Execute the basics of reliability and maintenance well and you will get guaranteed results. Part II
by Christer Idhammar
What are The Basics?
The most important and essential elements of the basics are listed above and include in more detail:
1. Maintenance prevention
With maintenance prevention we include everything 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 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.
1.1 Cleaning is an important element. Here we do not talk about general housekeeping but detailed cleaning of equipment and components. When detailed cleaning is done you cannot avoid but also doing 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 or 18 F. a 10 C increase in temperature will shorten electric motor life by 50%. For the same reason you should be careful not to paint motors with layers of paint than necessary. Another benefit of this basic element is that electric motors will pull less energy the cleaner and cooler they are.
1.2 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 right lubricant in the right volume at the right time, is an absolute key to achieve better reliability and lower costs. Lubricators must be trained execute lubrication in a well documented process that describes lubricant, volume and frequency in an optimally laid out route and in work orders for shut down oil changes and lubrication that cannot be done safely when equipment is operating. Filtration of lubricants has to be done to adequate standards e.g. down to 4 microns for many oils and central lubrication systems. Modern tools should be used to measure that the right volume is reaching the lubricated object. To control contamination it is vital that lubricants are stored in a professional way.
Figure 1 shows a world-class storage and contamination control of lubricants.
1.3 Alignment is another important element of the basic elements that prevent problems from occurring. Alignment should be done when equipment is in 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 millimeter 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 of the aligned component such as sprockets, sheaves and couplings. Precision alignments also prolong life and prevent problems with bearings, mechanical seals, chains, belts etc. Another benefit is reduced energy consumption for electric motor drives. A misaligned coupling increases temperature in both coupling and bearings significantly. 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.
1.4 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 prolong life of components and prevent problems from occurring. Vibration measurement should be part of quality control for any rebuild of these components.
1.5 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 they operate and what impact wrong startups and shutdowns have on components. Nor have operators been properly trained in 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 to not 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?
I know it is important that people are trained not only in “How” but also in “Why”. We call the training we do in equipment care for operators and others “Know Why” training.
Explain to the operators that a steam system must start up slowly for example 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 with 85 – 90 miles per hour or 135 – 150 kilometer per hour. 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 system is heated too fast this journal heats up and expands faster than inner race of bearing and this can lead to that the inner race of the bearing cracks.
Cold water on a dryer can or other hot object can cause deformation and/or cracks because of uneven shrinkage cause 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 Amperage ( I ) spikes by the square. Q = Heat, R = Resistance (Joules law Q = I2 X R).
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 amount of time. Mark redundant equipment A and B and then make sure operators shift to run only A equipment and then B equipment. This will prevent moisture build up in electric motors and bearings to be destroyed from brinelling caused by vibrations when bearing rolling elements are in same position. Packing material in glands will dry up and leak when pump is started after being idle for long time.
All of the above are examples of the basics of what we call Maintenance Prevention.
2. 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. It includes:
- Disciplined and right priorities on requested work.
- Condition Monitoring.
2.1 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 importance for the business. I have reviewed many backlogs in maintenance organizations all over the world and often find that the majority of work in the backlogs have been assigned priority 1; and some of the priority 1 work requests are over two years old! Two common reasons for these phenomena are:
- The maintenance organization is viewed as a service provider to operations.
- The requesters of maintenance work do not trust work will be done unless they assign priority 1 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 that you obey 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.
Do not make this too complicated. I have seen 19 pages long documents used as a guideline for assigning priorities on maintenance work and it is obvious that will not work.
In my opinion there are only two priorities: Do the work now or at what date it has to be completed; Very simple but it works because people understand the logic. The overall criteria for setting priorities should include risk for:
- Environmental or personal injury.
- High reliability cost for Quality, Time or Speed losses.
- High cost for maintenance repairs.
To get examples of priority guidelines please email email@example.com
Remember that the discussions you have between operations and maintenance to arrive to the agreed upon priority guideline is important because this is one step of many you do to build the operations – maintenance reliability culture.
2.2 Condition Monitoring
I like to use the term condition monitoring because the term Predictive Maintenance excludes the very important part of basic inspections that includes See, Listen, Smell, And Touch. When I here use the term Condition Monitoring I include all tasks you do to discover problems early. E.g.
- 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 below demonstrates this. Figure 2.
The following is an example of a basic inspection of a heat exchanger:
Many Preventive Maintenance inspection programs 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, Figure 3 works. That can be done with a simple sketch as in the example below Figure 7.
The function and components of the blue cooler, Figure 3, is described in the diagram, Figure 4. Most important is that the outgoing temperature of the cooled hydraulic fluid does not exceed maximum allowed temperature and system shall not start to operate before the hydraulic fluid has reached a minimum temperature. If a temperature gauge can be mounted on outgoing hydraulic fluid and marked with lower and upper temperature limits it is good. 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 planning and then scheduling of replacement or cleaning of cooler can be done before the system overheats. Explain that the consequence of operating the system above the maximum temperature will lead to a break down. This is because components such as packings in cylinders and valves will deteriorate fast at high temperature. This will lead to internal leaks in 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 ½ inch (12.7 mm) hole in which a rod made of zinc. The zinc rod will corrode before any other material in cooler, thus protecting corrosion of material in cooler. In this example it is designed in such a way that no one can see if it is gone or not. It shall be made in one piece of zinc, and then a small weeping hole is drilled about 1.5 inches (38.1 mm) 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 then schedule work before execution of corrective action to avoid breakdowns.
The link Early Discovery of a Problem – 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).
Inspections do not prevent anything at all unless the problems discovered during inspections are corrected before breakdowns occur.