Over the past decade, concrete producers have adopted polyurethane liners for central mix drums. In fact, most original equipment manufacturers now offer polyurethane liner kits as a standard option. Years of field research, performance testing and product evaluation have proven that polyurethane liners offer solid protection against the harsh production environment found in the concrete industry.
The strong track record of this liner material in mix drums has led to application success in other plant areas: Liner kits for aggregate bins, weigh batchers, directional chutes and dump cones are all available in high-performance polyurethane.
Switching to polyurethane liners is an investment in operational efficiency. The liner delivers longevity against impact and abrasive wear. Users of polyurethane kits report key performance factors including resistance to material build up; lighter weight—reducing loads on structures, drives, bearings and gears; shock resistance, vibration absorption and noise reduction; and extended durability.
Polyurethane liners typically come in kit form, with a variety of pre-cut shapes and sizes designed to fit specific process equipment. Several different attachment options are offered, and thickness can be adjusted to suit the application. Polyurethane liners are also available in standard sheet sizes from 4 x 8 ft. to 5 x 10 ft.
Line maintenance procedures
Polyurethane liners will perform for an extended period with proper care and maintenance. Performing the following installation and maintenance procedures throughout the life of the liner will ensure trouble-free operation, according manufacturer Argonics, Inc.
Installation. Many liner kits offer embedded steel disks. These are used as bolt anchors or tack welds to the structure. During installation make sure that every weld disk is completely attached. Once the liner has been properly installed and the plant is operational, make a daily visual inspection of the equipment.
Seam maintenance. During the installation procedure, special attention should be paid to seams or gaps, with the installer filling any seams or gaps that appear between the liner sections. A fast set polyurethane-based caulk adhesive with a 100-minute cure time or faster is recommended. If that is unavailable, then pure silicone caulk is a good second choice. It’s a good idea to contact the liner manufacturer with any questions regarding the installation. Seams should be inspected weekly, and resealed as required.
Plug fitting. All plugs should fit snug. If a plug pops out or becomes loose, material may penetrate though the weld hole. Use caulk to secure loose plugs and seal any holes as soon as possible.
Accidental gouges, tears. In the event that a gouge or tear occurs, use a polyurethane-based caulking adhesive to fill holes or fix damaged areas. The affected area should be cleaned, dried, stripped of grease or other contaminants, and patched. Repair should be completed as soon as possible after a gouge or tear is observed in order to eliminate aggravation of the affected area.
Cleaning. Liner cleaning will loosen and remove any material buildup that may occur during the course of normal production. Cleaning should be done at the end of each production period or more frequently if the plant is producing fast-setting mixes. Use a high-pressure hose to remove stubborn deposits before they have a chance to harden and grow. Cycles of clean aggregate may also be used if build up is wide spread (for example, when running cement treated base mixes).
Chipping. When chipping is required, use plywood boards to protect the liners from miscues that could result in gouges or tears. For areas around mixer blades, air chisels are more maneuverable and less bulky. For build up on seams or on other drum sections, use a hammer or another wide displacement strike tool. The resilient urethane should compress enough to release the concrete without chiseling.
Mixing blade, blade liner cleaning
Mixing blade liners often wear two times faster than drum liners. This is due to the shearing action of the material in the mix environment. Most blade liner kits are designed with replaceable tip sections at the perimeter. Because these areas are the most susceptible to wear, Argonics recommends welding bar stock along the leading edges of the blade liners. This welding creates a barrier that resists material penetration between the poly liner and the steel blade. Neglecting the blade tips could result in damage to the blades themselves, so be sure to replace blade liner tips as necessary.
Storage for future installation
Proper maintenance and care begins as soon as the liner kit is received. If the liner will not be installed in the near future, protect it from the elements. Ultraviolet rays, solar heat and oxidation of the weld disks may degrade the quality of the liner over time. If polyurethane-lined equipment is going to be out of service for a long period of time, position the equipment for proper water drainage. — Argonics Inc., 800/991-2746, www.argonics.com.