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Photo | Bosch Rexroth AG

Big as a building and producing 68,000 HP: a large marine diesel in the final manufacturing phase at CMD.

Reliability writ large

Chinese engine manufacturer CSSC-MES Diesel has adopted modular systems and halved delivery periods for its large marine diesel engines.

 

Large ships need powerful drives such as those built by Chinese engine manufacturer CSSC-MES Diesel Co. Ltd. (CMD) in Shanghai. That firm manufactures slow-running, high-power diesel engines – boasting cylinders 980 millimeters in diameter, turning at 97 revolutions per minute, and delivering 50,000 kilowatts. Their operational reliability is highly dependent upon vital control devices such as valve boxes and emergency control panels on the ship’s bridge and in the engine room.

A single supplier for the entire system

When the market started to boom, the delivery and assembly of these subsystems were not as punctual as CMD had hoped. That is why the company began looking for a more feasible solution. “As­sembling valve control boxes is an elaborate process that requires great care and usually has to be carried out within a limited period of time,” explains Zexin Fang, purchasing project manager at CMD. “That prompted an intensive search for a qualified supplier who could reliably handle all this integration work.” It was at exactly the same time that one of the firm’s suppliers converted to modular system concepts: Bosch Rexroth.

Up to that time the company had supplied a variety of pneumatic valves and the critical variable injection timing units. The latter control exactly when the fuel oil is injected into the cylinders; they also start, stop and reverse the engines. This change of direction uses pneumatic reversing cylinders developed especially for this application. CMD was so satisfied with this highly reliable collaboration that it charged the supplier with assembling the subsystems and delivering them on time. The supplier, in turn, quickly introduced decisive optimization ideas. At the Kangqiao assembly plant, located in Shanghai, Bosch Rexroth employees who specialize in marine technology have the expertise needed to assemble the valve control boxes. Adhering to the customer’s specifications, a number of valves and all the piping are integrated into a single cabinet. Thus the valve control box which CMD receives is entirely modular in its design.

Saving time and money

Closer collaboration also boosted efficiency. In the past the engine builder had to select the matching piping and housings for each of the individual valve components and, as well, find the appropriate suppliers. The company also had to fit the valves so that the boxes could ultimately be assembled. Ever since Rexroth began deliver­ing the complete module, the customer’s throughput time has been cut in half – from as much as four months to just two.

“We have taken the inlets and outputs for electrical power and air and matched them exactly to the housing,” is how Yuan Wang, pneu­matic applications manager at Bosch Rexroth, explains the time savings. “As a consequence CMD, right after delivery, can simply connect the piping – laid according to drawings – directly to the housing. The valve control box goes into service immediately. That saves a tremendous amount of time.” And the collaboration itself cuts costs, as Zexin Fang emphasizes: “The improvements have reduced overall costs for the project by five percent.”

Continuous improvement

Rexroth is recognized for its wideranging know-how and decades of experience in the field of control engineering. These both paid off while implementing a variety of applications. Even where several different end customers use identical engines, the valve control box will have to satisfy varying individual requirements in each case. Over and above that, optimization efforts continue unbroken. The system supplier forwards the technical feedback from CMD to the design engineers, paving the way for continuous improvement in the valve control boxes. Those engineers both consider the complete system and look closely at every detail.

To name one example, all the connection components on the case are labeled to facilitate installation and operation and the drawings are provided, enabling the final user to easily repair the control box if necessary. To make sure this never happens, however, Rexroth develops and tests all the components installed here in accordance with the specifications set forth by the marine classification societies. The appropriate approval procedures make it possible to demonstrate that this process has been followed, whenever the ultimate owner and operator might require that evidence. This is of special importance since, in the meantime, local manufacturers have begun to offer poor-quality copies. This can result in the complete failure of the entire system. And that is an unpleasant surprise one can well do without on the high seas.