Christer Idhammar

Founder and Executive

Vice President

IDCON INC

USA

 

In this second part of the article I will explain in more details what are the basics of reliability and maintenance, why many organizations fail to deliver achievable results, how to instill a culture of reliability and what good looks like.

Maintenance Prevention

In maintenance prevention we include everything that you do to prevent problems from occurring. We like to use the term “problems” because the context of total manufacturing reliability includes the functions of Engineering, Maintenance, Operations and Storeroom (Spare Parts and Material for Equipment) support. If we use the term “Failures” instead of problems we often focus our thoughts on equipment and maintenance issues and we mentally exclude operational and other issues such as raw material variances and changes in how a production line is operated.

Here we assume that your plant is in an operational phase and not in a position to procure new equipment. Instead you have to do better with what you already have.

Cleaning

Cleaning is an important basic element. Here we do not talk about general housekeeping but detailed cleaning of equipment and components. When detailed cleaning is done you cannot avoid doing also visual inspections, when you clean you also inspect. When equipment is clean it is easier to see abnormal conditions such as loose fasteners and leaks.

Another benefit is longer life of for example electric motors. It does not take much contamination on an electric motor to increase temperature in windings and rotor by 10 °C (ab. 18 °F), which will shorten the life of the electric motor by 50 %. For the same reason you should be careful not to paint motors with too many layers of paint. Another benefit of this basic element is that electric motors will pull less energy the cleaner and cooler they are.

Figure 4. What good looks like? Courtesy www.oilsafesystem.com

Lubrication and contamination control.

Even though awareness in this area increases, it is more common than not to find very poor practices. Precision lubrication, which includes the right clean lubricant in the right volume at the right time, is an absolute key to achieving better reliability and lower costs. Lubricators must be trained to execute lubrication in a well documented process that describes the lubricant, volume and frequency in an optimally laid out route, and in work orders for shut down oil changes and where lubrication cannot be done safely when equipment is operating. Filtration of lubricants has to be done to adequate standards e.g. down to 4 micron for many oils and central lubrication systems. Modern tools should be used to measure that the right volume is reaching the lubricated object. In order to control contamination, it is vital that lubricants are stored in a professional way.

Figure 4 shows a world-class storage and contamination control of lubricants. After reviewing all 43 lubricants used in this plant an expert narrowed it down to eight including hydraulic fluids. The lubricant storage has direct access from outside the building. All eight lubricants are automatically circulated and filtered periodically to assure cleanliness of 4 micron or less. Each container has a decadent breather to keep all moisture out and filter incoming air to 1 micron. To have lubricant storage like this costs some money but it costs much more over time not to have it. And the reduction in the number of lubricants from 43 to 8 is an immediate saving.

Alignment

Alignment is another important element of the basic elements that prevent problems from occurring. Alignment should be done when equipment is at operating temperature or with compensation for thermal growth. Jacking bolts should be installed to make precision alignment possible (you cannot align to 0.001 of an inch or 0.0254 of a millimetre with a sledgehammer).

More than three shims should not be used as more than that can cause a soft foot. Today most plants use laser alignment tools that make it easier to align and also keep track on alignments that have been done.

Alignment with precision does not only prevent problems and extend life of the aligned component such as sprockets, chains, sheaves, belts and couplings. Precision alignments also prolong life and prevent problems in bearings and mechanical seals. Another benefit is reduced energy consumption for electric motor drives. A misaligned coupling increases temperature significantly in both couplings and bearings. A brief and fast check of alignment can be done using a handheld basic infrared thermometer; increases in temperature of couplings, v-belts and chains indicate misalignment.

Balancing

Balancing of components such as an assembly of shaft and impeller for a pump, electric motors, rolls and other rotating equipment also prevents problems from occurring. Balancing of rotating equipment prolongs the life of components and prevents problems from occurring. Vibration measurements should be part of quality control for any rebuild of these components.

