Coast Guard Regulations, 46 CFR Part 54, require steam safety and relief valves to be provided with a substantial lifting device, capable of lifting the disc from its seat at what percentage of the set pressure?
• 46 CFR Part 54 – Safety and Relief Valves for pressure vessels • Purpose of a lifting device on steam safety valves (manual test of valve opening) • Relationship between set pressure and the pressure at which the disc must be manually liftable
• Ask yourself: Why does the Coast Guard require a manual lifting device on steam safety valves? Is it so you can test the valve before it reaches full set pressure, at set pressure, or well above set pressure? • Think about what would be safe and practical: At what fraction of the set pressure would you still be within a safe operating range for the boiler and also be able to verify that the valve operates properly? • Consider how often these valves are tested in service. Would a very low percentage of set pressure make a meaningful test, or would a very high percentage be too close to a dangerous condition?
• Verify in 46 CFR 54.15 and related sections that describe construction and testing of safety and relief valves. • Check that the percentage you choose would allow a functional test of the valve without putting the boiler close to an unsafe overpressure condition. • Confirm that the required percentage is expressed as a fraction of the set pressure (e.g., 0.XX × set pressure), not an absolute pressure value.
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