Remediation requirements for non-metallurgical cranes in use for lifting molten metal
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(1) If a general-purpose bridge crane has been used to lift molten metal, it should be replaced with a casting crane that meets the requirements of JB/T7688.15-1999 "Metallurgical Crane Technical Conditions Casting Crane".
If a unit that does not have the conditions to replace the casting crane due to factors such as plant and foundation, in addition to meeting the regulations and standards of general bridge cranes, t
he original crane must be modified and meet the following basic technical requirements:
1. Use a special motor for metallurgical cranes. When the temperature exceeds 40 degrees, a class H insulated motor should be used.
2. Two independent brakes (dual brakes) are installed.
3. A lifting weight limiter must be installed.
4. Equipped with different types of double limiters (double limiters) for the ascending limit position of different forms (usually combined with heavy hammer and rotary),
and should control different circuit breakers, lifting heights greater than 20m, The lower limit position limiter should also be installed as needed.
5. Use thyristor stator voltage regulation, eddy current brake, energy consumption brake, thyristor power supply,
DC unit power supply and speed regulation, and other hoisting mechanisms that may cause overspeed due to speed regulation and general-purpose
lifting mechanisms above 20T for lifting molten metal The bridge crane must have overspeed protection.
6. The hoisting mechanism should have the function of forward and reverse contactor failure protection to prevent the motor from losing power while the brake is still energized,
causing power loss and accidents.
7. The protection level of all electrical equipment should meet the requirements of relevant standards.
8. For hoisting machinery that has been working in a high temperature environment for a long time, protective measures must be taken for its electric control equipment.
9. Choose the steel wire rope suitable for high temperature occasions, and have sufficient safety factor.
10. Cast iron pulleys may be used.
11. If the original crane's wo
rking level is lower than A6 (excluding A6), the load should be reduced for use. The drop rate should be determined according to the actual working conditions,
but the specified lifting capacity after the load reduction cannot exceed 80% of the original rated lifting capacity.
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