Operating practices

Operating practices is often a forgotten part of maintenance and problem prevention. It is common that over 50 % of equipment failures and breakdowns are caused by poor operating practices. This is because operators are seldom trained in the function of the equipment that they operate and what kind of impact wrong startups and shutdowns have on components. Nor have operators been properly trained on how to inspect components. Let me emphasize this with some examples on questions I often get from operators:

• Why can I not heat up the steam system faster after a shutdown?
• I have been told not to let cold water come in contact with the drier cans when they are hot. Why is that?
• Why should I not try to start up electric motors too frequently?
• Why do we need to run redundant equipment equal hours?
• Etc.

I know it is important that people are trained not only in “How” but also in “Why” and so we call the trainings that we do in equipment care for operators and others “Know Why” training. Here are examples of the basics of what we call Maintenance Prevention:

Explain to the operators that a steam system must start up slowly. This is because you want to avoid water hammer and consequences from too rapid thermal expansion. In a cold steam system steam will condensate and steam traps must have time to trap the condensate and discharge condensate from the system. If too much condensate is built up in the system it can fill up a pipe to form a “water plug” which travels through the system at 135–150 km/h (85– 90 mph). When this “plug” hits a pipe elbow, it can damage the pipe.

If the system provides rotating dryer cans with steam for heating, the steam inlet is through a bearing journal shaft. If the system is heated too fast this journal heats up and expands faster than the inner race of the bearing and this can lead to bearing cracks in the inner race. Cold water on a dryer, or other hot object can cause deformation and/or cracks because of uneven shrinkage caused by thermal shrinkage.

When an electric motor is frequently started, the consequence is that windings might burn. This is because when starting up an electric motor, the electric current (I) and heat (Q) spikes by the square according to Joules law Q = I2 x R (Q = heat, I = current, R = Resistance).

Many plants have redundant equipment for critical steps in production. For example duplicate lubrication pumps for central lubrication. It is necessary to operate these pumps equal amounts of time. Mark redundant equipment A and B and then make sure operators shift to run only A equipment and then only B equipment. This will prevent moisture build up in electric motors and bearings being destroyed from brinelling caused by vibrations when bearing rolling elements are in the same position for a long time. Packing material in glands will dry up and leak when a pump is started after being idle for a long time.

Early Identification of Work

This part of the basics is very critical and if not done well, it is one of the major reasons why many maintenance organizations are reactive and very inefficient. This part includes: • Disciplined and right priorities on requested work.

• Condition Monitoring.

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Figure 5. Methods used to discover problems.

Disciplined and right priorities.

One of the two top reasons as to why maintenance work is not planned before the work is scheduled and then executed, is that priorities are too emotional and not based on objective judgment on what is most important for the business. I have reviewed many backlogs in maintenance organizations all over the world and often found that the majority of work in backlogs has been assigned to highest priority; and many of the high priority work requests are over two years old! Two common reasons for this phenomenon are:

• The maintenance organization is viewed as a service provider to operations.
• The requesters of maintenance work do not trust that work will be done unless they assign priority one to the work request.

If your maintenance organization is viewed as a service provider, you want to provide good service and this often leads to you obeying to requests from operations. This view must change to a working relationship where the maintenance organization is viewed as an equal partner with operations. The role of Maintenance is to deliver Manufacturing Equipment Reliability and Operations deliver Manufacturing Process Reliability. If your common goal is to improve manufacturing reliability and roles between partners are clearly defined and adhered to, you have laid out the foundation for success. As one of the first steps in creating this partnership, you should together agree to criteria for deciding priorities of maintenance work, but do not make this too complicated. I have seen 19 page long documents used as a guideline for assigning priorities on maintenance work and it is obvious that it will not work. In my opinion there are only two priorities: Do the work immediately because it is of vital importance or, at what date it has to be completed. This is very simple but it works because people understand the logic. The overall criteria for setting priorities should include risk for:

1. Environmental or personal injury.
2. High reliability cost for Quality, Time or Speed losses.
3. High cost for maintenance repairs.

To get examples of priority guidelines please email info@idcon.com

Remember that the discussions that you have between operations and maintenance to arrive to the agreed, priority guideline is important because this is one step of many that you take to build the operations – maintenance manufacturing reliability culture.

Condition Monitoring

I like to use the term Condition Monitoring because the term Predictive Maintenance excludes the very important part of basic inspections including “See, Listen, Smell and Touch”. When I here use the term Condition Monitoring, I include all tasks that you do to discover problems early:

• Basic objective inspections.
• Basic Subjective inspections
• Vibration Analysis, Infrared measurements, Wear Particle Analysis, Ultrasonic material testing, Acoustic emission testing and other methods.

