To reduce the vibration values of the 800t hoisting mechanism to acceptable standards, local reinforcement of the trolley bottom plate and drum supports is permitted. On the premise that the natural vibration frequencies of the trolley frame,
hoisting mechanism, and related components must not change, the vibration energy of the new 800 t gantry crane drum shall be suppressed. Therefore, this method has been formulated to significantly improve and ensure the machining accuracy,
assembly precision, static balance, and dynamic balance of the new drum (open to discussion and improvement). High-precision machining and assembly, combined with high-accuracy static and
dynamic balancing of large-diameter, long-length drums, is the key to reducing vibration in the hoisting mechanism. Do not assume that herringbone gears can necessarily solve vibration problems. The requirement is that the vibration velocity of
the drum and driving pinion (including bearing housings) of this size and weight must meet the standard (vibration velocity < 7.1 mm/s) at rotational speeds of 23 rpm and below under existing trolley installation conditions.
1. Key Technical Principles
A. Definition of Balance A rotating body is considered balanced when its center of
mass lies on the axis of rotation. However, absolute balance is only an ideal state; static unbalance or dynamic unbalance commonly exists. Static unbalance (Mr) is proportional to the radius of the eccentric mass. Static
balancing is most suitable for low-speed disc-shaped objects but not effective for solving rotational vibration of long shafts. Dynamic unbalance (Mr²) is proportional to the square of the eccentric radius. Dynamic balancing is most suitable for high-speed
discs and long shaft components.
B. Necessity of Dynamic Balancing Static and dynamic balance are independent
concepts and cannot replace each other. Good static balance does not guarantee good dynamic balance. For long drums, eccentric masses in different cross-sections can cause dynamic unbalance along the length direction (“decoupling” effect),
producing opposing force couples and torsional vibration. For cases with previous vibration exceedance, dynamic unbalance detection and elimination are mandatory. Due to the single-piece drum (net weight 29.3 t excluding
bull gear and brake disc), no suitable dynamic balancing machine is available. Determining dynamic unbalance for such a large drum remains a technical challenge.
C. Vibration Energy Vibration power (Mgh × n, SI units) is expressed in watts (W). For
example, 1 kg of dynamic unbalance produces approximately 8.3 W; a force couple produces approximately 16.5 W. Larger dynamic unbalance results in greater
vibration and noise.
D. Material Considerations The softening point of the steel is approximately 440°C.
Annealing can cause the drum to lose roundness under its own weight.
Figure 1
This standard applies to the manufacturing process control of the 800 t gantry crane (three-section ring-welded) hoisting drum.
2. Key Points for Drum Rolling and Forming
2.1 Material Preparation (August 1) Divide and cut three segments of 80 mm thick
Grade 355 steel plate (ultrasonically tested).
Figure 2
2.2 Cylinder Forming Form the cylinder on a large plate rolling machine. Cut off
excess material at longitudinal seams, preheat and pre-bend the plate ends, and roll to target inner diameter accuracy of Ø2070 ±1 mm. The three longitudinal welds shall
be staggered by 120°.
2.3 Groove Preparation and End Plate Welding Perform bevel chamfering, allow
machining allowance for rope groove surface after quenching, and machine inner ends for minimal eccentricity. Weld end plates and shafts (August 28).
Figure 3 Figure 4
2.4 Sectional Alignment and Welding (August 30) Align drum sections on a lathe-rail
jig using 350 t hydraulic jacks for internal positioning and fixing to achieve full-length coaxiality within 0.5 mm. Apply low-deformation submerged arc welding with preheating (100–200°C) and post-weld heat or hydrogen elimination treatment.
Figure 5
2.5 Non-Destructive Testing (September 7)
Perform magnetic particle or penetrant inspection on welds and near-surface areas.
2.6 Rough Machining and Internal Reinforcement Weld drum shafts and webs. Install
internal reinforcing ribs in the three drum sections to control annealing distortion.
Figure 6
Figure 7
Note: Actual inner diameter is approximately 6 mm smaller than Ø2070. Jack-induced
roundness error is 0.5 mm.
3. Overall Annealing Heat Treatment (September 6)
Heat the drum slowly (≤80°C/h) to 580–610°C (max. 620°C), hold for more than 2 hours, then furnace cool to below 300°C followed by air cooling. Use multi-point external supports when placing horizontally in the furnace.
4. Machining and Balancing Procedure
4.1 Preliminary Static Balancing (September 18)
Perform preliminary static balancing before assembly of gears, brake discs, and
pressure plates.
Figure 8
Associated Transmission Components (herringbone gear measures to be confirmed):
Figure 9 Figure 10 Figure 11 Figure 12 Figure 13
4.2–4.3 Rough Machining
Machine shafts and outer cylinder using the mutual datum principle. Record circumferential runout at 8 equal divisions every 500–600 mm along the drum length (see attached Table GW-S-QZ-W243-1) for segmental static balancing reference.
Figure 14
Figure 15 Figure 16
Figure 17
4.4 In-Process Adjustment Ensure full-length radial runout does not exceed 0.05 mm.
Adjust internal balance iron plates (quantity, size, and position) based on flange
measurements.
Figure 18 Figure 19
5. Rope Groove Processing
Machine rope grooves, followed by surface quenching (9 m/h). Verify hardness HB300 ±20 and perform magnetic particle inspection.
6. Final Static Balancing
After assembling all parts, perform overall static balancing on V-type support test stand. First symmetrically balance the wire rope press plates, then conduct overall
static balancing.
7. Dynamic Balancing Verification
Mount the complete drum assembly on the lathe for dynamic balancing test at 23 rpm. Vibration velocity shall not exceed the target value (4 mm/s).
8. Other Components
Perform static balancing on the pinion shaft, bearings, and coupling.
