MONITORING STRESSES ON THE PV-4 ISOSTATIC PRESS FROM 1960 TO 1997
The PV-4 isostatic press has a very large working volume (98 ft{sup 3}) that was designed for routine operations at internal pressures up to 30 ksi and is, therefore, a unique and valuable component of the U.S. DOE Y-12 manufacturing capability. More than 13,000 pressing operations have been conducted since initiation of operations in September 1960. The pressure vessel portion consists of three concentric cylinders of high-strength steel with the outer two cylinders shrink-fitted on the imermost cylinder to minimize tensile stresses on the inner surface of the vessel. The third, outermost cylinder consists of two sections; each section is one-half the length of the pressure vessel. The vessel is contained within a large frame which is made of T-1 steel. In 1982 and 1983 precision strain gauges were mounted at selected locations on the frame and the outer surface of the pressure vessel to monitor the operating stresses. Where possible, locations of the gauges mounted in 1982 and 1983 were at or near the same locations as the strain gauges mounted in 1960 to monitor stresses on the frame and vessel during preoperational testing and design verification of the press. This report presents the information obtained with these strain gauges for tests conducted in September 1960 prior to any operation of the press and for the period July 1983 to August 1997. On September 8 and 9, 1960, Sturm & Krouse used 120 strain gauges on the frame and 20 strain gauges on the outer surface of the pressure vessel to measure strains in PV-4 as a function of operating pressure from O to 33 ksi. Although the design maximum operating pressure of the press was 30 ksi, to provide a safety factor for operations at 30 ksi and to assure totally elastic behavior of the steel components of the frame and pressure vessel at pressures above the design pressure, strains were also measured at operating pressures of 32 and 33 ksi. Sturm & Krouse observed that the stresses on the frame and vessel were a linear function of operating pressure over the test range from O to 33 ksi. They verified the design performance and parameters of the press and linear elastic behavior to at least 10% higher than the design operating pressure. Stresses calculated from strain gauge measurements taken between July 29, 1983, and August 5, 1997, at an operating pressure of 30 ksi are in good to excellent agreement with those obtained in September 1960 on the frame and are in excellent agreement with those obtained on the pressure vessel. In addition, slopes of the measured strain as a function of internal pressure have remained the same from preoperational testing on September 8 and 9, 1960, through August 5, 1997, the last date on which strain measurements were conducted. Also, there have been no systematic changes in the zero strain values for measurements taken with the same data acquisitions ystem. The excellent agreement of the stresses and slopes measured from 1983 to 1997 with those measured in 1960 indicates that no cracks, defects, or other flaws have developed in the pressure vessel that could affect the integrity of the pressure vessel. Also, this excellent agreement indicates that there has not been any relaxation of the original shrink-fit pressures that were employed in fabrication of the vessel. Therefore, the original shrink-fit pressures may be used for stress analysis of the pressure vessel and for estimating the fatigue life of the vessel. The excellent agreement of the stresses and slopes of strain as a function of internal pressure obtained for the period 1983 to 1997 with those obtained in 1960 are exactly as expected for the metallurgical structure of the steels of which the press frame and pressure vessel were constructed. To assure long-term integrity of the pressure vessel and that the shrink-fit pressures are not relaxed, continued monitoring of the vessel with precision strain gauges is required.
- Research Organization:
- Oak Ridge Y-12 Plant, Oak Ridge, TN
- Sponsoring Organization:
- USDOE Office of Defense Programs (DP)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 3108
- Report Number(s):
- Y/QS-0006; ON: DE00003108
- Country of Publication:
- United States
- Language:
- English
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