The QTZ31.5 tower crane is an upper-rotating, self-erecting tower crane with a horizontal jib, developed by Hongda Group based on over two decades of tower crane design and manufacturing expertise. It complies with standards including GB/T50311 “Tower Cranes” and GB5144 “Safety Regulations for Tower Cranes.” With a rated lifting moment of 31.5 t·m and a maximum lifting capacity of 3 tons, it is available in models such as TC4264, TC4075, and TC3883. The hoisting mechanism employs three-speed motor speed regulation technology, achieving optimal hoisting speeds and precise load positioning. The slewing mechanism utilizes variable frequency stepless speed regulation technology for smooth operation, while the traction mechanism features dual-speed motor drive for accurate positioning. The electrical control system incorporates imported components, with comprehensive and reliable safety protection devices—either mechanical or mechatronic. Foundations are available in fixed or counterweight configurations. This crane is widely used in various mid-to-high-rise construction projects.

QTZ31.5 Technical Specifications

Model	QZT31.5 (4264)	(4075)	(3883)
magnitude(M)	42	40	38
Free height(M)	27	27	27
Maximum height(M)	100	100	100
Maximum Lifting Capacity(T)	3	3	3
Wall-mounted bracket (rail)	5	5	5
Primary limb material	125×125×10 (angle steel)	125×125×10 (angle steel)	125×125×10 (angle steel)
Standard Section Dimensions	1.5×1.5 ×2.4	1.5×1.5 ×2.4	1.5×1.5 ×2.4
Lifting speed(a=2)m/min	53.7/26.6/5.2	53.7/26.6/5.2	53.7/26.6/5.2
Rotation speedr/min	0.6	0.6	0.6
Speed of changem/min	20/40	20/40	20/40
Base configuration	1. Crossbeam diagonal brace with weight-bearing mechanism 2. Crossbeam diagonal brace without counterweight	1. Crossbeam diagonal brace with weight-bearing mechanism 2. Crossbeam diagonal brace without counterweight	1. Crossbeam diagonal brace with weight-bearing mechanism 2. Crossbeam diagonal brace without counterweight

【Hoisting Mechanism】:

The hoisting mechanism (1334 kg) employs a YZD225M1-4/8/32 wound-rotor motor. The motor drives the gear reducer via a splined coupling, which in turn drives the drum. This configuration provides three distinct hoisting speeds, ensuring smooth start/stop operation with minimal impact. Speeds reach 53.7 m/min, 26.6 m/min, and 5.2 m/min.

A normally closed hydraulic push-rod brake is installed at the input shaft end of the reduction gearbox. A height limiter is mounted on one side of the drum, adjustable to the required height. It offers reliable control, simple operation, and easy maintenance. Configuration details are as follows:

Project	Model
Electric motor	YZTD200L2-4/8/32
Total Transmission Ratio of the Reducer	16.46
brake	YWZ3-315/45-10
steel wire rope	6×19W-13-1670-I-Light-Right-Handed  GB/T8918-1996

【Rotary Mechanism】:

The slewing mechanism is the transmission device that provides power for the upper slewing of the tower crane. This device consists of a torque motor, planetary reducer, pinion gear, slewing limiter, and other components. This tower crane employs one such device, positioned on one side of the slewing bearing and mounted on the upper support. Its pinion gear meshes with the large ring gear of the slewing bearing.

A normally closed disc brake is located at the rear of the motor; it can be used for tower crane jacking operations and for braking and positioning the boom during fixed-point operations.

The slewing limiter is designed to restrict the tower crane's rotation to 540° in a single direction, preventing cable breakage. Featuring a compact structure and aesthetically pleasing design, it reduces rotational impact. Configuration details are as follows:

Project	Model
Rotation Parameters	Module M = 10, Number of teeth Z = 10, Modulus shift coefficient X = +0.5
Electric motor	YZR132M2-6+YLEF112l-6-55N.M
Speed reducer	XX4-100147C-001
Hydraulic Coupling	YOX-280A
Slewing Bearing	Single-row ball slewing bearing QWA1120.32

【Variable-Angle Mechanism】:

The hoist mechanism (180 kg) employs a dual-speed motor YEZS100L-4/8. This motor drives the drum via a planetary gear reducer, enabling the load trolley to traverse the boom at three speeds—40 m/min, 20 m/min—through wire rope transmission.

The motor tail features a disc brake that provides delayed braking when the trolley motor is de-energized.

The amplitude limiter prevents misoperation by stopping the trolley before it contacts the buffer at the base of the boom.

