canadian puregas equipment limited
Proactive Maintenance and Air Dryers Ingolf Plath C July 14,1996 Canadian Puregas Equipment Limited Table of Contents 1. Introduction 3 2. Pressurization 4 3. Maintenance 5 3.1. Types of Maintenance 5 3.2. Proactive Maintenance 6 3.3. Allocating for Proactive Maintenance 7 4. Summary 9 1. Introduction Pressurization of cable was first instituted in the 1940’s to protect telephone cables from moisture intrusion and subsequent problems due to sheath and/or splice integrity faults. A dry pure gas such as air was forced, under pressure, into the cables. This pure gas under pressure within the cable prevents moisture from entering the cable and purges the cable of any inherent moisture. Over the years, pressurization use has been expanded to include other types of communication carriers such as F.O. cable, coax and waveguide. Air dryers have also changed from the original refrigeration type to heatless regenerative dessicant to the newest technology of permeable membrane dryers. This discourse shall provide an understanding of the basics of a good maintenance program and why a maintenance program utilizing the latest techniques is important for proactive maintenance. This is not a complete in-depth analysis on pressurization, but rather a primer on maintenance programs to help those persons who require information to understand the benefits of a good maintenance program and how it can improve the bottom line. 2. Pressurization Pressurization of cables is done to preclude moisture from entering within the sheath of the cable by way of natural humidity and water by way of sheath faults and susceptible splices and terminations. The ideal outside plant (cables) will have no leaks, a constant air pressure and low air flow. Due to the actual integrity of systems and their inherent leaks many systems were built with air pipe distribution so that the air can be distributed to extended sections of the cable. Otherwise these sections would have no flow or pressure as the air introduced at the beginning of the cable would have exited the cable through the leaks. One of the reasons for this low cable pressure integrity is the lack of complete monitoring and proactive maintenance. With a good monitoring system and proactive maintenance pressurization of the outside plant can be efficiently achieved with a good quality air source, properly sized and minimal air feeder pipe or none at all. When cables were originally pressurized from nitrogen bottles, and if there were no leaks at all, the pressure in the cable would stabilize. Once the pressure is stabilized then there is zero flow. Since it is almost impossible to have a completely airtight system (and there are reasons not to) we always have air flow into our cables. Air is introduced at the beginning of a cable at the central office (C.O.) which has a certain flow and pressure. As long as the flow is constant the pressure in the cable will stay constant. The air dryer must provide the air flow necessary to achieve a constant pressure at its normal capacity. If the dryer must provide higher flows than its normal rated capacity then a secondary or larger dryer must be installed. If this is not done or the cable flows not reduced the maintenance costs will increase dramatically or the dryer will fail. Conversely if the dryer need only produce a flow less than its normal capacity and maintenance is routinely performed according to manufacturer’s specifications the dryer will last indefinitely. 3. Maintenance 3.1. Types of Maintenance There are three types of maintenance that can be performed to maintain a dryer and correct breakdowns. They are reactive, preventative and predictive maintenance. Reactive or emergency maintenance is a repair that is done after a breakdown has occurred. This is usually due to a dryer operating beyond its normal capacity or lack of routine maintenance. Too often the main cause is due to a lack of proper routine maintenance because of a shortage of time, manpower or skills. This is the most costly and inefficient way to maintain a dryer. It is analogous to not fixing the hole in the roof of your house until it is raining, in which case the repair becomes more costly and leads to more damage and complaints from the customer, i.e. your spouse. Companies that rely only on reactive maintenance procedures in a highly competitive market usually lose their customers and their maintenance costs soar until they become insolvent. Preventative or preemptive maintenance is scheduled or routine maintenance. This is the most common form of maintenance which is based on the equipment manufacturer’s or industry recommendations. It is considered proactive. This scheduling of maintenance is fundamentally to prevent emergency repairs by improving or repairing equipment before failure occurs. Preventative maintenance has a structured and known cost, but due to the nature of a cable plant and myriad external influences emergencies will not be eliminated. There will always be unscheduled breakdowns. Predictive maintenance is unscheduled maintenance based on data collected from the actual plant. It also falls under the proactive maintenance category. From the data collected during routine maintenance we can see the condition of the equipment and plant and base our maintenance procedure upon this condition. This provides us with information so that we can conduct our maintenance accordingly and greatly reduce our maintenance and downtime costs. Recommendations provided from the results of data collected must be followed to increase the efficiency of the plant and preclude future emergencies. The three types of maintenance can be compared to the maintenance of a roof. If you replace the roof covering of your house only when it leaks so thoroughly that you have water damage this would be considered emergency maintenance. If you replace your roof when the manufacturer recommends this is considered preemptive maintenance, even though you may have problems before this time or the roof covering may have an actual longer life span. If you monitor or inspect your roof twice a year and repair it before it leaks, be it before or after the recommendation of the manufacturer, you have performed proactive maintenance and preempted any emergency and ancillary damage, and received the useful active life of the product. Your cost of monitoring is minimal compared to damage costs of emergencies and the cost of unwarranted replacement. 