Lubricant Sampling and Analysis

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Return to Condition Monitoring - Predictive Maintenance Techniques

Contents 1 Oil Analysis Tips 2 What is Lubricant Analysis and Why Use It? 3 Lubricant Sampling Approach 4 Grease Sampling for Low Speed Rolling Element Bearings 5 The Likely Effect of Poor Sampling Practice

Oil Analysis Tips

What is Lubricant Analysis and Why Use It?

Lubricant Analysis is typically called Oil Analysis. It involves the measurement of lubricants with the objective to determine:-

• The condition of a lubricant and its deterioration
• The condition of the equipment or of specific components being lubricated
• The level of contaminant in the lubricant or from a particular source
• The effectiveness of filters

Some measurement or assessment of lubricants can occur on-site but more typically a small sample of the lubricant is taken and sent to a Laboratory for analysis. Lubricant Analysis is one of the most powerful Condition Monitoring methods available to understand the current health of equipment and to predict its future health. The location, method, frequency and rigour used to take the sample are critical to the effectiveness of the monitoring.

Why is the Lubricant Sampling Process So Important?

If a lubricant sample is not representative of either the system as a whole and/or the lubricant around components, the analysis results may be misleading. If a lubricant sample does not reflect the actual condition of the machine and its lubricant, then maintenance recommendations made may be incorrect.

Most of the power from condition Monitoring comes through trending and comparisons between measurements. Poor sampling process will give inconsistent results and will make trending and comparisons difficult. These ineffective and inconsistent results can easily lead to undetected equipment failures resulting in potentially substantial costs to the plant.

Efficient maintenance planning requires adequate warning of failures, which is maximise by a good monitoring, sampling, & analysis strategy. Lube analysis gives excellent data to eliminate the causes of defects and poor sampling could allow these opportunities to be missed. Getting it right will give big $$$ saving for production and maintenance.

Reliability Improvement - Detecting defects early allows minimising the consequences of failures but it does not reduce the number of failures. Finding and understanding the causes of failures enables the causes to be eliminated or minimised. This is what makes possible increases in equipment reliability. A key Root Cause of many equipment failures is contamination of the Lubricant. Another cause is low oil level or lack of lubricant.

There are many sophisticated oil analysis tests to measure contamination levels. There are many contamination root cause symptoms that can be observed on-site while collection of the samples. For Example:

• Covers and openings uncovered or poorly sealed (eg dipstick hole)
• Seal damage
• Unmaintained, damaged or inadequate filters and breathers

Two main categories of lubricant contaminants are solids and moisture.

Solid Contamination - Particles between 3um & 10um in size bridge the lubrication gap in bearings & other components! Human hair = 60um to 80um

Relatively small amounts of dust & dirt can seriously affect equipment reliability. Very small amounts of airborne dust can contaminate a lubricant sample. Bearing fail three times faster in dirty oil (Fig 4.3).

Moisture in oil – Some of the effects are listed below.

• Causes corrosion of system components.
• Increased oil degradation rates (up to 30 times greater risk in systems with Cu present).
• Increased depletion & precipitation of oil additives.
• Loss of lubricity - increased wear and sticky operation.
• Reduced oil film instability – increased cavitation
• Filterability problems and sludging.
• Biological growth in oil.
• A small amount of water has a significant reduction on rolling element bearing life.

What you need to know to achieve sampling objective?

• What Lubricant parameters will be measured?
• How often it should be measured?
• Where the best location is to draw an oil sample to ensure the best sample is collected?
• What the best tools are for drawing a sample from a specific location?
• How a consistent sample can be drawn each time from the specific selected location?
• What other information is required to carry out the analysis and make recommendations for the analysis?

Possible On-site Lubricant Analysis Parameters

There is a wide range of parameters that can be monitored without having to use a laboratory analysis. These use no or only simple test equipment.

• Oil level or grease quantity. This is a major priority for inspection
• Appearance - Colour , clarity
• Odour
• Free Water
• Sediment or debris
• Temperature
• Crackle test detect water
• Magnetic plugs detect steel wear particles
• Grease sparkle test detect steel wear particles
• Filter debris analysis (cutting open used filters)
• Bottom/Sludge sampling
• Viscosity
• Patch test or Filtergram

Appearance - A hazy or cloudy appearance often indicates water contamination, while a gradual darkening occurs as the oil is oxidized. The unaided eye can detect particles as small as 40 microns and this provides an indication of gross particulate contamination. It cannot be used for oils that are dark to begin with.

