Five Senses Inspection of Equipment and the Surrounding Area
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Return to Condition Monitoring - Predictive Maintenance Techniques
What is 5 senses inspection of equipment?
Condition Monitoring is about finding equipment defects. Condition monitoring is an excellent approach for finding equipment defects but it won’t assist in finding all defects. There is a large range of equipment defects that are most easily found by simple ‘Look, Listen & Feel’ inspections. They're also called ‘5 Senses’ inspections. Examples of 5 Senses observed defects:
- Seeing a fluid leak from a pipe
- Hearing an air leak from a valve
- Seeing a damaged electrical control box
- Seeing a bolt that has lost a nut
- Hearing a clicking noise from a machine
- Feeling that a gearbox has a high temperature
5 Senses inspections should take very little additional time during a data collection or inspection route but greatly increase the value of the activity. Never let 5 Senses inspections become a time waster. At least 90% of the activity should be done in parallel with the routine monitoring activity. Use of the term monitoring will include inspections.
Why is 5 senses inspection so important?
It is not unusual, especially where equipment being monitored is reliable, that the greatest value from monitoring comes from defects found from other observations away from the prime focus of the inspection. For example
- Finding machine defects that are unrelated to the monitoring
- Observing defects or potential defects in surrounding processes and equipment
- Performing simple defects fixes such as tightening loose bolts, greasing bearings and fixing minor safety issues.
One of the common problems in maintenance is that rigorous equipment inspections are not done or the personnel used are inexperienced or unmotivated. It is imperative that effective equipment inspections are a part of the Predictive and Proactive strategy. Information learnt from equipment inspections can lead to improvement opportunities both for the equipment and the monitoring process.
Understand what you are inspecting?
The key to effective equipment inspection is understanding what you are looking at and recognising what is out of the ordinary or changed. Many people would have had the experience of looking at something and not recognizing any defects. Then after learning more about the issue or item, upon further observation instantly see a defect.
If you come across a word you have never seen before, you will not be able to recognise if it is spelt or used incorrectly. If you look the word up in a dictionary you are likely to instantly recognise a spelling error or incorrect use next time you see this word used. The equivalent to a dictionary for industrial machinery are equipment manuals, drawings and asking experienced people.
The other key factor is the desire to understand. Not everyone aspires to be a good speller but if you are involved with equipment inspection, to do it well, you must develop the talent. When you are looking at a piece of equipment or a plant process, ask yourself “what don’t I understand here?” & “what would be the easiest way to find out?”.
Health, Safety, Security and Environmental Inspections - The first focus of all inspections should be the health and safety issues for yourself and others. Condition monitoring and inspection usually involves working in close proximity to operating equipment, so all hazards need to be properly identified and managed. The key formal tools for this are the ‘Job Safety Analysis’ (JSA) and ‘Take 5’. The JSA is completed before starting a job and the ‘Take 5’ done while the job is being carried out. These processes could be called other names. You should be aware if dangerous chemicals or gasses, high pressures, high temperatures, excessive noise etc. occur at your working locations or are associated with equipment you are monitoring. One major source of major injuries and death is mobile equipment. Before you start concentrating on your data collection you must assess the risks from mobile equipment entering your work area. A large number of injuries come from slips and trips so you should assess the flooring around machines before you start monitoring.
If you find a serious issue, you should make it safe and communicate or fix the defect as soon as possible.
Understanding the Operational or Production Process
Sometimes the most difficult thing to understand is not individual items of equipment but how they work together as an operational process. This is not always the highest priority thing to learn but it is important in a number of ways. Often there are operational problems that can be easily observed that are not related to any particular item of equipment. These problems can be extremely important to the plant. Examples are, process materials having incorrect temperature, size, flow, moisture or colour.
Understanding the operational process lets you better understand the criticality of equipment defects that you find.
- What will the effect be if the equipment fails?
- Is there redundancy (duplication) in the process?
- What is the cost per hour of operational stoppage?
- How long will a repair take and what would be the rough cost?
Understanding Machines and Machine Elements
As the main role of condition monitoring data collection is the find defects in machines, you must have a good understanding of the particular machines being monitored and how they can fail. It is useful to understanding the function of a machine within a process and how they work to perform the function.
It is also useful to understand what is inside a machine. To understand what you are seeing, hearing and feeling on the outside of a machine, usually requires an understanding of what you can’t see inside. The best source of information on what is inside a machine and how it works comes from cross-sectional or exploded drawings. These are most readily available from manuals. Actual disassembly and repair experience is also valuable of course.
