Water Distribution Grade 1 Certification Practice Exam

What is the best seal to use for a pump operating under high suction head conditions?

1. A packing seal

2. A mechanical seal

3. An O-ring seal

4. A lip seal

The correct answer is: A mechanical seal

When operating a pump under high suction head conditions, a mechanical seal is the best choice. Mechanical seals are designed to prevent leakage between the stationary and rotating parts of the pump, providing a reliable barrier against fluids. They are particularly effective in applications where high pressures and suction conditions are present, as they can handle varying temperatures and pressures without compromising the seal integrity. The mechanical seal typically consists of two flat surfaces that face each other; one is fixed to the pump housing while the other rotates with the pump shaft. When the pump is operating, the pressure difference on either side of the seal helps keep it pressed together, preventing leaks. This design makes mechanical seals more suited for high suction conditions compared to other types of seals, as they can better handle the stresses involved without failing. In contrast, packing seals, while they can be used in various applications, may not provide the same level of reliability and can wear out faster under high suction conditions due to friction and heat build-up. O-ring seals, although effective in many static applications, generally do not perform well under the dynamic pressures of a pump. Lip seals, while they function well for certain types of sealing applications, may not withstand the high suction dynamics as effectively as a mechanical seal. Therefore, for high