The petrochemical industry plays a vital role in the national economy, and chemical process pumps, as essential auxiliary equipment, are receiving increasing attention. Due to the complex nature of chemical media and the continuous evolution of user requirements, it is crucial for manufacturers to make informed choices. The key considerations include material selection, corrosion resistance, temperature handling, and sealing performance. This article provides a brief overview based on our company's product features and personal insights into the fundamentals of selecting chemical pumps, aiming to benefit professionals in this field.
Corrosion resistance is one of the most critical factors in chemical equipment design. Even minor oversights can lead to equipment damage or even serious accidents. Statistics show that about 60% of chemical equipment failures are due to corrosion. Therefore, selecting the right materials for chemical pumps is the first step. A common misconception is that stainless steel is a universal material suitable for all environments, which is dangerous. Below are some key points for selecting materials for different chemical media:
1. **Sulfuric Acid**: As a strong corrosive medium, sulfuric acid has varying effects depending on its concentration and temperature. For concentrated sulfuric acid (over 80%) at temperatures below 80°C, carbon steel and cast iron offer good corrosion resistance, but they are not suitable for high-speed flow. Stainless steels like 304 and 316 have limited use. High-silicon cast iron and high-alloy stainless steel (20 alloy) are commonly used for pump valves. Fluoroplastic pumps, such as F46, are economical options. Our products include IHF lined pumps, PF (FS) highly corrosion-resistant centrifugal pumps, and CQB-F fluoroplastic magnetic pumps.
2. **Hydrochloric Acid**: Most metals, including stainless steel, are not resistant to hydrochloric acid. Non-metallic materials like rubber and plastic (e.g., polypropylene, fluoroplastic) are better choices. Our product range includes IHF fluorinated lined pumps, PF (FS) corrosion-resistant centrifugal pumps, and CQ polypropylene or fluoroplastic magnetic pumps.
3. **Nitric Acid**: Most metals are corroded by nitric acid, but stainless steel is widely used. Molybdenum-containing stainless steels like 316 may not perform better than standard grades. For high-temperature nitric acid, titanium and titanium alloys are preferred. Our products include DFL (W) H chemical pumps, DFL (W) PH shielded chemical pumps, and others.
4. **Acetic Acid**: One of the most corrosive organic acids, acetic acid severely corrodes ordinary steel. Stainless steel, especially 316 with molybdenum, is an excellent choice. For high-temperature or high-concentration conditions, high-alloy stainless steel or fluoroplastic pumps are recommended.
5. **Alkali (Sodium Hydroxide)**: Steel is widely used for sodium hydroxide solutions up to 80°C and 30% concentration. At higher temperatures, titanium or high-alloy stainless steel is needed. Our company offers cast iron pumps for low-temperature applications, with stainless steel or fluoroplastic pumps available for special needs.
6. **Ammonia (Ammonia Hydroxide)**: Most metals and non-metals are minimally affected by ammonia. Copper and copper alloys should be avoided. Our pumps are generally suitable for ammonia transport.
7. **Saline (Seawater)**: Ordinary steel corrodes quickly in seawater. Paint protection is often used for lower concentrations. 316 stainless steel is preferable for long-term use. Many of our pumps are made with 316 material.
8. **Alcohols, Ketones, Esters, Ethers**: These media are generally non-corrosive. Common materials like stainless steel or carbon steel are suitable. However, care must be taken when selecting sealing materials, as these substances can dissolve many types of rubber.
There are many other media not covered here, so it’s important not to choose materials arbitrarily. Always consult reliable sources or learn from proven experience.
**Cooling Requirements**: High-temperature media demand more robust pump designs. For temperatures below 120°C, self-cooling is usually sufficient. For temperatures above 120°C, cooling systems are necessary. Our pumps like DFCZ, GRG, and HPK are designed for high-temperature applications.
**Sealing Issues**: Leak-free operation is the goal of chemical equipment. Magnetic and shielded pumps are popular, but challenges remain regarding sleeve life, material pitting, and static seal reliability. Mechanical seals are widely used, with double-end seals suitable for high-temperature or viscous media.
**Viscosity Problems**: High viscosity affects pump performance, reducing head and flow while increasing power consumption. For viscous media like pulp or paste, screw pumps are recommended. Our DFGG single-screw pump can handle viscosities up to 1,000,000 cSt.
In conclusion, proper material selection, understanding of media properties, and attention to cooling and sealing are essential for optimal pump performance in the chemical industry.
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Suzhou Cheerchem Advanced Material Co., Ltd. , https://www.szcheerchem.com