1 Scope
This document specifies the general classification of cranes and their components based on the operating conditions established. The operating conditions are mainly represented by the following parameters
Indication:
The total number of working cycles that the crane should achieve during the specified design life;
The load spectrum factor, which indicates the relative frequency of lifting different loads;
the average displacement.
This document applies to cranes as defined in ISO 4306.
2 Normative references
The contents of the following documents constitute essential provisions of this document through normative references in the text. Where a reference is dated, only the version corresponding to that date applies to this document; where a reference is not dated, the latest version (including all amendment sheets) applies to this document.
ISO 4306 (all parts) Crane terminology (Cranes-Vocabulary)
3 Terminology and definitions
The terms and definitions defined in ISO 4306 apply to this document.
4 Symbols
The main symbols used in this document are as defined in Table 1.
5 Use of classification
5.1 General rules
There are two practical uses of classification (see 5.2 and 5.3) which, although related, can be considered as two different purposes.
The determination of a reasonable crane life requires consideration of the effects of economic, technical and environmental factors as well as the ageing of the equipment.
5.2 Commercial use
Classification is applied when purchasers and manufacturers of cranes and/or lifting appliances need to agree on the operational tasks of the crane. This is where classification can be used as a contractual and technical reference.
For cranes, lifting spreaders or components designed for series production, classification can also be used to specify their operating conditions so that they can be selected according to their intended use.
The defined classification should be specified in the crane operating manual.
5.3 Design use
A second use of the classification is to provide the designer with a calculation basis for design analysis and to verify the ability of the crane or component to achieve the expected life under the specified operating conditions.
As a specialist crane technician, the designer can incorporate into the design analysis specific operating conditions provided by the purchaser or pre-determined by the manufacturer (e.g. when designing a series of cranes), taking into account other factors affecting the individual components.
Crane operation causes increases in stress or load on the metal structure and components of the crane (e.g. wire ropes, slewing bearings, wheels, railings etc.) and the history of these increases can be used to classify specific components. For the grading method can be specified in the appropriate standards, such as GB/T 30024 for metal structures.
6 Complete crane classification
6.1 General rules
The crane operating tasks are determined by the following parameters:
a) The total number of working cycles during the design life;
b) the relative frequency of lifting different loads (load spectrum, load state);
c) the average displacement.
When using a range of parameters for the working level, the maximum value of the parameters within the specified level shall be used as the basis for design. Intermediate parameter values are allowed, but specific design values should be specified and levels should not be used instead.
6.2 Total number of working cycles of the crane
In the same task, the crane's work cycle is a series of actions from the preparation of lifting a load to the start of lifting the next load. The task r can be characterised by a given combination of crane configurations and a defined sequence of movements.
When the crane is used for regular operations (e.g. grab unloading), the total number of working cycles can be obtained from the number of working hours and the number of working cycles per hour. In other operational situations, the number of cycles is not easily determined and needs to be estimated empirically, e.g. for mobile cranes used for different operational tasks. The total number of duty cycles C is the number of all duty cycles of the crane during the design life cycle.
The total number of cycles in the design life of a crane can be divided into a number of cycles corresponding to typical tasks.
The total number of working cycles of a crane is related to the frequency of use (e.g. daily) and the life expectancy (years). The total number of working cycles of a crane.
7 Classification of crane components and mechanisms
7.1 General rules
The classification of typical components can be applied to series hoisting mechanisms, large and small crane running mechanisms or boom luffing mechanisms. The classification of individual components of the same crane may vary.
The operational task of the component is determined by the following parameters:
a) The total number of working cycles of the component during its design life;
b) the relative frequency of lifting different loads (load spectrum, load state);
c) the average displacement;
d) the average of the number of accelerations per movement (e.g. positioning).
When using a range of parameters for the working level, the maximum value of the parameters within the specified level shall be used as the basis for design. Intermediate parameter values are permitted, but specific design values should be specified and levels should not be used instead.
7.2 The total number of working cycles of parts
The total number of working cycles of the components can be derived from the working cycles of the crane.
Sometimes the number of working cycles of the components is less than the number of working cycles of the crane. Examples include the following:.
a) Pitching of the jib of a ship unloader;
b) Installation/dismantling of mobile cranes or tower cranes;
c) movement of a harbour crane from one working position to another.
Under the above operating conditions, the total number of working cycles during the design life of the component shall be determined as a certain value or proportion of the total number of working cycles of the crane.
The use class of the parts shall be carried out in accordance with the provisions of Table 2.
7.3 Load condition
The load spectrum factor K. is one of the parameters for determining the operational tasks of crane components. The load spectrum coefficient is determined individually for each component and indicates the change in load effect (stress) within the number of cycles of work of the component.
In the case of lifting mechanisms, this represents the change in load during the operation of the mechanism.
For large or small vehicle running mechanisms, the different transport masses are represented, including the effective lifting weight and the dead weight.
The load spectrum factor is used to characterise the load effect of a component to a specific magnitude in relation to the maximum load effect, and the corresponding number of operating cycles.
The load spectrum coefficients and load state levels for components shall be as specified in 6.3 and shall be replaced by K. Q, respectively, K., Qp.
7.4 Working class
According to the use level specified in table 2 and the load state level specified in table 3, the working level of the whole machine specified in table 4 can be obtained. A is replaced by Ac in the table.
See Appendix B for a guide to the conversion of machine working levels.
7.5 Average displacement
The average displacement of crane components can be carried out as specified in 6.5.
7.6 Number of motion accelerations
The expected number of accelerations when the load reaches a predetermined position is one of the parameters for crane components under the specified working conditions. These accelerations are considered in 6.1.4 in GB/T 22437.1-2018, for example.
The average value p of the number of accelerations is divided into four levels as specified in Table 8, see the example in Figure 2.
7.7 Stress history
The stress history is a numerical expression of all stress changes that have a significant effect on fatigue. The wire rope load history or wheel pressure load history is similar to the stress history.
The stress history is expressed by the parameter s. The method of determining this parameter can be given in an appropriate standard, e.g. GB/T 30024 gives the method of determining the stress history parameter for metal structures.
The stress history parameter s can be divided into 12 levels S. For metallic structures, level S7 means that the number of working cycles under full load is the same as the number of working cycles corresponding to the reference point 2X10*, as specified in 6.3 of GB/T 30024- -2020.
For fatigue assessment, it is necessary to derive the stress history at the location under consideration. When only one load spectrum factor is used in the classification process to describe the load being lifted, the relative frequency of the maximum fatigue damage should be derived. This is because for the same number of load spectrum factors, different frequencies of net lifting weight will produce different fatigue effects at a given location.
Appendix A (Informative) Average displacement example
Appendix B (Informative) Guide to the conversion of mechanism working levels
Bibliography
1 Scope
2 Normative references
3 Terminology and definitions
4 Symbols
5 Use of classification
6 Complete crane classification
7 Classification of crane components and mechanisms
Appendix A (Informative) Average displacement example
Appendix B (Informative) Guide to the conversion of mechanism working levels
Bibliography
