Upon opening the main sea-water circulating pump for examination and overhaul, the following checks are to be conducted:

Shaft

• Inspect the condition and check for signs of wear, particularly where it contacts gland packing and bearings. Use a dial gauge or straightedge to verify shaft alignment. A bent or worn shaft can lead to vibrations and misalignment.

Pump casing

• Inspect for Cavitation, Corrosion, and Pitting. These signs indicate damage caused by turbulent flow or corrosive seawater. In many cases, it may require the casing to be resurfaced or replaced.

Wear Ring

• Use Callipers to measure the diameter and check the condition of wear, check the wear on the wear ring and compare it to manufacturer recommendations. Excessive wear can reduce pump efficiency and lead to cavitation.

Impeller

• Inspect for Wear, Corrosion, and Sliding Marks. Check for uneven wear patterns or corrosion that may affect the impeller’s balance. Replace if heavily worn to maintain pump performance.

Shaft Sleeve

• Examine Contact Points. Check for wear or corrosion. Measure the diameter and compare it with the manufacturer's specifications. A worn sleeve can result in leakage around the gland packing.

Mechanical Seal/Gland Packing

• Inspect condition and check for wear or leakage. It’s recommended to replace the seal or packing during the overhaul to prevent future leaks.

Bearings

• Check Inner and Outer Races. Look for signs of damage or corrosion. Measure the inside diameter and compare it with standard values. If damaged, replace the bearing to avoid potential pump failure.

O-Ring

• Check for deterioration, deformation or wear. Replace O-rings if damaged

Shaft Coupling Bolts

• Inspect for wear, cracks, and damage. Damaged bolts can lead to misalignment and noise. Replace any worn or cracked bolts.

Clearances

• Check clearance between the impeller and casing ring. Excessive clearance can reduce efficiency and allow cavitation.
• Check clearance between the shaft sleeve and submerged bearing. Renew parts if clearances exceed maximum limits.

Common operational faults:

Cavitation:

• Caused by bubbles forming due to low pressure around the impeller, often due to water temperature near saturation. Cavitation can lead to damage in both the impeller and pump casing. To avoid this, ensure suction water temperature is below the saturation level for the system’s vacuum level.

Excessive Wear of Wear Ring:

• Friction can increase the clearance between the wear ring and impeller. Replace the wear ring if wear exceeds the recommended limit.

Shaft Damage from Gland Packing:

• If the shaft shows wear from gland packing, replace the shaft or fit a new sleeve if possible.

Bearing Damage:

• If the bearing shows wear or scoring, replace it.