The Basics: How to Securely Anchor Machinery

A proactive business owner knows that providing a hazard-free workplace by adhering to OSHA will help create a successful work environment. Reducing workplace risk is a priority that benefits all elements of a business.

A basic knowledge of how to securely anchor fixed machinery to prevent movement (OSHA regulation 1910.212(b)) is one important way to achieve a protected work environment.

First, consult the machinery’s manufacturer recommendations for specific anchoring instructions. Typically, a wedge anchor may be recommended to adhere equipment because it provides the highest and most consistent holding values of any mechanical type expansion anchor in solid concrete. This mechanical type expansion anchor is made of four parts: the threaded anchor body, the expansion clip, a nut, and a washer.

Technical Specifications: 
To ensure safe and proper wedge anchor installation, certain technical specifications must be considered. Wedge anchors come in a variety of diameters, lengths, and thread length and are available in three materials: zinc plated carbon steel, hot-dipped galvanized, and stainless steel.

304 Stainless Steel Wedge Anchors
This wedge anchor is used in submerged, wet environments, with spacing between each anchor more than 10 anchor-diameters apart.

316 Stainless Steel Wedge Anchors
This wedge anchor is used in caustic, wet and/or moist atmospheres with a minimum distance from an unsupported edge of five anchor diameters.

Hot Dipped Galvanized Wedge Anchors
This wedge anchor is used in moist environments with a holding value depending on the diameter of wedge anchor and the depth of embedment. The hardness of the concrete base material increases the holding value.

Length:
To determine the length of the wedge anchor required, add the thickness of the material to be fastened, plus minimum embedment, plus the thickness of the nut and washer. The sum of these three items equals the minimum wedge anchor length. The wedge anchor requires no maximum hole depth. The depth of the hole in the base material should be at least the length of the anchor minus the thickness of the material being fastened. This will provide some extra depth to accommodate a minor amount of concrete cuttings that may not be able to be easily cleaned out of the hole.

Spacing:
The forces on a wedge anchor are transferred to the base material in which it is installed. If the anchors are installed too close together, an interaction of the forces might occur to reduce the holding power of the anchor. The expansion anchor industry has established a minimum standard of ten anchor diameters for spacing between anchors and five anchor diameters from an unsupported edge. When vibration or sudden impact is part of the load conditions, the spacing between anchors should be increased.

Sizes
To determine the minimum length of wedge anchor to use, add the thickness of the material to be fastened to the minimum embedment for the diameter of the anchor to be installed with space for the nut and washer. These anchors can be installed at a deeper embedment than the minimum embedment depth. In most cases, this will provide better holding values.

Minimum Embedment Depth by Diameter of Wedge Anchors

Through Fixture - If the anchor is going to be installed while the fixture is in place, the hole in the fixture can be slightly larger than the designated diameter of the anchor (see chart below). The anchor can be embedded at least to the minimum embedment depth, (see chart above).

Direct into Concrete - the anchor is embedded into the concrete the required distance (see minimum embedment chart above). A minimum of three to five threads can be below the surface of the concrete and with enough threads above the surface to accommodate the thickness of the material being fastened and space for the nut and washer.