USNS Apache (T-ATF-172)

USNS "Apache" (T-ATF-172) is the last of the "Powhatan" class of fleet ocean tugs. "Apache" was delivered to the United States Navy in 1981. She is operated by Military Sealift Command and crewed by 16 civil service mariners (CIVMARS) with a complement of up to 4 Navy enlisted personnel to operate communications equipment. She is designed to provide the Navy with towing service, and when augmented by Navy divers, assist in the recovery of downed aircraft and ships. There are quarters onboard for up to 25 additional personnel.

Background

Fleet ocean tugs are used to tow ships, barges and targets for gunnery exercises. They are also used as platforms for salvage and diving work, as participants in naval exercises, to conduct search and rescue missions, to aid in the clean up of oil spills and ocean accidents, and to provide fire fighting assistance.

Features

The "Apache" is equipped with a 10 ton capacity crane and a bollard pull of at least 87 tons. A deck grid is fitted aft which contains 1 inch bolt receptacles spaced 24 inches apart. This allows for the bolting down of a wide variety of portable equipment. The large back deck is also painted for helicopter operations to allow for vertical replenishment at sea. There are two GPH diesel off-ship fire pumps supplying three fire monitors with up to 2,200 gallons of foam per minute. A deep module can be embarked to support naval salvage teams.

Propulsion

The "Apache" has twin GM EMD 20-645F7B diesel engines providing a total of 7,200 shaft horsepower capable of hauling large tows at speeds up to and exceeding 8 knots, and light boat at 14.5 knots. The shafts are connected to controllable pitch propellers (CPP). The engines can be operated from one of three stations on the bridge, at the engine operating station, and from an aft control station looking astern. Usually controlled from the bridge by deck officers, they allow control of the engines' RPMs and propeller pitch independently. Together with twin rudders and a 300 horsepower bow thruster, the ship is highly maneuverable at slow speeds with extremely quick engine response.

Towing equipment

The vessel can employ one of two winches for towing operations. The main towing winch for large, long distance tows is a single drum, closed-loop SMATCO electro-hydraulic drive winch, with a mechanically, pneumatically, or hydraulically actuated band brake and an air-actuated dog brake which are capable of holding 500,000 lbf of tension. The winch has 2,500 feet of 2¼ inch IWRC 6x37 wire rope with a poured end fitting and a breaking strain of 424,000 lbf (1.89 MN). The cable weighs approximately 8.5 lb per foot (12.6 kg/m), making the weight of the wire approximately 21,500 lb (10.75 short tons) excluding the weight of any chain bridle used on the vessel being towed.

The second winch is a traction machine capable of handling up to 15 inch synthetic hawsers used for smaller, shorter distance tows. The traction machine is capable of line pulls of up to 200,000 lbf.

The stern employs a tow-pin box capable of capturing either the wire or synthetic towing lines, as well as norman pins at the quarters.

ources

* [http://www.msc.navy.mil/inventory/ships.asp?ship=6&type=FleetOceanTug Military Sealift Command Ship Inventory: USNS "Apache" (T-ATF-172)]
* [http://www.navy.mil/navydata/fact_display.asp?cid=4400&tid=700&ct=4 U.S. Navy Fact File: Fleet Ocean Tugs – T-ATF]
* [http://www.navybuddies.com/atf/atf172.htm Unofficial U.S. Navy Site: USNS Apache (T-ATF 172)]

References