Case Study on Advantages of Proper alignment of Rotating Machinery Assemblies

Hi,

Good, within tolerance, mechanical alignment between the driving motor and driven components is one of the basic health requirements.

I came across an excellent case study for which the link is given below.

Proper alignment helps one plant keep on pumping.

Please go through and be enlightened.

Kaycee

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Combine vibration monitoring and ultrasound for more cost-effective predictive maintenance

Hi all,

predictive maintenance is one area that needs no introduction. Combination of techniques and tools available currently makes this a very competitive process. With this process, we can determine when to do any maintenance. Yes, preventive maintenance processes also will be followed, but instead of doing them mechanically as per a time schedule, it gets done when it is required to be done.

In most cases, the buffer time provided for time based preventive maintenance schedules is too much and we end up over-maintaining the equipment causing the following:

  • Doing maintenance on fully functional, healthy and operational equipment
  • Replacing the mandatory spares and consumables every time we do maintenance
  • Creating a condition where the equipment could fail due to man-made mistakes during assembly of equipment, post-maintenance.

I came across a wonderful article covering predictive maintenance using a combination of techniques and tools. The link is given below.

Predictive Maintenance: Combine vibration monitoring and ultrasound for more cost-effective predictive maintenance.

Please take some time to look up the link, read and be enlightened.

KayCee

Good vibrations – Bad vibrations – Back to Balance

Hi all,

Years spent operating and maintaining marine gas turbines on ships have left me very sensitive to the issue of bad vibrations. The salt-laden humid sea air entering the compressor section of the marine gas turbines leave salt deposits on the blades. If not attended to regularly, the deposits will tend to foul the air flow and lead to something known as “Compressor surge”, that leads to air flow becoming disturbed and oscillating from and to the turbine end. This surge can cause catastrophic failure of the turbine as a whole, due to the sporadic and violent directional changes in axial loading on the bearings.

Taking another type of equipment this time; High speed exhaust blowers connected to automobile paintshops tend to collect paint sludge and vapour condensation on the blades over time. This causes imbalance to the rotor and leads to bad vibrations. If not corrected in time, premature bearing failure and catastrophic damage to the equipment can occur.

I came about a well written article in the recent edition of Plant Services e magazine. The link to the article is given below.

Tactics and Practices: Back to balance.

Please read and be enlightened.

Condition Based Maintenance or Predictive Maintenance practices for critical equipment can help the maintenance personnel to lesser job stress and higher labour productivity.

Kaycee

Look, Listen and Feel – in Condition Based Maintenance

Hi all,

With due respect to all the gadget geeks and proponents of high-tech equipment to carry out condition based maintenance; the age-old classic forms of observations as indicated below are still valid in the field of condition based maintenance; probably as the first information report function.

Look ………. Listen ………. Feel!

The basics of good maintenance start from the careful, systematic, periodic inspection of equipment and system elements – the first step. Recording of observations is the second step. Analysis of the observations by a maintenance team leader would be the third step.

Essential Safety Precautions for the Look / Listen / Feel Work

Wear all essential personal protection equipment prescribed for each installation. Examples – for high noise areas, ear defenders are a must; eye protection is essential where high dust, fumes, vapours, flying sparks etc conditions exist. Safety shoes are required to be worn in all conditions. Rubber soled shoes with fibre re-inforced toes are to be worn while working on electrical panels and equipment.

Individuals must be deployed for such jobs only after successfully being certified in safety aspects and equipment skills.

Visual inspectionLook

Before starting an equipment or systems: Good maintenance practices exhort users and maintainers to do a full visual inspection of equipment and systems before they are put into use, each time and every time. Such a visual inspection could reveal tell-tale oil or lubricant leaks, discolouration of protective paint due to overheating, corrosion spots, damaged parts, missing elements such as belt / chain guards, dust and debris collection, physical obstruction etc. Clearing all the abnormalities before putting the equipment or systems to use will increase their reliability.

Identifying “Lock Out Tag Out (LOTO)” Conditions: Visual inspection of control (mechanical / electrical) elements will help in identifying the LOTO conditions. In case the equipment is tagged out or locked out; operations are not possible till that condition is cleared by the person who locked it or tagged it.

