Increased clearances and backlash
Wear of mating surfaces is the root cause from which vibration, noise and excess energy consumption develop. Below are 57 industrial test reports in which the geometry of the assembly was measured before and after treatment: by feeler gauge, dial indicator and micrometer, with signatures and company seals.
Measurements are given in the units used by the executing party: clearance and runout in millimetres, tooth thickness in millimetres over the constant chord, relative change in percent where the report itself calculated it.
Causes of clearance growth
Clearance is a design value specified by the designer to maintain the oil wedge. As operating hours accumulate, material is carried away from the mating surfaces, clearance increases and lubrication conditions deteriorate: wear thereby accelerates itself.
Mechanics of progression
- Loss of the oil wedge. Increased clearance reduces the load-carrying capacity of the oil film. For part of each revolution the assembly operates under boundary friction, where wear is orders of magnitude higher than under hydrodynamic conditions.
- Deviation of form, not only of size. Ovality of the journal, taper of the liner and wear of the tooth profile alter the geometry of the contact patch. The load ceases to be distributed over the entire working surface and concentrates at the edges.
- Abrasive component. Wear products remain in the oil and act as an abrasive, accelerating material removal. The metal content of the lubricant therefore indicates the rate of the process, not merely its occurrence.
Measurement procedure
Clearances and runouts are measured with the unit shut down: radial and axial clearance of bearing supports by dial indicator, backlash in the gear mesh by feeler gauge or lead impression, tooth thickness by gear tooth vernier caliper over the constant chord. Values are compared with the maximum permissible limits stated in the manufacturer's repair documentation.
Geometry is the primary indicator with respect to vibration, noise and energy consumption: it explains them, whereas they only signal it.
Treated assemblies
Geometry was measured directly at the mating pairs: bearing supports, gear drives, machine tool guideways, the cylinder-piston group.
Equipment types
Test reports
Fifteen reports with the maximum recorded change out of 48 containing a direct measurement of geometry. Units are given as in the original: millimetres for clearances and runouts, percent where the relative change was calculated by the report itself. The full list is in the catalogue.
| ENTERPRISE | YEAR | CHANGE | PARAMETER MEASURED |
|---|---|---|---|
| SE KhMZ FED | 2014 | ↓ 33-50% | radial and axial runout of the spindle mounting seat |
| Rumyantsev Mine State Enterprise | 2001 | ↓ 16-24% | bearing radial clearance, 0.29-0.31 → 0.22-0.26 mm |
| K. A. Rumyantsev Mine | 2001 | ↓ 16-24% | bearing radial clearance, 0.29-0.31 → 0.22-0.26 mm |
| Dalnevostochnoe Locomotive Repair Depot | 2009 | ↓ 15% | oil clearance of engine connecting-rod bearing shells, 0.14-0.19 → 0.09-0.17 mm |
| Dneprovagonrembud JSC | 2001 | ↑ 6.7-15.4% | gear wheel tooth thickness at constant chord on the worn points, 3.5-3.9 → 4.04-4.16 mm |
| InGOK OJSC | 2000 | ↑ 6.1-17.4% | tooth thickness, KTs-2-750, 9.2-16.3 → 10.8-17.3 mm |
| OJSC SevGOK, Kryvyi Rih | 2001 | ↑ 4.2-4.5% | tooth thickness, 16.70-16.85 → 17.40-17.60 mm |
| Baku Carriage Depot, Azerbaijan Railways | 2007 | ↑ 2.4-4.2% | tooth thickness at the mid and inner rim diameter |
| Zaporozhstal OJSC | 2013 | ↑ 0.05-0.15mm | gearbox tooth thickness, 5.8 → 5.9 and 6.0 → 6.15 mm |
| Tomakovskiy Expanded Clay Gravel Plant | 2007 | ↑ 0.1-0.5mm | tooth thickness over the constant chord on all four gear rims of both gearboxes |
| UKROLIIA LLC | 2007 | ↑ 0.2-0.5mm | tooth thickness of stage I and II gear drives, 4.0-6.9 → 4.3-7.2 mm |
| DONETSK - VTORMA LLC | 2005 | ↑ 0.05-0.15mm | tooth thickness of the gear drives of both gearboxes |
| Mini Maritsa-Iztok, Troyanovo-3 mine | 2004 | ↑ 0.20mm | gear wheel tooth thickness, 12.50-19.00 → 12.70-19.20 mm |
| ZhP Traktsia depot, BERL, FINTEHMASH | 2004 | ↑ 0.1-0.3mm | tooth thickness gain of the traction motor reduction gear over 45 132 km of mileage |
| ZhP Traktsia Lokomotivi, BDZ EAD | 2003 | ↑ 0.47mm | small gear tooth thickness, average; deviation from nominal 0.50-0.57 → 0.00-0.03 mm |
All 57 test reports in the catalogue →
Limits of data applicability
- Variability of results. The measurements presented reflect the actual performance on the specific equipment of the enterprises studied. No exact reproduction of the percentage figures on other units is declared, since initial wear, load regimes and lubricant properties are strictly individual.
- Documentary transparency. All figures stated are officially confirmed. A full scanned copy of the original industrial test report is placed under each case described, available for detailed examination and download.
Treatment procedures for these assemblies
Rolling bearings, oil-lubricated · Open Gear and Chain Drives · Industrial reducers and transmissions · All procedures