The multi-pole motor connects to a planetary gearset, driving the boom drum's movement and achieving variable boom speeds through pole switching. The gear reducer is housed within the drum, offering a compact structure and aesthetically pleasing appearance. Configuration details are as follows:

Project	Model
Electric motor	YDEJ100-4/8
Speed reducer	The gear ratio of the first-stage worm gear drive is 37.
steel wire rope	6×19-6.2-155-Ⅰ-Light-Right-Handed  GB/T8918-1996

【Standard Tower Section】:

Overall standard section dimensions: 1500×1500×2400 Main limb material: L125×10/Q235B

 Tower sections are available in two specifications based on design strength: reinforced sections and standard sections. Reinforced sections are connected using 8-M24 special high-strength bolts, while standard sections are connected using 8-M24 special high-strength bolts. A resting platform is provided every three sections, and standard sections of the same specification are interchangeable.

【Rotating Tower Body】:

The lower end of the rotating tower body is connected to the upper support via a pin shaft, while its upper section is pinned to the tower top. The front and rear lug plates are respectively connected to the counterweight arm and the lifting arm. A load limiter is installed on the upper section.

【Boom】:

, The boom cross-section is triangular, with the upper chord made of seamless steel pipe and the lower chord formed by closed-end channel steel. The boom consists of seven sections, each equipped with a tie rod lifting point on the upper chord of the second and sixth sections. Sections are connected via pins. The first section houses the trolley traction mechanism, while the boom tip features a wire rope anti-twist device.

【Balancing Arm】:

 The total length of the counterweight boom is 10.175 meters. Using pins, the counterweight boom and its tie rods are integrated with the rotating tower body and tower top. Guardrails and walkways are installed on both sides of the counterweight boom.

【Upper and Lower Supports】:

 The upper support is mounted on the slewing bearing and connected to its inner ring. The lower support is a box-shaped support for the non-rotating section of the crane. Its upper surface is fitted with the outer gear ring of the slewing bearing. The lower support is bolted to the outer ring of the slewing bearing, enabling relative rotational movement between the upper and lower supports via the slewing mechanism. The upper bearing connects to the rotating tower body above, while the lower bearing connects to the standard tower sections below.

【Rotary Limit Switch】:

【Tower Top】:

The top of the tower is a sloping cone, its upper end connected to the lifting arm and counterweight arm via tie rods to maintain the horizontal alignment of both arms, while its lower end is secured with four pins to

 The rotating tower body connection features a work platform and pulley system at the top of the tower to facilitate the installation of the boom tie rods and counterweight boom tie rods.

【Driver's Cab】:

 The cab serves as the operator's workstation for controlling the tower crane, fixed to the right side of the rotating tower body. The indicator lights and control handles of the integrated control console are positioned on both sides of the operator's seat, offering convenient operation and a wide field of view.

 The cab electrical control box is located at the rear of the cab, housing the main circuit breaker, lighting circuit breakers, auxiliary circuit breakers, and other devices.

【Attachment Frame】:

 Anchoring frame is an anchoring device attached to the side of a building to enhance stability and maintain lifting capacity when a tower crane has reached its free height and requires further upward jacking. It consists of a ring beam and four struts. During installation, the ring beam is tightly fitted to the tower body. Both ends of the struts are hinged to the ring beam and to embedded supports in the building structure. By adjusting the tensioning bolts, the four struts are tightened to securely connect the tower crane to the building structure perpendicular to the horizontal plane, ensuring the crane's axis remains vertical to the ground.

【Load Limiters】:

【Electrical Control System and Safety Devices】:

 The QTZ31.5 electric control system employs a state-of-the-art PLC + variable frequency drive (VFD) control approach, significantly enhancing system reliability, operability, stability, and machine efficiency. The incorporation of a VFD enables stepless speed regulation for the slewing mechanism, substantially improving overall equipment stability. This results in markedly enhanced positioning performance and higher operational efficiency.

 The electrical control components of this system are globally sourced from leading manufacturers such as OMRON, Yaskawa, Schneider Electric (TE), and Taiwan's Mingwei. This global procurement strategy significantly reduces the failure rate of the electrical control system, providing effective assurance for enhancing users' production efficiency. Safety devices are comprehensive and reliable, including: - Lifting height limiters - Slewing limiters - Multi-functional limiters for lifting moment, load capacity, and trolley span Additionally, electrical safety devices such as anemometers and obstruction lights are incorporated, alongside mechanical safety features including trolley shaft break protection and traction rope break anti-runaway mechanisms.