Metallurgical cranes refer to bridge cranes used in metallurgy, casting, and other places for lifting molten metal and can be divided into metallurgical single-girder cranes and metallurgical double-girder cranes. The safety rules for bridge cranes are specified in Part 5 of the Safety Regulations for Hoisting Machinery (Bridge and Gantry Cranes). In addition to meeting various requirements of ordinary cranes, metallurgical cranes should also meet the following requirements:
- Anti-radiant heat device and fireproof board
1.1. The bottom of the driver’s cab directly exposed to heat radiation by the crane that lifts molten metal or incandescent objects should be equipped with a heat radiation shield.
1.2. The main beam and the bottom of the lifting beam directly exposed to radiant heat shall be equipped with anti-radiant heat devices for cranes that lift molten metal or hot objects (except for cranes with the following flanges as running rails).
1.3. Cranes with the following flanges used as running rails and hoisting molten metal or incandescent objects should be equipped with a vehicle heat radiation device at the bottom of the drafting trolley.
1.4. Reliable anti-fall measures should be provided for the heat-proof radiation plate.
1.5. For cranes that are directly affected by the flame (such as steel mill charging span casting cranes), fireproof boards should be installed at the part where the flame directly burns the main structure.
1.6. Insulation layer should be provided in the wiring parts of the channel and platform directly exposed to radiant heat by the crane that lifts molten metal or incandescent objects.
1.7. For cranes that lift molten metal or incandescent objects, protective measures should be taken for electrical equipment directly exposed to radiant heat.
- For cranes that lift molten metal or hot objects, a closed driver’s cab should be used. An effective thermal insulation layer shall be provided, and the thermal insulation layer shall be a flame retardant material.
- Requirements for metallurgical cranes:
3.1. For cranes that lift molten metal, the main hoisting mechanism (except electric hoists) transmission chain should meet one of the following conditions:
a) The main hoisting mechanism is provided with two sets of driving devices, which are rigidly connected to the output shaft;
b) The main hoisting mechanism is provided with two sets of driving devices. When there is no rigidity continuous on the output shaft or when the main hoisting mechanism is provided with one set of driving devices, a safety brake shall be provided on the wire rope reel;
Note: Two sets of driving devices refer to two electric motors, two sets of deceleration systems, one or more sets of winding devices and four sets of brakes.
c) For a crane with a rated lifting capacity of not more than 16t, its working level should be at least 2 levels higher than that required by the actual operating conditions when designing the hoisting mechanism, and the minimum working level should not be lower than M5.
3.2. For a crane that lifts molten metal, the steel wire of the main hoisting mechanism should meet the following regulations:
a) Four wire rope winding systems shall be used for double lifting points;
b) At least two wire rope winding systems are used for a single lifting point;
c) The safety factor shall comply with the relevant regulations in GB/T 3811, for cranes with a rated lifting capacity not greater than 16t. Its safety factor should not be less than 5.6.
3.3. For cranes that lift molten metal, the wire rope winding system of the main hoisting mechanism should not use balance pulleys.
3.4. When the rated lifting capacity of the crane for lifting molten metal is not more than 16t, the electric hoist can be used as the lifting mechanism. In addition to the requirements of JB/T 9008 (all parts), the electric hoist shall also meet the following requirements:
a) When the rated lifting capacity is greater than 5t, in addition to a working brake, the electric hoist should also be provided with a safety brake. The safety brake is set on the low-speed stage of the electric hoist, which can reliably support the rated load when the working brake fails or the transmission parts are broken.
b) When the rated lifting capacity is less than or equal to 5t, in addition to a working brake, the electric hoist should also be equipped with a safety brake on the low-speed stage, otherwise, the electric hoist should be designed according to 1.5 times the rated lifting capacity.
c) Choose an electric hoist with a high-temperature heat insulation function.
d) The working level of the electric hoist should not be lower than M6.
3.5 A crane that lifts and transports vertical and thermally heat-treated workpieces. The brake of the hoisting mechanism shall be provided with an emergency release device.
3.6 The items lifted by the forging crane shall be placed on the support surface. Bear regular impact load and produce vertical displacement. The corresponding hoisting mechanism shall be provided with a buffer device and a brake release mechanism.
