Texas tug operator builds fleet to handle bigger ships


Mazu Capt. Nick Payne stood by while mate Brandon Conner approached the containership Molly Schulte midway between Bayport Channel and Barbours Cut in the Houston Ship Channel.

Conner, who was training in real time on the new tugboat, maneuvered to the stern. Ordinary seaman Richard Fernandez attached the heaving line to the hawser and got the line on the ship centerline aft.
With Mazu tethered to Molly Schulte, Conner steered to starboard out of the ship’s wake. Mazu ran with the cargo ship on its way to the Barbours Cut Container Terminal.
Jobs like this one are common in the Houston Ship Channel, and as ships get bigger, tugboats that work them are getting more powerful and more capable. Mazu, the third Z-Tech 30-80 tugboat in the Suderman & Young Towing Co. fleet, is but one example.

The wheelhouse in the Robert Allan Ltd. Z-Tech 30-80 design is clean and functional with large windows for all-around visibility.

Gulf Island Shipyards of Jennings, La., built the 98.5-by-42.6-foot tugboat based on an updated Z-Tech design from Robert Allan Ltd. of Vancouver, British Columbia. Two earlier tugs in the series, Ted C. Litton and Apollo, joined Suderman & Young’s 22-tug fleet earlier in 2019. Mazu is the company’s 13th z-drive tug. The vessels work in the Texas ports of Houston, Galveston, Texas City, Freeport and Corpus Christi.

“As our customers’ ships have increased in size, we continue to meet their needs by servicing them with larger, more powerful tugs,” Suderman & Young President Kirk Jackson said. “Specifically, increasing demand to escort and assist VLCCs (very large crude carriers) and larger container vessels was a big driver.”

Suderman & Young is a longtime Robert Allan Ltd. customer. The Houston-based towing company welcomed the 4,300-hp z-drive tugboat Jess Newton in 2001. Six years later, the 6,300-hp Z-Tech 30-75 tugboat Thor joined the company’s fleet. Suderman has five Z-Tech 24-60 tugs.
The Z-Tech platform incorporates the best characteristics of a true tractor tug and an ASD tug with one hawser winch on the bow, the tug’s working end. The Z-Tech tugboats have good omnidirectional speed, and bollard pull is comparable whether the vessel is pulling forward or astern.


Mazu’s Markey DEPCF hawser winch is sturdy enough to handle larger tankers and containerships regularly calling Texas ports. The winch is wound with Samson Saturn-12 mainline.

The new class of Z-Tech 30-80 tugs evolved from the 30-75 design. The vessels are built to meet Subchapter M standards, which did not exist during earlier iterations. The new design also incorporates sponsons that add 44 inches to the width of the tug. This feature helps provide greater stability and safety while improving escort performance.

Xuhui “Bill” Hu, project director at Robert Allan Ltd., has said the firm developed the unique sponson hull form specifically for escorting large vessels. Adding the sponson to the hull form generates greater steering and/or braking forces hydrodynamically at speeds of 8 to 10 knots, he said in an interview last year about Bay-Houston Towing Co.’s Mark E. Kuebler, which shares the same design.

“The proven escort performance of the Z-Tech was enhanced by the addition of hull sponsons,” Jackson said of the 30-80 series.
Gemini and Mercury, the final two tugs in a five-vessel order by Suderman, are scheduled for delivery by 2021.

Mazu works the 2,345-TEU containership Molly Schulte in the Houston Ship Channel with mate Brandon Conner at the controls.

The machinery space aboard Mazu, fore to aft, consists of two 125-kW John Deere generators followed by two Caterpillar 3516E Tier 4 main engines driving Schottel z-drive units in the aft drive room. The Cat engines produce 6,772 total hp at 1,800 rpm, delivering 81.5 metric tons of bollard pull.

“All of our tugs in the new class pulled in excess of their design specification of 80 metric tons,” Jackson said.

The extreme flare common on modern ships influenced the tug’s design. The heavily fendered bow has a flat sheer leading to a house located well aft for work under the flare. Similarly, the bulwarks are sloped back and lowered, and the stacks are located inboard, aft of the house.
Mazu’s Cat engines utilize a selective catalytic reduction (SCR) system to reduce NOx in engine exhaust emissions and meet EPA Tier 4 requirements. The system consists of a catalytic converter on each engine and insulated, stainless-steel tankage for 2,134 gallons of diesel exhaust fluid (DEF) made from a water and urea mixture.


Propulsion aboard Mazu comes from two Cat 3516E Tier 4 engines paired with Schottel z-drives. The spacious engine room in Z-Tech 30-80 series tugboats leaves plenty of space for chief engineer Joe Wiegand, standing at left, and OS Richard Fernandez.

The SCR dosing system mixes a precise combination of compressed air and DEF, then transfers it to the SCR module and injects it into the exhaust stream. The water evaporates and the DEF is converted into ammonia.
Mazu chief engineer Joe Wiegand predicted the SCR equipment would require a bit more vigilance to detect leaks before they cause corrosion. Urea must be contained and transferred in stainless-steel tanks, piping and fittings.

The name Mazu is a departure from Suderman & Young’s typical naming practice of following a Roman or Greek mythology theme. “For this series of tugs, we researched other cultures’ mythology and felt the name, Mazu, fit in well since she was both a goddess of the sea and protector of seafarers,” Jackson said.

Mercury, Gemini and Apollo are named for the first three NASA manned space programs — fitting, given the proximity to the nearby Johnson Space Center. Apollo was delivered a few days before the 50th anniversary of the Apollo 11 landing on the moon, Jackson noted.

Markey Machinery supplied the robust, reliable hawser winch on Mazu’s bow. The Markey DEPCF-52 winch with Render/Recover is driven by a 75-hp electric motor. The winch is wound with Samson Rope backer line, mainline and pendant, a configuration Samson dubs “The Ultimate Towing System.”

Crew spaces aboard Mazu are comfortable and well appointed.

Back in Barbours Cut, Conner powered up the tug and performed a full-powered indirect pull to starboard, turning Molly Schulte around Morgan’s Point and into the cut. He then ran inline/slack line with the ship to the turning basin and executed a direct 90-degree pull to port. He responded, as directed, to the pilot’s commands, from slow to full power, and pulled the ship around.

Once the ship was turned and facing outbound, Fernandez took in the line and Conner quickly maneuvered the tug around to the port quarter. Fernandez put a line up to the containership and Conner docked the vessel.

Conner, a graduate of Texas A&M Maritime Academy’s four-year program, spent a year decking on Suderman & Young’s conventional tugs before training on its z-drive vessels. He had a good teacher in Payne, who has 32 years of tugboat experience and has delivered or worked on 10 ASD tugs in the fleet.
Payne is complimentary of the new Z-Tech tugs, particularly their handling. Taken together, they’ll help Suderman’s crews handle all comers along the Texas coast.

Highlights: Updated Z-Tech design • Hull sponsons boost stability, performance • First Tier 4 vessels in fleet
By Professional Mariner Staff