How to interpret the performance parameters of Dalian Chemical Pump?

The performance parameters of Dalian Chemical Pump are the core indicators for measuring its working ability and applicable scenarios. When interpreting, it is necessary to comprehensively analyze the process requirements, medium characteristics, and system design. The following provides an explanation from the perspectives of key parameter definitions, interrelationships, and practical applications:

1、 Analysis of Core Performance Parameters

1. Traffic (Q)

Definition: The volume (m ³/h, L/min) or mass (kg/h) of the medium transported by the pump per unit time is determined by the material transfer volume of the process system.

Key points of interpretation:

It is necessary to distinguish between rated flow (design operating point flow) and maximum/minimum flow:

The rated flow rate is the operating point with the highest pump efficiency, and the actual operating flow rate may fluctuate within a certain range due to changes in pipeline resistance (such as valve opening);

The minimum flow rate should avoid being lower than the "critical flow rate" of the pump (usually 30% -40% of the rated flow rate), otherwise overheating or cavitation may occur due to impeller idling.

Example: If a chemical process needs to transport 10m ³/h of corrosive liquid, the rated flow rate of the pump should be ≥ 10m ³/h, and a margin of 10% -20% should be reserved to cope with fluctuations in operating conditions.

2. Head (H)

Definition: The energy increment (m) obtained per unit weight of medium through a pump, used to overcome pipeline resistance, lift height, or provide pressure.

Key points of interpretation:

Attention should be paid to net positive suction head (NPSH):

The sum of static pressure energy and kinetic energy of the liquid at the pump inlet must be greater than the saturated vapor pressure of the medium, otherwise cavitation (manifested as vibration, noise, and impeller damage) will occur;

When designing, it is required that the NPSH (NPSHa) provided by the device is greater than the NPSH (NPSHr) required by the pump, usually leaving a margin of 0.5-1m.

3. Power and efficiency

Shaft power (P): The power obtained by the pump shaft from the motor (kW), calculated by the formula: P=QH ρ g/η (where η is the pump efficiency).

Motor power: It needs to be greater than the shaft power, considering transmission efficiency (such as coupling transmission efficiency of 95%) and safety factor (usually 1.1-1.2 times).

Efficiency (η): The ratio of the effective power of the pump to the shaft power, reflecting the energy conversion efficiency. The high-efficiency zone is usually within the range of 80% -110% of the rated flow rate.

Example: Under the same flow rate, for every 5% increase in efficiency, the annual power consumption can be reduced by about 10% (calculated based on 8 hours of operation per day).

4. Speed (n)

Definition: The number of revolutions per minute (r/min) of the impeller directly affects the flow rate, head, and cavitation performance.

Related characteristics:

According to the law of similarity:

Q∝n，H∝n2，P∝n3；

High speed pumps have a small volume but are prone to cavitation (such as high-speed magnetic pumps), while low-speed pumps are more suitable for high viscosity media (such as screw pumps).

5. Medium characteristic parameters

Density (ρ): affects the head (pressure) and shaft power calculation of the pump. For example, when conveying liquids with a density greater than 1000kg/m ³, the shaft power is higher at the same head.

Viscosity (μ): When the viscosity is greater than 20mPa · s, the efficiency of the centrifugal pump significantly decreases, and a positive displacement pump (such as a gear pump or a plunger pump) needs to be used instead.

Corrosive/Abrasive: Determine the material selection (such as stainless steel, fluoroplastics, ceramics), and choose corrosion-resistant materials for impellers and pump bodies (such as 316L, Hastelloy) for corrosive media.

Vapor pressure (Pv): For media with high vapor pressure (such as volatile organic solvents), the installation height should be lowered or a self-priming pump should be used to avoid cavitation.

2、 Matching relationship between parameters

The significance of performance curve

The Q-H curve (flow head curve) of the pump shows its operating characteristics:

Steep drop curves (such as multi-stage centrifugal pumps) are suitable for scenarios with small flow changes and large head fluctuations (such as boiler feedwater);

Flat curves (such as single-stage centrifugal pumps) are suitable for scenarios with large flow changes and stable head (such as pipeline transportation).

