The working level of a crane is one of its main technical parameters. The size of the working level is determined by two capabilities: one is the frequency of use of the crane, which is called the crane utilization level; the other is the size of the load that the crane bears, which is called the load state of the crane.
1.Utilization Class of the Crane
During its effective lifespan, a crane has a certain total number of work cycles. A work cycle of crane operations begins with the preparation to lift a load and ends with the completion of lifting the next load. The total number of work cycles characterizes the utilization level of the crane and is one of the basic parameters for classifying cranes. The total number of work cycles is the sum of all the work cycles a crane performs during its specified lifespan.
The total number of work cycles is related to the crane's frequency of use. For convenience, the total number of work cycles is divided into 10 utilization classes (U0 to U9) within its possible range, as shown in follow table 1.
| C lass of utilization | Total number of crane working cycles, C |
| U0 | C ≤ 1.6 × 104 |
| U1 | 1.6 × 104 < C ≤ 3.15 × 104 |
| U2 | 3.15 × 104 < C ≤ 6.3 × 104 |
| U3 | 6.3 × 104 < C ≤ 1.25 × 105 |
| U4 | 1.25 × 105 < C ≤ 2.5 × 105 |
| U5 | 2.5 × 105 < C ≤ 5 × 105 |
| U6 | 5 × 105 < C ≤ 1 × 106 |
| U7 | 1 × 106 < C ≤ 2 × 106 |
| U8 | 2 × 106 < C ≤ 4 × 106 |
| U9 | 4 × 106 < C ≤ 8 × 106 |
Table 1 Classes U of total numbers of crane working cycles , C
2.Load State of the Crane
The load state is another fundamental parameter for classifying cranes. It indicates the extent of the load borne by the crane's primary mechanism, the hoisting mechanism. The follow table 2 lists the load states of cranes, each numerically representative of a corresponding nominal state of loading.
| State of loading | Load spectrum factor Kp | Remarks on the use of crane |
| Qp0 | Kp ≤ 0.0313 | Cranes which hoist usually very light loads and the rated load very rarely |
| Qp1 | 0.0313 < Kp ≤ 0.0625 | |
| Qp2 | 0.0625 < Kp ≤ 0.125 | Cranes which hoist the rated load occasionally and , normally, light loads |
| Qp3 | 0.125 < Kp ≤ 0.25 | Cranes which hoist the rated load fairly frequently and , normally, moderate loads |
| Qp4 | 0.25 < Kp ≤ 0.50 | Cranes which hoist the rated load frequently and , normally, heavy loads |
| Qp5 | 0.50 < Kp ≤ 1.00 | Cranes which are regularly loaded close to the rated load |
Table 2 Classes Qp of load spectrum factors , Kp
3.Working Class of the Crane
The working class of a crane, or its classification, is determined by the crane's utilization class (Table 1) and the crane's load state (Table 2). The working class of a crane is denoted by the symbol A and is divided into 8 levels, from A1 to A8. Any level higher than A8 is collectively referred to as A8.
| Classes Qp and load spectrum factor Kp | Classes U and total number of work cycles | ||||||||||
| Class Qp | Design value of load spectrum factor Kp | U0 | U1 | U2 | U3 | U4 | U5 | U6 | U7 | U8 | U9 |
| 1.6×104 | 3.15×104 | 6.3×104 | 1.25×105 | 2.5×105 | 5×105 | 1.0×106 | 2.0×106 | 4.0×106 | 8.0×106 | ||
| Qp0 | 0.0313 | A03 | A02 | A01 | A0 | A1 | A2 | A3 | A4 | A5 | A6 |
| Qp1 | 0.0625 | A02 | A01 | A0 | A1 | A2 | A3 | A4 | A5 | A6 | A7 |
| Qp2 | 0.1250 | A01 | A0 | A1 | A2 | A3 | A4 | A5 | A6 | A7 | A8 |
| Qp3 | 0.2500 | A0 | A1 | A2 | A3 | A4 | A5 | A6 | A7 | A8 | A9 |
| Qp4 | 0.5000 | A1 | A2 | A3 | A4 | A5 | A6 | A7 | A8 | A9 | A10 |
| Qp5 | 1.0000 | A2 | A3 | A4 | A5 | A6 | A7 | A8 | A9 | A10 | A11 |
Table 3 Classes A for group classification
Where the Qp and U classes are not specified and only the A class is given , the design calculations shall be based on the number of full load cycles , Cf, as given in the table 4.
| A- class | Design number of full load cycles , i .e . Kp = 1 Cf |
| A03 | 500 |
| A02 | 1 000 |
| A01 | 2 000 |
| A0 | 4 000 |
| A1 | 8 000 |
| A2 | 16 000 |
| A3 | 31 500 |
| A4 | 63 000 |
| A5 | 125 000 |
| A6 | 250 000 |
| A7 | 500 000 |
| A8 | 1 000 000 |
| A9 | 2 000 000 |
| A10 | 4 000 000 |
| A11 | 8 000 000 |
Table 4 Design basis by classes
