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(RT) were investigated three years ago. This included evalu- ating of acoustic emissions and acoustic holography. Ultrasonic testing (UT), already in exten- sive use for naval work and pro- visionally allowed by ABS, was confirmed to be the only suitable alternative.

ABS hull-weld inspection re- quirements were evaluated in the context of inspection practice, failure histories, ductile rupture and brittle fracture probability, and a simplified fatigue crack- growth analysis.

The researcher's identification of the UT checkpoint length which yields "the same order of reject rate as for RT" suggests that

ABS qualified plate, welders and weld procedures are sufficient to justify acceptance of weld qual- ity based upon random sampling and application of statistical laws.

Shipbuilders who achieve consist- ently good welds would inspect less.

This view was supported by a recent description of a Failure

Analysis Associates' (FAA) re- port. "When a supertanker devel- oped welding cracks during con- struction, the firm was asked to determine whether similar cracks might occur in an already launched sistership and result in disaster.

Using statistical analysis, FAA reported that the risk involved in continuing to operate the sister- ship without modification was ac- ceptable."

Thus, there is already substan- tial thinking that suggests re- search to develop a statistical ap- proach for assessing weld quality.

Since statistics is a form of ap- plied mathematics, it is a logical tool to use for increasing owner, regulator and shipbuilder UT as- surances while opening the way to more improvements in produc- tivity.

Another project was undertaken to reduce the cost of shipboard electrical installations by ex- panded use of less costly and readily available material from the larger electrical equipment markets that exist for general, residential and specialized (tank farms, mines, etc.) construction industries. By this time the re- search management had adopted the same format for proposed changes to the Code of Federal

Regulations (CFR) as used by headquarters members of the CG.

The reason being to perform every logical task, even adminis- trative in addition to applied re- search and analysis, that would facilitate a regulator's under- standing.

The main emphasis of these requests is on the necessity to adopt standards of the National

Electric Code (NEC) and Na- tional Electric Manufacturer's

Association (NEMA) unless there is an absolutely manifest need peculiar to ships and/or the ship- building process. Traditionalists and some suppliers who are de- votees of the generality "com- mercial marine practice" are up- set by the growing knowledge that the electrical equipment re- quirements of other industries, petrochemical for example, are frequently much more severe than those of the marine indus- try. More of such knowledge ob- tained through applied research and analysis and widely dissem- inated is the only way to counter their negative reactions.

The CG is encouraging requests resulting from the research be- cause they show that shipbuilders are collectively doing their "home- work" instead of expressing frus- tration with the CFR. Further, the CG already has mechanisms for public participation in rule making as is now being demanded in Congress. No matter what the mechanisms are, they cannot do anything without responsible in- put. The shipbuilders' collective thinking is included in such input through guidance furnished by the Ship Production Committee.

An added degree of responsibility is the wide distribution of such requests to the industry, via the

Ship Production Committee, to (continued on page 16)

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Marine Electronics...From Those Who Really Care

November 1, 1977 15