Replacement of 42 Anchor N+Bolts in a Mitsubishi–MAN Diesel Engine 18V52/55B

The Problem and Solution

Unit 5 of the Mitsubishi-MAN diesel engine at the CUC power plant on the island of Saipan developed vibration problems, forcing a reduction in engine speed to avoid major damage, and resulting in decreased efficiency.

Using our expert techniques and state-of-the-art equipment, our team of specialists completed the job in a timely and efficient manner, following a six-step process that included 

1. Diamond core drilling
2. Diamond wire cutting
3. Removal of concrete blocks
4. Installation of new anchor bolts, 
5. Rebar and concrete replacement
6. Regrouting with our high-performance Alphatec 800 green epoxy grout

The Procedure

Alphatec Engineering mobilised a highly experienced team, including specialists in diamond core drilling and diamond wire cutting. Because of the remote location, all materials & equipment required to complete the repair work, except for reinforcing steel and ready-mixed concrete, had to be shipped to the island.

The first step was to cut out concrete on both sides of the engine foundation using diamond wire in the form of twelve blocks (total volume 32 m3). This allowed the existing 2.31 m long anchor bolts to be chipped out and removed.

Next, new 3.2 m long anchor bolts were set in place (21 on each side). Formwork was installed to contain the first pour of the Alphatec 800 epoxy grout which embedded the lower 1000mm of the anchor bolts. After 24 hours of curing, the first batch of replacement concrete, up to one metre below floor level, was poured.

Prior to that, a layer of Alphatec 440 epoxy bonding agent was applied to all surfaces to ensure adherence between the existing and new concrete. Then a further grout of Alphatec 800 was poured into the anchor bolt cavities to a level 15 cm below the base frame of the engine.

After curing, Alphapad hydraulic jack units were set in place to take the weight of the engine and the engine frame was aligned. A second pour of replacement concrete was then done, bringing the level up to 280 mm below floor level. Finally, Alphatec 800 epoxy grout was poured to floor level.

A series of injection holes were drilled alongside the engine and alternator foundation, to a depth of 3.6 m, and Alphatec 342 epoxy resin was pressure injected to repair the “cold joint” that became apparent just above the 45° sloping part of the foundation, as well as other separations and stress cracks, raising the effective damping inertia of the foundation.

Finally, the engine crankshaft was aligned using a digital web deflection tool, and the anchor bolt nuts were replaced with Supernuts to eliminate any movement of the crankcase after alignment. The successful completion of this project ensured the continued smooth operation of the engine, maintaining productivity and safety in the power generation process.

Conclusion

At Alphatec Engineering, we take pride in delivering high-quality solutions for our clients’ unique needs, and the successful completion of the foundation repair project for the Mitsubishi-MAN diesel engine at the CUC power plant on Saipan is a testament to our commitment. 

Our team of highly skilled specialists leveraged their expertise and state-of-the-art techniques to address the vibration problems that were causing decreased efficiency, and we were able to ensure the continued smooth operation of the engine. 

By choosing Alphatec Engineering, you can trust that your machinery will be in good hands, and we will work tirelessly to maximise your productivity and minimise downtime.