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Southern Mills Improves Weaving Efficiency

LTG Weave Direct system provides better conditions for less money.

An ATI Staff Report

mitchell_637S outhern Mills’ Plant Ellis dramatically improved its weaving efficiency, significantly reduced warp stops and improved fabric quality with the addition of an LTG Weave Direct system.

"The Weave Direct system has proven out," said Steve Mitchell, vice president, manufacturing, Southern Mills. "We have seen a 20-percent reduction in warp stops and a 5-percent increase in efficiency throughout the weave room since we installed it. Quality has also improved."

The 20-percent decrease in warp stops is an average. For some styles, the improvement was even greater. The improved efficiency makes a significant contribution to the plant’s bottom line.

Weaving machine vendors and industry analysts estimate that a one- percent improvement in weaving efficiency is worth about $1,000 per loom per year. Southern Mills management agreed that this is a valid figure but declined to name a dollar amount for the productivity gain.

Figures for the plant, which has a unique product mix — 22 different fibers and blends not counting yarns purchased outside the company — would probably be very different from those of a more conventional weaving operation. The plant’s fiber mix includes aramids, cottons, nylons and polyesters. Yarn counts vary from Ne 4 to Ne 40.

The plant was built in 1961 to be a gray operation. Throughout the plant’s history, six major changes or additions have been made. In its current incarnation the plant is a vertical operation going from fiber through fabric. Major end-uses for the plant’s fabrics include the laundry and technical fabrics market segments.

Additional Benefits

In addition to productivity gains and quality improvements, the Weave Direct system has reduced the plant’s need for conditioned air, decreased possible fiber-to-fiber contamination and opened up the weave room’s overhead space.

The LTG system required much less infrastructure, allowing for a smaller air washer and smaller ductwork. For example, the Weave Direct system requires 272,000 cubic feet of air per minute (CFM), compared to 400,000 CFM for a conventional system.

Cross-fiber contamination was a major cause of defects prior to the installation of the LTG system. There were more than 40 separations in the weave room during ATI’s visit.

"Contamination was something that we talked about early on," said Lee Lipscomb, plant manager, Plant Ellis. "One of our objectives was to minimize flow across the room and with it the possibility of contamination."

The additional overhead space has made it easier to change out patterns using the plant’s quick style change system. Maintaining clearance for quick style changes was a particular concern since the weave room runs many styles and changes styles regularly. It is not unusual for the plant to have 45 or more styles running at any given time and to have 15 to 20 style changes every week.

"One of the main things that I like about the LTG system is the improved aesthetics of the weave room," Mitchell said. "The way that they retrofitted the system for our plant really opened the weave room up. The Weave Direct diffuser is not in the way. You can see across the room, and it still performs and does a great job."

Conditions under the old system could be very uncomfortable. "The old system made conditions in the room hard to control," said Wayne Gammon, weaving manager at Plant Ellis. "Outside conditions had a big impact."

Evaluating Needs

loom_636When Southern Mills began to look for a new humidification system that would meet its needs. The process involved looking at several systems and visiting a number of facilities to gauge the effectiveness of various technical approaches to the problem.

"We saw that we had to have an improved HVAC system in weaving," Mitchell said. "We had the old Humiduct system and old chillers that needed to be replaced. At the same time, we wanted to improve weaving performance."

Part of this search included a trip to Europe to see LTG’s Weave Direct system at plants in Germany and France. Mitchell was impressed with what he saw there.

The weave room that Mitchell visited in France had been built in two phases. One half was constructed using a conventional air conditioning system. When the room later doubled in size, an LTG Weave Direct system was chosen to support the new looms. The plant was equipped with Sulzer weaving machines. Interestingly enough, it had 24 new Sulzer looms with Weave Direct and the same number of older Sulzer machines serviced by a conventional air conditioning system.

Mitchell quickly noticed that the newer looms had the same weaver assignment even though they were running 20-percent faster. On comparable styles, the new looms has an efficiency that was five- to six-percent higher than the older machines. The new Sulzers also had about a third fewer stops.

"It was a perfect example of looking at a conventional system versus the Weave Direct system," Mitchell said. "I saw that they were able to improve efficiency. I was really impressed. Faster machines, which typically have more loom stops, had the same loom assignment as the looms under the conventional system weaving the same fabrics."

Installation Phase

The installation of the Weave Direct system went very well. The plant replaced its old Humiduct system and upgraded its air washers and chillers. It was a complex project involving four or five different contractors.

"LTG’s work on this site was as good as I have experienced in any project that I have done," said Barry Flippo, plant engineer, Plant Ellis, Southern Mills. "It was a major installation. We were running production concurrently with the installation. They did an excellent job of working with us."

"The biggest and most challenging aspect of this project was the size of the duct running through the room," Flippo said. "At some points, I went back to LTG and just demanded that we work around some things that we had in the room. They were good to make those changes."

Weaving And Humidity

Conventional conditioning systems have always had to compromise due to space and cost considerations. With a conventional weave room conditioning system, the control sensors which regulate the amount of moisture being delivered to the room are mounted on columns in the isles between looms. This location is intended to provide an average room condition.

Normally the humidity is set between 65- to 80-percent relative humidity. Potential problems such as condensation on walls or structural members and employee comfort levels seldom allow higher set points for conventional systems. To provide this average condition throughout the entire volume of the room requires large quantities of humidified air.

"As an example approximately 50-percent more air is required to maintain an average condition of 75-percent relative humidity versus 65-percent relative humidity," said Steve Plane, president, LTG Air Engineering Inc.

"This requires much larger air washers, fans, ductwork and filtration components, as well as higher operating costs."

The air in the immediate area of the warp is also warmer than in the isles due to the motors and the weaving process itself. Therefore the relative humidity in this area is much lower than at the sensor. On average this difference is usually 10- to 15-percent. In fact, it is not unusual to record a 50- to 60-percent relative humidity at the warp, which is significantly below optimum conditions.

In 1992, LTG introduced a series of systems designed to address this situation.

The LTG Weave Direct system is designed to place the high humidity required at the process, not in the large volume of the weave room. By delivering the air directly to the warp, from either above or below, the 10- to 15-percent relative humidity difference can be reversed, providing, for example, 75-percent relative humidity at the warp and 60-percent relative humidity in the room.

This approach has proven to provide significant improvements in weaving efficiency and product quality due to the higher relative humidity at the process. The lower relative humidity in the isles also provides workers with an improved comfort level.
January 2000