Membrane Dryer Saves 12 Hours/Week Maintaining Refrigeration Dryer
Switching to a membrane dryer saved 12 hours per week that a manufacturer of forestry equipment previously spent maintaining a refrigerant dryer used to remove moisture from compressed air. Drying compressed air is critical to Windsor Forestry Tools, Milan, Tennessee, because moisture causes sticking and other problems in pneumatic drives used in production machinery. In the past, the company’s maintenance department was kept busy repairing refrigerant air dryers. Despite that fact, the refrigerant dryers were unable to keep moisture out of compressed air lines during humid summer months with the result that machines were often down due to problems with pneumatic cylinders and valves. The company switched to Balston SMD series dryers from Parker Hannifin Corporation's Filtration and Separation Division, Tewksbury, Massachusetts, that combine coalescing technology with an innovative membrane system to supply clean, dry fresh air without any moving parts. "The new dryers are so reliable that we have not had a single machine go down due to moisture problems since they were installed," said James Johnson, Maintenance Manager for Windsor Forestry Tools. "And the only maintenance they require is changing the filter every eight to ten months or so."
Windsor Forestry Tools manufactures cutting chain and guide bars for chain saws and commercial timber harvesting equipment in a modern 60,000 square foot manufacturing facility. Windsor has been manufacturing cutting chain products since 1948. With products sold in over 50 countries, over 75% of Windsor’s sales are outside of the United States. In 1986, Windsor Machine Corporation was acquired by Sandvik AB of Sweden. In 1999, Windsor was acquired by Snap-on Incorporated as part of the Sandvik Saw and Tool Division. Since 2000, Windsor has been part of the Outdoor Products Group of Blount, Inc. The Outdoor Products Group manufactures and markets chain, bars and sprockets for chain saws and timber-harvesting and processing equipment for the world's timber industries; concrete cutting equipment; specialty lawn mowers (ZTR - zero turning radius); lawn mower blades; and accessories for these products. The Group is based in Portland, Oregon and has six manufacturing locations - one in Brazil, another in Canada, and four in the United States. It sells to original equipment manufacturers and to consumer end users through a strong, diverse network of distributors and dealers. Besides Windsor Forestry Tools, other operating units include Oregon Cutting Systems Division, Dixon Industries, Inc. and Frederick Manufacturing Corporation.
Importance of moisture removal
Compressed air is one of the most critical inputs to the company’s manufacturing operations. Pneumatic cylinders drive a wide range of automated production equipment used to build Windsor’s products. The compressed air that drives these cylinders must be free of moisture in order to prevent rust and other problems that can cause pneumatic valves and cylinders to stick. When sticking occurs, the equipment must be shutdown while repairs are made, generating costs of hundreds of dollars per hour in lost production. In the past, Windsor used refrigerant air dryers to treat compressed air generated by four Gardner-Denver and one Quincy compressors, each rated at between 325 and 375 horsepower. "Refrigerant dryers are very complex machines with many potential points of failure," Johnson said. "Because of the critical nature of the application, we had to perform continual maintenance on them. But in spite of all that effort, they were often unable to deliver moisture-free air during the humid summer months. That caused problems with cylinders or valves sticking and meant that our maintenance people were even busier trying to keep the production machinery running." Johnson said that additional disadvantages of the refrigerant dryers were that they generated a lot of noise and used fluorocarbons, which the company is trying to eliminate in order to improve the environment.
Membrane filtration technology
Johnson stated one day a Parker / Balston representative visited the company to provide information on membrane dryers. He noted that these dryers work on an entirely different principle than the refrigerant dryers. Prior to entering the membrane drying portion of the system, the compressed air passes through two high efficiency coalescing pre-filters. The pre-filters remove water droplets and particulate contamination with an efficiency of 99.99% at 0.01 micron. The air leaving the prefilter is laden only with water vapor that will be removed in the membrane module.
Next the air passes into Balston dehydration membranes. These consist of bundles of hollow membrane fibers, each permeable only to water vapor. As the compressed air passes through the center of these fibers, water vapor permeates the walls of the fiber, and dry air exits from the other end. A small portion of the dry air (regeneration flow) is redirected along the length of the membrane fiber to carry away the moisture-laden air that surrounds it. This moisture-laden sweep gas is vented to the atmosphere while the remainder of the dry air is piped to the application. The liquids removed by the filter cartridge continuously drip into the bottom of the housing where they are automatically emptied by an autodrain assembly. The dryer delivers air with a dewpoint of 35 degrees F. No electrical supply is required to use these dryers.
Working with the Parker / Balston representative, Johnson configured a two-phase drying system. The first phase is a Balston coalescing filters that remove compressor lubricant, condensate and solid contaminates from the air stream. It utilizes microfibre® matrix technology that provides consistent, superior performance for common compressor lubricants, including UltraCoolant and Sullube. The high efficiency coalescing prefilters protect two Balston 76-500 membrane dryers that each deliver 500 standard cubic feet per minute (SCFM) at an operating pressure of 100 pounds per square inch gauge (psig). Balston dryers are available in 14 different models that can deliver dry, compressed air at flow rates up to `1200 SCFM. The Balston Membrane air dryer is designed to operate continuously 24 hours per day, 7 days per week. The only maintenance required is changing the prefilter cartridges every 6 to 12 months. This takes only 5 minutes. No electrical supply is required to use these dryers, which makes them much less expensive to operate compared to refrigerants. Another advantage of membrane air drying is that it does not produce condensate. An average 100 CFM compressor system can produce up to 1,800 gallons of oily condensate per year, adding a disposal cost to the operation as well.
Eliminating downtime and reducing maintenance
The installation of the new dryers solved both the maintenance problems and the production downtime problems at the plant. "As soon as we installed the Balston dryers, we eliminated the need to perform maintenance on the refrigerant dryers," Johnson said. "The membrane filters have no moving parts so there is nothing to wear out or break down. All we have to do is change the filters about every 8 or 10 months or so. Now we can devote the time that we used to spend working on the refrigerant dryers to our production machinery instead. We obtain additional savings from the fact that the membrane dryers do not consume any electricity. Finally, from an environmental standpoint, I like the fact that the membrane dryers don’t use fluorocarbons or any other substances that could have a harmful impact on the environment."
Johnson noted that the new dryers are temporarily out of service because the associated compressors had to be shut down as part of a cost-saving move. "We are anxious to get them back into operation because the membrane dryers are able to keep the air dry during the humid summer months," Johnson continued. "We frequently experienced downtime in the past because water would seep into pneumatic valves and cylinders and we would have to shut down production machines in order to make repairs. The Balston dryers keep the compressed air dry all of the time so no matter how humid it gets our machines keep pumping out parts. The extra production is probably worth much more than the time we save in reduced maintenance, but the savings are tough to calculate. The important thing is that membrane dehydration eliminates the time and energy that both our maintenance staff and our production workers used to spend worrying about how dry the compressed air was. That means we can spend much more time and energy focusing on our main job -- producing a quality product for our customers."
For additional information, contact Parker Hannifin Corporation, Filtration and Separation Division, 100 Ames Pond Drive PO Box 1262, Tewksbury, MA 01876-0962. Tel: 800-343-4048 Fax: 978-858-0625.