Diaphragm Couplings Versus Gear Couplings for Marine Applications

The gear coupling has been in existence for over 50 years. As advances in marine propulsion have occurred, so have advances in gear couplings. There are many variables in gear couplings that can affect their characteristics, including tooth design, materials, and lubrication methods. All couplings react on connected equipment. A system designer must consider these reactions when designing a system. If a gear coupling is chosen, there are many characteristics which are difficult to predict; therefore, one must conservatively estimate the maximum forces and moments that can be anticipated. This usually will make the system rather large and heavier than may be required. The diaphragm coupling usually has more predictable coupling characteristics, which can make a designer's life easier. This paper compares the characteristics of diaphragm couplings versus the gear (dental) type couplings in marine applications. Applications of couplings for main propulsion and auxiliary equipment are discussed. The methods used to analyze the design and calculate the forces and moments generated by both the gear coupling and the diaphragm coupling are also provided. These analyses are used to show that the forces and moments generated by a diaphragm coupling are not only predictable, but are usually lower than those of a gear coupling. The paper shows that a diaphragm coupling can provide a more predictable, reliable alternative to the gear coupling for advanced marine applications.