How Significant and Effective is the Torque of the Dredger Pump?

1. The Meaning of Torque in Dredger Pump and Supporting Power

Torque is a unique moment in physics that induces rotation in an object. In the context of a sand dredger pump, engine torque refers to the torque output from the crankshaft of the power equipment. With fixed power, engine torque is inversely proportional to the speed of the power equipment—higher speeds result in lower torque, and vice versa. This relationship reflects the load capacity of the power equipment within a certain range. External torque is referred to as torsional moment or external moment of a couple, while internal torque is known as internal torque or simply torque.

Torque is typically measured in Newton-meters (Nm), although it can also be expressed in units such as kg·m and lb-ft. For instance, since $F=mg$, where 𝑔=9.8 m/s2g=9.8m/s2, the force of 1 kg is equivalent to 9.8 N. Therefore, 1 kg·m equals 9.8 N·m. Similarly, lb-ft is a torque unit where 1 lb is approximately 45536 kg and 1 ft is equal to 0.3048 m, making 1 lb-ft approximately 0.113826 kg·m. Informally, torque is often referred to as torsion in everyday language.

To illustrate, consider a person in motion: power can be likened to the body’s endurance, speed to the frequency of motion, and torque to the body’s explosive power. When using a shovel to dig sand, the shovel represents torque, the digging frequency represents speed, and the person’s physical strength represents power. With a fixed level of physical strength (power), using a larger shovel (high torque) for excavation results in a lower frequency (low speed), whereas a smaller shovel (low torque) allows for a higher frequency (high speed). Ultimately, the amount of sand dug depends on the individual’s physical strength (power).

In sand pumping processes, when the matched power remains constant, large particle gravel sand dredger pumps and marine sand suction pumps operate at low speeds, resulting in higher torque. Conversely, small sand pumps and submersible sand pumps operate at high speeds, leading to lower torque. However, regardless of the type of sand pump, a higher torque generally yields better results.

2. Torque Calculation Formula for Supporting Power of Dredger Pump

The formula for calculating the torque of a dredger pump power is 𝑇=9550×𝑃𝑁T=N9550×P​.

Where:

• $T$ is the torque,
• $9550$ is the conversion coefficient,
• $P$ is the rated power of the dredger pump, and
• $N$ is the rated speed of the power equipment.

This formula demonstrates that torque and power are directly proportional and inversely proportional to speed.

For example, let’s consider the marine diesel engine Weichai 6170ZC600-4. With a rated power of $450\text{kW}$ and a speed of $1500\text{rpm}$ (refer to Figure 1 for parameters), the calculated torque is 𝑇=9550×4501500=2865 N⋅mT=15009550×450​=2865N⋅m, consistent with the curve (refer to Figure 2).

The same calculation formula applies to motor torque. Taking the YX3-90S-6 motor as an example, with a rated power of $0.75\text{kW}$ and a rated speed of $910\text{rpm}$, the applied formula yields 𝑇=9550×0.75910=7.87 N⋅mT=9109550×0.75​=7.87N⋅m, in line with the parameter list (refer to Figure 3). For a motor with the same power, the torque decreases with higher rotation speed. For instance, considering the YX3-801-2 motor with a rated power of $0.75\text{kW}$ but a rated rotation speed of $2840\text{rpm}$, the calculated torque is 𝑇=9550×0.752840=2.52 N⋅mT=28409550×0.75​=2.52N⋅m, consistent with the parameter list (refer to Figure 4). This indicates that at $910\text{rpm}$, the torque is significantly greater than at $2840\text{rpm}$.

3. Torque Application in Dredger Pumps Design

The torque of the dredger pump directly impacts its maximum pumping capacity and overload capacity under extreme conditions. A well-designed torque ensures stable operation and long service life of the sand dredger pump unit in harsh working conditions. When designing the sand pump for sand extraction, engineers consider the torque’s practical utility during operation, designing large torque river sand dredger pumps to meet various working conditions. To achieve consistent flow head conditions, design engineers increase the pump impeller’s outer diameter and width while reducing the rotation speed. This not only enhances the torque effect but also reduces wear and tear on overflow parts. Low rotational speed and high torque enable sustained and efficient sand extraction over time. Additionally, shaft and bearing designs for dredger pumps are strengthened to ensure stable operation under high torque conditions.

The Application of Torque in Assembly

Mechanical components require specific screw torque, including tightening torque and slack torque. Tightening torque should not exceed the breaking torque, typically set at 70%-80% to ensure proper fastening without slipping. Slack torque is crucial for screw longevity post-tightening and varies based on screw material and size, generally lower than tightening torque. Adhering to standardized operations prevents uneven pressure or loose screws in assembly.

