|Acquisition Program: ||NAVSEA PMS450 Virginia Class Submarine Program, ACAT I|| Objective: ||Develop and demonstrate capabilities of increased reliability reference cells for use in naval applications including submerged platforms and enclosed spaces.
|| Description: ||The legacy reference cells in use on VIRGINIA Class submarines have several performance and reliability issues which must be addressed to improve operational availability and lower maintenance and repair costs. No VIRGINIA class submarine to date has been delivered with 100% operational reference cells This has resulted in nuisance alarms, non-optimal operation of the Impressed Current Cathodic Protection (ICCP) system, and substantial rework and repair. In addition, reference cells in tanks and other confined spaces are frequently damaged or destroyed due to the lack of ruggedness and ease of damage in these areas.
Long term performance of existing and next generation digital controlled ICCP systems requires a high level of performance from reference cells. Condition based maintenance diagnostics for ships’ underwater hull and ballast tanks rely on reference cell gathered data. Unknown amounts of drift in reference cell readings and unplanned failures of reference cells can disable these advanced systems. The need exists for increased reliability/maintainability in reference electrode assemblies. New materials/chemistries or conceptual designs for a stable microprocessor controlled electrochemical half-cell for seawater environments, are of interest. These half cell sensor materials must be fully reversible under seawater conductivity and temperature regimes. They must be able to operate in seawater/freshwater solutions that have a range of resistivity from 18 Ohm-cm to 20,000 Ohm-cm, with an operating temperature range of 30-95F. Sensors that are able to survive harsh toxic environments (such as sulfide containing seawater solutions) that limit existing technologies, are of additional interest. Reference cells should be designed such that installation and power up is simple and straight forward and cabling connections should be designed to survive significant levels of hydrostatic pressure and pressure cycling. Life and reliability requirements are targeted at greater than existing technologies (12 years). Reference cell drift should be minimized, controllable and well defined. On-board reference cell diagnostic or prognostic features are desirable. These features will aid in development of systems that can fully exploit reference cell capabilities and performance over time. Reference cells developed must operate in a seawater environment of varying conductivity and temperature and be compatible with ship systems in general. Reference cells should require minimal maintenance and designed so that components are modular and underwater replaceable.
|| ||PHASE I: Develop and demonstrate prototype reference cell performance for long term evaluation in a laboratory environment simulating Navy operational needs. Demonstrate manufacturability and installation parameters which lead to consistent, repeatable measurements under realistic conditions.
|| ||PHASE II: New reference cells could be applied to a broad range of military and civilian maritime and infrastructure applications where ICCP systems are relied upon for corrosion protection – for example, commercial shipping and interstate highway bridge maintenance.
|| ||PHASE III: As part of Phase III complete electrode assemblies will be evaluated to provide proof of conformance with pertinent shipyard specifications (these will be provided during development). Final prototypes meeting the relevant performance exit criteria will be installed by shipbuilder trades to demonstrate installation ability. After these tests, if selected, the products will be included in the FNC transition path. The FNC transition strategy includes integration of components by PMS450 into the R&D programs for VIRGINIA Block IV.
PRIVATE SECTOR COMMERCIAL POTENTIAL/|| ||DUAL-USE APPLICATIONS: New reference cells could be applied to a broad range of military and civilian maritime and infrastructure applications where ICCP systems are relied upon for corrosion protection – for example, commercial shipping and interstate highway bridge maintenance.
|| References: ||
1. K. E. Lucas, E. D. Thomas, K. I. Kaznoff and E. Hogan, “Design of Impressed Current Cathodic Protection Systems for US Navy Hulls,” Designing Cathodic Protection Systems for Marine Structures and Vehicles, ASTM, STP 1370, pp. 17-38, 1999.
2. Underwater Ship Husbandry Manuals, Chapter 19, Cathodic Protection Systems, S0600-AA-PRO-190, NAVSEA 00C5 (Distribution A).
3. R. A. Adey (ed), Modelling of Cathodic Protection Systems, Chapter 2, Shipboard Impressed Current Cathodic Protection System Analysis, WIT Press, 2005.|
|Keywords: ||Reference cells; electrochemistry; corrosion; condition based maintenance|
Questions and Answers:
Q: Additional Q&A from TPOC in response to FAQs for Topic N102-169:
1. What have been the three most common failure modes in reference cells in hulls delivered for the VIRGINIA class? Statistics like percentages of total failures or failures per hull could be useful.
