DUAL Project
Gasket Relaxation and Retorque Optimization
Released on: 04/20/2009
Duration of Work:
2 Semester(s)
Project Description
During initial launch countdown of STS-119, a hydrogen leak was detected and the launch was scrubbed until repairs could be made. The repair required removal and replacement (R&R) of the Pad A External Tank (ET) Gaseous Hydrogen (GH2) Vent interface Quick Disconnect (QD) and subsequently , the de-mate of the ET GH2 vent line 4-foot flexhose forward flange from the QD flange. Removal and reinstallation of the Ground Umbilical Carrier Plate (GUCP) 7 disconnect required a retorque at 30 hours per legacy specification. Preliminary engineering analysis of available data revealed that the time before retorque may be significantly shortened. Proof of concept testing performed by Launch & Recovery Systems Engineering provided results corroborating preliminary engineering analysis and indicated conservatively all measurable affects of relaxation in this system take place in the first 10 hours. The team concluded that a 15 hour retorque is equally effective as a 30 hour retorque and would not degrade the form, fit or functionality of the ET GH2 Vent Line flexhose and GUCP 7 disconnect flange interface. The retorque requirement was reduced to 15 hours and STS-119 successfully launched on March 15, 2009.
The configuration of the GUCP 7 disconnect flange is not uncommon of bolted joints across LC-39. Both hyper-system and cryo-system utilize this bolted joint configuration. These joints consist of 11 diameter flanges with concentrically serrated sealing surfaces joined by 16 stud bolts gasketed with Fluorogreen E600 and torqued to 206 ft-lbs to 226 ft-lbs. Significant operational value may be realized by optimizing retorque parameters of these system joints. This project will study the main effects and interactions of multiple parameters on bolted joint torque loss and develop an optimized retorque process for the hyper- and cryo-system bolted joints. The project will be phased to ensure timely information transfer.
Phase I of the project is to develop a test plan using Design of Experiment methodologies. Parameters shall include, at a minimum, gasket thickness, mating surface serrations (concentric & blank), lubrication (fastener friction - with and without Krytox), clamping load, retorque time, and retorque frequency. Considerations of flange design per ASME B16.5 and gasket relaxation testing per ASTM F38 shall be
taken into account in the development of the test plan. A documented test plan and test set-up will be produced at the end of Phase I. Completion of Phase I should be planned for Week 4 of August 2009.
Phase II of the project will be to execute the test plan, analyze the main effects and interactions, validate DOE model with a minimum of 3 confirmation runs, perform iterative optimization runs for the LC-39 cryo- and hyper-system configuration. Used gaskets shall be identified and retained. Deliverables for Phase II will be a confirmed DOE model and recommended retorque process. Completion of Phase II should be planned for Week 4 of December 2009.
In addition to the phase completion deliverables, a brief weekly status report is requested to monitor overall project performance and manage project risks.
Material Needed
The university will need to provide precision strain measurement device, statistical software package (e.g. Mini-Tab, JMP, QI Macros), all materials required to execute DOE test plan, confirmation, and optimization runs.
Material Available
USA will provide hardware installation specifications, STS-119 Engineering Analysis, and technical guidance via e-mail, conference calls, or occasional face-to-face at KSC or the University as needed.
Skills or field of knowledge required
This project is envisioned to be worked by an interdisciplinary undergraduate/graduate team of Material Science & Engineering, Mechanical or Aerospace Engineering, and Industrial Engineering students lead by one Faculty Advisor. Knowledge of statistical analysis techniques, specifically Design of Experiments, bolted joint design, and polymeric materials behavior is required. Personnel should be able to integrate technical theory into practical applications. Level of education and number of personnel is negotiable.
Contact Information:
Mentor: Kammerer Catherine C
Phone: 321/861-8123
Email: catherine.c.kammerer@usa-spaceops.com
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