Evaluation of valve packing materials for long-term use in molten nitrate salt
Chemical compatability between a number of compression packings and molten sodium nitrate-potassium nitrate was evaluated at temperatures of 288/sup 0/C (550/sup 0/F), 399/sup 0/C (750/sup 0/F), and 565/sup 0/C (1050/sup 0/F). The types of packing materials tested included graphite filaments, graphite ribbon, asbestos, teflon, aramid, glass and ceramic fibers, perfluorelastomers, and boron nitride. Packings were immersed for periods up to 1000 hours in a static test fixture which simulated their installation in a flow control valve stuffing box. Characteristics evaluated were visual indications of deterioration and salt absorption, weight change and microscopy of cross-sectioned samples. Several packings were chemically resistant to the molten salt at 288/sup 0/C, but the compatibility of packings at 399/sup 0/C and 565/sup 0/C was not adequate. Thermogravimetric analysis demonstrated that oxidation of graphite by nitrate salt was slow at 288/sup 0/C but increased rapidly at higher temperatures. The chemical and physical phenomena affecting compatibility are discussed and recommendations concerning materials selection are made.
- Research Organization:
- Sandia National Labs., Livermore, CA (USA)
- DOE Contract Number:
- AC04-76DR00789
- OSTI ID:
- 6080674
- Report Number(s):
- SAND-86-8207; ON: DE86008837
- Country of Publication:
- United States
- Language:
- English
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ALKALI METAL COMPOUNDS
CENTRAL RECEIVERS
CONTROL EQUIPMENT
EQUIPMENT
EVALUATION
FLOW REGULATORS
HIGH TEMPERATURE
MATERIALS TESTING
MOLTEN SALTS
NITRATES
NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
POTASSIUM NITRATES
SALTS
SEALS
SODIUM COMPOUNDS
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VALVES