Elevated operating temperature
Sustained heating of an assembly above its normal level indicates that the share of supplied energy dissipated in friction has increased. The register contains 28 industrial-test cases; the median temperature reduction is 15 %.
Causes of temperature rise
Friction work is converted into heat. As long as the mating surfaces are separated by an oil film, heat generation is low and is removed by the lubricant and the housing. As wear progresses, the actual contact area increases, the regime shifts from fluid friction to boundary friction, and the same load begins to generate appreciably more heat.
Mechanics of heating
- Shift of the friction regime. An increased clearance reduces the load-carrying capacity of the oil layer. During part of each revolution the assembly operates with direct contact of surface asperities, and heat generation grows non-linearly with respect to load.
- Feedback through viscosity. Heated oil loses viscosity, the film thins, the contact area increases — and the heating reinforces itself. For this reason the temperature rises slowly at first and then accelerates.
- Accelerated ageing of the lubricant. Elevated temperature shortens the service life of the oil and its additives: oxidation proceeds faster, and protective properties decline before the calculated replacement interval.
Measurement procedure
Temperature is measured at regular monitoring points under steady-state operation: on the bearing housing, in the crankcase, on compressor stages — with a contact thermometer, a regular sensor or a thermal imager. Values are compared at comparable load and ambient air temperature.
Significance lies not in the absolute level but in the excess over the level normal for the given assembly and over the temperature of adjacent bearings of the same type: it is the difference that indicates a local defect, whereas a general rise is more often related to the operating regime.
Treated assemblies
Temperature was measured at regular monitoring points; treatment was applied to the friction assembly: bearing supports, gearbox gearing, the cylinder-piston group of the compressor.
Equipment types
Test reports
Fifteen reports with the largest recorded reduction out of the 21 reports containing a direct temperature measurement. Values are given in the units used by the executing party: percent or degrees Celsius. The complete list is provided in the catalogue.
| ENTERPRISE | YEAR | CHANGE | PARAMETER MEASURED |
|---|---|---|---|
| PP “Dyvany-Mebli” | 2009 | ↓ 25% | oil temperature in the system, 80 → 60 °C |
| OJSC Kupiansk Bread Plant | 2000 | ↓ 21–25% | discharge air temperature in both cylinders, 140–160 → 110–120 °C |
| Kommunar PA | 1999 | ↓ 20% | oil temperature at 750 rpm, 60 → 48 °C |
| Zaporizhzhia NPP | 1999–2000 | ↓ 19–40% | oil temperature in the crank mechanism system, 80 → 48–65 °C |
| Zuevskaya TPP, Donbassenergo | 2001 | ↓ 17.9–24% | air temperature at stage V, 117–125 → 95–96 °C |
| Dniproenergo, Prydniprovska TES | 2000 | ↓ 15.2% | oil temperature at 41 kgf/cm², 59 → 50° |
| Sabson Energy Ltd | 2020 | ↓ 14% | oil temperature, 121 → 104 °C |
| SE “Zavod UB i VT” | 2000 | ↓ 10.8% | oil temperature in the gearbox at rated load, 65 → 58 °C |
| MZhK Khabarovskii JSC | 2002 | ↓ 10.5% | operating temperature of the hydrogen compressor, 95 → 85 °C |
| Almaty Railcar Repair Plant | 2002 | ↓ 6.5–11% | hydraulic oil temperature, 42–46 → 38–43 °C |
| DAT “Ukrspetstransgaz” | 2001 | ↓ 5.9% | engine oil temperature, 85 → 80 °C |
| Slovak Univ. of Technology, Bratislava | 2003 | ↓ 1.2–5.1% | exhaust gas temperature, 571–665 → 542–646 °C, all nine speed points |
| Gorlovskiy Machine-Building Plant | 2006 | 62.0 °C → 60.0 °C | Oil temperature |
| GPRUP “GPO Azot” | 2002 | 50 °C → 48 °C | Oil temperature |
| Isker JSC | 2002 | ↓ 5–7°C | stage and crankcase temperature, 45–85 → 40–78 °C |
All 28 cases in the catalogue →
Documents of the cases with a direct measurement: plant commission reports — 12, signed test protocols — 7, other documents — 2; the document type is stated on the case card.
Limits of data applicability
- Applicability. The figures relate to the equipment and operating conditions of the enterprises named in the reports; on a different unit the result depends on initial wear, load and oil.
- Source document. A scan of the original report is published under every case; if the card and the scan disagree, the scan is authoritative.