Centa series Centax L Coupling

Centa flexible couplings are found on larger vessles that have remote transmissions installed and aligned seperately from the main engines.  This particular vessel, a 130′ Alloy, was hauled out for an extensive dry-dock period.  The props had suffered some grounding damage and it was time for a running gear check.

A typical job for High Seas; shafts out and checked in our on-site machine shop Straight Line Marine, replace cutlass bearings, service the Kobelco Eagle seals (as mentioned in a prior post) and an Optical Scope Alignment check of all bearings and transmission locations.  Both transmissions required a minor alignment to square up to the shaft line.

With remote ZF transmissions the process requires removing the Centax L flexible couplings and adjusting the ZF mounts.  This particular vessel had adjustable mounts which is easier than the typical hard-mounted, chockfast arrangement.

Once the ZF transmission was aligned the engines required an alignment to be within Centa’s specifications for the flexible couplings.

Once everything is aligned the Centa couplings are reinstall paying strict attention to the manufacturer’s torque specification.  It is also important to install the “Links” (left part of the picture above) in the proper direction given the engine rotation.

Optical Scope alignment of ZF transmission with Centa Couplings on the ground

Milled Strut Base Plate for Alignments

On a recent strut alignment on a Cheoy Lee we ran into a situation with bottom clearance.  The vessel unfortunately sat on the bottom and the upward pressure caused the strut to bend or bow.  We dropped the strut and straightened it in our machine shop (see prior post).  Re-hanging the strut in the right aligned position requires a level of precision to get it right.   Once the strut pocket was cleaned and the strut was dry-fit for a test alignment we realized that the imperfections in the original strut casting left humps and hollows.  The high points contacted the hull in the wrong spots and prevented us from adjusting the strut to the right position.

The solution – mill a small amount off the strut pad – approximately 0.050-0.075″.  Not enough to cause any concerns with the integrity of the strut.  As you can see in the picture the original pad had plenty of beef.

Once properly aligned and assembled the vessel was launched and we went for our traditional sea-trial.  I always like to sea-trial a vessel to make sure it is vibration-free and the customer is satisfied.  It is also the right time to ask for a reference, which this Captain gladly allowed.