Running equipment or systems: Periodic visual inspection of equipment or systems while in operation is also essential.

  • This could be done manually by visiting each equipment, looking at the equipment as a whole, checking the relevant critical parameters from their respective meters, checking for abnormal visual vibrations, checking for visible leaks, checking for overheating, checking for spray or flow quality / quantity (example – cooling tower water nozzles),
  • Alternatively, for large installations with high automation and central controls, the visual inspection could be through CCTV cameras, monitoring of parameters through data loggers, online vibration measurement, etc.

ListenListen

This is mostly applicable to equipment with rotating elements (motor driven pumps, fans, compressors etc).

Loose components or sub elements on the equipment may cause audible rattling noise. If left unattended, these could lead to consequential damages.

This technique needs some skill and long involvement of the operator or maintainer with the equipment under his or her charge. The operator / maintainer need to develop a skill on “what to listen to” and on how to identify “wrong noise”. This comes from experience.

On the long run, an operator will be able to make out the change in noise at a motor bearing or a fan air cutting noise due to blade damage. At this point it may be subjective, but a requisition for more precision measurements could be initiated before a major damage occurs.

A long stem screw driver or a simple mechanical stethoscope made out of thin, rigid, long copper tube with a small brass ear cup (a simple washer would do) attached to it could be used as an effective listening aid.

Please be wary that very noisy equipment should not be listened to with unprotected ears and the listening aids mentioned above. Prolonged exposure to loud noise could lead to permanent hearing loss progressively.

FeelFeel

The “Feel” factor is an equally important tool in condition monitoring. One needs to be a bit cautious on this aspect since many of the running equipment could have hot surfaces and may not be directly touchable, without causing harm. On the same lines, there could be system elements that run very cold and touching them with unprotected hands could cause cold burns or skin peeling. The Maintenance managers need to decide on what can be touched to feel.

Safety is very important here since the “Feel” actions are generally done on running equipment. Care should be taken to avoid putting the palm very close to moving parts

The “Feel” gives you some idea on the difference in temperature, non-visual vibration level changes, flow quality (turbulent or otherwise), presence or absence of flow, presence or absence of a liquid in a container or pipe, heaviness or lightness of an item, rigidity or flexibility of an item, speed / velocity changes etc. “Feel” is  through the skin and the palm is the best suited body part for the purpose.

Combination of Look, Listen and Feel

Practised together, the above combination provides a very thorough basic condition monitoring technique. experience on the field and safe working habits bring in a slew of benefits in OEE and reliability.

One thing good about this is that it is a value addition to the service rather than eating into a lean and mean budget allocation.

The observations from the above technique could lead to more precise measurements of temperature gradient using a thermal imaging camera, vibration monitoring using hand-held equipment etc.

Visual Factory

Appropriate signage placed at strategic locations could make the Look, Listen and Feel inspection systematic.

Place pictures of eyes where visual inspection needs to be done. Pictures of ears and palm would indicate the listen and feel activities.

Added to these, station markings arrows could be marked on the ground indicating which positions the operator or maintainer should take and direction to face the equipment to make an observation.

Further arrow markings to indicate the direction to be taken while making observations could be done to optimise effort and time taken for observations.

Tail Piece

Smell The human nose can discriminate difference in smells. For example, the smell of overheated or burning oil in a diesel engine has a very recognizable odour.

Heated or burning electric insulation also has a very distinct odour.

The smell of a burning flourescent lamp choke is very discernible.

Smell of a dead rodent in a ventilation duct can be very disturbing.

So, the nose also can be a very reliable sensory organ in equipment / system condition monitoring.

Comments are solicited on my thoughts expressed in this post.

KayCee

Five Pitfalls in Predictive Maintenance Techniques

Many organizations have cut their maintenance costs through Predictive maintenance efforts, simultaneously improving quality, safety, reliability and productivity. Unfortunately, there are a few pitfalls into which unsuspecting organisations get into while using the predictive maintenance approach. Identifying these traps will enable you to steer clear of them and set up an effective Predictive Maintenance program.

