GRUNDFOS Pump Seal Hole 90mm Pump Mechanical Seal

Q1: What is the primary function of the mechanical seal in a Grundfos CR pump with a 90mm seal hole?

A1: The mechanical seal's primary function is to create a hermetic, leak-free seal between the stationary pump casing (the seal housing or gland) and the rotating shaft, preventing the pumped fluid from escaping into the atmosphere and preventing air from entering the pump.

Q2: What are the standard seal face materials for a Grundfos CR pump mechanical seal, and why are they chosen?

A2: The standard configuration for clean water applications is a pairing of Silicon Carbide (SiC) versus Silicon Carbide (SiC). This is chosen for its exceptional hardness, excellent wear resistance, high thermal conductivity, and superior chemical inertness, which ensures long seal life and reliable operation.

Q3: What is the critical preparatory step before installing a new mechanical seal into the 90mm seal housing?

A3: The most critical step is to meticulously clean and inspect the seal housing bore and the shaft sleeve. Any burrs, corrosion, or old gasket material must be removed to ensure a perfectly clean, smooth surface. The shaft sleeve must also be checked for scoring or wear, as any imperfections will compromise the seal's integrity.

Q4: How is the correct axial installation position of the cartridge mechanical seal achieved?

A4: Cartridge seals are pre-assembled and preset. Correct installation is achieved by following the manufacturer's instructions to bottom out the cartridge on the shaft, then tightening the clamping collar. The installation fixtures or tabs are then removed, and the seal is automatically at its designed operating length. No manual setting of the spring compression is required.

Q5: What is the most likely cause of a repetitive, premature failure of a mechanical seal in this application?

A5: The most common cause is face deflection due to improper gland (seal housing) flatness or excessive pipe strain. If the 90mm gland is not perfectly flat or the pump is misaligned due to piping stress, it induces uneven pressure on the seal faces, causing them to open slightly and leak, or wear prematurely. Dry running, resulting in heat checking of the seal faces, is another primary cause.