What are the core indicators to refer to for the selection parameters of Dalian Chemical Pump

Dalian Chemical Pump is the core equipment for transporting corrosive, toxic, flammable, explosive and other special media in the chemical production process. Its selection is directly related to the safety, stability and economy of production. When selecting, it is necessary to comprehensively consider multidimensional indicators such as medium characteristics, process parameters, and safety requirements. The following is a detailed analysis of the core reference indicators:

1、 Media characteristics: the fundamental basis for selection

The complexity of chemical media is the main consideration for selection, and the following parameters need to be analyzed in detail:

Corrosivity: The pH value, concentration, and corrosion mechanism (such as oxidation corrosion and intergranular corrosion) of the medium determine the material selection. For example, dilute sulfuric acid is made of 316L stainless steel or fluoroplastic; Pure titanium or Hastelloy alloy is used for concentrated nitric acid; Strong alkali (NaOH) using 304 stainless steel or PVDF; Fluoroplastic (F46) or graphite lining is used for hydrochloric acid.

Viscosity: For media with a viscosity higher than 50cSt (such as crude oil and syrup), centrifugal pumps should not be selected (efficiency drops sharply), and volumetric pumps (gear pumps, screw pumps) are needed; High viscosity media also need to consider the starting torque and impeller clearance of the pump.

Solid content: For media containing particles (such as mud and crystalline liquids), wear-resistant materials (such as high chromium cast iron and rubber lining) and open impeller centrifugal pumps, diaphragm pumps, or screw pumps should be selected to avoid particle blockage of the impeller.

Temperature: High temperature media (>150 ℃) should be made of heat-resistant materials (such as duplex steel, Inconel alloy) and equipped with cooling systems (such as mechanical seal flushing, bearing cooling); Low temperature medium (<-40 ℃) requires low-temperature steel (such as 0Cr18Ni9Ti) to prevent material brittleness.

Volatility and toxicity: For low boiling points (such as methanol, ether) or toxic media (such as cyanide, benzene), leak free pumps (magnetic pumps, screen pumps) should be selected to avoid safety accidents caused by shaft seal leakage; Flammable and explosive media also need to be matched with explosion-proof motors (Exd Ⅱ BT4 or Exia Ⅱ CT6 grade).

2、 Process parameters: Core matching of pump performance

The process requirements directly determine the key performance of the pump, such as flow rate and head, and require precise calculation

Flow (Q): Determine normal flow, maximum flow, and fluctuation range according to production demand. Select a pump with a rated flow rate ≥ 1.1 times the normal flow rate during continuous operation; Intermittent operation can appropriately reduce the margin.

Head (H): It is necessary to calculate the total resistance of the pipeline (along the way resistance+local resistance) and leave a margin of 10% to 15%. For example, for a pipeline with a conveying distance of 100m and a diameter of DN80, the resistance along the way is about 10m, the local resistance (bends, valves) is about 5m, and the total head needs to be ≥ 16.5m.

Cavitation allowance: Ensure that the NPSHa of the device is greater than the required NPSHr of the pump plus 0.5m. When NPSHa is insufficient, it is necessary to raise the storage tank position, increase the suction pipe diameter, or choose a low cavitation pump (such as a double suction pump or induced impeller centrifugal pump) to prevent damage to the impeller due to cavitation.

Power and speed: Shaft power=(Q × H × ρ)/(3600 × 1000 × η) (where ρ is the medium density and η is the pump efficiency), with a margin of 10% to 20% for motor power; Prioritize selecting a speed of 1450rpm (4-pole motor) to reduce vibration and noise, and extend lifespan.

3、 Pump Type Selection: Suitable for Process Scenarios

Select the appropriate pump type based on the medium and process parameters:

Centrifugal pump: simple structure, high efficiency (60%~90%), suitable for low viscosity, high flow rate (>50m ³/h), and low to medium head scenarios; But it is not suitable for media with high viscosity (>50cSt) or solid content>5%.

Positive displacement pumps: gear pumps (small flow high head, such as lubricating oil transportation), screw pumps (high viscosity, containing particles, such as asphalt transportation), diaphragm pumps (leak free, corrosion-resistant, such as strong acid transportation), suitable for small flow (<50m ³/h) and high head (>100m) scenarios.

Leak free pumps: magnetic pumps (magnetic coupling transmission, no shaft seal), shielded pumps (motor and pump body integrated, no leakage), suitable for toxic, flammable and explosive media, such as solvent transportation in the pharmaceutical industry and chlorine gas transportation in the chemical industry.

Special pumps: jet pump (no moving parts, suitable for vacuum systems), mortar pump (wear-resistant impeller, suitable for slurry transportation).

4、 Sealing and Material: Ensuring Safety and Lifespan

Sealing method:

Mechanical seals: single end face (low pressure, non hazardous medium), double end face (high pressure, strong corrosion, requiring washing solution);

Packing seal: Low cost, but large leakage, suitable for non-toxic media (such as cooling water);

Magnetic/shielding seal: no leakage, suitable for hazardous media, attention should be paid to the risk of demagnetization of magnetic pumps (when overloaded).

Material matching:

Metal materials: cast iron (non corrosive medium), carbon steel (concentrated sulfuric acid), 316L stainless steel (universal corrosive medium), duplex steel (resistant to chloride ion corrosion), Hastelloy alloy (strong corrosion such as hydrochloric acid);

Non metallic materials: fluoroplastic (F46/PVDF, resistant to strong acids and alkalis), ceramic (wear-resistant and corrosion-resistant, such as conveying mud), rubber (lining, wear-resistant).

5、 Safety and Environmental Protection: Compliance Requirements

Explosion proof level: When transporting flammable and explosive media, the motor must comply with GB3836 standards, such as Exd Ⅱ BT4 (applicable to methane and ethane), Exia Ⅱ CT6 (applicable to hydrogen and acetylene).

Leakage detection: High risk medium pumps need to be equipped with leakage alarm sensors (such as mechanical seal leakage detection) and linked shutdown systems.

Environmental requirements: Leak free pumps (magnetic, shielded) are the trend, reducing VOCs emissions and complying with environmental regulations.

6、 Operating costs: long-term economic viability

Efficiency: Centrifugal pumps have higher efficiency than volumetric pumps, and high-efficiency pumps (such as IE3 motors) are preferred to reduce energy consumption;

Maintenance cost: Choose pump types with simple structure and few vulnerable parts (such as centrifugal pumps) to reduce the frequency of spare parts replacement;

Spare parts: Prioritize mainstream models (such as IS centrifugal pumps and CQB magnetic pumps) to ensure timely supply of spare parts.

The selection of chemical pumps should be based on "medium characteristics as the core, process parameters as the basis, safety and environmental protection as the premise, and economic efficiency as the goal", and comprehensively weigh pump type, material, sealing and other indicators. For example, when transporting 20% hydrochloric acid (temperature 80 ℃, flow rate 50m ³/h, head 30m), a fluoroplastic magnetic pump (CQB-F type) made of F46 material, double end mechanical seal, and explosion-proof motor Exd Ⅱ BT4 should be selected. Reasonable selection can avoid problems such as corrosion leakage and cavitation damage of pumps, ensuring continuous and stable production operation.