Air ConditioningBy Edward J. Elliott, Consulting Editor How To Put Conditions On The MoneyNational Textiles' engineered system monitors and controls temperature and humidity in its yarn plants. At the risk of sounding simplistic, there are three possible ambient conditions that can prevail within a yarn mill: It can be too wet, too dry or just right. The "just right" condition means that the grains of moisture in the air surrounding the fiber/yarn is reflected by the proper temperature and humidity.National Textiles LLC has adopted the Duke Solutions (Techtrol) engineered system to monitor and control the temperature and humidity in the yarn mills of the Sanford (N.C.) and Gastonia (N.C.) Plants.
Ring-spinning machines at National's Gastonia (N.C.) plant produce more consisten quality yarn after installation of the company's new moisture monitoring and control system.
At Sanford, Rick Jones, plant manager, says this modern open-end spinning plant uses 100% cotton and 50-50 polyester-cotton blends. He and Charles Branch, plant engineer, explained to TEXTILE WORLD during a recent visit that control of air quality in the mill is critical in producing the high-quality open-end yarn this plant is famous for. They cited that in earlier days, one or two air conditioning technicians stayed busy attempting to measure room humidity and temperature by checking chart recorders and/or making manual sling-psychrometer readings.Out-of-spec readings required manual adjustment of air dampers and/or chiller water flow. This activity was often time-consuming and prevented the technicians from attending to other tasks. Recognizing that temperature and humidity were the two most critical factors, the Sanford Plant contracted with Duke-Techtrol to study, design and install the computer, sensors and software to achieve better control. As Jones says, "We immediately saw a dramatic leveling-out of room conditions. There was far less variance in room conditions with the computer-engineered system." The lesser variance from set-points means that when any slight deviation occurred, the sensor/computer system had less variance to adjust. Thus correction was made in minimal time, resulting in maintenance of a uniform ambient condition. Besides contributing to yarn quality, this control mode relieved the air conditioning technicians from the mundane tasks of peering at charts and twisting and turning valves.During TWs visit, Jones said that the plant was in the midst of replacing the 55 Schlafhorst Model SE-8 frames with 16 Model ACO 312 machines with SE-11 spin boxes. National has been pleased with the ability of the Duke-Techtrol system to function seamlessly in spite of the disruption of room conditions that normally occurs with removing and installing machinery.Open-end spinning needs quality air because the air is "drawn-into" the almost totally enclosed spinning machine. Quality air affords quality yarn without the serious problems of "lap-ups" which can cause thick places in the yarn. Since the Sanford Plant uses a single room to house opening, carding, drawing and spinning, the plant selects a single set-point for room humidity/temperature control, thus all the plant air is conditioned to the same set-point. Jones recognizes that there might be a slight advantage if different set-points were used for each separate operation, but the single room (without barriers) dictates that management select the optimum control points for all the manufacturing operations.At Sanford, Techtrol manipulates signals to three Trane chillers (800- ,800- and 1,100-ton) and/or dampers to outside air flow. The computer calculates (via an algorithm) the outside air temperature, percent relative humidty and room conditions and allows the most efficient control mode to be actuated. It is always preferable to use outside air for cooling when possible. In the "old days", the damper settings were often "locked-in" for an entire day, regardless if the night-time outside air temperatures were lower than daytime values. As can be seen, chilled water was used almost all day longwhether needed or notwith resultant excess electric energy demands. The Duke-Techtrol system allows maximum efficiency of air quality with associated efficiency in energy usage.At the Gastonia Plant, Steve Cagle, plant manager and Tim Waters, plant engineer, buttressed the experiences of the Sanford Plant. Here, Duke-Techtrol controls the room conditions for the 30 Toyota RX 240 SF ring-spinning machines, running only 100% cotton fiber. Cagle anticipates the plant will pursue controls for the opening, carding and drawing stages based on the good results from the system in spinning and winding. In ring spinning, room air surrounds the entire spinning machine, where the fiber/yarn is exposed to the ambient air. Air movement depends on natural convection within the room. There is no mechanical "push" to the air surrounding the machines. At times this air flow may be laminar, thus air quality conditions are important, and uniformity of air quality is critical. Proper air control results in less fiber friction, resulting in less fiber damage and less lint in the room air. This, of course, prevents lint being entwined into the yarn, making a more attractive environment for employees.Gastonia's two Carrier chillers (450 ton each) are able to maintain the spinning/winding room conditions of temperature and humidity without any interruptions. At this plant, the system has proven the advantages of a computer checking parameters many times per minute and sending correction signals to the chillers or air washers. One of the visible characteristics of the smooth control is the level electrical consumption which now avoids peaks and valleys (swings) common with manual control of chillers during varying outside temperature/ humidity conditions. Previously, air conditioning technicians would tune to radio/TV weather forecasts to be prepared to visit the plant when a rain storm (usually at night) was expected because there would be a need to manually adjust chiller/air-washer settings.
Open-end spinning machines at National Textiles' Sanford (N.C.) plant now operate on a much more even keel since installation of new temperature and humidity monitoring control system
As in Sanford, this plant has a modem wired to Duke-Techtrol 24 hr/day, seven days/wk, so either party can monitor room conditions at any time. In fact, National has installed Explorer software for Internet connection from management's corporate offices, staff's home or from any telephone access site. The ease of access to current data within the plant has afforded National the opportunity to assure that yarn quality is consistent and uniform.These two plants (an OE and a ring spinning), including Sanford going through a major spinning machine installation, and each plant's ability to control and maintain the exact room conditions required for the efficient production of quality yarns is vivid evidence of the significant advantages of a properly designed/ engineered/installed humidity and temperature control system.November 2001