Very Targeted Retrofit: the Turbocharger (Source: WWW.DIESELGASTURBINE.COM)
In times of tightening emissions limits and uncertain fuel prices, there is one word that is often heard within theworld of engine manufacturers — retrofit. Retrofitting is an important area of activity for the MAN Diesel PrimeServ organization. There are several retrofit capabilities in the company’s portfolio, including engine upgrades, conversion from liquid to gaseous fuels, common rail technology, splash oil monitoring, emission control and engine control, among others.
One product category that is gainingprominence in the array of retrofit offers by PrimeServ is turbochargers. They have become so popular that the company dedicated a team of three people specifically to these projects. This number is destined to increase in the future to cope with the flow of customers’ requests.
One of those involved is Marijana Saric, project engineer in the Augsburg, Germany-based PrimeServ Service Retrofit Turbocharger team. She explained that the retrofit of a turbocharger presents several advantages for the efficient operation of the engine. “First of all, the engine’s useful life is extended, while at the same time performance and emissions-related issues are improved,” said Saric. “Also, don’t forget the cost-saving aspect related to the high price of spares for obsolete turbocharger models.”
Saric said a turbocharger retrofit could not only mean the replacement of an older unit with a new model, but also the installation of the latest technology to current models. In this case, it would be the installation of the new MAN Diesel variable turbine area (VTA) technology. “This operation involves the exchange of a fixed nozzle ring with a nozzle ring with adjustable vanes, plus the addition of the necessary controls,” said Saric. Such retrofit interventions can also include the production of tailormade adapting parts and flanges.
VTA technology allows the optimization of turbocharger compressor output by varying the pressure of the exhaust gases on the turbine. Demand of charge air from the engine at any load point can be matched to power demand from the propeller. According to Saric, this type of intervention is especially popular in times of high fuel prices, as operators reduce vessel speed to save fuel.
A dedicated team is responsible for all turbocharger retrofit projects, and every project is different. Lately, the PrimeServ team has reported many inquiries for the retrofit of MAN Diesel type KSZ two-stroke engines, manufactured in the 1970s and 1980s. According to Saric, field experience showed that KSZ engines are usually affected by combustion chamber component problems, caused by poor combustion air delivery. These problems are particularly evident at lower loads, with the deterioration of turbocharger performance.
In the particular case of KSZ engines, MAN Diesel offers the high-efficiency type TCA55 and TCA66 axial turbochargers for retrofit. MAN Diesel PrimeServ estimated that, depending on overall engine condition, a turbocharger retrofit would allow the engine to exceed the operating values originally achieved in its shop tests.
The presence of a PrimeServ supervisor for on-site technical consultation and advice on installation and attachment is often included in the retrofit intervention. A mandatory commissioning and turbocharger matching by the MAN Diesel specialist follows.
Saric also underlined how retrofitting obsolete turbochargers can bring additional benefits due to easier spare part procurement with less expensive part prices, a reduction or an avoidance of engine downtime, the attraction of a new standard one-year warranty for the turbocharger and a secure long-term parts supply.