- Parts requirements:
4.1. Steel wire rope
4.1.1. For cranes that lift molten metal or incandescent objects, high-temperature resistant steel wire ropes with performance not lower than the metal rope core or metal strand core specified in GB 8918 shall be used.
4.1.2. Cranes for lifting molten metal. The safety factor shall comply with the relevant provisions of Table 44 in GB/T 3811-2008. For cranes with a rated lifting capacity not greater than 16t, the safety factor shall not be less than 5.6.
4.2.1. Gray cast iron pulleys should not be used for lifting and transporting the molten metal.
4.2.2. Rolling pulleys are recommended for metallurgical cranes. When using the cast iron wheel, it should comply with the provisions of GB/T 27546.
4.3.1. The welding fork of the crane that lifts molten metal, its force direction should be consistent with the rolling direction of the steel plate and the extension fiber direction, and the mechanical properties of the steel plate should not be lower than the Q345B steel plate in Table 1 of GB/T 1591-2008.
4.3.2. The lower flange plate of the hoisting beam of the hoisting molten metal crane shall not have butt welds.
4.3.3. The main bearing parts of the lifting beam towel of the molten metal crane, such as the side plate of the pulley block, the lifting lug plate, etc., when the plate thickness exceeds 0.04m. Ultrasonic testing should be carried out before cutting and should reach the I-level quality specified in Table 4 in GB/T 2970-2004.
4.3.4 For cranes that lift molten metal, measures should be taken at the hook group and the lifting beam, etc. to protect the wire rope from the direct influence of radiant heat, and prevent the molten metal from splashing on the wire rope.
4.3.5. When the hot objects and workpieces lifted by the crane need to enter the liquid medium, measures should be taken to prevent liquid splashing at the movable pulley block of the hook.
4.3.6. Coarse cranes for handling and stacking bar billets during continuous casting and rolling in steel mills. The rough teeth of the material target should be made of Q345 steel whose material properties are not lower than those listed in Table 1 of GB/T 1591-2008, and the butt joint of the rake teeth; that is, the seam should be well penetrated, the post-weld annealing treatment, and the radiographic inspection should meet the requirements of GB/T 3323 The quality requirements of BII welded joints in JB/T 10559 should meet the quality requirements of L class in JB/T 10559.
- Lifting mechanism for hoisting molten metal and other dangerous goods. The control of the brake shall take measures to prevent control failure due to damage and sticking of a contactor.
- The cables directly exposed to heat radiation on the cranes that lift molten metal and hot objects should use flame-retardant and high-temperature resistant cables or take heat insulation measures for the cables.
- Cranes that lift molten base metal or incandescent objects should use a cab, remote control, or non-following and other operation methods away from heat sources, and ensure the operator’s operating field of vision. Cranes using the remote control or non-following operation should be provided with safe passages for operators.
- For cranes that hoist molten metal and other dangerous goods, the hoisting mechanism should be equipped with Overspeed protection, except for electric hoists with a rated lifting capacity of not more than 5t.
- For cranes hoisting molten metal, the main hoisting mechanism should be equipped with different forms of double secondary protection devices at the lifting limit position and can control different circuit breakers. When the lifting height is not greater than 20 m, the lowering limit should also be set. position limiter.
- For a crane that lifts molten metal, if the main hoisting mechanism (except the electric hoist) is equipped with two sets of driving mechanisms and the output shaft has no rigid connection or is provided with one set of driving mechanisms, safety brakes should be set on the wire rope drum. For cranes that lift molten metal with a rated lifting capacity not greater than 16t and greater than 5t, in addition to a working brake, the electric hoist shall also be provided with a safety brake on the low-speed stage of the electric hoist. If the rated lifting capacity is not greater than 5t, the electric hoist shall not In addition to setting a working brake, it is also advisable to set a safety brake on the low-speed stage of the electric hoist, otherwise, the electric hoist should be designed according to 1.5 times the rated lifting capacity.
The use of metallurgical cranes is a piece of more dangerous equipment than ordinary cranes. Relevant units should purchase products from manufacturers with production qualifications and accept the inspection of special inspection departments.