INSPECTION OF A MAIN BEARING (CSM SURVEY)

1. Preparation and safety: Stop the engine, secure the turning gear, drain the lubricating oil, isolate pressurised sources, and obtain the maker's manual. Prepare a work/risk assessment and tooling, and lift the crankshaft/ bearing cap to give access to the main bearing.
2. Remove the bearing cap: Remove the main bearing cap (and the upper shell) to expose the journal and the lower shell.
3. Clean the bearing: Drain the oil; clean the bearing shells and the journal with a clean cloth/ solvent and inspect.
4. Visual inspection: Examine the white-metal surfaces for cracks, pitting, wiping, scuffing, scoring, overheating (discoloration) and looseness of the white metal from the shell (detect by tapping). Check the shell seating, dowels/ locating lugs and the bolt/ stud condition.
5. Measurement of clearances: Measure the bearing clearance (diametral) using a feeler gauge at the parting faces, or the maker's clearance gauge/ plastigage/ lead-wire method, and record against the specified limits. Also measure the bridge gauge (the crankshaft position relative to the bedplate) to check the bearing wear/ alignment.
6. Check bolt torque and stretch: Confirm the bearing bolts are at the maker's torque and measure bolt stretch/ elongation as applicable.
7. Inspect the journal: Check the crank journal for scoring, pitting, out-of-round and taper (micrometer); check for cracks (NDT).
8. Inspect the oil ways and feed holes: Ensure the journal oil holes and the bearing supply drillings are clear and clean.
9. Check the bearing shells alignment to the journal by bluing/ contact marking.
10. Record all readings and findings on the survey/overhaul sheet for trend comparison.

• Isolate and secure the barring gear; tag the engine not-to-run.
• Use correct lifting gear and properly sling the bearing cap/ crankshaft; secure against swinging.
• Keep the working area clean, dry and well lit; observe oil/ chemical hygiene.
• Protect precision surfaces (journal, shell) from damage and contamination.
• Handle the white-metal shells carefully - they are soft and easily damaged.
• Never re-use damaged or distorted bolts; use genuine spares and correct tooling.
• Use the correct torque wrench setting and sequence; check bolt stretch.
• Keep fuel/ oil away from heat or ignition sources, and use the correct PPE.

• Overheating/ wiping of white metal: from oil starvation, excessive clearance, overloading, or misalignment. Rectify: renew the shell, correct clearance/supply.
• Cracking/ sinking of white metal: fatigue from cyclic loading and/or poor shell seating. Rectify: renew shell, check seating.
• Scoring/galling: from contamination (dirt, abrasive), oil starvation, or misalignment. Rectify: clean system, renew shell, check oil filter and clearance.
• Pitting: from water/ acid in the oil or cavitation. Rectify: address oil condition, renew shell.
• Loose shells (shell not seating/ hammering): from incorrect clearances, fretting of the shell back or damaged locating lugs. Rectify: renew shell, repair lugs.
• Excessive clearance: from normal wear. Rectify: renew/stim shims to restore the clearance range.
• Seizure of bearing: from severe oil failure; engine may have suffered consequential damage - renew bearing and fully investigate.

• Confirm the bearing clearance is to specification (feeler/plastigage) and record.
• Torque the bolts to specification and check bolt stretch.
• Carry out an oil-flow/ priming check: turn on the lubricating oil, allowing oil to reach the main bearing and confirm oil is discharged from the feeds.
• Bar the engine several revolutions by turning gear to confirm free rotation and no tight spots or binding.
• Re-run the engine at low rpm initially and check for abnormal noise, temperature rise of the bearing, and oil pressure/temperature.
• Perform a full power run and monitor bearing temperature and vibration; confirm no excessive heating.
• Verify the securing/locking of all bolts and oil connections.