Torque Application in Dredger Pump and Related Power Equipment

Diesel engines feature large torque and explosive force, ideal for extreme conditions with low-speed operation, minimal wear, and extended lifespan. Common low to medium-speed engines include brands like WEICHAI, Zichai, and Yuchai. Adding a gearbox reduces engine output speed while increasing torque, with negligible power loss. Motors exhibit similar torque characteristics, with low-speed machines recommended, such as 10 poles > 8 poles > 6 poles > 4 poles > 2 poles. Greater torque in the dredger pump signifies enhanced power, enabling operation under challenging conditions with large particles or high concentration.

4. Matching the Diesel Engine and Gearbox for Maximum Torque

1. Calculate Shaft Power: Begin by calculating the shaft power of the dredger pump based on the specific gravity of the medium and applicable working conditions. Traditionally, shaft power is multiplied by a factor of 1.2-1.3 to determine the required power. Similarly, the diesel engine power is also multiplied by a factor of 1.2-1.3 for compatibility.
2. Match Engine Speed: Match the speed of the diesel engine to that of the dredger pump. For domestic brand engines, 80% of the engine’s rotation speed is considered the economy speed, while imported brand engines adhere to their rated speed. Ensure proper matching to prevent issues in operation.
3. Consider Gearbox or Pulley: If the dredger pump does not match the required gearbox or pulley, adjust the power speed accordingly. Ensure that the rated torque of the diesel engine or motor exceeds that of the dredger pump to maintain optimal performance.
4. Account for Pulley Belt: When using a pulley belt, anticipate significant torque loss and adjust horsepower accordingly to compensate for the loss.
5. Verify Rotation Direction: Pay close attention to the rotation direction of both the dredger pump and the diesel engine. Select gearboxes with hydraulic control for forward and reverse motion, ensuring minimal power loss from the diesel engine and preserving gearbox longevity.

By meticulously matching the diesel engine and gearbox to the dredger pump’s requirements, you ensure optimal torque delivery and efficient operation under varying conditions.

5. Application of Torque Design in Dredger Pumps

Tai’an Ocean Pump Co., Ltd. prioritizes meticulous attention to every stage of the dredger pump production process. When designing dredger pump impellers and bearings, a focus is placed on achieving high torque capabilities to ensure continuous and stable transportation of sand and mud over long distances, even in high-concentration and high-flow conditions. Bolts are meticulously installed with precise torque specifications to guarantee uniform stress distribution, preventing slippage during continuous operation. For powering the dredger pump, cost-effective power equipment from renowned international and domestic brands is selected to maximize torque output. Deep collaborations with auxiliary equipment manufacturers, such as gearbox factories, ensure the selection of low-speed ratio gearboxes suitable for sand dredger pump applications, thereby aligning power and torque curves with the requirements of the diesel engine and sand mining pump.

Illustrative Case Study: A domestic customer from Jiangxi province opted for the 450GN-40 marine sand dredger pump for offshore sand pumping operations. Through field surveys conducted by our technical engineers, it was determined that the local sand conditions required a high-torque solution to mitigate pipe plugging risks. The 450GN-40 marine sand dredger pump boasts a flow capacity of 3100m3/h, a head of 40m, and a rotation speed of 550rpm, resulting in a calculated shaft power of 441.6kW. Utilizing torque calculations, the rated torque was determined to be T=9550441.6/550=7667.8Nm. Engineers selected a Jichai 12V190 type 1200 horsepower/1350rpm engine, paired with a Hangzhou gearbox 1260 type with a reduction ratio of 2:1. Through torque calculations, the resulting torque was T=9550900/675=12733.3Nm, exceeding the pump’s torque requirements. During actual sand pumping operations, with sand concentrations reaching 1,000 cubic meters per hour, the dredger pump torque peaked at 11,000 N*m. Thanks to the ample torque margin provided by the diesel engine, the dredger pump operated smoothly, resulting in a highly satisfied user experience.

6. Conclusion

Tai’an Ocean Pump Co., Ltd. is a certified New Hi-tech Enterprise recognized by the Government, serving as a leading manufacturer, supplier, and exporter of sand pumps and sand dredgers since 1996. With a team of over 30 technical experts and a 15,000 square meter factory, we offer a comprehensive range of sand pumps, slurry pumps, sand dredgers, and related parts to meet diverse pumping requirements. Our commitment to product innovation, quality assurance, and customer satisfaction is unwavering, ensuring the delivery of finest quality products and comprehensive solutions to customers worldwide.

For inquiries related to program design and equipment issues concerning dredging and pumping, please feel free to contact us anytime.