Selection of ISO Standard for Crane Working Class

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

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

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

Where the Q_p 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 , C_f, 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