Odour - Most oils have a bland or non-descript odour. They will develop a more pungent or "burned" odour as they oxidize in service. Any unusual odours can indicate contamination such as fuel dilution from gasoline. Usually the stronger the odour is, the greater the oxidation or contamination. Vapours can collect over long periods of time in closed systems such as reservoirs or storage tanks & may incorrectly signal a defect.

Crackle Test – Detects moisture contamination and only requires a small hot surface of around 160oC (eg cigarette lighter onto a piece of steel).

Magnetic Chip Collectors - Magnetic chip collection (MCC) is the simplest and most economical method of predicting bearing and gear failure in oil lubricated systems. A Magnetic Plug or Chip Collector captures and retains magnetic particles from in-service oil and is monitored by a relatively simple visual inspection.

The size and quantity of particles captured can be directly related to component health. Magnetic Chip Collectors have been used for decades to successfully predict failures in military and civilian jet engine.

There is a simple on-site method of quantifying magnetic debris collected for a magnetic chip collector to allow long-term trending.

Figure 4.8 – Magnetic Debris Figure 4.9 – Damage to Bearing

Some Laboratory Lubricant Analysis Parameters

• Spectrographic analysis of additives (ppm)
• ppm of wear metals (only small particles < 8microns)
• PQ – Measures larger magnetic particles
• Viscosity and % Water
•  % Fuel, Glycol, Soot (engines)
• Oxidisation (temperature effect)
• Nitration (high temperature effect)
• TAN or TBN – Acidity of oil indicates oxidisation
• Filtergrams or patch tests – Microscope analysis
• Particle counts for ISO cleanliness

Patch Tests or Filtergram – The standard method of measuring oil cleanliness is with a laboratory particle counter with an output of an ISO cleanliness code. Fig 4.11 below shows some examples of ISO two number codes with X50 microscope pictures. There is also an ISO three number code system shown in Fig 4.12. The last number for both ISO code systems indicates the severity level of particles > 14 microns (bigger the number the worse the contamination).

Patch tests are a widely used method of on-site analysis of cleanliness. The most common approach uses a 47mm diameter filter paper and a 100mls of oil is drawn through the filter with a vacuum pump. Heavy oils are usually diluted with a solvent to assist with filtration. The filter paper is then inspected with a small X50 microscope and a comparison.

When a patch is inspected with a microscope it is often easy to determine the type of debris causing the cleanliness issue. This always gives good data to assist in determining the cause of the contamination. The other widely used approach is to determine the debris type causing solids contamination by cutting open and inspecting used filters.

Interpretation of Oil Analysis Reports – As there can be up to 20 to 30 parameters reported in a laboratory oil analysis report, the most important thing is appropriate parameter alarm levels are set. The person who sets the levels should have an understand of your equipment, your operating environment and of oil analysis technology. It is dangerous to always assume that the alarms used by a lab will be fully relevant for your particular environment. This is especially so if they have not got full details of your oil specification, the time the oil has been in service and the type of equipment it came from.

You also need to be sure that the Laboratory Analysis parameters you are using are appropriate for your equipment and its application. Good technical advice should be sought when setting up your oil analysis strategy. Some key items are:

• Type of water test used for moisture critical applications
• PQ or equivalent parameter is used to quantify magnetic particles
• ISO cleanliness is measure regularly or occasionally, especially in contamination critical applications.

Lubricant Sampling Approach

Sampling Strategy - “Garbage In = Garbage Out”.

• The sample must be representative, accurate, repeatable, safe, efficient & traceable.
• The sampling process must identify be right location, right tools, right procedure & people involved must have the right training and right attitude.
• Goal of monitoring should be recorded and understood
• All details required for sampling should be recorded and understood
• Required information to be recorded on bottle, including service hours or time

Information recording and Sample Analysis

• Full equipment technical details should be available to lab and CM Engineer
• Any background operational problems (equipment running hot) should be recorded
• Data for the equipment from other CM technologies should be available
• Lab should use trained experienced personnel
• QA systems in place (regular calibration tests etc.)

