When purchasing a centrifugal centrifugal pump, it is necessary to select the appropriate model according to technical parameters and usage conditions before purchasing. In addition, the material, seal type, flushing scheme, and installation foundation of the centrifugal pump must also be considered, which is the complexity of industrial water centrifugal pumps. If these factors are not fully considered when providing centrifugal pumps and ancillary components, many problems will occur during subsequent use. In this article, the editor will briefly share how to select the seal type of the centrifugal centrifugal pump according to the characteristics of the medium.
1、 Physical Properties of the Medium:
1. Temperature: The seal material must be able to withstand the temperature around the medium. If the medium temperature is above the boiling point, lubrication will deteriorate, so this must be considered when choosing the seal design and material.
2. Viscosity: The viscosity of the medium will affect the lubrication and leakage of the seal. The viscosity of most media depends on temperature, and single seals are suitable for media with dynamic viscosity below 2500 cP. For higher viscosity media, a back-to-back seal configuration should be used.
3. Particle diameter and gas content: These factors will affect the system's head and gas cavitation margin calculation. For example, when conveying media containing solid particles, special attention should be paid to the wear resistance and corrosion resistance of the seal.
2、 Chemical properties of the medium:
4. Corrosiveness: This is an important factor in selecting the material and seal type of a centrifugal pump. For media with strong corrosiveness, materials with better corrosion resistance should be prioritized, such as carbon fiber seals or ceramic seals.
5. Toxicity: Some media may be toxic, which requires the seal material to comply with cleanliness and guidelines for resisting pumped media, and be able to undergo CIP (clean-in-place) and SIP (sterilize-in-place).
3、Operating Conditions:
6. Pressure and speed: Seal pressure refers to the pressure around the seal. For high-pressure applications, a balanced seal should be used. If the speed is high, a balanced seal with a rotating seat must be used to reduce seal imbalance.
7. Environmental factors such as altitude, ambient temperature, and whether portability is required should also be taken into consideration.
4、Selection of Shaft Seal Type:
1. Mechanical seal: suitable for various media, with low leakage and long service life, but complex in manufacturing. For media with strong corrosiveness, mechanical seal is recommended, especially for hard-to-hard pair materials, such as silicon carbide or tungsten carbide.
2. Packing seal: with simple structure, low cost, and easy installation, but high power consumption, suitable for general media. However, it is not suitable for high temperature, flammable, explosive, and corrosive media.
3. Magnetic fluid seal: suitable for high-speed operation and high vacuum conditions with low temperature.
4. Diaphragm seal: suitable for conveying highly toxic, flammable, explosive, or valuable media.
5、 Other Important Notes:
1. When selecting a shaft seal, it is also necessary to consider the operating range of the centrifugal pump and the specific requirements for the liquid being pumped listed in the centrifugal pump catalog. If the operating range is exceeded, the life of the shaft seal will be shortened.
2. In special applications, such as in the flue gas desulfurization system of a power plant, the mechanical seal of the long-shaft submersible centrifugal pump should be used, and the friction pair material should have a high hardness to prevent wear.
When selecting the type of shaft seal for a centrifugal pump based on the physical and chemical properties of the medium, it is necessary to consider various factors such as temperature, viscosity, solid particle content, corrosiveness, and toxicity of the medium, and combine them with operating conditions and environmental factors to select an appropriate shaft seal type to ensure efficient operation of the centrifugal pump and prolong its service life.