Ash Grove chooses Markey mooring system for Willamette River site

Ash Grove Control Panel

(SEATTLE) — Oregon’s Port of Portland on the Willamette River is home to Ash Grove Cement Company’s privately-owned deepwater facility with 230 feet of berthing space and silos with a 1,400-ton storage capacity.

Inbound bulkers and barges cross the world’s most dangerous bar, transit 100 river miles of the Columbia River, and navigate 10 miles of the Willamette before reaching this import terminal. Ash Grove’s terminal is where clinker, limestone, and other raw materials are offloaded and processed into finished products used to construct concrete roadways and buildings or increase the grain yield of the Willamette agricultural valley.

Ash Grove approached Markey to supply a mooring winch system capable of maintaining constant line tension and vessel position within a range of +/- 0.5 feet over the course of several days’ time vessels are alongside. The challenge for Markey’s designers was produce a machine-control system to counter twice daily tidal changes and artificially high river currents caused by 100 years of dredging this section of river running through Portland.

With Ash Grove’s operators providing key local knowledge, Markey winch engineers arranged a system of two winches reeved through intermediate fairleads producing twin breasting lines running parallel the wharf. Winch placement and line arrangement drove the requirements to work 125 feet of 1-inch diameter rope for mooring. Reviewing designs of existing robust mooring winches, engineers identified a Markey model DESMG-20 with drums having 20-inch barrels, 34-inch diameter flanges and 20-inch widths as a well proven and suitable design for Ash Grove’s application.

Numerical modeling supported a decision to use 15-horsepower encoder-brake-motors driving the drum through two speed reducers, all rated for around the clock (continuous) duty. The winches produce 29,500 pounds of needed line pull with up to 15 feet per minute speeds.

Electrical engineers developed a bespoke power and control system with selectable modes tailored for this terminal’s operations. Ash Grove operators choose from three operating modes when mooring vessels, transferring cargo or recovering lines. Choosing the manual mode permits joystick control of drum direction and speed for passing lines, taking up slack, and tensioning or recovering hawsers.

Ash Grove Control Panel
Markey Machinery photo

With fore and aft breast lines tensioned, selecting the automatic mode allows the operator to adjust the maximum torque the winch motors exert on the mooring lines. Take the example of compensating for river current. Under most conditions operators will set the downstream winch tension to a particular percent value and set the upstream winch to a value 20 percent higher. The higher pull of the fore breast line holds the vessel fast to the dolphins and also prevents the current causing the bow to yaw. Conveniently, lowering the torque setting of one winch while raising the setting of the other provides the operator a safe and precise way to shift the vessel – improving the efficiency of conveyor operations.

With auto mode engaged on both winches, a push button – start position hold – pops up on the touch-screen display. Pressing this push button activates the positioning mode. When activated, algorithms assume control of the system by constantly monitoring the scope and tension on both the mooring lines and position of the vessel and automatically and precisely adjusting the moor. As changes in draft occur during operations, the systems control algorithms sense changes in actual line tension and calculates how much the position has drifted before automatically readjusting mooring line tension and correcting the vessels position.

To replace tell tales spliced into traditional lines, the mooring controls feature operator-customizable alarm settings that are triggered by excessive line tensions, vessels out of position, motor controller alarm conditions or air conditioner failures. Ash Grove terminal operators report their new mooring system so effective for terminal operations, they often set the controls and forget the system is operating until its time to recover mooring lines.

– Markey Machinery

By Professional Mariner Staff