You may find yourself waiting in the maintenance office. Find out where they store the machine manuals and take the opportunity to try to find and copy the cross-sectional drawings of a machine you don’t fully understand or don’t know the details of the internal components. Technical information on bearings, gears and couplings is also very useful.
Inspection for Machine Force and Lubrication Issues
Parameters such as vibrations felt by the hand are generated from varying machine forces, typically related to a components rotation. The prime sources of these forces are unbalance, looseness, misalignment, bent shafts, damaged components, electrical forces, hydraulic forces, resonance and friction.
Observations can yield significant information about what is causing machine forces to increase. eg:
- Seeing that a machine element has been changed may make misalignment more likely
- Seeing a grease nipple is damaged or dry may make friction more likely
- Seeing a lot of dust and moisture around a fan inlet may make unbalance more likely
Friction problems caused by poor lubrication are a major cause of equipment failures and should be a major focus for inspection. Eg:
- Checking oil levels, temperature, oil appearance and smell for all compartments
- Checking for signs of inadequate greasing eg. Dry nipples or lacking grease purged from seals.
- Sources of lubricant contamination or poor handling of top-ups.
Inspection of Equipment Mounting & Support Issues
How the equipment is mounted and supported can have a significant effect on both vibration levels and failures. If a machine is mounted on a tall relatively flimsy support structure, the level of Velocity vibrations will be much higher than would be normal and has to be taken into account when assessing defect severity. Similarly if the equipment is mounted on springs or rubber mountings.
Inspection of support structures for issues such as low design stiffness, corrosion, cracks, looseness, damage or concrete spalling is important. How machines are mounted to the support structure is also important. Items to check for are loose bolts, corrosion around mounting shims etc.
Machine misalignment is a consequence of poor mounting practice and/or support deterioration. Some rubber style coupling designs can give a visual deterioration of failure by deposits of rubber debris directly under the coupling.
The Five Senses Inspection Process
Ask yourself the right questions during inspection and monitoring.
- What am I seeing, hearing and feeling?
- What should or could I be seeing, hearing and feeling instead?
- What could the difference indicate?
- Are there any patterns over time or space?
When you inspect a machine you observe 1000’s of things at once. Your mind tends to focus on things that appear unusual or different to normal. Often we ignore these things because they appear trivial, but sometimes they are symptoms of something significant. For example: You see a small pool of liquid on the floor. You can see no obvious reason for it to be there & remember seeing it there last inspection. The liquid has a chemical smell up close. There is pipework above the area but no drips. Inspection Comment: Small pool of chemical smelling liquid at location XX, could be an intermittent leak from the pipework above.
Vision – Using of your eyes
When most people are doing an equipment inspection they will tend to use all their ‘look, listen & feel’ skill simultaneously. This training material encourages you, while you are trying to develop these skills further, to do these three activities separately. This reduces the likelihood of missing useful information.
Vision is the most powerful of the human senses and is linked to brains ability to recognise colours, shapes and patterns. Items we have observed intently forms an image in our mind and even small changes over time are often easily identified.
Human sight is not designed to work at night or where the light intensity is low. A mandatory inspection tool to carry is the battery powered torch.
Another useful tool to assist visual inspection is the strobe light. It can make rotating and reciprocating equipment appear stationary. Used widely for V belts inspection. Be aware of safety issues with its use on rotating equipment where you can forget an object is moving. What should I look at?
Get an area overview before concentrating on the monitored equipment.
- What operational or maintenance activities are occurring?
- Could the activities create a hazard to you?
- Could they impact on the monitoring?
- Do the activities give any clues to current equipment defects?
- What is the operational process and overall equipment status?
- Are there any issues in the work area or areas you are pass through that may need reporting?
- Safety issues such as damage to hand rails, guards missing, obstructions to walkways or other hazards.
- Damage, leaks, build-ups or problems with other equipment
- Any issues with connecting components between the equipment you are monitoring and the rest of the process eg. Pipework
Make a note of all overview issues for inclusion into the site report Get an overview of the equipment being monitored.
- What has changed since you last saw the equipment?
- Are there any new hazards? Review existing hazards. Trips, temperature, heights etc.
- Is there any evidence that suggest maintenance has occurred?
- Guards moved, machine elements changed, equipment cleaner, equipment dirtier or maintenance related materials in the area.
- Is there any evidence that suggests operational problems?
- Leaks, spills, adjustments, operating tools left etc.
- Is the equipment running?
