High velocity was a major consider a severe casualty involving an escort tug within the Corpus Christi Ship Channel final 12 months, based on the National Transportation Safety Board (NTSB). The tug was already working close to its most velocity initially of the evolution, and didn’t have sufficient additional energy to get away when issues began to go flawed. 

“We have recently seen incidents across industry, and the common factor is operators trying to perform advanced maneuvers at high speeds, which gives a higher risk factor with no reward,” operator G&H Towing instructed NTSB after the casualty. 

On January 22, 2023, the ASD tug Mark E. Kuebler and 4 different harbor tugs had been dispatched to help the Saudi tanker Nisalah, which was inbound on the Corpus Christi Ship Channel. The vessel had pilots aboard for a transit to South Texas Gateway Terminal in Ingleside, the place she was scheduled to load a cargo of crude. The vessel was in ballast situation. 

The Mark E. Kuebler was assigned to take the starboard quarter place throughout the escort evolution. The mate had the conn, and he determined to method the tanker with the tug shifting stern-first, which might give the tow line probably the most favorable result in the chock on the tanker’s starboard quarter. The mate’s plan was to make up tow with the tug’s bow winch to the chock, then full the transit to the terminal whereas shifting astern. This association would place the tug alongside the tanker’s parallel midbody and away from the flare of the strict throughout the remainder of the transit. 

All six vessels had been shifting by means of the channel at a velocity of about 10 knots. As the Kuebler’s mate maneuvered off the tanker’s starboard quarter and commenced to spin the tug by means of 180 levels, the tugboat was drawn again in the direction of the Nisalah’s stern by hydrodynamic suction forces. The mate elevated energy however couldn’t stop the Kuebler from being pulled in the direction of Nisalah’s prop. Seconds later, the pilots on Nisalah’s bridge heard a noise as Nisalah’s propeller reduce into the Kuebler’s hull. From begin to finish, this sequence of occasions took about 60 seconds. 

The grasp of the Kuebler relieved the mate and took over the helm, and initially he thought that the harm was restricted to the tug’s mast. He radioed the pilots and stated that each one was nice and the escort job may proceed. However, he quickly radioed again and reported a bilge alarm. The crew checked the tug’s equipment compartment, and so they discovered vital flooding within the Z-drive compartment. 

As the tug confronted an actual danger of sinking as a result of flooding, the captain of the Kuebler determined to deliberately floor the vessel on a financial institution outdoors of the ship channel. Nisalah continued on to the oil terminal as deliberate. 

The contact with Nisalah’s propeller ruptured Kuebler’s hull, puncturing the aft peak tank and the Z-drive compartment. Both areas crammed to the waterline, damaging gear. 

The harm to the Kuebler price about $3 million to restore, plus one other $1 million in salvage prices to retrieve the vessel from the financial institution. The Nisalah’s propeller was warped by the impression, and the invoice for the tanker’s repairs ran to almost $4 million. 

The main reason for the casualty was excessive velocity, based on NTSB. When the tug was drawn in the direction of the tanker’s stern by hydrodynamic forces, it didn’t have sufficient reserve energy to drag away – as a result of it was already shifting about as quick because it may. If all six vessels had been shifting at a statelier tempo, NTSB stated, the casualty won’t have occurred. 

“Owners and operators of Z-drive tugboats that perform harbor-assist operations should set speed limits for advanced maneuvers such as stern-first approaches,” suggested NTSB. “Tugboat operators should communicate these limits to ship masters or pilots.”

Operator G&H Towing agreed, and it has carried out a seven-knot velocity restrict for stern-first touchdown for its escort tug fleet.