Perhaps for the purposes of an initial illustration, it is appropriate to start with something that many, if not most people associated with equipment and plants, all have in common, i.e. vehicles.
In many modern vehicles a computer indicates and informs of the need for an engine oil change. The message from the dealer may be the same or maybe not. The vehicle computer does not monitor the engine oil quality but relies on some predetermined calculations, which the manufacturer has established and takes into consideration towards making it recommendation. Those factors the manufacturer uses are, for example, the number of starts, distances driven, total time period since last oil change, etc.. The dealer, on the other hand, may say, “see you in 6 months or another 5,000 km later”. Both or neither may be totally applicable for a particular vehicle based on the actual usage and/or the geographical location. The cost of an oil change, especially if compared to the cost of the new vehicle, or the replacement engine, may not appear all that significant. There may still be the concern for warranty and thus the issue of which of the two bits of information one should follow.
Without paying for or having access for a lab analysis of the oil there is a crude way of trying to get some idea of the oil quality. Before starting the engine and after a period of non operation of the engine, one can remove the oil pan drain plug, and carefully let some oil out. By doing so, one many observe and discover, the oil being drained is as clear and of the color, when first installed. That would be a good sign for various reasons. If the oil appeared much darker than when poured in, not a big problem but maybe it is time for an oil change. Observing some shiny metal particles (mixed in oil) or a distinct color of antifreeze (before flow of oil) would not be all that good and indicating that the engine will most likely need more than an oil change, either then or in near future. By driving the vehicle somewhere for an oil change, most likely none of the above mentioned observations would be possible or even been paid attention to. Only oil analysis in a lab would then provide detail of the oil and some aspects of the engine.
While looking at changing 6 or so liters of oil every 6 months or so, is not all that significant. For systems that may contain few hundred or thousands of liters of oil, not even a visual observation may be enough. Taking a sample of the oil and having its condition analyzed in a lab makes a lot more sense. That will more precisely tell whether the oil system should be changed and/or of the condition of the components of the system. The cost of the lab analysis would well pay for itself in either cost of oil or predicting other issues.
Most vehicles are equipped with a spare tire. To increase space and/or reduce weight, the spare tire may be such that it will be sufficient to drive “slowly” to the nearest shop (which hopefully is not far). If one travels in isolated areas or where ground conditions are not suitable for that kind of a spare wheel, one may look into other alternatives.
In some vehicles the spare is installed on the underside of the vehicle. To allow easy access, there may be a winch that one operates from the back of the vehicle and which is supposed to lower the spare wheel without having to get under the vehicle to get it. If the vehicle is operated in Arizona, one may not have to be concerned (the winch operates as per design and as per information in the vehicle owner’s manual). In many other location one may find that, by the time one actually needs to access the spare wheel, the cable between the winch and the spare tire has rusted and is thus, either partially or completely seized. That usually would occur inside the tube that shields/guides the cable. The instructions most likely do not say that the operator should pay attention to see that the tire actually starts to come down as the winch is being turned. By the time one realizes the winch moves but the tire does not, the cable may have become tangled around the winch drum. If that was to happen, the spare/winch most likely would no longer move up or down. In that situation the operator will quickly discover that only a grinder or torch will help; the cable, the winch and the rest of the associated parts are all above the tire, not visible or accessible. Usually, there is no provision to release the tire from the underside without first bringing it down with the winch. Had one paid attention and tried to release or see that tire is released before the cable got tangled in the winch, one may have been able to salvage the situation without the use of a grinder (or burning torch). The owner’s manual does not provide any information for that kind of eventuality but it can and does happen.
The manual does usually indicate that the emergency brake should be operated every time the vehicle is parked. By doing that, there is an additional benefit (beyond the actual intention of the instruction), the brake cable should not become seized. If one does not use the emergency brake with any kind of regularity, one may find that, by the time one finally decides to use the emergency brake, the foot/hand leaver may move, perhaps not all that easily but the brake will be activated. When it comes time to release the emergency brake, the spring force that is supposed to release the brake does not match the force one may have applied to activate the brake and the actual brake stays on. There is certain amount of similarity to the winch situation but, someone reading the owner’s manual may not related the secondary end result for either of the conditions.
