How to Make sand dredge pumps More Wear-Resistant?

The wear resistance of sand dredge pumpshas always been an industry-wide challenge. How to improve the wear resistance of sand pump, reduce the frequency of parts replacement, cut maintenance costs, and thereby achieve lower costs and higher efficiency is a consistent expectation of customers, as well as a goal pursued by sand pump manufacturers. The technical team of Ocean Pump Industry has been continuously thinking and exploring this issue. After years of R&D and practice, we have developed a comprehensive solution for enhancing the wear resistance of sand pumps. Below, we elaborate in detail from aspects including product design, material selection, mold manufacturing, production process control, installation methods, and scientific application.

I. Scientific Fluid Design to Improve Wear Resistance

A sand pump is a type of centrifugal pump that extracts and transports materials through the flow of liquid slurry. During sand pumping, the mud containing a large amount of sand will impact and wear the pump casing, guard plate, and impeller. Obviously, with the same flow rate, the slower the flow velocity, the lighter the wear on the pump body, and the longer the service life of the sand pump. Therefore, under the condition of constant flow rate, a larger impeller diameter results in a lower rotation speed, fewer sand particles per unit area, and lighter wear on the impeller. However, a larger impeller is not always better. A too-large impeller will increase the pump volume and weight, leading to higher costs and inconvenience in installation and use.

Ocean brand sand dredge pumpsfrom Tai'an are designed based on the solid-liquid two-phase flow theory. Key parameters such as flow velocity and impeller diameter ratio are fully calculated, and reasonable proportions are determined through 3D modeling. Depending on the pump type, the designed rated rotation speed ranges from 400 rpm to 1000 rpm, and the flow rate ranges from 20 m³ to 7000 m³, meeting the needs of most working conditions.

Meanwhile, when matching power, priority is given to low-speed and high-torque power sources to give full play to the performance of both the sand pump and the power unit, achieving an optimal combination.

II. Selecting Wear-Resistant High-Chromium Alloy Materials to Enhance Wear Resistance

Common materials used for sand dredge pumpsinclude cast iron, cast steel, and wear-resistant alloys. The analysis of each material is as follows:

Cast Iron

Cast iron is a general term for alloys composed of iron, carbon, and silicon. The cast iron used in sand dredge pumpsincludes the following types:

• 1.Gray Cast Iron: With a carbon content of 2.7% to 4.0%, carbon mainly exists in the form of flake graphite, and its fracture is gray (hence the abbreviation "gray iron"). It has a low melting point (1145-1250¡ãC), small shrinkage during solidification, compressive strength and hardness close to carbon steel, and good shock absorption. Due to the presence of flake graphite, it has good wear resistance, as well as excellent castability and machinability. It is used to manufacture structural parts such as machine tool beds, cylinders, and boxes. Its grade is represented by "HT" followed by two groups of numbers. For example, HT20-40: the first group of numbers indicates the minimum tensile strength, and the second group indicates the minimum bending strength.
  Gray cast iron is the most widely used material for sand dredge pumpsdue to its simple casting and processing technology and low investment and production costs. Currently, most sand pump manufacturers still use this material in large quantities.
  
• 2.Ductile Iron: Obtained by spheroidizing treatment of gray cast iron melt, the precipitated graphite is spherical (hence the abbreviation "nodular iron"). All or most of the carbon exists in the form of free spherical graphite, and its fracture is silver-gray. It has higher strength, better toughness, and ductility than ordinary gray cast iron. Its grade is represented by "QT" followed by two groups of numbers. For example, QT45-5: the first group of numbers indicates the minimum tensile strength, and the second group indicates the minimum elongation.
  Ductile iron is widely used in flow passage components such as pump casings, impellers, and guard plates of sand pumps, making full use of its high strength and toughness to improve wear resistance.
• 3.High-Chromium Alloy Cast Iron: Obtained by adding appropriate alloying elements (such as silicon, manganese, phosphorus, nickel, chromium, molybdenum, copper, aluminum, boron, vanadium, tin, etc.) to ordinary cast iron. Alloying elements change the matrix structure of cast iron, thereby endowing it with properties such as heat resistance, wear resistance, corrosion resistance, low-temperature resistance, or non-magnetism.