Learning to identify and avoid the recurring traps in your maintenance program will help you to be more effective in the application of both preventative and predictive maintenance techniques.

Pitfall #1: Capital Expenditure for equipment, but not for training

When maintenance budgets are submitted, and ultimately cut down, many companies fail to provide funds for adequate training to support the new Predictive maintenance related equipment. For example, some organisations invest on expensive infrared thermography equipment, but do not provide funds for proper training of personnel to exploit the full potential of the equipment. Thus the equipment would remain as an expensive toy with very little return on investment.

While OEM training on the basic operations and capabilities of the supplied equipment is essential, investment in the right kind of training is critical. OEM vendors may provide basic how-to-use training, but this may be inadequate for the users to utilise all the possible features and further more. Training by a brand-neutral or independent trainer for a particular technique using the new equipment would be beneficial on the long run. Training more than one person is also recommended to ensure year round availability of specialists. A word of caution – Do not train and allow too many people to handle expensive equipment since accountability for
equipment faults, damage etc becomes less.

Pitfall #2: Applying one predictive technique for all situations

If the only tool you have is a spanner, then every problem looks like a bolt. For instance, if you only have a vibration analyser, would you be able to identify loose connections in an electrical enclosure? Understanding the proper application of the different predictive tools is paramount to implementing and sustaining your system. Most predictive techniques are used together to improve reliability, aid in root cause analysis and improve safety. Organizations have obtained good results using a combination of predictive techniques like contact ultrasound, vibration analysis, oil analysis and thermography on gearboxes. They have been able to cut repair costs significantly by identifying a failing component instead of replacing an entire assembly.

Pitfall #3: Failing to properly re-inspect after corrective work is complete

The above scenario occurs all too often, in far too many operations. Predictive maintenance identifies problems that usually are undetectable by human senses. If the problem could only be seen with the predictive equipment, then the same reasoning should be applied when re-inspecting it. There are many instances where a repair has left the equipment in worse condition than before. For example, corrosion develops inside an electrical connection and maintenance makes the situation worse by tightening the connection. Or, in disassembling piping to repair an air leak, mistakes are made when putting the piping back together.

Without proper re-inspection, we would have no idea of the havoc we have caused in our own system. When you are using predictive techniques to identify a problem, ensure that your system schedules a re-inspection using the same technique.

Pitfall #4: Predictive Maintenance Corrective work orders get lower priority

Organisations that haven’t made the transition from reactive or breakdown maintenance to preventive maintenance will not be very effective in adding predictive maintenance to their work strategy. Maintenance supervisors will tend to prioritize more obvious problems.

All personnel involved in the maintenance process, especially those that have been working in a “reactive” maintenance mode need to understand that predictive work orders are a priority.

Predictive maintenance replaces parts before they fail—and this is a mindset that only comes with training and practice. The savings can be tremendous when parts are replaced before catastrophic failures take place to full machine assemblies.

Pitfall #5: Lack of a supporting maintenance system

While many companies will spend enormous amounts of time and money on tools, equipment, parts and materials, they will not focus on developing the foundation of a good maintenance organisation—the maintenance system. Using predictive techniques without an effective maintenance system in place only optimizes your reactive maintenance program. It will result in marginal savings and less-than-anticipated payback. Predictive maintenance is good, but you must have the other programs in place to support it.

Watch your step

In summary, recognising and avoiding the above mentioned five pitfalls of Predictive maintenance adds substantial value to any maintenance organisation.

Adapted from an article by Mark Pond of Marshall Institute – Posted by Maintenance Technology

Case Study on Reliability

Hi all,

A recent article in one of the websites covered the process followed by a large industry that won the “Best Practices Award” for them. The continuous process industry had followed a Reliability – Decision support system combination to trigger the maintenance scheduling, depending on the equipment condition.

The article makes a good reading to understand the theory in simple terms. The processes projected by other contenders for the awards are also covered in the end.  

Best Practices Awards: Reliability — Decision-support system lets rules dictate maintenance
Refinery uses protection systems in conjunction with condition-monitoring and decision-support software.

Read and try out in our operations.

Kaycee