Using computer-based control systems became commonplace in the industrial refrigeration industry 20 years ago. Since then, techniques designed to enhance the operation of refrigerated facilities have progressed extensively. Modern computerized control systems provide benefits that can be categorized into four distinct areas: time, money, information management and improved work conditions. In short, improving control of a refrigeration facility through computerized systems can streamline operations and enhance profitability.
TimeToday, virtually every piece of equipment in a refrigerated facility is monitored and controlled by a computerized system in order to minimize the time required to check for proper operation, take readings and make adjustments. The automation of these routine tasks allows employees to focus on other non-routine duties, or to take on additional responsibilities. When new facilities are acquired, they often can be operated and maintained without hiring any additional personnel.
In many cases, the facility maintenance time requirement also is reduced due to the shorter run-time of equipment, which extends overhaul intervals. For example, instead of continuously running the maximum number of compressors necessary to carry the anticipated peak load, a good control system will sequence units on or off as the refrigeration load varies. This kind of cycling can substantially cut the hours expended in rebuilding compressors. Fan cycling and variable-speed control of fans and compressors also can contribute to a longer equipment service life.
Better monitoring of the plant operation also can minimize maintenance requirements by permitting early detection of faulty equipment. Computerized control systems provide information that would otherwise be unavailable to enable personnel to identify malfunctions quickly before a complete failure occurs. In addition, time spent troubleshooting problems can be decreased. A common example is the detection of leaking liquid refrigerant valves or defective surge drum level control switches by monitoring and recording the on/off cycles of these devices. The computerized control system provides data that will pinpoint the source of a flood-back problem quickly.
Refrigerated storage warehouses often are unmanned much of the time, and regular checks must be made to ensure that proper conditions are maintained. However, as companies increase their storage capacity and spread out geographically, keeping up with this vital task becomes more difficult. Computerized control systems provide a means to stay in touch easily using software that enables remote access by a modem, a network or the Internet. All of the control system functionality that is available locally at the warehouse can be accessed from anywhere in the world. This feature is especially useful for operations personnel at night, on weekends or holidays, and while on vacation.
MoneyComputerized control systems can improve the profitability of an industrial refrigeration operation. Although it is difficult to quantify, one of the most important financial benefits is the enhanced product quality that results from precisely controlling the optimum temperature and other process conditions. Critical parameters can be maintained accurately when a computerized system is in control. The prevention of shrivel and weight loss, which can be as much as 5 percent in some products, are important factors in quality and thus revenue.
Some control system techniques also have a substantial impact on the amount of energy required to operate an industrial refrigeration system. Fan cycling and variable-speed control of evaporator fans generally offer the greatest potential for cost reduction, cutting the electrical energy usage by 25 to 50 percent annually. Efficient control methods for compressors and condensers not only reduce maintenance costs, but they also have a significant effect on power costs.
The time-savings potential of computerized control systems, which reduces operation and maintenance expenditures, also has a positive impact on business profitability.
Additionally, the extensive monitoring features of a good control system can be used to minimize the risk of casualty loss. If the system requirements for temperature or other parameters exceed the adjustable limits, alarms are activated to alert personnel quickly. If no one is near the control computer, an alarm panel or a telephone auto-dialer will call emergency numbers to ensure that the problem is brought to the attention of responsible personnel. High system pressures, ammonia leaks and equipment failures are some of the conditions that can activate the alarm system. Insurance coverage might provide relief when damage to product or equipment occurs, but it is far better financially to avoid or minimize such mishaps.
Information ManagementComputerized control systems offer a significant advantage to the operation of a refrigerated facility by performing many data management functions such as generating the reports and historical records needed for government agencies or customers. This information also is useful for management decisions, quality analysis and other analyses.
The computer is a versatile tool for generating printed or electronic reports for logs or general plant operation. Historical records are archived automatically on the computer hard drive for subsequent retrieval and analysis. This feature can be vital for international sales. Historical records also provide a means to compare year-to-year operational parameters such as energy use, ambient temperature conditions, criteria for process conditions and equipment operation. Plant operators find that the increased information provided by computerized control systems helps them to understand more about their facility and how better control and efficiency can be achieved.
Alarm generation is also pertinent to the discussion of information management because operations personnel can be notified immediately whenever critical conditions exist.
Improved Work ConditionsOnce industrial refrigeration facility operations personnel have used a computerized control system, rarely do they express a desire to go back to less sophisticated control methods. It is a relief to eliminate the guesswork of inaccurate readings and constant control device adjustments. A twice-daily walk-through of the plant and quick scan of the information displayed on computer screens is usually all that is required. The rest of the day can be spent performing maintenance or other non-routine tasks, or a greater number of facilities can be operated than would otherwise be possible.
The elimination of off-hour inspections is probably the most significant work-conditions benefit of a computerized control system. A network or modem link from a remote computer puts operators in control of the facility regardless of their location. It now is possible to check the plant from home when an alarm company or auto-dialer wakes the operator in the middle of the night. The operator might be able to fix the problem remotely or determine if it is serious enough to visit the plant in person.
One other fringe benefit is the opportunity to work with state-of-the-art control equipment. Many plant operators have limited computer skills before a computerized system is installed. Some have become quite proficient with the use of computers as a result of their exposure to the capabilities of new control systems. It is rewarding to learn new skills and keep up with technological advancements.