Lubricant Sampling – General Comments

• Always sample well-mixed oil after running equipment at least 15 minutes or after normal operating temperatures are reached.
• Machine must be out of service for no longer than 10 minutes prior to sampling
• Install dedicated sample points for sampling during operation if practical
• DO NOT allow dust, dirt or other contamination to enter sample.
• When sampling during changing of oil, always drain when hot.
• If you are sampling several compartments it is sensible begin with the cleaner systems to minimise contamination risks (hydraulic systems, then transmission, gearboxes or steering system, and finally engines).
• Dispose of used sample tubes and the waste oil from flushing properly
• If using sample pump do not fill bottles to top or tilt bottles, as this will contaminate the underside of the pump and pump itself.
• Ensure cleanliness of sampling equipment to avoid cross contamination of samples
• Always use fresh tube for each sampling pump sample
• Always clean any residue from sample pump prior to attaching bottle
• Always replace lid on sample bottle as soon as sample is drawn
• Never turn pump on its side or upside down after drawing the sample
• Ensure that the bottle is labelled with a permanent marker with the full and correct data, including date!!!!

Sampling When Changing Oil

• Ensure sample comes from main oil compartment and is likely to be a representative sample.
• Ensure engine or machine is run for at least 15 minutes before oil drained or oil is at operating temperature
• Remove cap off sample bottle within its zip (Zip Lock) bag and place bag is an accessible position near the drain point.
• The drain plug area should be cleaned, then remove the drain plug/ open drain valve and allow oil to run into a waste container.
• Remove sample bottle from zip bag while allowing oil to run for a short period. Place sample bottle directly into oil flow and ¾ fill.
• Immediately take lid from the zip bag & replace & clean bottle.
• DO NOT take sample as oil starts to drain.
• DO NOT take sample as oil finishes draining.
• DO NOT take sample from oil collected in another container.

Oil Sample Collection Report Sheets – A document is required to document the oil sample collection route. This sheet can also take the role of a sampling report sheet as in the example below.

Flushing for Sampling - Flushing is required where oil sample contamination is a problem, such as for particle counting and spectrographic analysis (almost all sampling). If lines supplying the oil sample point can’t be guaranteed to be clean & representative, then oil needs to be flushed to a waste oil container to clean out lines. All sample valves need to be flushed. Vacuum pump sampling tubes should be flushed if the tube can become contaminated during handling or insertion. Table gives an indication of flushing volumes.

Sampling with Vacuum Pump Sampling Gun – This procedure is for locations that have dust in the air (most locations have some level of dust). Zip bags can be eliminated in clean environments.

• Ensure underside of pump is clean.
• Cut a new sample tube (45o) & insert tubing into gun with 2 cm extending below the base.
• Insert pump hose into the compartment to the specified depth or half oil depth. Ensure the tube end does not become contaminated.
• If tube could be contaminated on or before insertion (or if specified) carry out the below steps.
  • Install the used sample bottle on the suction pump.
  • Operate pump for required flushing volume (discard sample before 3/4 full).
• Install clean sample bottle within a zip (Zip Lock) sealed bag onto pump and fill to 3/4 full, remove and replace cap still within the sealed bag.
• Invert pump to drain oil from tube back to tank and cut the sample tube at the top of the pump and remove it from below. Discard tube properly.
• Ensure the label is competed & correct and forward this sample to lab.

Determine tube insertion length - Measure and cut new tubing to 300mm plus the length of the dipstick or the determined inserted length. If the compartment you are sampling does not have a specified insertion depth, cut the tubing so that it can reach about halfway into the oil depth. The dipstick depth is also often used as the specification. The tube should never touch the bottom of the compartment (unless taking a bottom sample). Cutting the tube at an angle will assist with not accidentally taking a bottom sample.

Fitting sampling tube to the sampling pump - Insert the tubing through the head of the vacuum pump and tighten the tube-retaining nut. The tubing should extend about 2 cm beyond the base of the vacuum pump head.

Cleaning pump - If oil enters the pump, disassemble and clean it before taking another sample.

Zip bags - Don’t remove sample bottles from the individual zip bag or open bag until sample is taken and the cap replaced. Can all be done within the bag. Recheck cap tightness after removing from the bag.

Control of the sample tube during insertion - The natural bend in sample tubes may make it difficult to position inside a compartment where longer lengths are required. A preinstalled sample tube guide is best approach for this problem (see Fig 4.16). Where this is not possible and where safety allows, a small diameter plastic rod or stiff wire can be used as a sample tube guide. If there is any risk of the guide rod being caught in a mechanism, then a non-metallic guide should be used. The rod or wire must be clean. The plastic sampling tube is tied to the rod with plastic ties. The bottom of the sample tube is tied at the appropriate standoff depth from the bottom of the rod (see Fig 4.14). If the guide rod is to be reused it must be cleaned.

