condition monitoring
››› be scheduled when needed rather than at pre-determined intervals.
Most third party CM systems for propulsors either lack the accuracy or scope to properly determine the condition of a complete thruster, Wärtsilä asserts. More importantly, without the class recognition specifically applicable to Wärtsilä equipment, such systems cannot be used to extend an ABS internal survey interval of five years. It is therefore not possible to maximise the availability of installations with these CM systems. To substantiate its claims, a team of PCMS data analyst specialists who are also propulsion experts has been established by Wärtsilä Propulsion Services. Additionally, the personnel are ISO-certified in vibration analysis for Condition Monitoring (ISO 18436-2/3) and trained in root cause analysis.
Data arriving from a vessel is automatically processed by the PCMS central core, which informs the data analyst of faults and irregularities. The results of the automated data analysis are always manually checked for validity by the analyst. Automatic processing, Wärtsilä explains, ensures that the analyst has sufficient time to determine the root cause of problems and to support the customer in resolving issues. Data analysts are backed up by Wärtsilä’s mechanical, hydraulic and control system specialists as well as by metallurgists. DNV and Lloyd’s Register also provide guidelines for condition monitoring, Wärtsilä’s PCMS being designed in full accordance with DNV rules for the classification of ships on machinery CM and classification notes regarding ‘Thruster CM’. According to DNV, condition monitoring on thrusters is intended to replace visual internal inspections. For DNV-classed ships, a CM notation is granted to ship operators on a vessel-by-vessel basis; Wärtsilä can supply draft documentation to smooth the application procedure. Lloyd's Register states that the operator is responsible for assessing the suitability and competence of contractors undertaking CM. In its guidelines for owners and managers, however, LR provides typical assessment criteria, with which Wärtsilä’s PCMS complies (including ISO 18436 certification for data analysts). LR is currently defining procedures and requirements for condition monitoring based-planned maintenance schemes for thrusters. • Each thruster unit covered by Wärtsilä’s PCMS is served by a cabinet equipped with the following as standard: six accelerometers (50 kHz); four pressure transmitters (50Hz); two temperature transmitters; an oil monitoring unit; and a torque measurement system (100Hz). Accelerometers are used to monitor ›››
86 I Marine Propulsion I February/March 2012
www.mpropulsion.com
decreasing failure rate
normal failure rate
increasing failure rate
early infant mortality rate
observed failure rate normal (random) failures wear out failures time Types of fault that can occur progressively during the lifetime of equipment
failure rate
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 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132