Oil pressure drop
A drop in lubrication system pressure is the signal routed to the instrument panel of every unit and the first one to trip. The register contains 30 industrial-test cases; the median increase in lubrication system pressure is 30 %.
Values are given in the units used by the party performing the work: kilogram-force per square centimetre, bar, or percentage of increase. Measurements are comparable with each other at equal speed and equal oil temperature.
Causes of the pressure drop
Pressure in the lubrication system is not a property of the pump but the result of a balance between its delivery and the total leakage through the clearances of the lubricated friction pairs. The pump is serviceable, yet pressure falls: the enlarged clearances pass more than before, and the head fails to reach the remote points.
Mechanism of the drop
- Increase in leakage through clearances. Wear of the main and connecting-rod bearing shells, camshaft bushings and bearing supports increases the total flow area of the leakage paths. Through them escapes the flow rate intended for delivery to the remote lubrication points.
- Loss of viscosity due to heating. Increasing friction heats the oil, heated oil loses viscosity, and less viscous oil passes through the same clearances more easily. The pressure drop and the overheating reinforce each other.
- Wear of the pump itself. An increase in the axial and radial clearances of the oil pump gears reduces its volumetric efficiency. This is a separate cause, distinguished by the fact that pressure falls on cold oil as well.
Measurement procedure
Pressure is measured with a reference gauge at the standard take-off point, on a warmed-up unit, at the rotational speed specified in the documentation — as a rule, at idle and at rated speed separately. The standard sensor is not suitable for comparing measurements: its error is not standardised.
A pair of values at different speeds is indicative: a drop at idle only points to clearances in the friction pairs, a drop across all modes points to wear of the pump itself.
Treated assemblies
Pressure was measured in the lubrication system; treatment was applied to the friction pairs through whose clearances the flow escapes: crankshaft bearing shells, bushings, bearing supports.
Equipment types
Test reports
Fifteen test reports with the maximum recorded increase out of 25 containing a direct pressure measurement. Units are given as in the original. The full list is in the catalogue.
| ENTERPRISE | YEAR | CHANGE | PARAMETER MEASURED |
|---|---|---|---|
| Agria AD, Plovdiv | 2002 | ↑ 75% | oil pressure in the lubrication system, 8 → 14 atm |
| Troyanovo-3 mine, Maritsa Iztok | 2004 | ↑ 46–50% | oil pressure at 300–1200 rpm, 2.6–4.2 → 3.8–6.2 bar |
| SE “Ukrvodput” | 2001 | ↑ 21.4% | oil pressure at 750 rpm, 2.8 → 3.4 kgf/cm² |
| Vityaz LLC, Zaporizhzhia | 2004 | ↑ 15% | oil pressure at warmed-up idle, 4.0 → 4.6 kgf/cm² |
| OJSC “Spetsdormekhanizatsiya No. 2” | 2007 | ↑ 14–30% | oil pressure in the ZIL lubrication system, 1.0–3.6 → 1.3–4.1 kgf/cm² |
| Tatneft, Almetyevsk UTT-1 | 2001 | ↑ 11–33% | oil pressure at 2000 rpm, 2–6 → 4–7.1 kgf/cm² |
| JSC “JV Rosava” | 2004 | ↑ 0.2kgf/cm² | transmission oil pressure in all modes, 0.5 → 0.7 kgf/cm² |
| MTA Company, Plovdiv | 2004 | ↑ 2bar | oil pressure in the machine hydraulic system, 17 → 19 bar |
| Ukrzaliznytsia, Shevchenko depot | 2003 | 2.1 kgf/cm² → 2.3 kgf/cm² | Engine oil pressure |
| GPRUP “GPO Azot” | 2002 | 1 atm → 3 atm | Oil pressure |
| Isker JSC | 2002 | 2.4–2.5 kgf/cm² → 2.5–2.55 kgf/cm² | Oil pressure |
| Volgograd Steel Wire Rope Plant (VSPKZ) | 2002 | ↑ 1.7kgf/cm² | oil pressure, compressor of machine No. 112 |
| OAO Tatneftegazstroi, SMU-46 | 2001 | 1.6 kgf/cm² → 2.0 kgf/cm² | Oil pressure at idle speed |
| SKLO LLC | 2001 | 1.1 kgf/cm² → 1.15 kgf/cm² | oil pressure |
| Pervomaisk SE “KHIMPROM” | 2001 | 2.8 → 2.95 | oil pressure |
All 30 cases in the catalogue →
Documents of the cases with a direct measurement: plant commission reports — 18, signed test protocols — 7, other documents — 0; 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.