Metal bellows expansion joints as a solution to problems originated in ship engines
Most large transport vessels use internal combustion engines or gas turbines for propulsion. These reciprocating engines generate large amounts of vibration, which must be controlled to prevent damage to the engine and exhaust system. The best way to avoid vibration-induced damage is to incorporate one or more metal bellows expansion joints into the exhaust pipe, to provide a flexible connection that dampens vibration in the system.
These metal exhaust expansion joints are often covered with some type of insulation, to prevent excess heat in the exhaust gases from radiating into the engine room. Typical exhaust of a marine engine. Consider the insulation covering the bellows. As a cost saving measure, these exhaust bellows are typically made from a single sheet of stainless steel.
This single sheet design is typically used to accommodate higher pressures and gradual movements, such as those encountered due to thermal expansion in a steam system. Unfortunately, its design is not optimal for damping engine vibration, and two things happen as a result. First, the vibration is transferred through the piping system where the piping anchors, dampers, or bearings can be damaged.
Second, the resulting stresses quickly fatigue the metal bellows, so soon cracks will begin to appear in the bellows and the exhaust will begin to leak into the engine room. Operators must act quickly to replace the bellows, which can be problematic if the ship is at sea.
Solution proposed by Codinor
To avoid this problem, a different bellows construction should be considered; instead of a single sheet of material, the bellows can be made from two or more sheets of thinner-walled sheet metal, which are nested one inside the other before the bellows-forming process. This multilayer bellows may cost a bit more than single ply bellows, but they offer much better performance. The multiple sheets of metal in the bellows work to dampen vibration much more effectively than single sheet bellows. That means the bellows will last longer and protect the engine and exhaust from costly repairs resulting from excess vibration.
Codinor has the expertise to design engine exhaust bellows that will provide years of trouble-free operation, and we offer full product type approval by BV and other marine classification societies. Whether installing a new exhaust bellows or upgrading an old one, we have the experience to ensure maximum service life. If improving safety and reliability while reducing overall costs is important to you, you can contact us for solutions designed for your toughest applications.