3.2. Proactive Maintenance In today’s competitive market it is imperative to have your system operating at peak efficiency without downtime. Predictive maintenance (monitoring) is completely proactive. A proactive maintenance program produces long-term gains if properly implemented. Part of this implementation includes training and purchase of tools to monitor the plant and its trend or contracting of maintenance to qualified companies. Fully effective proactive maintenance requires a disciplined and well structured maintenance management program. Most proactive maintenance programs require a significant corporate investment in time and resources for implementation. Many companies tend to be penny wise and pound foolish with maintenance programs which inhibits proactive maintenance. There are few short-term gains. It is an investment for long term gains and when fully and correctly implemented those gains are substantial. Predictive maintenance can deliver benefits to your company on many levels. Studies have proven that predictive maintenance on average is one third the cost of reactive maintenance due to continuous savings. For an example of savings calculate the cost of a repair when a dryer fault is found and repaired by a technician during routine maintenance before any problems arise to the cost of repair and downtime if the dryer failed on a weekend and a cable was lost. These costs can be measured in actual dollar figures. As a direct result of eliminating emergencies the tangible effects of any revenue loss can be determined. By implementing a proactive maintenance program corporations willing to invest resources will gain real tangible benefits. In the communications industry the outside plant is the factory that produces revenue. The foundation (production machine) of the plant is the cable. The dryer maintains the cable. If the cable (machine) is maintained there is no factory downtime and loss of revenue. Other benefits are: savings in personnel and time, efficient use of ancillary equipment such as air dryers, improvement of the overall efficiency of the outside plant and customer satisfaction. 3.3. Allocating for Proactive Maintenance To benefit from a successful proactive maintenance monitoring system proper allocation of resources is a requirement. First of all a plan must be developed for implementation. This plan must be adhered to for the success of the program. The first emphasis in allocation is on the training for the personnel assigned to the maintenance. When properly trained these same technicians can also give recommendations on equipment and procedures for efficiency. Untrained personnel doing improper maintenance will create problems. Education of personnel contributes to the overall success and acceptance of the proactive maintenance program. Proper tools for maintenance means having not only the normal mechanics tools, but also special tools required to accurately discern the characteristics of each dryer. These tools are used to acquire information to be used for predicting the next maintenance cycle and recommending improvements to equipment. Monitoring of dryers in this way during routine maintenance and using this information in a computerized maintenance program results in predictive maintenance. Other tools required, but often overlooked, are manufacturer’s manuals and specifications, factory training and periodic upgrading and manufacturer’s technical expertise, i.e. consultations or technical help desk. One of the most important tools is the maintenance checklist. This list or inspection sheet should be specific for the type of equipment and information required. It should not have check boxes for these are not specific. The technician must be directed by the inspection sheet, i.e. instead of a check box for ‘ Flow check ‘ the mechanic should have to write in the actual readings and conditions. It should also have a list of all the tests required to ascertain the condition of the dryer so the technician can record these for later input into the database. From this information recommendations can be made for further savings. This information will tell us whether the dryer is sized properly for the air flow required and recommendations can be made. This information also gives us the monitoring ability for predictive maintenance. For ease of maintenance and time saving all equipment should be standardized. This not only saves on information required, but also saves immensely on time and tools that are required due a great variety of equipment. It is much easier and less time consuming to maintain equipment that is similar and has not been altered (except upgrade modifications) from a standard. Another benefit of standardizing is that parts are more common and therefore inventory levels are lower. The initial cost of purchasing replacement equipment for old or non standard equipment is quickly paid back by the savings in maintenance and breakdown costs. Accurate record keeping is a must for a proactive maintenance program. Ideally a computerized database should be maintained daily. Information should be input at least after every routine inspection on a timely basis. The database should be integrated with a maintenance management program that forecasts maintenance based upon input of information (from inspection sheets) received from the maintenance technicians. The maintenance program will then predict routine maintenance based upon actual indications of each dryer and routine maintenance can be performed when required. This predictive maintenance program will greatly reduce unforeseen failures. Recommendations can be easily made for equipment upgrade or replacement and the condition of equipment is easily known. The maintenance program can also be allocated to an outside contractor. This can be a more cost effective way of implementing a proactive maintenance program. Of course the contractor must have trained personnel, the proper tools and be familiar with proactive maintenance, including maintaining a computerized predictive maintenance program. 4. Summary A good proactive maintenance program is a combination of the latest technology, educated personnel, and management support. Achieving a very successful proactive maintenance program requires planning, training and a good information system. Adequate implementation planning and training will ensure the highest use and best value of the air dryers. The savings after implementation of the system will come from many sources. They include improved personnel utilization, reduced overtime, improved plant performance, reduced downtime, increased plant reliability and reduced emergencies. The major savings come from reduced loss of revenue when the plant is shutdown (cable loss) and equipment replacement cost due to failure caused by ineffective maintenance.
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