Check and record if necessary any relevant operating parameters. Pressures, temperatures, flows, currents, voltages, loads, speeds etc. Recommended technique for gauges is to cut a small strip of green electricians tape and stick it to the gauge face on the normal operation position. This highlights any changes that occur between visits. Inspection of machine elements and components What defects can be observed and what has changed?
- Leaks
- Wear
- Damage
- Visual indication of fumes and air flow
- Items missing
- Damaged bolts
- Component movement
- Oil levels
- Grease nipple and purge symptoms.
Hearing and Smell – Using your Ears & Nose
Vision is such a powerful sense it can distract us from the minor sounds and smells that are present. Sounds and smells are sensed in similar ways and so can be used together. Get an overview before concentrating on just the monitored equipment.
To further develop your sense of Hearing and Smell for inspection, it is recommended you stop all other activity for a few seconds to listen and smell. It may be appropriate in some situations to remove hearing protection for this for a very short period of time but this should generally be avoided. Try to identify the source of any noises and smells in the area and decide if any seem unusual. You may have to move positions to help identify the source location. Any unusual noise or smell coming from the equipment being monitored should be further investigated.
Noises or smells coming from other equipment should be investigated especially if they seem serious. If the source from other equipment can’t be identified, just record what has been heard or smelt and the location and check next time. As with sight, often small changes in noise or smell can be detected once familiarity with the equipment has been gained.
Hearing – Using your Ears
There is a range of tools to assist hearing. Listening rods, stethoscope, electronic stethoscope, Ultraprobe ultrasonic meter and amplified accelerometer output into earphones.
Assisted listening is a comparative technique. Listen to the equipment position of interest and then listen to a similar component to detect a difference. The ideal for comparison is the same position on an identical piece of equipment. Also compare to other positions on the same machine.
Most of the best vibration analysts still use assisted listening during data collection as an integral part of their monitoring. There are a number of machine defects which may be difficult to detect with the most advanced vibration instrumentation but can be easily detected with the human ear. eg minor clicking or ticking noises, audible harmonic tones and low speed bearing defect patterns. The Japanese steel industry widely & successfully uses listening rods up to 2 meters in length for monitoring of slow speed bearings.
Noise is a possible defect symptom for almost all equipment eg: Bearings defects, gears defects, friction from any moving component, rotational touches, component resonances, structural resonances, flow noises, impact noises, electrical hums, electrical arching, bubbles, material cracking, pressure leaks, minor explosions etc.
As with vibration, the frequency and amplitude of the noise is important. Any variation or unusual characteristics of a noise should be noted. For rolling element bearings above 600rpm, development of a consistent noise that can easily be heard by the unassisted ear is important. It is often a trigger for a relatively urgent repair action.
Noise can be analyzed identically to vibration with the use of a microphone rather than an accelerometer. This can be useful for monitoring where direct housing contact is not available and fixed transducers are not installed.
Smell – Using your Nose
Unlike most other senses there have not been many technologies to measure or amplify the sense of Smell. Some examples are: Sniffer dogs, dangerous gas detection sensors, biological odor sensors.
Smell is a possible symptom for the following defects:
- Electrical defects (Ozone)
- Temperature fumes smells
- Chemical fumes
- Fumes, powder and smoke from deteriorating components
- Dangerous gasses
- Process material smells and fumes
- Moisture smell
- Rotting smells eg. seriously deteriorated oil
Touch- Using your Hand & Body as a Sensor
Get an area overview before concentrating on just the monitored equipment. You can often feel vibration with your feet when getting closer to equipment, especially for larger equipment or where equipment is mounted on a steel structure. If vibrations can be easily felt in the supporting structure, check if the source is external to the machine eg. A nearby crusher, pulverisor or screen. This can cause special failure problems. A high temperature source may be detected by the skin of the face or hands, either from radiant energy or from heated air movement.
Using human touch as a vibration transducer during data collection
Vibration you feel through your hand can be most closely correlated with RMS Velocity Vibrations. Vibration frequencies over 1,000Hz (60,000cpm) can not be felt by your hand. Some people can feel higher frequencies using their fingernails. Very low frequency sounds, such as from large piston air compressors, can be felt through the chest cavity.
Inspection of machine elements and components.
There are hazards in touching machine component. Before touching equipment, do a visual check that there is no sharp object, pinch points, moving parts & ensure no loose clothing or instrument cables are exposed. Hold your hand a few centimetres from the component for a second to detect very high temperatures. Then do a quick finger touch to check for temperatures above 60oC, which is the temperature you can comfortably leave your hand on for more than a few seconds.
If working around furnaces, be sensitive to temperature through shoes as a safety issue. Once shoes get hot, you may get burned before you can get to a safe area to remove them.
