In river sand mining, quarry operations, harbor dredging, and reservoir desilting projects, the sand concentration discharged by a sand dredge pump directly affects productivity and operating costs. Many operators encounter a common issue: the pump delivers a large volume of water, but the sand content is much lower than expected, resulting in reduced production efficiency.
So, what causes low sand concentration in a sand dredge pump, and how can it be solved? Based on years of field experience, Taian OCEAN Pump provides a detailed analysis below.
What Is Sand Concentration?
Sand concentration refers to the percentage of solid particles (sand, gravel, slurry, or sediment) contained in the pumped mixture.
For example:
Total mixture flow rate: 1,000 m³/h
Actual sand volume: 300 m³/h
The sand concentration is approximately 30%.
Generally, higher sand concentration means:
* Higher production output
* Better equipment utilization
* Lower operating costs
* Improved project efficiency
Typical concentration ranges:
| Application | Sand Concentration |
| —————————– | —————— |
| River Sand Dredging | 15% – 30% |
| Sand Mining Operations | 20% – 40% |
| Dredging Projects | 10% – 25% |
| High-Density Slurry Transport | 30% – 60% |
If the concentration remains below the design value for a long period, troubleshooting is necessary.
1. Insufficient Material Supply
This is one of the most common reasons for low sand concentration.
Many operators assume there is a problem with the pump itself, while the actual issue is that there is not enough sand around the suction inlet.
When the sand layer is thin, scattered, or heavily compacted, the pump draws mostly water instead of sand, resulting in a low-density slurry.
Common Symptoms
* Large discharge flow rate
* Clear water at the outlet
* Lower-than-normal motor current
* Thin or compacted sand layer
* Deep excavation pit around the suction area
Solutions
Install a High-Pressure Water Jet System
A high-head, high-pressure water pump can be used with water jet nozzles to loosen and suspend sand deposits.
Benefits include:
* Breaking up compacted sand layers
* Suspending settled sand particles
* Increasing sand concentration around the suction inlet
* Improving dredging efficiency
This is a common solution used in jet suction dredgers and sand mining vessels.
Adjust the Suction Position
Move the suction inlet regularly to areas with higher sand deposits.
Avoid operating in the same location for extended periods after the sand has already been removed.
Add an Agitation Device
For compacted sediment layers, consider using:
* Hydraulic agitators
* Mechanical agitators
* Cutter heads
These devices loosen the material before pumping.
2. Suction Inlet Blockage
Large gravel, cobblestones, shells, wood debris, and other foreign materials can block the suction inlet.
When blockage occurs:
* Water can still pass through
* Sand cannot enter efficiently
As a result, the discharged slurry contains very little sand.
Common Symptoms
* Reduced flow rate
* Lower sand output
* Increased vibration
* Abnormal pipeline pressure
* Mostly clear water at the discharge outlet
Solutions
Inspect the Suction Strainer
Regularly remove:
* Stones
* Aquatic plants
* Plastic waste
* Wood debris
Keeping the suction inlet clean ensures stable performance.
Increase the Screen Opening Size
If the sand particles are relatively coarse, increasing the mesh size can reduce blockage.
Remove the Screen for Testing
If operating conditions allow, temporarily remove the screen and observe whether the sand concentration improves.
Use an Agitator Sand Pump
Submersible sand pumps equipped with agitators can effectively prevent blockage and improve material intake.
3. Pump Head Is Too Low
This is another frequently overlooked issue.
Many users focus only on flow rate while ignoring the required discharge distance and total dynamic head.
A sand dredge pump must not only suck up the sand but also transport it through the pipeline to the designated location.
If the pump head is insufficient:
* Pipeline velocity decreases
* Sand particles begin to settle
* Pipeline blockage may occur
* Sand concentration drops significantly
Common Symptoms
* Normal performance immediately after startup
* Gradual reduction in sand concentration over time
* Increased pipeline pressure
* Reduced discharge flow
* Failure to achieve the designed transport distance
Solutions
Install a Booster Pump
For long-distance transport systems such as:
* 500 meters
* 1,000 meters
* 2,000 meters or more
A booster pump can maintain sufficient slurry velocity and prevent sedimentation.
Upgrade to a Higher Head Sand Pump
For example:
* Existing pump head: 20–30 meters
* Actual requirement: 50–60 meters
In this case, a higher-head model is required.
Optimize the Pipeline Design
Reduce:
* Excessive bends
* Sudden pipe diameter changes
* Unnecessary pipeline length
This helps minimize friction losses.
Maintain Proper Slurry Velocity
For sand and slurry transportation, a pipeline velocity of approximately 2.5–4 m/s is generally recommended to prevent solids settlement.
: 4. Severe Impeller Wear
After prolonged operation, the impeller, liners, and wear components gradually erode due to the abrasive nature of sand and gravel.
As wear increases:
* Suction capacity decreases
* Pump head drops
* Pump efficiency declines
Ultimately, sand concentration becomes lower and lower.
Inspection Methods
Check for:
* Reduced motor current
* Reduced flow rate
* Lower discharge head
Inspect the impeller and wear parts regularly.
Solutions
Replace worn components such as:
* Impeller
* Pump liners
* Suction liners
* Wear plates
For longer service life, use high chrome alloy materials such as Cr26, Cr28, or Cr30.
: 5. Air Leakage in the Suction Pipeline
Air entering the suction system reduces vacuum pressure and significantly affects the pump’s ability to draw sand.
Common Leakage Locations
* Flange connections
* Rubber joints
* Sealing rings
* Suction pipe fittings
Solutions
Inspect all connections carefully and:
* Replace damaged gaskets
* Tighten bolts
* Repair leakage points
Proper sealing is essential for efficient dredging performance.
: 6. Incorrect Pump Selection
Some users select equipment based solely on purchase price without considering actual working conditions.
This may lead to:
* Insufficient flow rate
* Inadequate pump head
* Improper pipe sizing
* Reduced sand concentration
Information Required for Proper Pump Selection
To select the right sand dredge pump, the following information should be provided:
* Dredging depth
* Discharge distance
* Vertical lifting height
* Sand particle size
* Slurry concentration
* Required production capacity (m³/h)
Professional calculations can ensure optimal performance and lower operating costs.
: Conclusion
Low sand concentration is not always caused by poor pump quality. In most cases, it results from a combination of material supply conditions, pipeline design, pump performance, equipment wear, and operating practices.
When experiencing low sand output and excessive water discharge, it is recommended to inspect the system in the following order:
- Verify whether sufficient sand is available at the suction area.
- Check for suction inlet blockage.
- Inspect the pipeline for air leakage.
- Confirm that the pump head meets project requirements.
- Examine impeller and wear component conditions.
- Review whether the pump selection matches the actual working conditions.
Why Choose Taian OCEAN Pump?
Taian OCEAN Pump specializes in the design and manufacture of:
* Sand Dredge Pumps
* Gravel Pumps
* Submersible Sand Pumps
* Slurry Pumps
* Dredging Equipment
* Sand Dredgers
Our engineering team can provide customized pump selection solutions based on your flow rate, head, discharge distance, particle size, and slurry concentration requirements, helping you maximize production efficiency while reducing operating costs.
TAIAN OCEAN PUMP CO.,LTD
DORIS CHEN
EMAIL : oceanpump12@tsbeng.com
WHATSAPP :+86 18562293319
