Ergonomics Evaluation Of Portable Pneumatic Extinguisher

Portable pneumatic extinguisher is one of the important equipment for forest fires in China. The bad working environment, unreasonable operating mode, vibration and noise of portable pneumatic extinguisher will cause the increasing of fatigue and workload. It is necessary to ergonomically evaluate this machine, then propose reasonable operating rules and optimization suggestion. The operating characteristics, the measurement of vibration and noise, and the influence of vibration and noise on human body of this machine were researched. The main contents and results of the research are showed as follows:1. The carrying postures and motions of 6MF-30 was evaluated at static state from heart rate, electromyography, reaction time and subjective assessment. There are three types of carrying posture, which are associated with an oblique strap, a vertical strap, or no strap. Motion had two levels: stationary, and swinging. The result showed that the effects of the carrying posture on the increasing ratio of heart rate (p<0.001),%MVC of the palmaris longus (p=0.001),,%MVC of the biceps brachii (p=0.015), the rate of movement time (p=0.026), the degree of comfort of the left arms (p<0.001), and the degree of comfort of the right arms (p<0.001) were significant, and the effect of motions on the rate of perception reaction time (p=0.017) was significant. The other situation were not significant. The results indicated that the no strap was worst and the oblique strap was best.2. The vibration of different positions of 6MF-30 and HB2302 at different rotational speed, and the law of vibration along the sequence of handle-hand-forearm-upper arm were studied. The result showed vibration acceleration increased with rotational speed, and the vibration of front handle of 6MF-30 was bigger than rear handle. The acceleration of front handle and rear handle in 7000r/min are respectively 75.3 m·s-2 and 46.3 m·s-2. The larger the rotational speed, the smaller the vibration transmissibility would be. More vibration energy was absorbed by arm.3. The noise of different positions of 6MF-30 and HB2302 at different rotational speed, and the evaluation of the noise on heart rate and reaction time were researched. The result indicated that the noise of the portable pneumatic extinguishers are too great and have more high frequency. The effects of noise on the increasing ratio of heart rate (p=0.863) and reaction time (p=0.995) were not significant and the heart rate is not linearly increased with the rotational speed.4. The 6MF-30 and HB2302 from the aspects of vibration, noise and the influence of vibration and noise on human body at different rotational speed. In the maximum power speed, the vibration transmissibility from handle to hand of 6MF-30 and HB2302 are 20.1% and 27.5%, respectively. The left parotic noise of 6MF-30 and HB2302 are 96.5 dB(A) and 94.5 dB(A), respectively. The low frequency noise of 6MF-30 is higher than HB2302. Therefore, the design of HB2302 about vibration and noise is superior to 6MF-30. The vibration and noise of 6MF-30 should be reduced.5. The influence of 6MF-30 and HB2302 at different rotational speed on heart rate and reaction time was evaluated, while the subjects were influenced by vibration, noise and weight. The results showed that the interaction of vibration and noise can be classified identified factor. The influence of weight on heart rate and reaction time was bigger than the interaction of vibration and noise, and weight is the primary factor of the optimization of portable pneumatic extinguisher.6. The suggestion of operating instruction were proposed as follows. When the 6MF-30 was working, the strap was required, the oblique strap was chose to be best carrying posture, the maximum working time of subjects was 3343 h. The optimization about vibration and noise reduction of the 6MF-30 should evade the peak frequency,40 Hz and 160Hz. And the vibration of handle and the noise of engine should be lessen. The optimization about weight reduction of the 6MF-30 should choose the materials of light weight and the engine with moderate power and light weight.