Touching components to measure vibration
Touch all components that are measured. For small items use one finger. For larger items use either hand or finger (usually depending on how dirty). If the component is very hot or very dirty, use a solid probe to transfer the vibration.
The finger is a very good sensor for differential movement between components. You just place your finger along the interface between the components. It is important to try to correlate patterns of vibration from touch, noise and vibration amplitudes. Velocity ‘vibration to touch’ and acceleration ‘to noise’.
Touching components to measure temperature.
Temperature monitoring with hand is adequate for many applications. Cheap contact and non-contact temperature meters are available where accuracy is required. Contact sensors are more accurate but non-contact are easier and quicker to use and more flexible. Non-contact sensors can be used for measurement of rotating components.
If unusual temperature patterns are suspected then a thermal imaging camera is the correct instrument to fully assess potential defects.
Touch for measurement of air flow
Airflow is necessary for cooling and ventilation in many industrial applications and the human face, hands and arms can be used to give an indication of flow. It is often important to confirm adequate airflow for motor, gearboxes, heat exchangers and electrical equipment. There are also relatively cheap hand held airflow instruments available if required.
Taste – Using your tongue as Sensor
Taste should NEVER be used in typical industrial and mining applications. It is difficult to find a useful application for use of Taste and it is extremely unlikely to find a situation where the possible Health and Safety hazards would make the test worthwhile.
Using the Five Senses of Others
You may only visit a specific equipment area once a month and a lot of issues could occur in between. Building good relationships with people working regularly in that area is very useful. This will help you to find out about relevant equipment incidents or problems. These may include:
- Operators who work in area or operate equipment (high priority)
- Maintenance people who work in the area
- Regular contractors
- Operational supervisors
If there is a regular lubrication person, make sure you know who it is and make regular contact to assist with follow-ups. There can be many reasons why area people may suspect a defect with an item of equipment. It is also important that they understand the importance of your inspection and monitoring work.
Operators can give information on equipment performance, unusual noises on start-up or shutdown and machine failures. Other maintenance personnel can give information on repair tasks carried out, procedures used, reported defects and equipment failures.
What Changes can be Observed at the Equipment
- What changes have occurred since previous measurements.
- Is there any evidence of maintenance activity
- Any evidence of previous recommendations having been carried out
- Has bearings been greased (fresh grease on nipple) or oil been added (disturbed dust etc. at fill point)
- Is there evidence of new grease purged through seals
- If greasing is a possible issue, try cleaning the grease nipple so it becomes obvious at next visit if greasing has occurred.
Cleaning to aid inspection
It is often necessary to do some quick cleaning to be able to inspect effectively. Try to get operators involved with helping with the cleaning. Off-line cleaning may be necessary if there is a serious leakage or spillage defect. Good relationships with operators and other personnel is a major advantage to get equipment cleaning executed.
5 Senses Site investigations
- Investigate defects indicated by previous monitoring report
- Carry out relevant 5 senses inspections for defects identified last inspection
- Ask other if he has specific issues that require inspection or investigation
- Investigate if any item appears changed or out of place.
Appendix 1
Ultraprobe 2000 bearing monitoring procedure
- Install contact (stethoscope) module to Ultraprobe, plug it in & put on the headphones. Set the frequency selector to Fixed Band (or 30) and mode selector to Lin.
- Set the Ultraprobe Sensitivity Dial to the setting predefined for the monitoring route or machine. This will be a level where a typical good reading will give a level of 20 on the meter.
- Find the predefined spot on the bearing housing and contact the spot with the probe. If the monitoring spot is not marked, select it using the information on the previous slides and mark it for the future (Options are black felt pen cross or white spot with marking paint. Centre popping the location can also assist for long term).
- Approach the bearings at the same angle each time, ideally perpendicular to the surface and contact with a reasonable contact force (0.5 to 1 kg).
- Record the meter level reading and assess dB increase from previous or baseline measurement (20 increase on the meter = 3dB). The sensitivity will have to be adjusted if the meter is full scale.
- Listen to bearing sound pattern through headphones. Change sensitivity if required to hear the sound pattern more clearly. Adjust the filter if required to make the sound clearer.
- If anything even slightly unusual is heard, select reference bearings of the same type, under similar load conditions and same rotational speed and compare patterns & levels.
- If a problem is suspected, carry out defect identification including locating the local point of highest meter reading, the area background levels, possible airborne interference, bearing temperature, assisted listening for audible noises and other 5 senses techniques.
- Record likely defect, severity and recommended action.