Retrofitting Sampling Tube Guides

Sampling tubes allows sampling from the optimum location in a compartment while the equipment is operating. Tubes can be bent as required before installation. The design shown indicates the inserted length required for the sampling pump tube, by having a magnetic chip collector tube installed. External sampling tube can be extended to an accessible point if there are access problems (see Fig 4.16).

Sampling for Splash, Slinger Ring & Flood-Lubricated Components - Sample from active zone and is typically 50% of fluid depth. Flushing will be required.

Sampling with a Sampling Valve - A suitable sampling valve can be connected to an oil line to a turbulent or active zone. The external side of the valve should be fitted with a pipe plug or cap. Before taking an oil sample, the required flushing volume of oil should be run off in order to eliminate any residual contamination in the oil lines.

Ensure equipment has operated for more than 15 minutes or if necessary has stoped less then 10 minutes ago. Where safety allows, run engines at low idle. Remove the dust cap from the sampling valve and clean fitting. Connect the sampling device to the valve and open valve to collect required flushing volume of oil into a waste container. (For engines at low idle, have someone accelerate the engine to high idle while extracting the sample).

Use a sample bottle with a zip bag as in Fig 4.18. Insert the sampling probe into the opened sample bottle through the plastic and fill bottle 3/4 full. A vent hole in the plastic may be required. Replace the cap while bottle still in bag. Remove bottle from bag & check cap tightness.

Special Oil Sampling Valves - There are several commercially available sample valves. Ball valves are widely used for low pressure or unpressurised lines, as there is no metal-to-metal seat. One good choice for pressure applications is the Minimess sample valve (Fig 4.19). These are similar to a check valve. They have a dust cap with an o-ring for second stage leak protection. The adapter has a hose barb on one side that accepts standard 1/4" O. D. plastic tubing. As the adapter is threaded onto the sample port it unseats the check ball in the valve and allows fluid to flow. These valves can be used on systems from low pressure to 5000 psi (Fig 4.17, 4.20 & 4.21).

Another benefit for the minimess sampling valves is that they retain a very small volume of static oil (dead volume). This results in less oil needed for flushing prior to taking a sample. On pressurized systems ranging over 2000 psi, consider safety eg. handheld pressure reducing valves can be used.

Options for Sampling Pressurized Fluid Lines

Vacuum Pump Assists the Oil Flow of High Viscosity Lubricants on Lower Pressure Systems

Fluid Sampling from Recirculating Systems - If possible always take a fluid sample from a main return flow line for external tank system. If this is not possible, sample from reservoir in an active zone. For small wet sump recirculating system the sample should be taken from the supply side of the filter (eg engines).

Primary Sampling Ports - The Primary sampling port is the location where routine oil samples are taken. The oil fluid from this sample location is usually used for monitoring oil contamination, wear debris and the chemical and physical properties of the oil. Primary sampling locations vary from system to system, but are typically located on a single return line prior to entering the sump or reservoir.

Secondary Sampling Ports - Secondary sampling ports can be placed anywhere on the system to isolate upstream components. This is where contamination and wear debris contributed by individual components will be found.

Optimum Sampling Point in Circulating Oil Systems

Sampling from Splash lubrication Compartments - Where Should Oil Sampling Be Taken - Consistent samples should be accessible with relative ease.

• Lube Systems
• Pressure and return lines
• Recirculation lines
• Tank if required
• Gearboxes
• Dipstick into sump
• Level plugs
• Recirculation lines
• Hydraulic Systems
• Pressure & return lines
• Tank if required
• Hoses if necessary
• Sample tap fitted to oil feed pipes

Materials Required for Lubricant Sampling - Required Materials

• Previous report, sample route details and a blank site report sheet
• Belt mounted pouch to store items
• Note book and 2 pens
• Small Torch (focusing type best)
• Sample bottles (“Clean”) in individual zip bags within a backpack or plastic case
• clean plastic tubing in zip bags
• Multi tool pocket knife or scissors
• vacuum sample pump in plastic bag & spare “O” rings
• lint-free cloth, dust brush, scraper and a cleaning fluid
• tape measure
• fine & thick black felt tip pens
• container for waste flushing oil
• rubbish storage for used tubes

Optional Materials

• pre-printed labels
• Sampling connections for pressurised sampling points in plastic bags
• Wire brush, Shifting spanner, Screwdriver
• Temperature meter, assisted listening instrument
• Digital camera
• Green Electricians tape (for marking operating point on gauges)
• Information tags for identifying the location of defects
• Extra PPE such as Gloves and Goggles
• Small diameter plastic rods of various lengths that can be joined together. Plastic ties.
• Copper tube with spoon attached one end
• Duct tape

