User:Charliecombs/draft article on Safeguard-class

The Safeguard-class rescue and salvage ships are a class of four United States Navy ships operated by the Military Sealift Command (MSC). This is the most current class of auxiliary rescue and salvage class of vessels used by the US Navy. When built they were commissioned US Navy ships, but starting in 2006 the class was decommissioned and transferred to MCS. As rescue and salvage ships they are capable of recovering objects from the sea, tow or de-beach stranded vessels and provide firefighting assistance. Like fleet ocean tugs, these ships are able to lift objects as heavy as downed aircraft and stranded or grounded ships. A key advantage of these ships is their ability to rapidly deploy divers to conduct rescue and salvage operations. The rugged construction of these steel-hulled vessels, combined with their speed and endurance, make the Safeguard-class well-suited for rescue and salvage operations throughout the world.

Mission and capabilities
The Safeguard-class rescue and salvage ships serve as an element of the United States Navy's Maritime Sealift Command Services Support and provide rescue and salvage services to the fleet at sea. The ships also supported the protection of forces ashore through post-assault salvage operations in close proximity to the shore. Each is designed to perform combat salvage, lifting, towing, off-ship firefighting, manned diving operations, and emergency repairs to stranded or disabled vessels.

Salvage of disabled and stranded vessels
Disabled or stranded ships might require various types of assistance before retraction or towing can be attempted. In the 21000 cuft salvage hold, each Safeguard-class carries transportable cutting and welding equipment, hydraulic and electric power sources, and de-watering gear. The Safeguard-class also has salvage and machine shops, and hull repair materials to effect temporary hull repairs on stranded or otherwise damaged ships.

Retraction of stranded vessels
Stranded vessels can be retracted from a beach or reef by the use of the towing machine and propulsion. Additional retraction force can be applied to a stranded vessel through the use of up to six legs of beach gear, consisting of 6000 lb STATO anchors, wire rope, chain, and salvage buoys. In a typical configuration, two legs of beach gear are rigged on board the Safeguard-class ship, and up to four legs of beach are rigged to the stranded vessel.

In addition to the standard legs of beach gear, each ship of the class carries 4 spring buoys. The spring buoys are carried beneath the port and starboard bridge wings. Each spring buoy weighs approximately 3100 lb, is 10 ft long and 6 ft in diameter, provides a net buoyancy of 7½ tons, and can withstand 125 tons of pull-through force. The spring buoys are used with beach gear legs rigged from a stranded vessel when deep water is found seaward of the stranded vessel.

Towing
The Safeguard-class propulsion machinery provide a bollard pull (towing force at zero speed and full power) of 68 tons.

The centerpiece of class's towing capability is an Almon A. Johnson Series 322 double-drum automatic towing machine. Each drum carries 3000 ft of 2+1/4 in, drawn galvanized, 6×37 right-hand lay, wire-rope towing hawsers, with closed zinc-poured sockets on the bitter end. The towing machine uses a system to automatically pay-in and pay-out the towing howser to maintain a constraint strain.

The automatic towing machine also includes a Series 400 traction winch that can be used with synthetic line towing hawsers up to 14 inches in circumference. The traction winch has automatic payout but only manual recovery.

The caprail of each ship is curved to fairlead and prevent chafing of the towing hawser. Included are two vertical stern rollers to tend the towing hawser directly aft and two Norman pin rollers to preven the towing hawser from sweeping forward of the beam at the point of tow. The stern rollers and Norman pins are raised hydraulically and can withstand a lateral force of 50000 lb at mid barrel.

Two tow bows provide a safe working area on the fantail during towing operations.

Manned diving operations
Each ship of theSafeguard-class has several diving systems to support different types of operations. Divers descend to diving depth on a diving stage that is lowered by one of two powered davits.

The diving locker is equipped with a double-lock hyperbaric chamber for decompression after deep dives or for the treatment of divers suffering from decompression sickness.

The MK21 MOD1 diving system supports manned diving to depths of 190 ft on surfaced-supplied air. A fly-away mixed gas system can be used to enable the support of diving to a maximum depth of 300 ft.

The MK20 MOD0 diving system allows-surface supplied diving to a depth of 60 ft with lighter equipment.

Each ship carries SCUBA equipment for dives that require greater mobility than is possible in tethered diving.

Recovery of submerged objects
In addition to the two main ground tackle anchors [6000 lb Navy standard stockless or 8000 lb balanced-fluke anchors] Each ship of the class can use equipment associated with her beach gear to lay a multi-point open water moor to station herself for diving and ROV operations.

A typical four-point moor consists of an X pattern with four Stato Anchors at the outside corners and Safeguard-class ship at the center, made fast to a spring buoy for the close end of each mooring leg with synthetic mooring lines. Using her capstans, the ship can shorten or lengthen the mooring line for each leg and change her position within the moor.

All ships of the class have a 7.5-ton-capacity boom on the forward kingpost and a 40-ton-capacity boom on the aft kingpost.

Heavy Lift
Each Safeguard-class ship have a heavy lift system that consists of large bow and stern rollers, deck machinery, and tackle. The rollers serve as low-friction fairlead for the wire rope or chain used for the lift. The tackle and deck machinery provide up to 75 tons of hauling for each lift. The two bow rollers can be used together with linear hydraulic pullers to achieve a dynamic lift of 150 tons. The stern rollers can be used with the automatic towing machine to provide a dynamic lift of 150 tons. All four rollers can be used together for a dynamic lift of 300 tons or a static tidal lift of 350 tons.

Each ship also has two auxiliary bow rollers, which can support of 75 ton lift when used together.

Off-ship fire-fighting
A Safeguard-class ship has three manually operated fire monitors, one on the forward signal bridge, one on the aft signal bridge, and one on the forecastle, that can deliver up to 1,000 gallons per minute of seawater or aqueous film forming foam (AFFF) When originally built, Safeguard had a fourth remotely controlled fire monitor mounted on her forward kingpost, but this was later removed. Safeguard has a 3,600-gallon foam tank.