Avoid serious accidents by selecting the right load hookup and rigging hardware.
By Bill Dundas
Sign installation is a challenging and potentially hazardous occupation. Inexperienced personnel typically learn installation techniques by observing veteran mechanics. But even experienced installers may be unfamiliar with the engineering standards that define safe rigging practices for heavy signs, poles and related structures. ACRA Enterprises Inc. (Stevensville, MI), which provides crane and hoist training and seminars, publishes the Rigging Handbook, a booklet that enables job supervisors to determine suitable load hookups and rigging hardware. Combined with practical experience, observing these guidelines ensures safe field operations. Hoisting hardware The hardware that attaches a sign or pole to your hoisting apparatus is critical to safety. When fabricating a sign, this hardware must be selected carefully and fastened securely to sturdy portions of the sign's structural frame. Even lightweight cabinets comprising primarily aluminum extrusion should incorporate strong, internal braces onto which the lifting hardware can be attached. A well-built sign cabinet or frame should resist lifting forces without substantial distortion. However, if a sign isn't sturdy enough to be lifted from the cabinet or frame top, lifting slings should be wrapped entirely around the sign in a choker configuration. Eyebolts and steel angles typically attach lifting slings to sign cabinets. Eyebolts' load-bearing capacities can be determined more accurately and are, thus, used more frequently than steel angles. When using eyebolts for lifting purposes, four factors are critically important for safety. First, the eyebolt should incorporate a shoulder to stabilize its shank when the bolt is tightened. Second, the eyebolt should be threaded completely through the nut inside the sign cabinet. Third, an eyebolt's plane should always be aligned with the direction in which hoisting force is being exerted (Fig. 1). If this plane is perpendicular to the direction of force, the bolt is more susceptible to shear force. Finally, split-type (which have a gap in the "eye" ring), and bent or distorted eyebolts should never be used for lifting purposes. When an eyebolt is attached to a sign cabinet, it should be tightened carefully to avoid distorting the "eye" or bolt shank. If a shipped sign is received with bent or damaged eyebolts, replace them immediately with new bolts of the proper type and size. A relatively lightweight sign equipped with a single hoist connection centered atop the frame allows a straight, vertical hoist. This lifting configuration maximizes the rigging hardware's rated load capacity. Because this capacity is reduced when lifting force is applied at various angles to the vertical (Fig. 2); heavy signs equipped with more than one lifting point require some special considerations.
| Fig. 2: Working Load Limit of Machinery-Type Eye Bolts with Shoulder (Forged Alloy Steel) Working load limit expressed in pounds | ||||
| Size | 90 | |||
Did you enjoy this article? Click here to subscribe to the magazine.