 |
Cases Techno Fysica BV is a Dutch-based engineering company, highly specialised in solving all kinds of problems related to the dynamic loading of machinery and installations. For this, several measuring and analysis techniques are used. In a series of articles, we will give examples of what can go wrong in the engineering and operating of vessels, and what errors lie at the root of the damages observed.
|
|
|
Unwanted
behaviour of load control/load sharing systems
|
| On a pipe laying ship, eight diesel generator sets are installed to power the thrusters that are used for dynamic positioning during pipe laying. The diesel engines are connected to the alternators through an elastic coupling. Several of the rubber couplings failed during the five years the ship is operational. Originally it was assumed that the quality of the couplings was inferior. However, changing over to another make of coupling resulted in the same damages and did not solve the problem. The useful lifetime of the couplings is totally random and ranges between 1000 hours and 28000 hours. In total, 14 couplings have failed which accounted for hundreds of thousands of Euros. |
|
Lifetime of rubber elements of elastic couplings on a pipe laying vessel |
| Because the torsional vibration load of the individual sets was checked and found to be low, as calculated, and no instability was found the suspicion rose that the load control system that governs the load distribution over all eight sets can cause the damages. In the past, there have been problems with the stability of this system, which resulted in severe oscillations of all diesel generator sets connected to the grid. To check this, all eight engines are now coupled to a customised data-acquisition system that records dynamic engine speed and load continuously and sends this data to the shore base for analysis as soon as pre-set alarm levels are exceeded. |
|
Damaged rubber element |
| For more info, please contact techno Fysica BV in the Netherlands at: Techno Fysica BV p.o. box 351 2990 AJ Barendrecht The Netherlands Tel. +31 180 620211 Fax. +31 180 620705 info@technofysica.nl www.technofysica.nl |
