For high suction head conditions, which seal is best?

• A. Lip Seal
• B. Cartridge Seal
• C. Mechanical
• D. Packing

Answer: (C)

High suction head means a large pressure difference across the seal, so you need a seal that maintains a tight barrier under differential pressure and shaft movement. A mechanical seal achieves this by using precision mating faces with a spring or energy source to keep the faces in contact, plus an effective secondary seal to prevent leakage. This design minimizes leakage and resists wear under high suction lift better than packing (which leaks and requires constant adjustment), lip seals (which rely on a single dynamic surface and can leak with shaft movement or dirty liquid), or cartridge seals (while robust, the broad mechanical-seal approach is favored for handling the stresses of high suction head).