Naval architect Glosten and Markey Machinery collaborated on the design of a custom headline winch for a new SLSDC tug that maximises workability and safety for the crew
Extending some 3,700 km into the North American heartland, the Great Lakes and the Saint Lawrence Seaway system creates a vital economic artery for the movement of industrial and agricultural goods valued at US$6Tn annually. Keeping ships moving along the longest deep-draught inland navigation system in the world requires locks to be maintained year-round, buoys to be tended and dense ice to be managed during the winter months.
To support this effort, last year the Saint Lawrence Seaway Development Corporation (SLSDC) ordered an 18-m ASD harbour tug from US-based Washburn & Doughty. Designed by Seattle-based naval architect Glosten, the ‘do-it-all’ Harbor Series HT-60 tug will replace 1997-built tug Performance when delivered in 2021.
Glosten marine operations and business development lead Captain Peter Soles tells International Tug & Salvage, “The HT-60 is a versatile ASD (Z-drive) tug designed to capitalise on the operating advantages afforded by a broad bow form with a semi-raised foc’sle deck and full visibility, and winch controls from a single operating station in the pilothouse.”
Since it will operate in ice-infested waters in the winter, Capt Soles says the hull and all propulsion machinery have been ice-strengthened to ABS C0 and Baltic 1C standards. He says that while the HT-60 is not meant to be an ice-breaking tug, operating in ice conditions was still a primary consideration in the vessel’s design.
“The Performance replacement – though not an ice-breaking tug – will be called upon to maintain a navigable channel in key areas of the waterway by actively pushing ice broken by the larger SLSDC tug, Seaway Guardian,” notes Capt Soles. “It will also perform all ice removal operations inside the Eisenhower and Snell Locks.” For that work, Glosten designed a fendered stem bar that extends to the waterline (for pushing large chunks of ice) and a custom ice scraping appendage that secures to the quarter bitts on either side of the tug, just forward of the Z-drive units.
Other operational requirements that influenced the design of the new harbour tug are its mission to recover and install buoys and associated moorings, and periodic installation and removal of the ice scraping appendage – both of which drove the selection and placement of the Heila deck crane, according to Capt Soles.
With a length of 18.2 m, the new harbour tug is “right-sized for manoeuvring inside lock chambers,” he says, with an 8.5-m beam “to improve performance in ice and enhance stability for deck crane operations.” Propulsion is supplied by a pair of Schottel Z-drive units driven by two Cat C18 diesel engines turning carbon-fibre shafts for a combined 1,320 bhp (984 kW) at 1,800 rpm.
Compact winch design
One of the challenges Glosten faced when designing the tug was finding a production model headline winch that would enhance the crew’s workability and safety on deck, while meeting the tug’s compact size, and requirements of operating in winter conditions in the Saint Lawrence Seaway.
“One issue is that the tug is rather small, and, as such, working deck space is inherently limited,” says Capt Soles. “Yet the bow, particularly, is an important work area for a crew that is expected to handle lines and make-up to barges several times per day. While the broad bow and nearly flat foc’sle deck of the HT-60 help with this to an extent, we were interested in conserving as much working space as we practically could in this area. We knew we could enhance the workability of the deck by selecting a compact winch and positioning it forward of the house, so that crewmembers can easily walk around it and not have to step over anything,” he emphasises.
In its design, Glosten specified Markey Machinery DESMG-17 electric headline winch, or equal, satisfying a short list of required specifications, including maximising the workspace on deck.
Glosten needed a winch with a compact footprint to maximise working deck space in the bow and knew this could be achieved by locating the electric drive motor and brake cylinder below deck. ’Undermounting’ these mechanical components would also afford protection from winter conditions in the Saint Lawrence Seaway. Snow and ice accumulation on the brake cylinder in particular could potentially impede the operability of the band brake and, therefore, the safe operation of the winch itself.
Having worked with Markey Machinery on many past projects, including Foss Maritime’s Arctic-class tugs, Glosten turned to the deck machinery designer with a request for a compact design winch with the drive motor mounted beneath the winch skid, so that it resides and remains accessible inside the forepeak.
When the request from Glosten came, Markey Machinery vice president sales Scott Kreis says the Seattle-based custom winch manufacturer saw an opportunity.
“When Peter described the tug Glosten was developing, and the need for a compact headline winch for cold weather operations, we saw a chance to springboard from one of our recent winch designs,” says Mr Kreis. “There never seems to be enough room on the bow of a tug – for the equipment nor the deckhands – and our design had addressed similar space constraints.”
Consulting with Capt Soles and the Glosten team, Mr Kreis says Markey Machinery was able to make a few ‘strategic changes’ to an existing design to satisfy the particular requirements for this project. “The anchor chain lifter was replaced with a warping head, a drum clutch was added, the fixed-speed electric drive was upgraded to a variable frequency system,” he says, “and the linkage for the drum and band brake was redesigned to locate these items below deck. Working with the Glosten team, the winch and its supporting systems (ie VFD drive panel, dynamic brake resistors, pneumatic logic panel, and control console) were integrated into the tug design.”
Capt Soles says the winch maximises usable working deck space in the bow of the vessel. “It keeps the bow area tidy in appearance and, at the same time, isolates the prime mover and the most crucial components of the brake assembly from the outside environment. Yet, these components remain easily accessible for maintenance from inside the forepeak.”
In addition, the custom winch makes work easier and safer for the crew “by not inhibiting their movement in the bow area the way a winch with a larger footprint certainly would,” notes Capt Soles. “This is especially important for safe operation of the warping head, which can be a dangerous piece of equipment to use in a confined area. We also asked Markey to mount the clutch lever 70° off horizontal, which will maintain a nice clear walkway in the space between the winch and the deckhouse.”
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