclosure to listen for and mark where the leaking ultrasounds are emanating from. Returning ultrasound levels are dependent on seal compression. Typically, the higher the pitch, the greater the leak. When performing vessel cargo hatch inspections, an open hatch value (OHV) is obtained, a value >10% denotes seal failure.


After repairs or seal replacement, a


Professional equipment ensures safe and effi cient enclosure integrity


valve <10% of the OHV the enclosure is considered weathertight.


Tony Dale reports on enclosure integrity testing using acoustic ultrasound


A pass result of <10% means water will not penetrate through the enclosure in any sea condition, and by extension, air and gaseous emissions at atmospheric pressure. Regardless of surrounding decibel noise


levels, the ultrasonic acoustic emission works just as well in noisy engine rooms. Furthermore, the system is applicable for all enclosure types, i.e. water and weathertight doors, deck hatches, manhole covers, scuttle ways and tank hatches, etc. Ultrasound emission and its detection


is so eff ective that classifi cation societies and P&I clubs have accepted it for locating leakage sites around ship cargo hatches and coamings, to mitigate multi-million-dollar cargo losses due to faulty seals and openings. Noise, smells and water ingress, no matter


how small, are unacceptable. Ingress of gases into a hold, machinery space or into the accommodation, including the loss of stability from water ingress does not bode well for any MODU or fl oater. Keeping enclosures closed and proactively testing seal integrities with ultrasonics is the pitch perfect and cost-eff ective means for your RMS to call out an approved inspector before the next drilling campaign or rig move.


Tony Dale is managing director of Geotherm. www.geothermltd.co.uk


www.engineerlive.com 17


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56