Give Your Mechanical System A Physical (November 1999)
The correct approach and the answer to this question involves looking into planned, preventive, and predictive maintenance - of not only the mechanical equipment, but of the much overlooked distribution system that serves this equipment. As facility engineers/managers, we should be cognizant of the different methods and applications to apply in establishing the most effective health plan for maximum mechanical system life.
Today's technology provides the facility engineer/manager with the proper tools to build a planned, preventive, and predictive maintenance program that will encompass all the essential components in a mechanical system. Associated with these tools are standard maintenance software, tests, and procedures that will provide the necessary information to minimize equipment downtime and failures. It will also aid in maximizing useful service life of equipment.
Developing a comprehensive maintenance program will also provide the documentation necessary to determine the remaining useful life of a mechanical system with confidence. Without these tools, documenting and validating mechanical system upgrades - and backing up recommendations and decisions - without challenges from upper management or the building owner may prove difficult.
Computer-Aided CoverageFacility engineers/managers will agree that every facility needs a planned maintenance program; most would prefer a computerized maintenance management system (CMMS) to assist with that task.
Unfortunately, not all facilities have the available personnel to run a CMMS. Then there are those who buy a state-of-the-art CMMS and find out afterwards that the purchase cost is only approximately 10% to 15% of the money needed to get the maintenance program up and running efficiently and effectively. The remaining cost incurred comes from equipment data retrieval, data entry, and the actual implementation of the program. As a result, these programs sometimes never get implemented.
The CMMS is the blueprint to building a proactive maintenance health plan. Purchasing a system may be easier to justify in larger facilities, where having such a system in-house can be demonstrably cost-effective. However, smaller facilities' owners and managers shouldn't lock themselves into purchasing a CMMS if they are not committed to the time required, or don't have the resources to effectively run the system. The foundation to a maintenance health plan is the recordkeeping associated with a CMMS program. Without this paper trail, commitment, and participant commitment, the opportunity for maximum mechanical system life will be lost before the equipment fails.
There are facility support service firms that will manage the CMMS off-site and provide the necessary paperwork for day-to-day compliance for a lot less money than it would cost to purchase and implement a CMMS in-house. This can be a creative solution for smaller facility building owners. Whether a manager takes on that responsibility or outsources it to such a firm, a CMMS action plan provides a blueprint for success.
Preventive Maintenance: Building A PlanIn industry today, preventive maintenance is at the forefront of most successful maintenance strategies. Here are some tricks of the trade that can prove to be helpful when setting up a preventive maintenance program.
During new construction or renovation, involve the maintenance staff from the beginning. They can provide helpful suggestions to the design team during the equipment selection phase of the project; a good example suggestion is to make sure all filters are accessible. Also standardize the inventory when possible (e.g., use only 2- by 2-ft filters) on air handlers rather than numerous, assorted sizes.
Address the annual operating, maintenance and energy cost of equipment being purchased and installed. Budget estimates for equipment operating costs are better than no estimates at all. The maintenance person is a design engineer's best friend when it comes to setting up equipment to be operated and maintained effectively. Work together to create an initial budget profile.
Log all the equipment into your maintenance program before it is even on-line. This will ensure the maintenance program is ready and in place when it is time to start up the new system. As soon as an equipment shop drawing is approved, get its pertinent data into the CMMS database.
Try not to group all the equipment preventive maintenance (PM) tasks together. Don't include equipment that historically proves to be more cost effective to let run until it breaks. Divide equipment into three different groups:
- Safety-related maintenance. Equipment and systems that fall into this category are tagged as highest priority in the CMMS system. Equipment in this category must be maintained on the date and interval required. Examples include equipment that effects the life safety of the occupants: emergency generator testing, fire dampers, fire alarms, sprinkler systems, and smoke protection systems.
- Efficiency-related maintenance. Equipment that falls into this category may be primary equipment but still secondary in importance to the above category. This equipment is maintained to maximize the useful service life and maintain the design efficiency. Examples include chillers, central air-handling units, boilers, pumps, deaerators, and cooling towers.
- Optional maintenance. Equipment that falls into this category is the lowest priority, and should not be included in the PM program. Much of this equipment may be relatively inexpensive to replace when compared with the preventive maintenance costs that would accrue over several years. Examples include unit heaters and small motors.
Prioritizing equipment is an effective way to attack the maintenance that needs to be completed on time. This concept also will prove helpful for all the understaffed facility maintenance crews that only have time for the first two groups of workorders, deferring the rest of the maintenance.
Don't forget to incorporate "estimated equipment useful service life" benchmarks into your maintenance program. This is helpful in planning for future budgets and aids in preventing unplanned capital projects from sneaking up on you.
Pipes And PredictionsAnother important piece of the maintenance blueprint is predictive maintenance (PDM). PDM is an extremely useful tool, yet it's often underutilized by facility engineers/managers.
The facility engineers/managers that are performing PDM use traditional inspections that test the operation and condition of their equipment. Examples include vibration analysis for rotating equipment, infrared surveys on electrical components, and oil analysis for refrigeration equipment. These proactive inspections focus on predicting the useful service life of the equipment.
What about the piping systems serving this equipment and serving the building? The Achilles' heel of PDM is the distribution systems.
