Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1399684
www.machinerylubrication.com | July - August 2021 | 45 If this value is compared to the remaining useful life of a bearing, as shown in Figure 3, this would mean that the life of a bearing is reduced to half of its useful life. erefore, it is important to keep track of water contam- ination, especially in applications with high humidity or wide ambient temperature ranges that may result in water condensation. Particle Quantifier Index (PQ) Particle Quantifier Index (PQ) Description: "Measures the mass of ferromagnetic wear particles/debris in the oil irrespective of the size of the ferrous particles." "Particle Quantifier (Ferrous Density) exposes a lubricant to a magnetic field. e presence of any ferrous metal causes a distortion in the field, that is represented as the PQ Index." Interpretation: "A lthough PQ does not provide a ratio of small to large ferrous particles, if the PQ Index is smaller than iron parts per million (ppm) by Inductively Coupled Plasma (ICP), it is unlikely there are any particles larger than 10 microns present. If the PQ Index increases dramatically while the iron ppm remains consistent or goes down, larger ferrous particles are being generated." is means that there is a possible internal failure for the unit, such as broken reduction components. Elemental Analysis by ICP Elemental Analysis by ICP Description: Provides elemental metal analysis of up to 24 metals in the oil repre- senting wear metals, additive metals and contaminant metals. Measures metals less than 10 µm in size and results are reported in ppm. e most common elements to be found on an oil analysis report are listed in Table 2. Interpretation during trending: When compared to the baseline oil analysis, this can provide insight into either wear particles or contaminants in the oil. For example, during the break-in of a gearbox, the reduction components start to wear by removing asper- ities that are the result of a machining and heat treatment processes. ese worn asperities will affect the oil analysis result by increasing the iron particle count. is is common for most reduction components. When it comes to cycloidal reduction components, both iron and chrome ppm increase at a similar ratio since the material used on cycloidal reduction components differs from conventional gearing. It is important to be familiar with the elements present in both gearboxes and lubri- cants; doing so can help identify elements present in the oil in an unused state and which components are being worn out during the operation of the gearbox, allowing the neces- sary action to stop wear or replace potentially damaged components to be taken. Case study: Chain Conveyor Case study: Chain Conveyor e gearbox in Figure 4 has been oper- ating on a chain conveyor for around 10 years. e load depends on the type of product that is being handled (moderate to high shock load) and operates continuously for 24 hours, six days a week, with no starts and stops during operation. e oil analysis results are shown in Figure 5. e following characteristics were monitored during oil analysis: • Viscosity. • Oxidation. • Water content. • Particle Quantifier Index. • Elemental Analysis. is case study excludes baseline data, and a target of 100ppm of iron was set by the end-user. Regarding oil viscosity, it can be observed that the viscosity increased from around 150 cSt to 220 cSt. e trend can be observed in Figure 6. e reason is that the manufactur- er's recommendation is to use an approved oil with a 150 cSt viscosity. However, an unap- proved 150 cSt viscosity oil was being used. After consulting with a lubricant specialist, it was decided to schedule an oil change and replace it with a 220 cSt viscosity oil, even though the oil used was not approved by the manufacturer. It is important to point out that in this case, there is historical data in both oil anal- ysis and application that backed the use of an unapproved oil, and with the help of a lubri- cation specialist, it was possible to find the right oil properties and viscosity to properly lubricate the gearbox. Even though a solution Figure 3: Percentage of Bearing Life Re- maining VS Percentage of Water in Oil Figure 4: Gearbox on chain conveyor application. ML ML