Tai'an Ocean Pump Industry has introduced advanced foreign casting technologies and experience. After a series of tests under various working conditions, we finally selected the proportional combination of alloying elements such as chromium, nickel, molybdenum, and copper. Through multiple heat treatment processes, the material achieves both high hardness and good toughness, greatly improving wear resistance. This material is called high-chromium alloy due to its high chromium content.

After adopting high-chromium alloy materials, the overall service life of Ocean sand dredge pumpshas been significantly improved. Statistics from thousands of customers in projects such as the Yellow River sediment regulation, Caofeidian reclamation, and Binhai New Area land creation show that some parts need to be replaced after pumping about 500,000 cubic meters of sand, and in some working conditions, parts replacement can be extended to about 1,000,000 cubic meters. In long-term use, customers' parts costs have been reduced by 50%-60%, and the long parts replacement cycle reduces downtime, further lowering labor costs, ensuring construction continuity, and improving economic benefits.

III. Strict Control of Mold Precision and Optimization of Casting Process to Improve the Quality of Flow Passage Components Such as Pump Bodies and Impellers

A sand pump works by the centrifugal motion of water caused by the rotation of the impeller. When the sand pump starts, the pump shaft drives the impeller and water to rotate at high speed; the water undergoes centrifugal motion, is thrown to the outer edge of the impeller, and flows into the pressure pipeline of the water pump through the flow channel of the volute pump casing. The impeller is the component that converts energy, and its geometric shape and size have a decisive impact on the performance of the centrifugal pump, which is determined through hydraulic calculation.

The impellers of sand dredge pumpsgenerally have three, four, or five blades. Previously, due to the limitations of mold processing technology, the blades were geometric arcs polished manually, resulting in inconsistent or significantly different arc degrees for each blade. Moreover, each mold box closing and pressing required installing blade molds one by one, further increasing errors. This led to inconsistent geometric accuracy and smoothness of the formed impellers, which easily caused turbulent flow during the flow of sand-containing slurry, accelerating the wear of the impeller.

Tai'an Ocean Pump Industry uses a machining center to reprocess and manufacture impeller models, replacing the material with aluminum. The impeller blades manufactured by the machining center have small geometric accuracy errors, and the aluminum model has little deformation and a longer service life. In addition, a dynamic balance test is conducted during impeller processing to ensure the balanced operation of the impeller and avoid wear caused by impeller jitter and vibration.

IV. Strict Control of the Production and Manufacturing Process and Strengthening Quality Inspection to Attract Customers with Quality

Tai'an Ocean Pump Industry strictly controls the quality of each sand pump. From design drawings to parts processing, high-quality brand products are selected for standard parts such as bearings, bolts, and oil seals, and quality records are kept carefully. Quality is the bottom line of Tai'an Ocean Pump Industry; any parts or assembly problems that violate quality requirements will be rejected. sand dredge pumpswith quality problems are strictly prohibited from being delivered to customers to avoid additional losses to customers.

For each model of sand pump produced by Tai'an Ocean Pump Industry, the accuracy issues such as dimensional errors are strictly controlled throughout the design, manufacturing, and assembly processes. After assembly, the sand pump must be tested on the performance test platform to check whether its flow rate, head, and sealing performance meet the design requirements. The specific testing steps are as follows:

• 1.Install the sand pump at the designated position on the test bench and connect the motor or gearbox according to the test requirements;
• 2.Select the water inlet and outlet pipes according to the diameter of the sand pump;
• 3.Close the outlet valve and start the vacuum pump to extract air from the pipeline and the pump;
• 4.Open the water inlet valve and the air release valve to check if there is residual air in the pipeline. If there is still air, continue to extract it with the vacuum pump, and close the water inlet valve after completion;
• 5.Start the sand pump, check whether the pump shaft rotates, whethe the rotation direction meets the requirements, and whether the sand pump has sealing problems such as water leakage or spraying;
• 6.Close the inlet and outlet valves to check the pressure-resistant sealing performance of the sand pump;
• 7.Open the regulating valve to the maximum and divide the flow points within the maximum flow range for experimental point arrangement;
• 8.Record the data of each instrument after the operation of each flow point is stable;
• 9.After completing the point test, shut down the sand pump and valves in sequence;
• 10.Dismantle the sand pump and restore the test platform to its original state.

Based on the experimentally measured parameters such as flow rate, head, shaft power, and efficiency, a performance parameter table is filled out. After verifying the parameter table, a sand pump performance curve is drawn. The test performance curve is compared with the design performance curve to analyze the performance difference and determine whether it meets the design requirements, thereby judging whether the sand pump needs to have its design dimensions modified.

Each sand pump of Tai'an Ocean Pump Industry has a corresponding delivery record, which records detailed information about the pump, including the actual flow rate, head, shaft power, and other data during factory inspection, and whether it meets the customer's working condition requirements, ensuring traceability in the future.

V. Selecting the Optimal Installation Method to Avoid Damage Caused by Cavitation

Cavitation, a physical term, refers to a phenomenon where the metal surface is eroded due to high-pressure and high-frequency impact, and the electrochemical corrosion of the metal surface by a small amount of active gases such as oxygen entrained in bubbles, resulting in a spongy or fish-scale-like damage on the impeller surface. According to the working principle of sand dredge pumps(centrifugal pumps), a low-pressure area is formed near the center of the sand pump impeller. This pressure is related to the suction height of the pump. When the pressure above the liquid storage tank is constant, the lower the pressure near the pump suction port, the higher the suction height. However, the low pressure at the suction port is limited. This is because when the minimum pressure near the blade inlet is equal to or lower than the saturated vapor pressure of the liquid at the conveying temperature, the liquid will vaporize and generate bubbles at this point, which flow with the liquid from the low-pressure area to the high-pressure area. The bubbles condense or burst rapidly under high pressure; at this time, the surrounding liquid rushes to the space originally occupied by the bubbles at an extremely high speed, generating a very large impact pressure at the impact point with an extremely high frequency. The impact causes the pump body to vibrate and produce noise, and the local part of the impeller is subject to repeated action of huge impact force, resulting in material surface fatigue, which develops from initial pitting to cracks, damaging the impeller or pump casing. This phenomenon is called cavitation.

When cavitation occurs, a large number of bubbles occupy part of the space of the liquid flow channel, leading to a decrease in the pump's flow rate, head, and efficiency. In severe cases, the sand pump cannot work normally.

During communication with customers, sales engineers of Tai'an Ocean Pump Industry will fully understand the customer's working conditions. It is usually recommended that customers order or make a floating platform for sand pump installation, so that the center of the sand pump is lower than the water level of the sand pumping river channel, allowing water to pour into the sand pump. This not only eliminates the step of priming water when starting the sand pump but also avoids cavitation, gives full play to the pumping efficiency of the sand pump, and improves its wear resistance.

VI. Selecting the Optimal Sand Pump Model and Supporting Facilities Based on Customer's On-Site Working Condition Requirements

Sales engineers of Tai'an Ocean Pump Industry will record the customer's working conditions during communication, mainly focusing on the following six issues that need to be investigated:

