Solution Summary: Permanent Recessed Anchor Point System
A permanent recessed anchor point system, such as the Anchor Thread by Ajustco, is a prevention through design (PtD) solution that addresses worker exposure to silica dust by eliminating the need to perform post core drilling on concrete structures for traditional anchor point installation. In addition, it addresses the risk of falls from elevation through the reduction of ladder time if drilling on concrete ceilings is required.
The Anchor Thread system can be installed in any concrete form including shear walls, elevator shafts, columns, and decks. Once installed, it acts as an immediate anchoring point for many application including, but not limited to: fall protection, leading-edge protection, safety netting, debris netting, shaft netting, ceiling systems, building maintenance safety connection points and temporary lighting connection points.
The installation of the Anchor Thread system is primarily embedded in concrete. The system (figure 1) consists of an anchor bolt, escutcheon, lock nut, lock plate and nails.
Figure 1. Components of the Anchor Thread System (Photo courtesy of Ajustco)
The first step of installation is by nailing the lock plate to the formwork. Next, the anchor bolt and lock nut assembly is inserted and turned 90 degrees clockwise onto the lock plate. The escutcheon cap is then tightened clockwise against the formwork to seal the locknut and lock plate assembly at the bottom. Once all systems are installed, the next step is to pour the concrete into the formwork and allow to cure. Finally, when a qualified person deems that the concrete has achieved the required strength, the formwork may be stripped and the escutcheon can be removed (figured 2). As a result, a caved-in concrete finish is created with a protruding anchor bolt within (figure 3). Each anchor can hold up to 5,000 pounds.
Figure 2. Escutcheon being removed by a provided escutcheon removal bit (Photo courtesy of Ajustco)
Figure 3. A resulting tie-off point after the escutcheon is removed. (Photo courtesy of Ajustco)
Drilling concrete is a dust-generating activity that uncontrolled would place workers at risk of lung disease, cancer, chronic obstructive pulmonary disease (COPD), lung scarring and silicosis with prolonged exposure. Further, core drilling require workers to clean bored holes by using compressed air to clear the dust prior to installing the anchors. Silicosis is an incurable, sometimes fatal disease. Such disease is well documented in many industries from granite quarries to concrete handling in construction. The NIOSH-recommended exposure limit (REL) for silica is 0.05 mg/m3 as a time-weighted average concentration for up to a 10-hour workday during a 40-hour work week. OSHA has a new construction permissible exposure limit (PEL) for respirable crystalline silica of 0.05 mg/m3 as an 8-hour time weighted average (TWA).
Climbing ladders during core drilling installation will increase the chance of a fall leading to an injury or even death. Fractures are the most common injuries associated with falling from a ladder, followed by strains, sprains, and abrasions.
In addition to the risk of falling during core drilling, there is a risk of falls when installing mechanical, electrical, and plumbing (MEP) systems overhead in buildings. The permanent anchors provide tie-off locations that can be used when installing MEP systems.
How Risks are Reduced:
Hazards associated with core drilling are eliminated by placing the anchor during the concrete pour. Moreover, ladder time (working at height) is reduced during ceiling anchor point installs.
- Another benefit the Anchor Thread System provides is a permanent location where fall arrest systems can be anchored to prevent falls during construction as well as during future building operations and maintenance.
- The anchor bolt is also protected from being damaged during construction.
- As is the case with any construction tool and equipment, users should follow manufacturer safety recommendations and comply with any applicable local, state or federal regulations.
Jean Christophe Le, MPH - CPWR The Center for Construction Research and Training.
John Gambatese, Ph.D, PE, M.ASCE. - Oregon State University