PCMS Engineering provides an ongoing Condition Based Maintenance (CBM) programme to one of the world’s largest providers of offshore service vessels. As part of an ongoing marine vibration analysis service, routine data is submitted on a monthly basis to establish and analyse the condition of critical assets throughout their ﬂeet of vessels.
PCMS engineers utilise multiple CBM technologies to determine an asset’s condition and remaining life-span. A recent data submission from an auxiliary generator, which provides power to the vessel during port calls critical to the operation of the vessel, showed a noticeable change.
Utilising vibration and stresswave spectral data, PCMS engineers were able to identify non- synchronous frequencies at the NDE of the engine. These are commonly associated with rolling element bearings, however, as none were located close to the measurement point, PCMS engineers requested information from the vessel operator in regards to other components.
The non-synchronous activity was identified as being 1.160 orders (2075rpm) of engine shaft running speed. Utilising the information provided by the operator, PCMS engineers were able to identify the closest frequency – item 10: oil pump 69 teeth so at 1800 rpm gear rotation is 80 / 69 = 1.15942 x 1800 = 2087 rpm.
As the engine was running at 1789.8 rpm, and using the information provided that 80 teeth are driving 69 teeth, PCMS analysts calculated that the oil pump would be operating at 2075 rpm. This matched the stresswave frequencies present.
As stresswaves are generated when metal is bent, impacted, scuffed and/or under increased friction, it was recommended that an inspection was carried out on the component while rotating at this speed.
The inspection of the oil pump gear found significant damage – see figure 1: data from the engine NDE and figure 2: oil pump gear damage.
The unit was replaced and all levels returned back to normal with a reduction in catastrophic failure risk to both the gear and pump, as well as reducing the risk of damaging particulate entering the engine.
The client avoided an unexpected pump failure and replacement while in operation, providing an estimated cost saving of £50,000. Furthermore, a catastrophic engine failure and replacement caused by the pump failure could have cost the client an estimated £1 million.
For more information on our marine vibration analysis service, contact us on +44 (0) 1709 876 712, email email@example.com.