BUMAX provides high-strength ship propeller fin cap solution


Mecklenburger Metallguss (MMG) uses BUMAX bolts to fasten its escap® (energy saving cap) in high torque applications.

MMG annually produces around 100 propellers at its foundry in Waren, northeast Germany. MMG propellers are used for various large container vessels, tanker, bulker and cruise ships and can be up to 12 meters in diameter.

Since 2020, BUMAX® 88 & BUMAX® 109 bolts have been used to fasten the MMG escap®, which can reduce fuel consumption by up to 3% by smoothing out the swirl behind the propeller cap. The escap® can be mounted onto existing propellers and the fuel savings typically provide a return on investment within three months.

High tensile strength bolting solution

“We began using BUMAX for our escap® as we needed a high tensile strength bolting solution for safely transmitting the torque in existing propeller applications,” says Jörn Klüss, Head of Design and Construction at MMG. “Using standard stainless steel bolts would require expensive re-machining additional and/or larger holes in a dry dock to deal with the required torque. With BUMAX, we can install the escap® while ships are in the water with diver installation teams as we don’t need addition holes with high strength BUMAX bolts.”

In addition, the good corrosion resistance properties of BUMAX® 88 and BUMAX® 109 bolts are essential as the fin caps are permanently submerged in seawater. The Fin caps also play an important role in covering and protecting the shafting parts that are typically made of carbon steel and are susceptible to corrosion.

The escap® is fastened by up to 24 bolts depending on the cap size and uses bolt dimensions up to M36.

“A number of container vessels and bulk carriers are already in operation around the world with an escap® secured by BUMAX bolts,” says Klüss. “The BUMAX bolts have performed very well and avoided the need for ship owners to undergo costly dry dock re-machining.”

Excellent BUMAX service and support

As with all its customers, BUMAX aims to provide prompt product delivers and is on hand to support with any technical queries.

“We have had very good cooperation with BUMAX as they have supported us with the design process and are always quick to respond to our queries,” explains Klüss. “We typically have a tight schedule on our projects with limited time for design and manufacturing – so fast support and delivery are very important for us.”

“We are currently working together with BUMAX to use larger dimensions of bolts to fit larger ships with escaps,” concludes Klüss. “We have a number of projects in the pipeline that promise to realize more fuel savings for shipping companies around the world.”

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