What are the key points to pay attention to when selecting pumps for Dalian Chemical Industry

1、 Analysis of Medium Characteristics

The main task of selecting pumps for Dalian Chemical Industry is to comprehensively understand the physical and chemical properties of the conveying medium, which is the foundation of the selection work.

Composition and concentration of the medium: The specific chemical composition and concentration percentage of the medium must be clearly defined. Different concentrations of acid-base solutions have significant differences in the corrosiveness of materials. For example, a carbon steel pump can be used for 98% concentrated sulfuric acid, while a special alloy or plastic pump is required for dilute sulfuric acid.

Temperature range: The temperature of the medium directly affects the material selection and sealing method. High temperature media (>120 ℃) need to consider the coefficient of thermal expansion, while low-temperature media (<-20 ℃) need to pay attention to material brittleness issues. The thermal fatigue effect needs to be evaluated for working conditions with a large temperature variation range.

Viscosity characteristics: Viscosity directly affects the selection of pump type. High viscosity media (>500cP) usually require the use of rotary pumps or screw pumps, while low viscosity media are suitable for centrifugal pumps. Non Newtonian fluids also need to consider shear sensitivity.

Solid content: The particle size, hardness, and content of solid particles in the medium determine the design and material selection of the pump's flow components. When the solid content exceeds 5%, it is usually necessary to use an open impeller or a specially designed impurity pump.

Corrosivity assessment: Select appropriate materials based on parameters such as the pH value and oxidation-reduction potential of the medium, and refer to the material corrosion manual. Special attention should be paid to local corrosion such as pitting and crevice corrosion.

Volatility and vapor pressure: For volatile media, the NPSH requirement should be considered, and for high vapor pressure media, special sealing design is required to prevent gas entrapment.

Hazardous characteristics: Flammable, explosive, toxic and harmful media must comply with ATEX explosion-proof standards and API682 sealing requirements.

2、 Determination of process parameters

Accurate process parameters are the technical basis for pump selection and require full communication and confirmation with the process profession.

Flow requirements: Clearly define the normal, maximum, and minimum flow conditions, considering a design margin of 20% -30%. Pay attention to the effects of periodic fluctuations and instantaneous peaks.

Head calculation: Determine the required head through detailed pipeline calculations, including static head, friction loss, equipment pressure difference, etc. Pay special attention to the range of variation of the system resistance curve.

Import conditions: Accurately calculate the effective cavitation head (NPSHa) to ensure that it is at least 0.5-1m higher than the required cavitation head (NPSHr) of the pump. For easily vaporized media, the safety margin should be larger.

Working pressure: Determine the higher working pressure at the inlet and outlet of the pump, especially for high-pressure systems, which need to consider the pressure bearing capacity of the shell and the limit of the shaft seal pressure.

Operation mode: Continuous or intermittent operation, which has a direct impact on the bearing and seal life. Frequent start stop conditions require special consideration.

System characteristics: Understand the system characteristics such as pipeline layout, tank level changes, and parallel operation to avoid surging or unstable working conditions.

3、 Principles for pump type selection

Reasonably select the type and structural form of the pump based on the characteristics of the medium and process parameters.

Applicability of centrifugal pump: Suitable for clean media with low viscosity, no solids or a small amount of solids, high flow rate and medium head. It can be divided into end suction, double suction, multi-stage, etc.

Selection of positive displacement pump: For high viscosity, solid content, or precise metering conditions, screw pumps, gear pumps, diaphragm pumps, etc. can be selected. Pay special attention to the influence of viscosity on volumetric efficiency.

Special pump applications: Magnetic pumps are used for high-risk media, shielded pumps are used for ultra pure media, submersible pumps are used for tank transportation, and self-priming pumps are used for difficult pumping situations.

Structural form selection: Horizontal pumps are easy to maintain but take up a large area, while vertical pumps save space but require complex maintenance. Reasonably choose according to the installation environment.

Material combination: The overcurrent component material needs to be resistant to medium corrosion, while the structural components ensure strength. Common material combinations include 304/316 stainless steel, Hastelloy, titanium, PP/PTFE, etc.

