Condition Based Maintenance – Monitoring Tools

Hi,

I keep getting updates on new products used in the maintenance field through various online subscriptions.

Here is a link that shows the us of Ultrasound devices in the condition based maintenance strategy. I am not trying to sell the product, but am just trying to propagate the techniques involved. Please connect to the link given below and learn more.

http://www.uesystems.com/new/applications/

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

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

Predictive Maintenance and Energy Savings

A predictive maintenance road map to energy savings

The connection between maintenance and energy savings is not well understood. In fact, many of us view energy savings as just an electrical issue rather than a holistic approach to all energy usage. We need to consider energy measurement as part of a predictive maintenance system; to save time, money and energy throughout the facility.

All facilities tend to lose energy (cost involved) through overheated electrical distribution systems, overloaded and misaligned rotating assets as well as lose expensive compressed air and steam through leaking pipes/fittings. We need to improve equipment reliability by fully leveraging predictive maintenance (PdM) technologies.

Step 1 – Assets Listing

It is crucial to gain a complete picture of all assets within a reliability program or at least the equipment targeted in the pilot project. Keep in mind that from an electrical standpoint, many organizations don’t breakdown the electrical systems to the component level (i.e. relays, breakers, and lighting panels).

If you are finding information gaps while compiling the assets lists, the best way to get the full is by walking through the facility with a simple facility layout drawing and notebook to capture asset name plate data.

Step 2 – Get the Energy Bill

This step requires review and analysis of energy invoices for two to three years to establish consumption patterns. The consumption pattern need to be broken up for all the specific major energy using equipment groups (HVAC, Compressors, Ovens, Blower groups etc) and groups geographical or logical location (Utility group / Data center / Paint shop / Pharmaceutical production modules / Major office floor / Lunch room etc

Step 3 – Prioritise Your Efforts

A simple prioritisation approach is to divide the gas, electric and oil bills into two usage categories; by building type or use and by equipment types which are common to a variety of process and applications, compressed air, pump and fan systems, etc.

The facility may have hundreds of fractional horsepower motors that cumulatively consume a lot of energy, but the labor, analysis and reporting costs of deploying PdM to each is more than the replacement costs. The PdM approach will be cost-effective on lesser number of critical equipment.

An asset criticality ranking process creates weighted scores based upon probability of failures, failure severities, value impact on associated personnel, systems, buildings and the overall organisation.

Ultimately, you end up with a comprehensive site equipment list and corresponding criticality score that can be easily sorted to identify the most critical equipment by asset classification, building, and cost center.

The list will be used to identify which equipment to focus on first with specific maintenance strategies. Equipment having a high-ranking will likely have more advanced PdM equipment strategies and analysis performed; whereas equipment having the lowest ranking may have a lower maintenance strategy such as “run-to-failure”.

Each organisation has a different profile. For example, industrials have a higher number of process related motor loads, pharmaceuticals more HVAC loads and commercial buildings more focus on the electrical, HVAC and roofing systems.

Step 4 – Calculate the Energy Savings

Electrical Savings – The key process requires capturing power consumption measurements taken when an anomaly is identified and after equipment is put back into service. The savings in energy will give us the annual cost savings for a given maintenance effort.

Steam Savings

Steam savings calculation will involve the collection of large data covering boiler efficiency, loading, losses, number of boilers, fuel cost per 1,000 BTU, steam pressures, water treatment chemical costs, labour burden, etc.  Further costing for PdM efforts to critical boiler components could be made to achieve cost-effective maintenance with equitable energy savings.

Electrical distribution Systems

Electricity and electrical distribution systems are the backbone of any infrastructure. The issue at hand is that much of the electrical generation and distribution systems age without too much maintenance effort at sub assembly or component levels. Many sub systems cross the designed life and become susceptible to failure and low reliability. Some of the problems faced are:

  • Unstable utility supply / line surges
  • Transient voltages
  • Unbalanced and overloaded transformer banks
  • Short circuits
  • Unidentified single-phase ground faults
  • Faulty power factor correction equipment
  • Upstream and downstream relay faults and tripping
  • Un-calibrated relays and meters

The above variables are often hidden but can manifest themselves as single phasing, shorted windings, overheated transformer banks and partially tripped over current protection. Such component level failures are caused due to lack of maintenance.

IR thermography

IR thermography captures thermal anomalies and variances in temperatures. It is ideal for capturing high resistance, overload, phase imbalance and loose electrical connections that cause overheating and wasted energy.

Ultrasound Scanning

Ultrasound scanning of steam, fire fighting water and compressed air systems will help in identifying leaky components such as isolation valves, traps etc, without physically opening the systems for maintenance.

Thus PdM initiatives will work towards holistic infrastructure energy savings.

Adapted from an article by Dale Smith, CMRP, in Plant Maintenance Aug 2010 Issue