Archive | April, 2014

Performing routine preventive maintenance on Nautical Structures Beam Cranes

By Chris Brown on April 21, 2014 in Cranes and davits, Cylinders

Installing Nautical Structure Beam Crane Cylinders using Yard Crane

We were recently hired to perform routine preventive maintenance on a pair of Nautical Structures beam cranes on a 155 foot Admiral yacht. The beam cranes are used to launch the tender or jet skis that are stowed on the main deck over either side of the boat. They are mounted to the underside of the upper deck and run athwartship, or at right angles to the keel, over the main deck but are hidden in the ceiling.

As part of the process, we removed all four cylinders from the cranes and rebuilt and repainted them in our hydraulics shop along with inspecting all of the bearings. We also replaced the Spectra Line on the cylinders. The four cylinders were located at the top of the beam crane on the port side of the boat. In order to remove the cylinders, we needed to extend the beam crane to pull the cylinders off.

Scaffolding used to install Nautical Structure Beam Crane Cylinders over water

Because of the way the boat was docked, coupled with the fact that it could not be turned around, we could not perform the procedure from the dock. This meant we needed to find a creative solution. Our answer to this problem: rig scaffolding on a floating dock and bring in the yard crane to remove and re-install the cylinders over the water.

When doing this type of work, the safety of our employees is the highest priority. Safety harnesses were used any time the crew was over the water. While this was not the first time we have rebuilt cranes, this was a first in doing so over water.

Performing routing preventive maintenance on Nautical Structures beam cranes is highly recommended after a couple of years of hard use. Finding the right shop that has the technical expertise and creative approach to getting it done will help to ensure trouble-free operations for years to come.

Hydraulic Accumulators Part Two – Re-installation of the Units

By Chris Brown on April 16, 2014 in Hydraulics

Earlier this month, we posted an article on the work we were doing on a hydraulic accumulator system aboard a 65M (213 foot) Palmer Johnson Yacht. As mentioned in the previous post, part of the job required us to relocate five of the eight accumulator tanks. We also had to run all new stainless steel tubing to re-connect the system to accommodate the new layout.

Hydraulic Accumulator Tank wall mounted to bulkhead

This job required us to do some creative bracketing fabrication work since we ran out of room to install all eight accumulator tanks in a very tight machinery space. To further complicate the matter, each tank weighs around 180lbs. when full, so this too needed to be taken into account when designing and fabricating the units.

As seen in the images in this post, one of the tanks was wall-mounted and bolted to the bulkhead while others were installed “condo” fashion, stacked one above the other.

“Condo” fashion mounting

Although the space was extremely tight and hard to work in, with a little ingenuity we were able to redesign, refurbish and relocate the hydraulic accumulator system to function in the space allotted and provide back-up power to the hydraulics for this yacht should they ever need it.

Machine Shop and Hydraulics Shop under one roof – convenience for the customer

By Chris Brown on April 15, 2014 in Cylinders, Hydraulics, Pitting

Hydraulic Cylinder Rebuild – Pitting on the Rod requires replacement

It is a fairly common occurrence for us to find pitting on hydraulic cylinders or shafts that we work on in our shop at High Seas Hydraulics. This is typically caused by corrosion from salt water, crevice corrosion or as a result of cheap stainless steel material used in fabrication. The lip seals on a hydraulic shaft or rod need a smooth surface or the hydraulic fluids will leak out causing a reduction in the performance of the units and, in this case, hydraulic fluid leaking into the ocean.

To fix this problem on large propeller shafts, we would perform a process called cladding at our machine shop, Straight Line Marine. Cladding or shaft weld-over, is the process of repairing a worn or damaged area on a propeller shaft or rudder shaft. Stainless steel shafts can be damaged by excessive wear in contact areas, such as bearings or seals, due to long life or misalignment. Shafts can also be damaged from crevice corrosion or stray current corrosion. Straight Line Marine is the only shop in Florida that is ABS approved to perform this type of work. Replacing a large shaft could cost up to $25,000 each shaft, depending on the size. However, the cladding repair is only a few thousand dollars. For smaller shafts like sailboat shafts or hydraulic cylinder rods, we would simply buy new rod material and scrap out the old rods.

Crevice Corrosion on Shafts will destroy a Lip Seal System

The convenience of having a machine shop Straight Line Marine and hydraulics shop (High Seas Hydraulics) under one roof ensures our customers that they can get the right level of expertise no matter how big or how small their needs.

Re-furbishing and Re-locating a Hydraulic Accumulator – takes the right tools and the right skills

By Chris Brown on April 10, 2014 in Accumulator, Hydraulics

Hydraulic Accumulator

We are working a complex hydraulic accumulator system that involves relocating a series of hydraulic accumulators on a 65M (213’) foot Palmer Johnson.

A hydraulic accumulator is a pressure storage reservoir in which a non-compressible hydraulic fluid is held under pressure by an external source. In this case the external source is plastic bladders filled with high pressure Nitrogen gas. An accumulator enables a hydraulic system to cope with extremes of demand using a less powerful pump, to respond more quickly to a temporary demand, or power the yacht’s hydraulic systems when the yachts main engine or pumps are not capable of providing the power.

A compressed gas accumulator consists of a cylinder with two chambers that are separated by an elastic diaphragm, a totally enclosed bladder, or a floating piston. One chamber contains hydraulic fluid and is connected to the hydraulic line. The other chamber contains an inert gas under pressure (typically nitrogen) that provides the compressive force on the hydraulic fluid. Inert gas is used because oxygen and oil can form an explosive mixture when combined under high pressure.

Hydraulic Accumulator with plumbing

As the volume of the compressed gas changes, the pressure of the gas (and the pressure on the fluid) changes inversely. As part of other work being done on the yacht, it was necessary for us to relocate five of the cylinders on this eight part system. Relocating part of the system required us to refabricate new brackets that hold the cylinders as well as re-plumb the hydraulic tubing to adjust to the new layout.

We also replaced a failed, leaking bladder in one of the accumulators before re-pressurizing each of the units to 1,250 PSI.

All this work requires very specialized equipment and knowledge to ensure the work is done right and that the hydraulic accumulator is ready when you need it most.

Rebuilding Stainless Steel Hydraulic Cylinders – Galling Problems

By Chris Brown on April 4, 2014 in Hydraulics

Welding stainless steel cylinders

We recently took a pair of stainless steel hydraulic cylinders off a swim platform on a hauled 130’ vessel Sunseeker. The cylinders needed to be rebuilt due to leaking hydraulic fluid. Rebuilding a cylinder is typically a fairly straight forward procedure, usually a few hours of shop time, when it is done right the first time.

Stainless steel hydraulic cylinders have a threaded stainless steel cap that is subject to galling and seizing during disassembly, if not probably lubricated with an anti-seizing agent the first time. Galling is caused by a combination of friction and adhesion between the surfaces, followed by slipping and tearing of crystal structure beneath the surface. This will generally leave some material stuck or even friction welded to the adjacent surface, while the galled material may appear gouged with balled-up or torn lumps of material stuck to its surface.When galling or seizing takes place, it becomes necessary to cut the barrels off the shafts of the stainless steel hydraulic cylindersto cut away the threads that are “welded”. This will result in many hours in the machine shop and extend the job and cost from a simple procedure to a much more time and money consuming process.

At times, the cost to custom machine and repair exceeds the cost of a new replacement. However, lead times and schedules often make the “repair vs. buy new” decision.

The moral of the story – be prepared for higher costs and longer delays getting back in the water if your stainless steel hydraulic cylinders are not done right the first time.