Data Required for Sampling and for Sample Labels - Required Label Info

• Sample date
• sample point I.D.
• machine I.D.
• lubricant I.D.
• Test required
• Hours or date since lubricant change

Optional Label Information

• Known current machine defects
• Deviations from standard sampling practice
• Deviations from standard operating status
• Initial of who sampled
• Equipment Criticality
• Bar code for sample location
• Machine type and manufacturers code
• Target cleanliness level
• Top up volume since last sample
• If oil has been changed

Documentation Required for Sampling

• Sampling method/tool
• Description of sample location
• Inserted tube length
• Flushing volume required
• Operating status on sampling
• Other tests/ observations required

Operating Hours Since Last Oil Change - Contaminant and wear debris levels build-up in lubricant during service. It can make a significant difference in the interpretation of lubricant analysis results by knowing the time or operating hours the oil has been in-service. Even significant lubricant top-ups can affect results.

Figure 4.23 – Effect of Service Life on Spectro Oil Particle Levels

The graph in Figure 4.23 shows two separate gearboxes with the same level of Iron contamination but because of the time difference in service it means something completely different. Where possible, information on service time since last oil change and top-up quantities should be collected and recorded on the sample bottle.

Labelling - Hand writing labels before and during sampling is widely used but this is a major source of errors and problems. Pre-printed labels may take a little time setting up but saves significant time overall and gives far more reliable results. Microsoft Word has a label printing system. A4 sticky back label sheets are readily available and work with most printers although laser printers give less likelihood of ink running. Printed labels allow more background information to be recorded for the lab, such as equipment type, manufacturer & specification. Room can be left for additional hand written comments.

Labels can be placed on bottles before collection or if more convenient placed on during the collection process. If bottles are stored in an ordered fashion such as in a plastic case then pre-labelling is probably best. If bottles are stored free in a bag, then applying labels during samples reduces waisted time searching for the right bottle.

Grease Sampling for Low Speed Rolling Element Bearings

A large number of slow speed bearings are grease lubricated. Example applications are conveyor main pulley bearings, hoist drum bearing, crane wheel bearings and slewing bearings on large mobile equipment. Both vibration analysis and ultrasonics are successfully used to monitor these bearings but not always with total success or cost effectiveness.

If a good grease samples can be taken, grease analysis is the most reliable technique for monitoring low speed rolling element bearing. The failure of these bearings involves generation of substantial metal wear debris, which is relatively easy to monitor. Many low speed bearings are purge lubricated so that excess grease from the bearing is extruded from bearing seals or grease relief ports. (check that seal lubrication is not used). A simple but often effective on-site monitoring process involves close analysis of any changes in extruded grease colour and a sample taken for a Sparkle Test.

Grease colour is very important. It is affected by contaminants such as water, dirt and process material. It is also effected by the friction, heat, wear processes and wear debris from within the bearing.

Getting a sample of the extruded grease from less accessible bearings can be difficult. One technique is using a copper tube with a spoon attached to one end. The tube can be bent to the required shape and the spoon assists with scooping up the sample from the side of the housing or from the ground. Always do at least a Take 5 Risk Analysis before putting any object into a guarded area. Consider ways that the object could be caught up or turned into a spear.

The Sparkle Test involves rubbing a sample of used grease on a cloth and viewing in the sun. Bearing wear material protected by the grease will be bright and sparkle in the sun. Housing and shaft wear material will also be obvious as well but usually does not have the same level of sparkle as bearing wear material. Both represent serious defects. Even extruded grease that is contaminated with dirt or process material can be tested, as the contaminant will unlikely to include bright material.

If results from the sparkle test are not certain, then a larger quantity of grease can be placed in a small container and a small magnet and kerosene added. After shaking the container well, the magnet is removed and the material on the magnet observed for the quantity of bright material. Again this can be rubbed onto a cloth & viewed in the sun.

For formal quantitative monitoring of the grease an uncontaminated sample is best. Some methods are described below.

For smaller plumber block bearing in relatively clean environments the equipment can be isolated, the bearing housings cleaned and the bearing cap removed. Always do a Take 5 to confirm that the shaft load is toward the base of the plumber block so the shaft won’t lift if the cap is removed. Take a grease sample from the active bearing area using a clean spatula and place in a normal oil sample bottle.

