🔍 Key Concepts

• Operation of a centrifugal pump under suction lift (negative suction head) • Purpose of the seal water / sealing line to the pump gland and its effect on cooling and air leakage • How loss of sealing water can affect suction, temperature at the gland, and cavitation risk

💭 Think About

• What happens to the stuffing box or mechanical seal if cooling and sealing water are reduced or cut off during operation? • Under suction lift conditions, how would air leakage at the gland affect the pump’s ability to maintain suction and NPSH (Net Positive Suction Head)? • Could more than one of the listed effects logically occur at the same time if the sealing line is restricted?

✅ Before You Answer

• Confirm the function of the sealing (gland) line: it both cools/lubricates and prevents air entry on suction lift systems. • Consider whether air entering through the gland under suction lift can cause loss of suction and promote cavitation. • Before choosing, ask yourself if only one, several, or all listed effects would reasonably follow from a restricted sealing line in real pump operation.