Common failure modes of the Ag/AgCl: poor stability, non-linear response and environmental contamination. This SBIR is essentially looking for a new type of highly reliable >12 year electrode with precision properties improved from Ag/AgCl, calomel and Cu So4 systems stabilities. Failure statistics are not relevant for this study and are considered operational in nature, thus classified. Cells can degrade due to contamination by copper, sulfides, oils, anti-fouling coating, chlorine.
2. What do you consider to be the three most significant defects in the design of available reference cells for ICCP systems on submarines?
Durability, Environmental Stability, reversibility and Industrial Ruggedness (the need to be in the real world ship operational environment)
3. How significant an issue is biofouling of reference cells over the life of a submarine?
Biofouling resistance is not key as long as performance is not degraded by fouling.
4. Can you recommend a source for the references cited in the SBIR description?
(1) K. E. Lucas, E. D. Thomas, K. I. Kaznoff and E. Hogan, “Design of Impressed Current Cathodic Protection Systems for US Navy Hulls,” Designing Cathodic Protection Systems for Marine Structures and Vehicles, ASTM, STP 1370, pp. 17-38, 1999. This is an ASTM publication and can be found at www.astm.org through the link ASTM’s Standards and Engineering Digital LIbrary
(2) Underwater Ship Husbandry Manuals, Chapter 19, Cathodic Protection Systems, S0600-AA-PRO-190, NAVSEA 00C5 (Distribution A). Website information for this document is: http://www.supsalv.org/manuals/uwsh/chap19/chap19Cover.html
(3) R. A. Adey (ed), Modelling of Cathodic Protection Systems, Chapter 2, Shipboard Impressed Current Cathodic Protection System Analysis, WIT Press, 2005. This is a WIT Press publication and can be found through: www.witpress.com
5. Are local water properties, especially pH, electrical conductivity, temperature, measured and recorded by systems on board the affected vessels?
This information is collected for key systems, but is not likely available to this system. These variables independently are of little functionality for Impressed Current Cathodic Protection (ICCP) systems, but could and do impact reference cell performance. It is not so much that the base potential cannot change, more that the excursion of all cells must be highly consistent and repeatable. The more independent a cell could be from these parameters the better the performance would likely be.
6. If a “smart” reference electrode were to measure those properties, would it be an asset or a waste of resources?
Nice information to know, but difficult to say if it would be useful or waste of resources because of the possible extreme cost of getting and storing this information and what to do with it ultimately. Bottom-line: If the reference cell is working fine, then in reality no-one needs this information.
Q: Additional Q&A from TPOC in response to FAQs:
1. What are the likely contaminants and their maximum concentrations?
A: Contaminants already stated in previous question set (Cells can degrade due to contamination by copper, sulfides, oils, anti-fouling coating, chlorine), concentrations unknown at this time.
2. How many and how high would the corresponding pressure cycles be?
A: End Product must meet Hydorstatic (MIL-C-24321 RevD).
NOTE: Corrections below for answer about temperature range (text did not translate correctly during first posting to website):
3Q: Can you provide the ranges of operational and test temperature over which the new reference electrode must function?
A: Operation through temperature excursions (0 degree C to 35 degree C) and seawater salinities(16 – 1000 ohm-cm)
4. What is the desired tolerance for the reference electrode signal? Put another way, “What part of the -0.85 +0.05 V vs. Ag/AgCl/Seawater that is the present tolerance for the ICCP system is available for variability in the reference electrode?”.
A: Near Two orders of magnitude improvement of <+/-1mV DC.
A: . . . response pending . . .
Q: What is the desired frequency range for the reference electrodes to work? Stated another way, we have electrodes that may work well down to time scales around 1 hour, but not for time scales longer than that. Would such electrodes be useful to the corrosion-monitoring task?
A: Unfortunately no. Reference electrode stability needs to remain without drift for months/years, not hours. This is because corrosion occurs and accumulates over months/years, not hours.
Q: Can you provide or recommend a source for MIL-C-24321 RevD (the hydrostatic testing requirements)?
A: Unfortunately there was a transposition of numbers in the original reference to the mil spec. The correct number is MIL-C-24231 Rev D. This mil spec can be found through a variety of sources including the website www.everyspec.com using the search option Document Num and 24231. Hydrostatic testing is defined in Section 4.7.4.