Case Studies in Quality Manufacturing

PQM201B Student Book Case Studies In Quality Manufacturing Given case study examples of PQM processes with troublesome outcomes, evaluate facets of existing QMS elements. Relate discussed PQM topic areas to each case and identify opportunities to apply them. • What failures of the system’s quality management system are evident? • Was the failure (A) Design related, (B) Workmanship related, (C) Material related, or (D) a combination? • What processes / components were Key to the item? Critical to the item? • What corrective actions (if any) were incorporated as a result of the situation? • How might the following PQM topic areas apply: • Integrated Manufacturing Planning • Continuous Process Improvement • Lean Manufacturing Teams consider their assigned case with these questions in mind. You are encouraged to consider other references and/or information when exploring these cases. Your team will be provided a discussion period after the lecture portion of the Quality Management lesson to share your impressions about your assigned case amongst yourselves. Each team will then present a summary of your findings to your classmates to conclude the lesson. v16.2 195 PQM201B Student Book v16.2 196 PQM201B Student Book The Loss of the USS THRESHER On April 10, 1963, the nuclear submarine USS THRESHER failed to surface from a test dive and was lost at sea. On the morning of April 10, the THRESHER proceeded to conduct sea trials about 200 miles off the coast of Cape Cod, MA. At 9:13am, the USS SKYLARK received a signal indicating that the submarine was experiencing “minor difficulties.” Shortly afterward, the SKYLARK received a series of garbled, undecipherable message fragments from the THRESHER. At 9:18am, the SKYLARK’s sonar picked up sounds of the submarine breaking apart. All hands were lost - - 129 lives. The Investigation The subsequent investigation of the disaster by the Navy identified a leak in an engine room seawater system as the most probable cause of the tragedy. Further, both the Navy’s investigation and a Congressional inquiry identified several additional probable causes linked to management, communication, and the practices and procedures employed by the Navy and the shipyards. The THRESHER was the first of a new class of nuclear submarine designed to dive significantly deeper than its predecessors. After nearly a year of record-breaking operations, the submarine underwent a scheduled shipyard overhaul that entailed significant alterations to its hydraulic power plant. Because of Fleet operational requirements and competition for resources with four other submarines under construction in the same shipyard, the overhaul was conducted under tight schedule constraints. The Navy’s investigation concluded that while the THRESHER was operating at test depth, a leak had developed at a silver-brazed joint in an engine room seawater system, v16.2 197 PQM201B Student Book and water from the leak may have short-circuited electrical equipment, causing a reactor shutdown and leaving the submarine without primary and secondary propulsion systems. The submarine was unable to blow its main ballast tanks, and because of the boat’s weight and depth, the power available from the emergency propulsion motor was insufficient to propel the submarine to the surface. Practices and Procedures After the investigation, the Navy embarked on an extensive review of practices and procedures in effect during the THRESHER’s overhaul. The reviewers determined that existing standards at the time were not followed throughout the re-fit to ensure safe operation of the submarine. Four issues were of particular concern: Design and Construction: The submarine was designed and built to meet two sets of standards. Because the submarine’s nuclear power plant was the focus of the engineers, the standards used for the nuclear power plant were more stringent than those for the rest of the submarine. As a result of the emphasis placed on nuclear- related aspects of the design, builders assigned less importance to the steam and saltwater systems, even though those systems were crucial to the operation and safety of the vessel. Brazing: Two standards for silver-brazing pipe joints were used during the THRESHER’s construction and overhaul. Brazing is a process that joins metal parts by heating them to a temperature sufficient to melt a filler material, which then flows into the space between the closely fitted parts by capillary action. Induction heating, which provides better joint integrity, was used for easily accessible joints. Where accessibility was restricted, hand-held torches were used. Reviewers determined that hand-held torches were used to heat many of the THRESHER’s crucial, but less accessible, pipe joints. Quality Assurance: A newly accepted nondestructive testing technology for quality assurance was not implemented for the THRESHER’s overhaul. The Navy had experienced a series of failures with silver-brazing, which resulted in several near misses, indicating that the traditional