For the transfer of **adipic acid** (or **hexanedicarboxylic acid**) through chemical pumps, a mechanical seal is required that must be resistant to the effects of this organic substance, as well as to its high viscosity and aggressiveness under certain conditions. Adipic acid is typically used in the production of nylon and other synthetic materials, and it is important to ensure tightness and safety during its transfer.
### Key aspects to consider when choosing a mechanical seal for the transfer of adipic acid:
### 1. **Seal materials**:
Adipic acid is not particularly aggressive compared to strong acids, but durable materials are necessary for reliable equipment operation and leak prevention.
- **Seal faces**:
- **Ceramic** (e.g. silicon carbide or aluminum oxide) — resistant to organic acids, with good wear and thermal resistance.
- **Graphite** — resistant to chemical attacks, but may require additional protective layers as it is brittle.
- **Stainless steel (e.g. 316, 904L)** — can be used in combination with other chemically resistant materials for the metallic parts of the seal.
- **PTFE (Teflon)** — one of the best materials for seals, resistant to chemical substances such as organic acids.
- **Elastomers**:
- **Viton (FKM)** — fluoroelastomer commonly used for seals in chemical equipment, with good resistance to organic acids and many chemical substances.
- **PTFE (Teflon)** — for O-rings and other contacts with chemical substances, as it is resistant to adhesion and chemical attacks.
- **EPDM** — can be used when the acid concentration is low and the operating temperature is not too high.
### 2. **Types of seals**:
- **Mechanical seals** — provide high tightness and prevent liquid leakage. This is the optimal choice for transferring adipic acid, especially in conditions where minimizing contact with the environment is important.
- **Wet seals** — can be used when additional cooling or lubrication is needed. This reduces the load on the seal and extends its service life.
- **Dry seals** — can be applied in specific conditions where the risk of overheating or leaks is minimal.
### 3. **Design**:
- **Cooling system** — for seals working with chemical substances, cooling systems are important to prevent overheating of the seal face, especially at high temperatures or high substance viscosity.
- **Dust seals and protective mechanisms** — to protect seals from mechanical damage and contamination.
- **Lubrication system** — for some designs, a lubrication system is important to reduce wear and maintain seal operation under optimal conditions.
### 4. **Operating conditions**:
- **Temperature**: Adipic acid can be pumped at temperatures ranging from -10°C to +150°C, depending on the concentration. The seal must be resistant to these temperature ranges.
- **Acid concentration**: Adipic acid can be in various concentrations. More concentrated solutions will require more resistant materials.
- **Pressure**: The mechanical seal must be designed for the working pressure in the system. Depending on the pump and system characteristics, the pressure may vary, and the seal must withstand the necessary parameters.
### 5. **Recommendations**:
- When choosing a mechanical seal for transferring adipic acid, consider the concentration and operating parameters (temperature and pressure). In most cases, combinations of ceramics or graphite with elastomers such as Viton or PTFE are used for adequate sealing and durability.
- For optimal operation, choose seals with a cooling or lubrication system, which will increase their durability, especially at high temperatures and pressures.
### Conclusion:
The proper selection of a mechanical seal for a chemical pump transferring adipic acid depends on specific operating conditions, including temperature, pressure, and acid concentration. Using materials with high chemical resistance, such as PTFE, ceramics, and fluoroelastomers, will ensure reliable and long-term equipment operation.