TECHNOLOGY AREA(S): Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS 500, DDG 1000 Class Destroyer Program

OBJECTIVE: Develop technology required to reduce or remove ingested air and debris from sea chests of new ship designs.

DESCRIPTION: Design requirements of current and future Navy surface ships limit the implementation of common intake sea chest and seawater system design practices. The current seawater intake system is prone to air, ice, and debris ingestion due to a non-conventional intake design driven by signature requirements. The ingestion leads to damaged downstream pumps and equipment, resulting in increased maintenance costs and degraded overall cooling performance. The implementation of sea chest intake improvements will rectify these issues by allowing for clean flow through the pumps. New technologies internal to the sea chest will be required to either reduce air and debris ingestion through the sea chest inlet or remove it from within the sea chest. Reduced air and debris entrainment will reduce noise and increase the service life of pumps and downstream equipment.

Current Zumwalt Class destroyers (DDG 1000) Sea chest openings must be flush to the hull, prohibiting bubble shields or raised inlets. This design requirement results in the ingestion of higher amounts of ice, debris, and air. Ice, debris, and air in the seawater cooling system will cause cooling water fouling that can result in pump, air binding, cavitation, and failure. The Navy desires a sea chest system on the DDG 1000 destroyers that will mitigate seawater system air and debris internally. Current sea chests are cylindrical shaped versus cubic.

Implementation of this technology has potential cost savings of secondary components by providing normalized cooling performance. Design requirements of current and future Navy surface ships limit the implementation of common sea chest and seawater system design practices. New technologies to reduce air and debris ingestion through the sea chest inlet will reduce system noise levels and increase the service life of pumps while providing sufficient cooling for downstream equipment.

Technological areas to explore include strainer plate and bar design, internal sea chest geometry, low-pressure drop filtration, and water treatment systems such as cyclonic separation. Developed technologies must be scalable to allow for flowrates of 1000-5000 gpm. Inlet flow velocities should be minimized to the lowest economical value, not to exceed 5.5 fps to achieve flow rate. Differential pressure across the system must not exceed 2.5 psi. The developed technology shall be in accordance with the American Bureau of Shipping Naval Vessel Rules.

If strainer plate or strainer bar development is pursued, they shall be removable to allow for periodic cleaning of sea chest sleeve. Underwater grating shall be painted with a MIL-PRF-23236 compliant coating system.

PHASE I: Define and develop a concept for an innovative sea chest water treatment system that will meet the objectives provided in the Description. Demonstrate the feasibility of the concept through calculations and 3D physics-based computer modeling. Include initial design specifications and a capabilities description to build a prototype solution in Phase II. Develop an Initial Phase II Proposal.

PHASE II: Develop and deliver a prototype that demonstrates the capability with equipment specifications defined during Phase I. Evaluate the demonstration on data collected and the prototype�s ability to prevent intake of or remove debris and air. Based on this analysis, recommend test fixtures and methodologies to support environmental, shock, and vibration testing and qualification. Determine, jointly with the Navy, the final system design for operational evaluation, including required safety testing and certification. Provide a technical work package to enable the system installation on board DDG 1000 destroyers, utilizing the test results and any lessons learned from the prototype testing.

PHASE III DUAL USE APPLICATIONS: Transition the technology to the Navy for shipboard use. New sea chest design could be applicable to any class ship in which signature or smooth hull considerations are a priority; and can be accomplished either through technical data package for Navy to procure or through the performer supplying the material.

The technology developed through this STTR topic can be used for commercial applications on merchant vessels and pleasure craft. Because the modifications to reduce ingested air and debris will be internal to a newly designed sea chest, no modifications would be necessary to the external hull of the craft. A smoother hull will also result is reduced hull drag. This technology could also be applied to waterjet intakes to reduce impeller damage.

REFERENCES:

1. Harrington, Roy. �Marine Engineering.� Society for Naval Architects and Marine Engineers, 1992. https://www.sname.org/pubs/books

2. Surtherland, T.F. et al. �Effect of a Ballast Water Treatment System On Survivorship of Natural Populations of Marine Plankton.� Marine Ecology Progress Series, Vol 210, 26 January 2001, pp. 139-148.� https://www.int-res.com/abstracts/meps/v210/p139-148/

KEYWORDS: Sea Chest; Air Ingestion; Pump Air Binding; Sea Water Systems; Cooling Water Fouling; Sea Water Strainer; Cooling Water Treatment