In control rooms, hand-arm vibration is rarely a problem. But significant levels of whole-body vibration (WBV) can often occur where the process vibrates and the control room is attached to the same structure as the process. This can occur, for
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FIGURE 7.10 Control room mounted on a primary crusher in a quarry. The WBV-weighted vibration on the floor of this control room exceeded 1.15 ms-2 on one axis. (Photograph by A. Nicholl.) |
example, where shakers are used in the process, or where a control room is mounted on a large vibrating machine such as a mobile crusher in a quarry (Figure 7.10). Vibrations from the process are transmitted to the floor of the control room, and hence to the operator’s chair.
As with noise, regulations produced under the EU Physical Agents Vibration Directive (2002) limit the average daily WBV exposure. The limits are based on comfort criteria. Vibration in control rooms is usually of low frequency; in the case of the quarry crusher, there were also random jolts as the rock was crushed.
The best solution to the problem of vibration is to isolate the control room from the process, a solution best introduced at the design stage of a project. Once the control room is installed, seats specially designed to reduce the seated operator’s vibration level may be needed in order to reduce the transmission of vibration to the operator. Such seats need to be designed for the range of frequencies found in the vibration, and also to be adjustable for the weight of the operator. They also need to damp vibration in the lateral and fore-and-aft directions as well as the vertical direction.
Whole-body vibration can cause a range of musculoskeletal problems. It causes the muscles to tense up in order to counteract the shaking of the body, leading to fatigue and stress, and it can aggravate back pain. This can lead to a reduced level of attention on the task. WBV can also make instruments, labels, and documents difficult to read, where either the operator or the instrument, or both, are vibrating.
