What are the special requirements of metallurgical cranes for lifting molten metal?

Metallurgical cranes refer to crane equipment used to lift molten metal. It can be divided into single-beam metallurgical cranes and double-beam metallurgical cranes . In 2007, after a serious production accident occurred in a steel plant in Tieling, Liaoning that caused 32 deaths, in order to ensure the safety of the use of this type of equipment, combined with the production and operation of the company, the relevant units learned from experience and proposed to the metallurgical crane used by the steel plant Clear technical requirements and standards, and order the user unit to make rectifications:

1. Non-metallurgical hoisting machinery in use for lifting molten metal rectification requirements

(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 "Technical Conditions for Metallurgical Cranes, Casting Cranes". If the 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 overhead cranes, the original crane must be modified and meet the requirements of the following basic technical conditions:

1.  Use special motors for metallurgical lifting. When the ambient temperature exceeds 40°C, use Class H insulated motors;
2.  Two sets of independent brakes (dual brakes) are installed;
3.  A lifting weight limiter must be installed ;
4.  Equipped with different forms of double limiter (double limiter) of the ascending limit position of different forms (generally the combined use of heavy hammer type and rotary type), and should control different circuit breakers, cranes with a lifting height greater than 20m, and The lower limit position limiter should be installed according to the needs;
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 for lifting molten metals above 20t The bridge crane must have overspeed protection;
6.  The hoisting mechanism should have the function of forward and reverse contactor fault protection to prevent the motor from losing power while the brake is still energized and causing a stall;
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 a steel wire rope suitable for high temperature occasions, and have a sufficient safety factor;
10.  Cast iron pulleys are not allowed;
11.  If the original crane's working level is lower than A6 (excluding A6), it should be used at a reduced load. The drop rate should be determined according to the actual working conditions, but the specified lifting capacity after the load reduction shall not exceed 80% of the original rated lifting capacity.

(2) For all types of hoisting machinery with a rated lifting capacity greater than 10t and electric hoist as the lifting mechanism, it is not allowed to lift molten metal.

(3) For all types of hoisting machinery with a rated lifting weight less than or equal to 10t and using electric hoists as the lifting mechanism to lift molten metal, the original crane must be replaced or modified and meet the requirements of the following basic technical conditions:

1.  Do not use ordinary electric hoist as lifting mechanism;
2.  With supporting brake and safety brake;
3.  There are different types of ascending double limiters (for cranes with a lifting height greater than 20m, a descending limit position limiter should also be installed);
4.  With lifting weight limiter;
5.  Electric hoist with high temperature insulation protection function;
6.  It has a sufficient safety factor for the working conditions of lifting and transporting molten metal, and the working level must reach M5 (including M5) or higher;
7.  Choose steel wire rope suitable for high temperature occasions, and have sufficient safety factor;
8.  As far as possible, use remote control and other operation methods far away from the heat source, otherwise a safe passage for the operator must be set up.

(4) The transformation of the above cranes must be carried out by a unit with the qualification for transformation permits, and the transformation must be carried out informing procedures. The transformed cranes must be supervised by a qualified inspection and testing agency in accordance with the "Lifting Machinery Supervision and Inspection Rules" and the requirements of this article. It can be put into use according to regulations only after passing the inspection.

(5) The transformation of the crane for lifting molten metal should be completed before June 30, 2008. The user unit should immediately formulate a replacement plan or transformation plan, and implement it quickly, otherwise it should stop using it. During the implementation of the transformation, the user unit shall monitor the use and must take effective measures to ensure the safe operation of the equipment.

(6) The periodic inspection period of cranes for lifting molten metal has been shortened from 2 years to 1 year.

2. New factory installation of crane requirements for lifting molten metal

Newly installed cranes for lifting molten metal refer to the lifting machinery for lifting molten metal that has been delivered and installed from the date of publication of this article, and does not include the lifting machinery for lifting molten metal that is overhauled, modified, or relocated.

(1) The requirements for newly installed cranes for lifting molten metal are as follows:

1.  Cranes with a rated lifting capacity greater than or equal to 75t must be used for casting cranes that meet the requirements of JB/T7688.15-1999 "Technical Conditions for Metallurgical Cranes, Casting Cranes".
2.  For cranes with a rated lifting capacity of less than 75t, a general-purpose bridge crane with a working class of A7 (including A7) or higher should be selected, but its configuration and other requirements must meet the 11 basic requirements of the modified crane in the first (1) above Technical conditions and corresponding requirements.
3.  Cranes that use electric hoist as lifting mechanism to lift molten metal can only be used in working conditions with rated lifting capacity less than or equal to 10t. The configuration and other requirements must meet the basic requirements of the above-mentioned first (3) after transformation. Technical conditions and corresponding requirements, among which the working level of electric hoist is required to be raised from M5 (including M5) or higher to M6 (including M6) or higher.

(2) Cranes for lifting molten non-metallic materials (the temperature is lower than molten metal) and hot solid metals may be appropriately relaxed according to the degree of danger in the workplace, or they may be handled with reference to the above requirements.

Local quality and technical supervision bureaus should take effective measures as soon as possible to do a good job in the rectification of non-metallurgical cranes used in the metallurgical industry to prevent the recurrence of similar accidents. If you have any problems in your work, please report to the Special Equipment Safety Supervision Bureau of the General Administration in time.

The bridge crane used in metallurgical occasions is a relatively special type of equipment, and its requirements are much higher than those of ordinary types of cranes. In order to ensure production safety, relevant units must select regular manufacturers in accordance with the standards.

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