Suspended Access Equipment – Calculating Counterweights

Suspended access equipment—Counterweights

Explain dangers

Without the right number of counterweights, suspended access equipment (SAE) can fail, leading to injury or death.

Identify controls

Here’s how to calculate the number of counterweights you need to support the SAE.
Since we need to build in a safety factor of 4, the effect of the counterweights holding the equipment up must be at least 4 times greater than the load pulling the equipment down.
Another way of saying this is:
• Multiply the load of the counterweights by the distance of the outrigger beam from the fulcrum to the centre of the counterweights (L).
• This number must be at least 4 times greater than the distance of the outrigger beam from the fulcrum to the suspension point (X) multiplied by the capacity of the SAE.
Let’s look at an example:
1. The outrigger beam is 18 ft long. At least 2 ft of space is required by the counterweights at one end of the beam (CWL). There is 1 ft of overhang at the other end of the beam after the fulcrum.
18 ft (beam) – 1 ft (centre of CWL) – 1 ft (X)
L = 16 ft
2. The SAE can support a load of 1,000 lb (LL). The distance from the fulcrum to the suspension point is 1 ft (X). Multiply these numbers to get the maximum force that will be pulling down.
1,000 lb (LL) x 1 ft (X) = 1,000 ft lb
3. The resisting force that is holding up the SAE must include a safety factor of 4.
1,000 ft lb x 4 (SF) = 4,000 ft lb
4. The load required by the counterweights is determined by dividing the resisting force by the distance on the beam from the centre of counterweights to the fulcrum (L).
4,000 ft lb ÷ 16 ft (L) = 250 lb
5. Assuming the counterweights are 55 lb each, here are the number required.
250 lb ÷ 55 lb = 5 counterweights
Before deciding whether or not to add more counterweights, keep in mind that every manufactured steel outrigger beam has a defined limit to the number of counterweights that can be placed and secured on it. This limit must be indicated on the beam label.
If labels on an outrigger beam are missing or not readable, do not use the beam.
Remember—only use counterweights that have been specifically manufactured for the particular outrigger beam you are using.
Counterweights should be securely attached to the outrigger beam so that the vibration or movement of the beam will not dislodge or move
them.

Demonstrate

Demonstrate as you talk. Calculate the number of counterweights required for SAE on the site.

For more information, visit the IHSA website.