Solution Summary: Silo Mortar Dispensing Systems
A silo mortar dispensing system is an engineering control that can reduce musculoskeletal disorders from manual material handling, including lifting, carrying and shoveling. Mortar silos are delivered to the jobsite, and are equipped to be moved easily within minutes by a contractor's forklift as the masons move around the jobsite. Material is loaded above the silo by means of a forklift. Material is dispensed by gravity into the contractor's mortar mixer of choice from the bottom of the silo.
Mortar silos are delivered to the jobsite, and are equipped to be moved easily within minutes by a contractor's forklift as the masons move around the jobsite. The silo should be placed on level ground, downwind from the work area to avoid dust exposure. Material is loaded above the silo by means of a forklift. Material is dispensed by gravity into the contractor's mortar mixer of choice from the bottom of the silo. The amount of material dispensed by the silo can be controlled with a cut-off handle. The gravity feed is not dependent upon pressurized water hook-ups, electrical power, or gasoline motors. Therefore, no external connections are needed.
The design of the silo is simple and highly efficient when dry mortar mix is being produced on site. Silos can be used whether the worksite is small or large. This system will greatly reduce the cost of labor and the amount of waste (sand, cement, paper bags). Silos can be fitted with dust curtains, screw augers, set at various heights, and can be used with any mixer available on the market. Some vendors of mortar mix will provide the mortar silo free of charge.
With a silo mortar dispensing system, pre-blended dry mortar ingredients, including sand, pigments and admixtures, are delivered to the jobsite in 3,000 lb bulk bags. These bulk bags are then moved by forklift or boom truck lifts over a funnel-shaped silo, where they are dumped by pulling a hitch pin on the bag. Silos are available in a variety of sizes and models, and hold from 1 to 10 bulk bags. When the silo chute is opened, dry, pre-blended mortar is gravity-fed directly into the mortar mixer below. The silos eliminate heavy lifting and twisting associated with the production of materials.
Figure 1. Watkin's Concrete PROMIX Silo System
Heavy lifting and carrying and stooped postures can cause low back disorders, such as muscle strain or a disc herniation (“slipped disc”), which is bulging of disc material possibly pressing on the spinal cord or nerves that go into the leg. The silo mortar dispensing system can help reduce heavy lifting and carrying by completing cement bag handling and sand shoveling mechanically.
Stressful hand and wrist activity can cause musculoskeletal disorders (MSDs) such as muscle strains; tendonitis, which is inflammation of elbow and wrist tendons; or carpal tunnel syndrome, which is compression of a wrist nerve, resulting in finger numbness and loss of hand strength. The silo mortar dispensing system can help reduce stressful hand and wrist activity by completing cement bag handling and sand shoveling mechanically.
How Risks are Reduced:
Using bulk pre-blended mortar and a silo dispensing system eliminates cement bag handling and sand shoveling from the mortar mixing process. All dry ingredients are handled mechanically, with either a forklift or boom truck, eliminating the risk of injury due to manual materials handling.
Cement bag handling is eliminated. Because bulk mortar bags are handled mechanically, with either a forklift or boom truck lift, there is no need to manually lift or carry heavy bags of cement. Masons will not need to lift or carry the 94 lb cement bags, thereby reducing the risk for developing musculoskeletal disorders of the back or shoulders.
Sand shoveling is eliminated. Because the bulk mortar producer pre-blends all dry ingredients including sand, shoveling is eliminated from the mortar mixing process. Therefore, masons will avoid awkward postures of the back, neck, and upper extremities. In addition, repetition and stressful hand and wrist activities required by the mason to manually shovel material will be eliminated.
Manufacturers of silo systems claim that heavy lifting, and awkward and forceful hand exertions are eliminated because all the bags are handled mechanically.
There have not been independent published studies measuring the effect of a mortar silos on reducing musculoskeletal disorders. Regardless, safety and health experts believe that masons will be less likely to develop musculoskeletal disorders if they use silo mortar dispensing systems on the jobsite.
Effects on Productivity:
Job productivity is increased because laborers have fewer tasks to perform in order to produce mortar for the masons. Many contractors believe these automated processes reduce material handling by mason tenders, freeing them to do other work, which can also free up jobsite space.
When using a silo mortar dispensing system, it is important to assess the risk of silica exposure in the mortar mixing station and ensure that appropriate controls are in place. Silo systems do not eliminate the risk of silica dust exposure in the mortar mixing station; however, dust curtains are available. Specific safety procedures must be followed when loading the silo, climbing the silo's ladder, and moving the system. The silo should be placed in a location that will minimize dust exposure to workers, and will facilitate the safe movement of vehicles/equipment needed to load the silo and handle mortar.
In addition to their ergonomic advantages, silo systems can also save space on congested jobsites, reduce material theft, and eliminate the problem of bag disposal (all bulk bags delivered to the jobsite are later removed by the supplier and either reused or recycled).
Mortar silo systems with built-in mortar mixers are currently available on the European market. These devices are closed systems. The silo is filled with the mortar components specified by the contractor and then sealed prior to delivery to the worksite. Electrical and water supply connections are needed. The mortar silo systems with included mortar mixers are pictured below.
Dan Anton, PT, PhD, ATC and Carlos Sanchez-Marin, DDS, MS – University of Iowa
To obtain information, visit http://www.quikrete.com or contact 1-800-282-5828