Lifting operations: manual 295-6 mechanical

The ftinction of the lift lever is to allow manual opening of the valve. Usually, when no extia-lever mechanism is provided, at least 75% of the system s set pressure is required to overcome the spring force by opening the valve manually with a lift lever. While it is required by code, it is judged unsafe to manually open a valve under pressure, especially at higher pressures and higher temperatures, as the person operating the lever would be too close to the valve. 

Muscle power is restricted to the manual effort required to operate portable lifting equipment. An example of this is the chain block shown in Fig. 19.8 capable of lifting loads up to around 5000 kg. The mechanical advantage is obtained through the geared block thereby reducing the manual effort required in operating the chain. 

Mechanical assistance involves the use of mechanical aids to assist the manual handling operation such as hand-powered hydraulic hoists, specially adapted trolleys, hoist for lifting patients and roller conveyors. 

Alarm activation points have to be clearly highlighted and marked.Their operation should be simple, direct, and consistent throughout the facility or company, especially if personnel may be transferred or rotated from one location to another. A protective mechanism is usually incorporated to prevent false activation of manual switches (e.g., protective lift cover, depress button, and puU to operate rather than just push to operate, etc.). 

Lifting and moving of objects should be done by mechanical devices rather than by manual effort whenever this is practical. The equipment used must be appropriate for the lifting or moving task. Lifting and moving devices must be operated only by personnel trained and authorized to operate them. Employees must not be required to lift heavy or bulky objects that overtax their physical condition or capability. 

---