Standardization level: Priority should be given to selecting pump types that comply with international standards such as ISO, API, ANSI, etc., to facilitate spare parts procurement and maintenance.

4、 Key component considerations

The selection of core components for pumps directly affects operational reliability and lifespan.

Sealing system:

Mechanical seal: Select balanced, unbalanced, double end face and other structures based on pressure, temperature, and medium characteristics

Sealing flushing scheme: Standard schemes such as PLAN01-54 are adopted, and the rapid cooling system needs to be considered for high-temperature media

Auxiliary systems: including buffer system, leak monitoring, etc

Bearing configuration:

Select bearing type and arrangement based on axial/radial load

Special lubrication and cooling design are required for high-temperature working conditions

Choose high-precision bearings for occasions with high vibration requirements

Shaft seal area:

The hardness of the shaft sleeve material should be higher than that of the sealing ring

Consider hot installation process and anti rotation structure

Surface treatments such as hard chromium plating, tungsten carbide spraying, etc

Impeller design:

Closed impeller has high efficiency but is prone to clogging

Open impeller has good passability but low efficiency

Special blade types such as vortex impellers are used for gas containing media

Shell structure:

Radial subdivision facilitates maintenance

Simple end suction structure

Double volute design reduces radial force

5、 Drive and Control System

A complete pump unit needs to consider power matching and control methods.

Motor selection:

Power calculation needs to consider medium density and efficiency

Explosion proof rating meets the requirements of regional classification

A protection level of IP55 or above is preferred

Energy efficiency rating of at least IE3

Variable speed control:

Variable frequency drive is suitable for working conditions with large flow changes

Pay attention to the low-speed limit

Consider harmonic suppression and heat dissipation issues

Coupling selection:

Elastic couplings can compensate for deviations

Rigid couplings have high transmission efficiency

Explosion proof type requires special design

Monitoring system:

Vibration monitoring to prevent mechanical failures

Temperature monitoring of bearing status

Leak detection ensures safety

Protector:

Dry operation protection

overload protection

Pressure/flow alarm

6、 Economic evaluation

Whole life cycle cost analysis is an important basis for selection decisions.

Initial investment: including procurement costs for pump body, motor, base, control system, etc.

Installation cost: Consider engineering costs such as foundation construction, pipeline connections, and electrical wiring.

Operating energy consumption: Calculate power consumption under different operating conditions and evaluate the energy-saving potential of frequency conversion.

Maintenance cost: Estimate the replacement cycle and cost of vulnerable parts such as mechanical seals and bearings.

Shutdown losses: Evaluate the shutdown losses caused by pump failures and weigh reliability investments.

Spare parts inventory: Pump models with high standardization can reduce the capital occupation of spare parts.

Technical lifespan: Consider process changes and equipment update cycles to avoid premature obsolescence.

7、 Special working condition handling

Certain special operating conditions require special attention and specialized design.

High temperature medium:

Adopting a central support structure to reduce thermal deformation

Bearing box cooling system

Thermal barrier design

Low temperature medium:

Requirements for low-temperature toughness of materials

Anti condensation design

Cold insulation measures

Gas containing medium:

Assessment of Gas Processing Capability

Special impeller design

exhaust

Corrosive media:

Material corrosion test data

Cathodic protection measures

Lining integrity inspection

Abrasive media:

Selection of wear-resistant materials

Flow rate control

Convenience of replacing vulnerable parts

8、 Key points of supplier evaluation

Choosing qualified suppliers is crucial for the success of the project.

Technical Capability:

Performance evaluation of similar products

Rich engineering experience

Design computing capability

Quality System:

Certification status (ISO, API, etc.)

inspection test procedure

Quality traceability system

Delivery capability:

Production cycle reliability

Logistics management capability

Emergency response speed

Service Network:

Localized service capability

Technical training level

Spare parts supply guarantee

Compliance:

Comply with local regulatory requirements

Legitimacy of patented technology

Compliance with environmental standards

By considering the above factors through the system and combining them with specific project requirements, a more suitable chemical pump can be selected to ensure the long-term safe and stable operation of the device.