In modern world where one has to rely heavily on allocated monies, one may be lucky to have a spare part for even the units where wear can be expected. One may find that for a $500,000,000 plant, only $2,000,000 was allocated when some similar plants were lucky enough to have $8,000,000 (even the $8M may not have been all that much, depending on the complexity of the plant or quality of the supplied parts or integrity of the original design).
For a vehicle, there is the previously mentioned owner’s manual. In some of them, early in the book, it may mention that the book is only the condensed version but may still consist of 300 or so pages. For a full manual, as informed in the provided manual, one should log onto the manufacturer’s site and get the full version, which may have 700 plus pages (just for a vehicle that may be worth $50,000). Even with 700 pages it may not be as complete as one may wish.
In the case of manufacturing plants, the situation understandably can be assumed to be much more complex; most times, there are no so called owner’s manuals, “pilot check lists”, etc.,. There may be and usually is a collection of manuals that will assist in resolving some specific issues, leaving many things for the plant people to find out and solve. Thus, a lot is left to the person(s) in charge (or doing the work) as to how and what approach to take.
By using methods such as preventive maintenance, predictive maintenance, condition monitoring, failure analysis, etc. one may “stay on top of the situations” and reduce, if not even eliminate, the impact caused by predictable or unpredictable emergencies/ failures.
The spares, the instruction manuals, various maintenance methods are all important, but the factor that still ends up bringing it all together are the people working in the plant. They are the ones who chose what to do to prevent a failure, to repair what is broken, how to improve so that it is better in the future and what options exist for when none of the supplied “tools” do not appear to be enough. They are the ones put it all together, not just as collection or parts but the methods, procedures, etc..
For example, hydraulic systems in a seamless tube mill can be very “large”. A power unit may supply hydraulic fluid to various components over a large distance. The components may need to work in unison with very fast cycle times. Even a split second variation in sequence may affect the operation and/or the product.
To set something like that up, one may need a multi channel recorder where the exact timings at each unit are recorded and analyzed later. After, the information is down loaded to where each phase can be observed and analyzed either in slowed motion and/or in over laid graphs. Sequencing the components where the timing is far too fast and critical without ability to slow down or pictorially display, would be almost impossible to do sufficiently accurately without knowing and having access to such instruments.
The power packs of such hydraulic systems usually contain, not the just the pump(s) to operate, but for standby as well. However, one can hardly allow a pump failure to happen; if the pump fails and the failure results in small particles, the particles will not be contained with the pump casing. They will travel with the fluid which now is pumped by stand-by pump (or other(s) if there are more than one operational pump). What would have started as a “simple” pump failure, will sooner or later contribute to the failure of other components within the system. This type accumulated failure would potentially go on till a complete flushing of the system is done. A complete flush of such a system may require days and thus the need to wait for some annual repair shutdown before it can be conducted. A good hydraulic person will monitor and recognize all that needs to be done to keep such systems reliably operational, replace the failing pump before destroying itself, and similarly monitor the other system components as well.
Where vibration analysis may work on some machines, there are many where it does not work. Some reducers may be subject high accelerations, stable “loaded times” of very short duration, followed by strong de-accelerations. Such conditions are usually not suitable for proper vibration analysis. If the person in charge does a bit of investigating he/she may find that monitoring the sound frequencies will give a good indication of the potential condition of the reducer. The expected sound levels may not be provided in any manuals but, the gear box manufacturer may be able to supply it, or one can always generate own historical information, especially if the history is started to be accumulated well before expecting problems.
No matter what the equipment, so much depends on the qualifications, skill sets, self initiative, etc. of the people who end up making the decisions and/or carrying out the actual work. When only part of the required information is available, one needs to recognize that and not be afraid to seek help.
Companies such as Wabi Iron & Steel Corp have the capabilities to re-engineer obsolete industrial plant replacement components, either as a casting, or a fabrication, or as a combination of both.