Previous articles discussed scaffold regulations and scaffold training requirements, issues that obviously are important but don’t necessarily tell us how to erect or use a mobile scaffold properly.
Mobile scaffolds, also known as rolling towers (formerly known in the old OSHA regulations as manually propelled mobile scaffolds), are commonly used when access to heights is required for a short period of time. These mobile scaffolds work very well but unfortunately there are a surprisingly high number of accidents associated with mobile scaffolds. These accidents are generally due to misuse of the scaffold although improper assembly of the parts and pieces contribute to the accidents. Consequently, this article addresses both the proper assembly of the scaffold and the correct use of mobile scaffolds.
Important Assembly Points
Using manufacturers’ guidelines, applicable regulations, and common sense, here are the important things to remember when assembling a mobile scaffold:
• The casters should be double locking so that the wheel cannot turn nor can the caster rotate.
• The casters must be pinned or bolted to either the screwjack or to the frame leg.
• The casters must be strong enough to support the anticipated load. (Most common 8 inch scaffold casters have a safe capacity of about 500 pounds.)
• The screwjacks should extend up into the frame leg at least 12 inches, preferably more.
• The mobile scaffold must always be plumb and vertical. Adjust the screws as required.
• Never have more than 12 inches of adjustment between the bottom of the frame leg and the top of the caster.
• All of the frames must be pinned together.
• All of the frames must have cross braces attached firmly.
• A horizontal diagonal brace is to be installed as close to the bottom of the scaffold as possible. This brace keeps the scaffold square.
• The horizontal diagonal brace should be installed approximately every 20 feet vertically on scaffolds 5 feet wide and approximately every 12 feet on scaffolds less than 5 feet wide.
• Provide access to all platforms of the scaffold. This can be a built in ladder, a clamp on ladder, or even a stairway if the scaffold is a very large mobile scaffold.
• If clamp on ladders are used, install them on the width side of the scaffold, not the length side of the scaffold.
• The ladder should extend at least 36 inches above the top platform unless there is a hand hold above the platform such as an access gate panel or guardrail system.
• A full guardrail system, consisting of both top rail and mid rail must be installed on all sides of the mobile scaffold.
• A toeboard must be installed on all open sides of the mobile scaffold unless other means of falling object protection is provided.
• The scaffold height must never exceed three or four times the minimum base dimension, depending upon where you are working. For example, California requires the base to be at least one third the height of the scaffold. This means that on a scaffold that is five feet wide, the height is limited to 15 feet, measured from the ground or floor to the top of the platform.
• If outriggers are used to increase the width of the mobile scaffold, be sure that they are securely fastened to the frames and properly braced.
• All planks used for the platform must be secured from movement. Hook plank are the best choice since they don’t hang over the ends and can be easily secured from movement.
Proper Use of a Mobile Scaffold
Despite proper assembly of a mobile scaffold, accidents can easily happen due to wrong use of the scaffold. Here are some things you should do to make sure that the mobile scaffold is used safely:
• Make sure everybody that will use the mobile scaffold is trained in the proper use of mobile scaffolds.
• Do not modify the scaffold unless you know the regulations and know what effect the modification will have on the stability and safety of the scaffold.
• Watch out for power lines when moving mobile scaffolds from location to location. (Rubber casters are insulators; you are a great conductor!)
• Always push the scaffold as close to the bottom of the scaffold as possible, but no more than 5 feet above the base.
• Never, never, pull yourself along from the top of the scaffold while riding it.
• Don’t ever use powered means to move the mobile tower unless it has been specifically designed to be moved by that method.
• Always lock the casters before getting on the scaffold to work.
• Take care when climbing the mobile scaffold so that you don’t pull the scaffold over. If necessary, climb on the inside of the tower.
• Do not remove the guardrail system unless alternate forms of fall protection are provided. If you do remove the guardrail system, reinstall it before anybody else uses the mobile scaffold.
Riding Mobile Scaffolds
A lot of accidents occur because people ride mobile scaffolds while they are being moved. You are strongly discouraged from riding mobile scaffolds because of the high inherent danger involved with riding mobile scaffolds. Manufacturers, suppliers, and the Scaffold Industry Association strongly discourage this practice. However, OSHA allows people to ride mobile scaffolds under certain conditions. They include:
• The surface on which the scaffold is being moved is within 3 degrees of level, and free of pits, holes, and obstructions.
• The height to base width ratio of the scaffold during movement is 2 to 1.
• Outriggers, when used, are on both sides of the scaffold.
• When power systems are used, the propelling force is applied directly to the wheels and does not produce a speed in excess of 1 foot per second.
• No employee is on any part of the scaffold which extends outward beyond the wheels, casters, or other supports.
Using a mobile scaffold safely is the responsibility of all workers. Using the guidelines above, safety information provided by your supplier, and following the applicable regulations, will result in a safe work environment for you.