If a larger diameter plastic tube can be inserted into the grease cavity then a sample can be taken with a suction pump. A reducer is required to connect the smaller diameter tube from the suction pump to the larger diameter tube. The grease is only sucked into the tube, not into the pump. A sample bottle length of the tube is cut off and placed in the bottle. For grease filled gearboxes and similar grease lubricated equipment, the end of the tube should be placed near the active lubrication area (Figure 4.24).

A larger diameter drinking straw can be used to take a sample by plunging it into the grease through a grease nipple or other hole to get a sample. Again put the straw into the oil sample container.

The best method for grease sampling is where a secondary tapped hole is available in the bearing housing (Fig 4.25). Grease is pumped into the housing during operation & a large diameter plastic tube over the secondary tapped hole collects the extruded grease.

With the equipment isolated the grease extrusion area at seals can be cleaned and new grease pumped into the bearing until the used grease is extruded. Grease is collected with a clean spatula and placed in an oil sample bottle. Even slightly contaminated samples can still be useful for monitoring PQ & Iron ppm.

Laboratory analysis of grease involves mixing clean solvent with the grease and analysing using mostly the same processes used for Oil Analysis. Iron ppm, PQ index and Silicon contaminants are parameters of most interest.

The Likely Effect of Poor Sampling Practice

Using a poor sampling procedure just one time could result in:

• Having to resample later wasting effort and money
• Changing the oil unnecessarily wasting effort and money
• Changing the oil too late causing damage to components
• Changing the oil too early wasting effort and money
• Missing a failure causing unscheduled downtime & high repair costs
• Triggering an unnecessary repair causing scheduled downtime & repair costs
• Not recognising the root cause of a defect resulting in reoccurrence of a failure

Problems with Lubricant Sampling - Samples taken from the bottom of tanks and sumps will show higher (and unrepresentative) concentrations of bottom sediment and water, as compared to system live zones. When oil physical properties, contaminants and wear metals are analysed, it is assumed that the sample is representative of the average oil condition, not specific concentrates in collection bowls, filters or tank bottoms.

Reservoir Sampling - Samples consistently collected from the turbulent zones of tanks and reservoirs provide trendable information on average oil properties. However, wear metals and many contaminants become hidden from view by filtration, dropout or dilution. This is because these solids, which are commonly ingressed or are generated at the working end of the equipment (hydraulic components, bearings, gearing, etc.), are then deposited in the large tank of cleaner fluid, or worse, removed by return-line filters in the case of many high-pressure hydraulic systems. Even if there is no return-line filter, once wear particles, water and solid contaminants enter the reservoir, their concentration will immediately and progressively change due to dilution, settling and off-line (kidney loop) filtration.

Upstream Sampling - Samples consistently taken on the feed-line of large circulating oil systems are typically the same oil with the same dropout problems as the tank sample described above. This also holds true for samples taken from off-line circulating systems (filters, heat exchangers, etc.). In this situation the actual concentrations of wear metals and contaminants are often lost from view. This is the easiest way to get a false negative (OK when it should be Warning).

Downstream Filter Sampling – In some situations it is preferable to take samples downstream of filters. In this situation you are not interested in analysing the presence of particulate matter in the oil. Particles of the size that filters typically remove will not be in the sample. What you will measure is filter effectiveness by comparing to tank cleanliness.

Dead-Zone Sampling - Getting an oil sample from a dead zone is the same as sampling the wrong machine. Dead-zone fluids (gauge-line extensions, regenerative loops, standpipe, etc.) are stagnant and typically possess properties and debris different from working fluids.

Wrong-Procedure Sampling - There are numerous sampling procedures commonly used that are far from best practice. These include using a vacuum pump incorrectly, inadequate flushing, dirty sampling hardware/bottles, etc. Although these procedures may be used consistently, they will also consistently fail to optimise the quality and precision of the sample taken. Often these methods are used simply for convenience, in a misguided attempt to save valuable time, at the expense of valuable data and ultimately valuable equipment.

Cold-System Sampling - Samples consistently collected from cold non-circulating systems will have altered concentrations of wear metals, contaminants and other insoluble suspensions. When at rest, anything heavier than the oil will begin to settle. It takes only two minutes for a 20-micron particle of Babbitt bearing metal to settle one-half inch in ISO 22 bearing oil.

Magnetic Chip Collectors vs Iron ppm and PQ index

In a small oil compartment such as a gearbox, the presence of a magnetic chip collector or magnetic drain plug can have the effect of reducing the levels of Iron ppm & PQ index levels. The presence of these items needs to be recorded.