Features of metallurgical cranes and the requirements they must meet
Category: Industry News
Release time:2020-02-13
To ensure the safe operation of metallurgical bridge cranes, and based on the specifics of metallurgical production and operations, these cranes must meet the following requirements:
1. Use electric motors specifically designed for metallurgical cranes; in environments where temperatures exceed 40°C, motors with Class H insulation should be selected.
2. Equipped with two independently operating brakes (dual braking system).
3. A load-limiting device must be installed.
4. Install dual limit switches (double limiters) with different mechanisms—typically combining a weight-type and a rotary type—to safeguard the uppermost lifting position. These switches should activate separate circuit-breaker devices. Additionally, for cranes with a lifting height exceeding 20 meters, a lower-limit switch should also be installed as needed.
5. Hoisting mechanisms employing thyristor stator voltage control, eddy-current brakes, regenerative braking systems, thyristor-based power supplies, DC generator-driven speed control, and other speed-regulating methods that could potentially lead to overspeed—such as those used in general-purpose bridge cranes rated above 20 tons for lifting molten metal—must be equipped with overspeed protection devices.
6. The lifting mechanism should feature positive and reverse contactor failure protection to prevent the motor from losing power while the brake remains energized, which could otherwise lead to a hazardous accident.
7. The protection levels of all electrical equipment must comply with the relevant standard specifications.
8. For lifting machinery that operates continuously in high-temperature environments, protective measures must be implemented for their electrical control equipment.
9. Select steel cables suitable for high-temperature applications and ensure they have an adequate safety factor.
10. Cast iron pulleys are available for use.
11. Cranes with a rated lifting capacity of 75 tons or more must use casting cranes that meet the requirements specified in JB/7688.15-1999, "Technical Specifications for Metallurgical Cranes—Casting Cranes."
12. Cranes with a rated lifting capacity of less than 75 tons should first be replaced with general-purpose bridge cranes of work class A7 or higher (including A7).
Keywords: Features of metallurgical cranes and the requirements they must meet
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