What should Dalian Chemical Pump pay attention to when transporting high viscosity media

1、 Characteristics of high viscosity media and their impact on pumps

High viscosity media usually refer to liquids with a dynamic viscosity greater than 1000cP at room temperature and pressure, such as heavy oil, asphalt, polymer melts, syrup, etc. This type of medium exhibits different characteristics from low viscosity liquids during transportation:

High flow resistance: The higher the viscosity, the greater the internal friction of the liquid, and the greater the resistance that needs to be overcome during flow, resulting in increased energy consumption of the pump.

Strong laminar flow tendency: High viscosity liquids have low Reynolds numbers and are prone to forming laminar flow rather than turbulence, which affects mixing and heat transfer efficiency.

High starting torque: When starting the pump, a larger torque is required to overcome the viscous force of the medium, which requires higher requirements for the motor and transmission system.

Temperature sensitivity: The viscosity of many high viscosity media varies significantly with temperature, and temperature control is crucial for the transportation process.

Shear sensitivity: some polymer materials or lotion may be degraded or demulsified due to excessive shear.

2、 Key factors in pump type selection

For high viscosity media, the selection of Dalian Chemical Pump needs to consider multiple factors:

1. Pump adaptability

Positive displacement pumps (such as gear pumps, screw pumps, plunger pumps) are usually more suitable for high viscosity media than centrifugal pumps because their flow rate is less affected by viscosity.

Single screw pump: Especially suitable for conveying high viscosity media containing solid particles, with stable flow and small pulsation.

Gear pump: simple structure, easy maintenance, suitable for clean high viscosity liquids without solid particles.

Cam pump: Strong adaptability to changes in medium viscosity, low shear force, suitable for sensitive media.

2. Key points of structural design

Wide flow channel: reduces flow resistance and prevents blockage.

Appropriate clearance: Consider the influence of medium viscosity on the internal clearance of the pump, ensuring both sealing and preventing jamming.

Strengthening bearings: Under high viscosity working conditions, bearings have high loads and require special design.

Heating/insulation structure: It is particularly important for media that experience a significant increase in viscosity due to temperature drop.

3、 Precautions for operation and running

1. Preparation before startup

Preheating treatment: For temperature sensitive media, preheating is required to reduce viscosity to a pumpable range.

Turning inspection: manually rotate the pump shaft to confirm there is no blockage, especially during low-temperature start-up.

Lubrication inspection: Ensure that the bearings and sealing system are well lubricated.

Pressure release: First open the outlet valve to avoid starting due to pressure buildup.

2. Control of operating parameters

Speed regulation: It is usually necessary to reduce the speed, and excessive speed can cause:

Shear heating may alter the properties of the medium

Increase cavitation risk

Accelerated wear and tear

Temperature monitoring: Maintain the medium temperature within a better viscosity range.

Pressure monitoring: Pay attention to the inlet pressure to avoid suction, and the outlet pressure should not exceed the rated value.

Flow control: Avoid overheating caused by prolonged operation at low flow rates.

3. Handling of special working conditions

Intermittent operation: Before stopping the pump, it should be flushed or emptied to prevent the medium from cooling and solidifying.

Medium changes: When viscosity fluctuates significantly, operating parameters need to be adjusted.

Abnormal noise: may indicate cavitation, dry running, or mechanical failure.

4、 Design requirements for supporting systems

1. Pipeline system

Pipe diameter selection: 1-2 levels larger than conventional to reduce flow resistance.

Insulation/heat tracing: To maintain the temperature of the medium, electric or steam heat tracing can be used.

Slope design: When not in use, it can be completely emptied to prevent residual solidification.

Filter setting: The coarse filter protects the pump, but the pressure drop needs to be controlled within the allowable range.

2. Drive system

Motor selection: Considering high starting torque requirements, a soft start device may be required.

Transmission device: Variable frequency control or mechanical transmission to adapt to viscosity changes.

Overload protection: Install reliable torque limiting devices.

3. Auxiliary system

Flushing system: For easily curable media, a solvent flushing circuit needs to be set up.

Exhaust device: It is difficult to exhaust high viscosity media and requires special design.

Pressure buffer: Reduce the pulsation effect of positive displacement pumps.

5、 Key points of maintenance and upkeep

1. Daily maintenance

Regular inspection: bearing temperature, vibration, leakage, and other conditions.

Lubrication management: Shorten the lubrication cycle according to the working conditions.

Sealing monitoring: wear of mechanical seals or packing boxes.

2. Regular maintenance

Gap adjustment: Adjust and restore performance in a timely manner after wear and tear.

Cleaning and maintenance: Thoroughly remove residual media to prevent solidification and accumulation.

Spare parts reserve: There should be sufficient stock of vulnerable parts such as gears, screws, and seals.

3. Common fault handling

Insufficient flow: Check the inlet filter, medium temperature, and pump wear.

Abnormal vibration: may be caused by cavitation, misalignment, or bearing damage.

Overheating phenomenon: Check the cooling system, whether the speed is too high, and whether the viscosity of the medium changes.

6、 Safety precautions

Thermal medium protection: High temperature and high viscosity media can easily cause burns, and insulation protection needs to be improved.

Mechanical injury prevention: Rotating parts should have reliable protective covers.

Pressure release: Before maintenance, the pressure must be completely released to prevent medium splashing.

Static protection: Static elimination measures need to be considered when transporting certain hydrocarbon media.

Emergency response: Develop emergency plans for situations such as medium leakage and solidification.

7、 Key points of selection calculation

Effective power calculation: Considering the influence of viscosity on power: Pe=(Q × H × ρ × g)/(3.6 × 10 ⁶) × (μ/μ w) ^ 0.25 (μ is the working viscosity, μ w is the water viscosity)

NPSH verification: High viscosity media are more prone to cavitation, and the effective cavitation allowance needs to be carefully calculated.

Axis power correction: Calculate the actual required power by searching for the correction coefficient based on viscosity.

Speed determination: Refer to the viscosity speed limit curve of each pump type to select the appropriate speed.

Transporting high viscosity media is one of the difficulties in the application of chemical pumps, which requires comprehensive consideration of various factors such as media characteristics, pump type selection, system design, and operation and maintenance. Correct selection and standardized operation can improve operational reliability, reduce energy consumption and maintenance costs. With the application of new materials and technologies, such as magnetic drive and intelligent control, high viscosity medium transportation technology will continue to develop, providing more efficient solutions for chemical production.