quality assurance method, hydrostatic testing, was inadequate. Therefore, the Navy directed the shipyard to use ultrasonic testing, a method newly accepted by industry, on the THRESHER’s silver-brazed joints. However, the Navy failed to specify the extent of the testing required and did not confirm that the testing program was properly implemented. When ultrasonic testing proved burdensome and time consuming, and when the pressures of the schedule became significant, the shipyard discontinued its use in favor of the traditional method. This action was taken despite the fact that 20 of 145 joints passing hydrostatic testing failed to meet minimum bonding specifications when subjected to ultrasonic testing. Records and Documentation: It was determined that records were incomplete or non- existent for numerous amounts of work to include critical practices and critical methods. Procurement: Finally, specifications for Government procurement were not strictly enforced. The Navy found that the reducing valve components installed in the pressurized air systems used to blow the main ballast tanks of the submarine did not meet design specifications. Because of the magnitude of the pressures anticipated, the valve manufacturer had added a strainer feature upstream of the reducing valves to v16.2 198 PQM201B Student Book protect the sensitive valves from particulate matter. When the Navy conducted tests on another THRESHER-class vessel, it found that the pressure drop across the component at high flow rates caused entrained moisture to accumulate on the strainers and form enough ice to block the air flow. Venturi cooling, as this phenomenon is called, was thought to be the reason that the THRESHER’s attempts to blow its main ballast tanks were ineffective. After an extensive underwater search utilizing the bathyscaph TRIESTE, oceanographic ship MIZAR and other ships, THRESHER’s scattered remains were located on the sea floor, some 8400 feet below the surface. Deep sea photography, recovered artifacts and an evaluation of her design and operations permitted a Court of Inquiry to determine that she probably sank due to a piping failure, subsequent loss of power and inability to blow ballast tanks rapidly enough to avoid sinking. Over the next several years, a massive program was undertaken to correct design and construction problems on the Navy’s existing nuclear submarines, and on those under construction and in planning. Following completion of this “SubSafe” effort, the Navy has suffered no further losses of the kind that so tragically ended the THRESHER’s brief service career. Lessons Learned: (1) Engineering, design and construction must place equal weight on nuclear and non-nuclear systems when the operation of either system can affect the safety or integrity of an overall system. (2) In selecting the standard for which a task is performed, the pressures of time and resources should not override the safe and continued performance of the result. Selecting the easy standard to save time and money increased the probability of a failed weld. (3) Communication of near-miss events by management to various departments, or feedback, helps resolve weaknesses or flaws that in future events could prove tragic. (4) Procurement of equipment and components must be checked upon receipt as well as tested under operating conditions to verify its suitability. Valves or other parts could be assembled with counterfeit bolts, which fail when stressed. v16.2 199 PQM201B Student Book The M-16 Rifle and Ammunition System In 1957, Eugene M. Stoner, a skilled civilian engineer, was commissioned by the United States Army to develop a shoulder fired weapon that weighed no more than seven pounds, and that was to be capable of automatic as well as semi-automatic firing. In less than a year, he delivered a prototype of the weapon to the Army at Fort Benning, Georgia where it was given a thorough testing. The Army found the rifle, which was named the AR-15, to be equal to its own M-14 in firing at distances of up to five hundred yards. The AR-15 was found to be superior to the M-14 in respect to weight, ease of automatic firing without climbing, and in the weight of its ammunition, which allowed a soldier to carry more rounds without weight increase. After months of testing, the United States Continental Army Command Board recommended that the AR-15 rifle be adopted to replace the M-1 rifle, of World War II fame, as the Army's standard basic infantry weapon. The recommendation was not adopted, and it was not until 1962 that 1,000 of the rifles were sent to Vietnam for months of testing in the hands of United States Advisors and Vietnamese soldiers. This was accomplished over the objections of the Department of the Army by the direct intervention of Robert McNamara, the Secretary of Defense. These tests in Vietnam proved to be the publicity needed to persuade the Air Force and the Navy to ask for initial purchases of the weapon, in order to equip their personnel serving in Vietnam.

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