Piping systems provide the lifeblood of the mechanical systems. Determining the condition of piping systems is essential in a good predictive maintenance plan. It is analagous to the arteries and veins within a body: The human is only as good as the distribution system of blood flowing throughout this body. The same can be said for mechanical pipe distribution. A blockage or rupture can be disastrous, and the same can be said when master planning the changing-out of mechanical equipment. The capital project retrofit should involve an investigation into the piping system that is connected to this equipment.
Applying today's computer technologies, it is possible to determine the deterioration rate and the life expectancy of the various piping that runs throughout most facilities. Experience has shown that although most facility engineers/managers are aware of performing routine preventive and predictive maintenance on various pieces of equipment in their plants, the piping serving that equipment is often overlooked. It is not unusual for mechanical systems (e.g., boilers, chillers, and deaerators) to be replaced and the piping that connected these components completely ignored.
A good question to ask is, "When was the last time you had your piping system inspected?" During an equipment retrofit, did someone determine the condition of the piping system prior to the changeout? These are questions that raise a lot of eyebrows in industry. Visiting central plants, it is not uncommon to find people unaware of the problems that can be associated with deteriorating systems (e.g., corrosion and thinning). Pipes have failed catastrophically in several cases over the years, typically in high-pressure steam plants.
The problem with pipe failure originates over time; various temperatures, pressures, and water-steam chemistry contribute to the thinning of pipe walls. A PDM plan should start early in the distribution life. At the same time, the concern may begin with a focus on systems that have been in operation twenty-plus years, and which have experienced various chemical treatment programs. For example, improper chemical treatment in condenser water systems and boiler feedwater systems is detrimental to the life of the piping.
NDT (Or, How To Precede The Puddle)"Don't wait until you see a puddle on the floor."
"Don't wait until there is an equipment retrofit, or a steam pipe lets go."
Service-related deterioration can take on a variety of forms; at the same time, the deficiencies generally can be detected by pertinent nondestructive testing (NDT). "Pertinent" implies that the NDT method selected for the inspection is capable of determining the type of service-related deterioration relevant to the particular situation. It also assumes that the nondestructive examination is properly performed and correctly interpreted.
There are several inspections available that give the facility engineer/manager a great picture of the systems condition. These inspections include conventional methods, such as magnetic particle, liquid penetrant, radiographic, ultrasonic, and eddy current examination techniques. Unconventional techniques such as replication, videoborescopic inspections, and capacitive strain gauge testing can also be useful. Each of these techniques is well-suited to detect certain types of service-related deterioration but is incapable of detecting all types.
NDT continues to gain popularity, especially when unscheduled interruptions in some systems could lead to safety hazards or costly production losses. Using these inspection methods can help predict the future for pipe systems. The result can be a mechanical system health plan that varies operating parameters in order to reduce deterioration of certain equipment and associated distribution piping. Utilize a PDM program that documents not only equipment history but also distribution system history, making it an integral part of the CMMS.
NDT is another tool that can determine the original thickness and material of all piping systems that carry steam, high-temperature feedwater, chilled water, etc. via the CMMS action plan. Initial values should be taken off the original specifications. Select locations that are susceptible to corrosion or thinning. Examples of these locations are directional flow changes, outlets of pumps, locations adjacent to valves, and pipes that are chemically treated.
Having an accurate inspection will develop a baseline for future inspections, providing valuable input into the CMMS. This process should be a time-driven workorder; information then should be used the following year to reinspect the same locations to determine the deterioration rate, if any. Comparing these values to the minimal acceptable parameters established by the American Society of Mechanical Engineers (ASME) can help estimate what useful service life remains.
Getting A Second OpinionUsing a reputable NDT company with certified technicians provides a building owner or manager with the necessary documentation for future reference. The inspection firm can also recommend the proper inspection interval for various pieces of equipment in your facility, and estimate the remaining useful service life of the equipment and distribution system.
There are several examinations that can be performed to determine the condition of the equipment and distribution systems. The most popular of the testing is ultrasonic thickness testing (UTT, Figure 2). UTT can determine the thickness of pipes, tanks, headers, etc. UTT can also be used in high-temperature applications while systems are still on-line. This method transforms an electric pulse into a mechanical signal that vibrates a piezoelectric crystal. This, in turn, creates sound waves that determine the thickness and display it on a digital display.
Magnetic particle (MT) testing is a popular method of testing welds on pipes and tanks for cracking. MT uses a wet, fluorescent solution that has particles suspended in it. The solution is sprayed on the weld while a magnet is placed on either side of the weld or adjacent to the weld pulling the particles into a crack and exposing it.
Liquid penetrant (LT, Figure 3) testing is another popular method used to determine cracks in welds. This method uses a red dye that is applied onto the weld by aerosol or brush and penetrates into a crack. The dye is then wiped clean with a cleaning solution. Finally, a white aerosol developer is sprayed onto the weld and this makes the red dye bleed out of the crack, highlighting the problem area.
There are many other methods used in performing NDT - videoborescope inspection, eddy current, replication, radiographic examination, and visual examination. These inspections provide the facility manager/ engineer with the tools to determine the condition of their pipes, tanks, equipment, and prevent an unscheduled failure.
SummaryFacility engineers/managers know that implementing any or all of the ideas mentioned herein is difficult at best, given downsizing and cutbacks in facility resources today.
Taking the correct approach in presenting the situation to decisionmakers is sometimes all it takes to get that CMMS approved or the chiller replaced. Maintaining a paper trail and documenting/trending equipment performance will show the decisionmakers just how important it is to implement a health plan for maximum mechanical system life, and how that can improve the bottom line. ES