Archive | April, 2017

Repairing a leaking Heat Exchanger in a Bow Thruster HPU

By on April 17, 2017 in Bow Thrusters, Hydraulic Power Units, Hydraulics

We were recently contracted to inspect a leaking heat exchanger on a 130 foot Westport yacht docked at a local marina. The heat exchanger was part of the hydraulic power unit (HPU) for the ship’s bow thruster system.  The HPU consists mainly of a motor, a reservoir tank and a hydraulic pump. These units can generate a tremendous amount of power to drive most any kind of hydraulic ram or motor. They can also generate high temperatures. Most heat exchangers used in the marine industry are water cooled and use a water control valve to regulate the flow of water though the exchanger to keep the hydraulic fluid temperature between 64 and 68 degrees C (147 and 155 degrees F). It is important to make sure the adjustments for the water control valve are set properly to avoid rapid overheating.

This particular model was a shell and tube design.  As its name implies, this type of heat exchanger consists of a shell (a large pressure vessel) with a bundle of tubes inside it. One fluid runs through the tubes, in this case hydraulic oil, and another fluid, water, flows over the tubes (through the shell) to transfer heat between the two fluids. The set of tubes is called a tube bundle and may be composed of several types of tubes.

Upon inspection, we found that the fittings in the heat exchanger were not properly seated and the sealant used was not sufficient for the job. In order to remedy the problem, we needed to remove the heat exchanger from the HPU and send it out for servicing. In order to do this, we had to disconnect the hard pipe Stauff clamps above the heat exchanger in order to spread the pipes apart to remove the heat exchanger from the bilge. We also disconnected and installed caps and plugs in the hoses connected to the heat exchanger. We resealed the adapters and fitting upon re-installation, connected the hydraulic hoses, installed Stauff clamp supports and tested the unit for leaks.

The heat exchanger is back in operation and helping to ensure that the hydraulic bow thrusters are doing their job helping to maneuver this yacht in tight places.

 

Overhauling BCS trim tabs on an 85 foot Ferretti

By on April 7, 2017 in BCS Trim Tabs, Ferretti, Hydraulics

BCS Trim Tab

Trim tabs are an essential component for any yacht. They improve performance, helping to increase speed, reduce pounding and on smaller boats offset prop torque. They help the vessel run more efficiently, reducing fuel consumption and engine laboring and eliminate “squatting.” But more importantly, they increase safety by improving visibility and handling along with reducing wake size and hull stress.

However, years of use and prolonged exposure to salt water can take a toll on their ability to function properly as was the case with an 85’ Ferretti that was hauled at Lauderdale Marine Center.

That is when our hydraulics team was called in to work on the BCS hydraulic trim tabs. Upon close inspection, we found that two of the four trim tab cylinders were corroded beyond repair and needed to be replaced. Because of manufacturer’s long lead time, we decided that we would machine new rods, barrels and re-build the cylinders in-house, using our machine shop, Straight Line Marine.

Corrosion in Barrel

The corrosion we found on the inside of the barrel was caused by salt water intrusion as a result of failed seals. Once the components were machined, we were ready to assemble the new hydraulic trim tab cylinders and re-install in the yacht. Unlike common trim tab cylinders, the BCS model does not use hydraulic hoses to distribute the hydraulic fluid to operate the trim tabs. The fluid is dispersed through a small pin hole in the transom bracket assembly. A clever design that eliminates hose failure external to the transom. However this creates a tricky install.

Pin Hole

The pin has multiple O-rings and requires a special touch to avoid pinching during installation. Great care must be taken in the removal of the old hydraulic trim tab cylinders and the re-installation of the new ones. Damage to the assembly as a result of scratching or scoring the unit would cause them to leak and render the trim tab cylinders useless.

We see these types of nuisances all the time. It takes a team of highly experienced hydraulics technicians to properly diagnosis the problems and take the appropriate actions to correct them.

Giving an Old Hydraulic Royal Boarding Ladder a “Face Lift”

By on April 7, 2017 in Boarding Ladder, Feadships, Hydraulics

From time to time, we see some pretty old yachts come into Lauderdale Marine Center as was the case with a 30+ year old Feadship. This old gal was in need of some work to bring her back to her glory days. We were hired to give her hydraulic royal boarding ladder a “face lift.”  A hydraulic royal boarding ladder is side mounted typically at mid-ship that retracts using hydraulic folding mechanisms when not in use, leaving your deck free of obstacles.

The job included stripping the boarding ladder for a new paint job, replacing the hydraulic hoses and hydraulic cylinders and installing new hardware right down to the nuts and bolts.

The royal boarding ladder now looks brand new with no traces of 30-odd years of use.