• 1.Application environment of the sand pump: It mainly includes seven categories: river dredging, riverbed sand pumping, mining, tailings treatment, bridge piling, sea reclamation, and sand blowing for road construction. The construction plan and equipment selection are determined according to the construction scenario.
• 2.Basic conditions of the pumped medium: Solid types, including soil, sand, pebbles, garbage, industrial materials, etc., as well as solid particle size, looseness, temperature, and pH value.
• 3.Production requirements of the sand pump: output requirements, mainly based on the flow rate of the sand pump. The approximate sand output can be estimated according to the concentration and proportion of the pumped medium, which is directly related to the benefits that the sand pump can achieve.
• 4.Vertical height difference and horizontal conveying distance of the sand pump: Due to different design principles, there are sand pump models with low head and large flow rate, as well as those with high head and small flow rate, which can be selected according to actual construction requirements. The head is very important for the selection of sand dredge pumpsand directly affects the use effect.
• 5.Size of the sand pump's suction and discharge pipelines: Whether there are existing pipelines laid at the construction site, or calculate the pipeline head pressure according to the flow rate and head to match the appropriate sand pump and pipeline.
• 6.Drive mode of the sand pump: If there is a sufficiently large transformer on-site, priority is given to motor-driven sand pumps. The supporting drive is mainly variable frequency start, and can also be adjusted to soft start, autotransformer step-down start, star-delta start, etc., according to the budget. If there is no transformer, diesel engine drive or diesel generator set drive is recommended. Diesel engine drive has the outstanding advantages of large torque and large instantaneous power. In some cases with relatively high concentration, hydraulic drive is selected for the sand pump, which has relatively low failure rate and short conveying distance, but its advantage in pumping high-concentration materials is incomparable.

VII. Providing Customers with Usage and Maintenance Guidance to Avoid Damage Caused by Improper Use

To ensure the safe operation and long service life of the sand pump, daily maintenance must be paid attention to. The following aspects should be noted for maintenance:

• 1.After fixing the sand pump at the work site, first check whether the main shaft of the prime mover is coaxial with the water pump shaft. If not, loosen the anchor bolts of the sand pump and re-adjust accurately. After confirmation, re-tighten the bolts and fix firmly. Check it regularly after a certain period of use.
• 2.The inlet and outlet pipelines of the sand pump should have load-bearing supports to avoid the pipeline gravity being applied to the pump body. Pipeline installation should extend outward from the pump inlet and outlet flanges, and support and positioning should be done immediately. The inlet and outlet of the pump should be equipped with flexible connections as much as possible to reduce vibration.
• 3.Before starting, check whether the inlet and outlet pipes are blocked; check whether the lubricating oil has been added; check whether the packing is fully filled.
• 4.A high-pressure clean water pump should be equipped when the sand pump is working to deliver clean water with higher pressure than the sand pump to the leak-proof packing for protection. Do not turn off the flushing water when the pump is working, otherwise, the packing wear will accelerate.
• 5.The uniform gap between the impeller and the guard plate has a great impact on the service life of the sand pump. An unreasonable gap will cause vibration and noise of varying degrees during pump operation. When replacing the impeller, attention should be paid to the gap between the impeller and the guard plate. The gap between the impeller and the front guard plate should be as small as possible. When adjusting the gap, first loosen the large screws on the bearing body gland, then adjust through the adjusting bolts under the bracket body (some pump models adjust the adjusting bolts on the bearing gland) to move the bearing body and the impeller forward and backward as a whole. When disassembling the impeller, remove the disassembly ring to easily remove the impeller.
• 6.The sand pump should be regularly checked and filled with lubricating oil.
• 7.If abnormal vibration, noise, or excessively high bearing temperature occurs during the operation of the sand pump, stop the machine immediately for inspection.

This article details the work done by Ocean Pump Industry to improve the wear resistance of sand pumps. Innovation is endless. We will continue to understand customers' usage conditions and feedback, strengthen exchanges with domestic peers, learn world-leading technologies, make Ocean brand sand dredge pumpssynonymous with "wear-resistant pumps", and create a world-class sand pump brand. If you have any questions about sand pumps, please contact us. Our professional sales engineers and technical team will select suitable products and provide high-quality services according to your specific needs. For details, please send INUQIRY

DORIS CHEN

WHATSAPP :+86 18562293319

EMAIL : oc@tsbeng.com

TAIAN OCEAN PUMP CO.,LTD