The highest point of the Q - η curve (flow efficiency curve) is the Better Efficiency Point (BEP), and actual operation should be as close to this point as possible to save energy.

2. The impact of system resistance on operating points

The actual working point of the pump is determined by the Q-H curve and the pipeline characteristic curve（

The intersection point of H=H0+kQ2, where H0 is the static head and k is the resistance coefficient, determines that when the valve is opened, the resistance coefficient k decreases and the operating point moves to the right (with an increase in flow rate and a decrease in head);

When the pipeline is blocked, the resistance increases and the working point shifts to the left (flow rate decreases, head increases), which may enter the low efficiency zone or cause overload.

3. Verification of NPSH

Calculation formula:

Inhalation (Pa is atmospheric pressure, hs is installation height, suction pipe resistance needs to be measured or checked in the table).

If NPSHa is insufficient, measures need to be taken:

Reduce the installation height of the pump (hs takes a negative value);

Increase the suction pipe diameter to reduce resistance;

Choose low NPSHr pump types (such as double suction impellers and inducers).

3、 Selection and application precautions

1. Response to fluctuations in working conditions

For systems with large changes in flow rate (such as intermittent reactor feed), the following can be configured:

Variable frequency motor regulates speed (energy-saving but high cost);

Bypass reflux valve (opens when the flow rate is below the critical value to prevent overheating).

2. Targeted parameters for special media

High viscosity medium: Priority should be given to volumetric pumps, paying attention to the matching of speed and viscosity (such as rotor pumps with speed ≤ 300r/min suitable for viscosity>1000mPa · s).

Medium containing solid particles: choose wear-resistant materials (such as tungsten carbide seals and rubber impellers), pay attention to particle size (less than 1/3 of the gap between the impeller and the pump casing) and concentration (volume concentration ≤ 15%).

High temperature/low temperature medium:

High temperature (>150 ℃) requires the selection of high-temperature resistant mechanical seals and bearings (such as ceramic bearings);

Low temperature (<-20 ℃) requires prevention of medium solidification or material embrittlement (such as using 304L stainless steel or PTFE sealing).

3. Balancing energy conservation and reliability

Priority should be given to selecting high-efficiency and energy-saving pumps (such as national energy efficiency level 2 or above), but the initial cost and long-term energy consumption need to be balanced:

Example: In a certain project, the initial cost of an efficient centrifugal pump is 20% higher than that of a regular pump, but the annual energy consumption is 30% lower. It is expected that the price difference can be recovered within 2 years.

Key processes such as reactor feeding and hazardous chemical transportation require the configuration of backup pumps or the selection of models with dual mechanical seals and bearing temperature monitoring to enhance redundancy.

4、 Common Misunderstandings and Risk Avoidance

Misconception: The higher the lift, the better

Excessive head can cause the valve to operate in a closed position for a long time, increase energy consumption, and may cause vibration. Therefore, the head should be selected based on the actual calculation (leaving a 10% margin).

Misconception: Ignoring the influence of medium temperature on parameters

The significant changes in density and vapor pressure of high-temperature media may result in actual flow rates lower than the design values, and the operating temperature of the media needs to be provided during selection.

Risk: Equipment damage caused by unverified cavitation

Case: When transporting benzene (with high vapor pressure) in a certain project, NPSHa was not calculated. After running the pump for one week, honeycomb shaped corrosion holes appeared on the impeller. Eventually, a self-priming centrifugal pump was replaced and the installation height was lowered to solve the problem.

Interpreting the performance parameters of chemical pumps requires "system matching" as the core, first clarifying the process requirements (flow rate, head, medium characteristics), and then comprehensively selecting based on the pump's hydraulic performance, material compatibility, and energy efficiency level. Focus on whether the working point is in the efficient zone, whether the cavitation allowance is sufficient, whether the material is resistant to medium corrosion, and reserve buffer space for working condition fluctuations. Through dynamic correlation analysis between parameters (such as the intersection of Q-H curve and pipeline characteristics), it can ensure that the pump operates safely and efficiently for a long time, avoiding equipment failure or energy waste caused by parameter misreading.