Water Distribution Grade 1 Certification Practice Exam

What is the common method used to secure an impeller to the shaft on a double-suction pump?

1. A set screw

2. A key and a tight fit

3. A welding process

4. Adhesive bonding

The correct answer is: A key and a tight fit

The appropriate method for securing an impeller to the shaft on a double-suction pump is through the use of a key and a tight fit. This method is pivotal because it provides a reliable connection that can withstand the mechanical stresses encountered during operation. The key serves as a mechanical link that prevents the impeller from slipping on the shaft, ensuring that rotational motion is effectively transferred from the shaft to the impeller. The tight fit further enhances this connection, providing additional friction that maintains the integrity of the impeller's attachment even under dynamic conditions. In pump design, particularly in double-suction pumps where the impeller needs to handle significant hydraulic forces, it is vital to have a secure and stable attachment. This prevents issues like misalignment or vibration that could lead to premature wear or failure. While other methods of attachment may be useful in different contexts, they do not provide the same level of reliability and suitability for the demands of a double-suction pump application as the combination of a key and a tight fit.