In several studies we have found that most problems are detected through basic inspections.

The example in Figure 5 is compiled three months after a process for basic inspections by operators and maintenance crafts was implemented; vibration and oil analysis had been in use for more than three years before this study. Operators and maintenance crafts were trained in basic inspection techniques and routes and detailed routes were documented and executed with a compliance of over 90 %.

The following is an example of the basic inspection of a heat exchanger:

Many Preventive Maintenance inspection programmes might describe the inspection of a cooler for a hydraulic unit as “Inspect Cooler” without any further explanation. I have used this example in numerous plants and most mechanics and operators admit they have no clue what to look for more than the obvious, such as leaks and looseness and perhaps temperature of the cooled outgoing media.

First you need to explain how the cooler works (figure 6) and that can be done with a simple sketch (figure 7).

The function and components of the blue cooler (figure 6) are described in the schematic diagram (figure 7). Most important is, that the outgoing temperature of the cooled hydraulic fluid does not exceed the maximum allowed temperature, and the system shall not start to operate before the hydraulic fluid has reached a minimum temperature. It is good if a temperature gauge can be mounted on the outgoing hydraulic fluid and marked with lower and upper temperature limits, a handheld infrared thermometer can also be used.

If the person doing the inspection is taught how the system works, it is easy for him/her to understand that it is important to track the position of the control valve. If the control valve is fully or almost fully open, it is time to report this condition so that the planning and then scheduling of a replacement or cleaning of the cooler can be done before the system overheats. Explain that the consequence of operating the system above the maximum temperature will lead to a breakdown because seals in cylinders and valves will deteriorate fast at high temperature. This will lead to internal leaks in the system, which in turn will generate more heat, faster deterioration, and then the system function ceases.

The sacrificing anode is made of a short bolt with an inside 12.7 mm (½ inch) hole in which a rod made of zinc is inserted. The zinc rod will corrode before any other material thus protecting corrosion of the cooler material. In this example this is designed in such a way that no one can see if it is gone or not. Instead it should be made of one piece of zinc, and then a small weeping hole is drilled about 38 mm (1.5 inches) into it. When the zinc rod is corroded to this point, it will show as a small leak and replacement can be planned and then scheduled before any damage is done to the cooler.

The above are examples on basic inspections and “Know Why” training. When done this way, not only will problems be discovered early, the inspection is also meaningful and more interesting to do. Inspections with the right method reveal latent problems at an early stage and this provides the necessary lead-time needed to plan and schedule work before the execution of corrective action to avoid breakdowns.

Some tools that can be used to enhance basic inspections include:

• High intensity flashlights will highly improve visual inspections.
• Inspection mirrors and fibre optics to enable inspections of areas difficult to see such as under coupling guards and inside components.
• Ultrasonic leak detectors are especially useful to detect vacuum leaks.
• Ultrasonic material testing can be used to discover thinning material in areas of high wear.
• Infrared thermometers are used to discover misaligned couplings, leaking valves and other components in hydraulic and media systems.
• Stroboscopes are used to visually stop moving parts to enable inspections while equipment is in operation.
• Dye penetrant can be used to discover micro cracks in material.
• Tensiometer to check and set correct tension of v-belts.
• Gauge to measure elongation of chains.
• Etc.

Figure 6. Cooler layout.

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Figure 7. Cooler schematics.

The most common technologies, often referred to as Predictive Maintenance, include:

• Vibration Analysis mostly used to analyze condition of bearings and unbalances in rotating equipment.
• Wear particle analysis including ferrography and spectrometric oil analysis.
• Acoustic emission used to discover early cracks in material.
• Infrared cameras used to visualize temperature patterns in equipment.

Inspections do not prevent anything at all, unless the problems discovered during inspections are corrected before breakdowns occur.

The link Early Discovery of a Problem – Prioritize urgency - Plan Corrective action – Schedule Corrective Action – Execute Corrective action is a vital foundation for any maintenance organization. It is often referred to as Condition Based Maintenance. (CBM).

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