School of Public Health, University of California, Berkeley, CA, USA.
Department of Bioengineering, University of California, Berkeley, CA, USA.
Ann Work Expo Health. 2017 Jul 1;61(6):700-710. doi: 10.1093/annweh/wxx041.
Hammer drills are used extensively in commercial construction for drilling into concrete for tasks including rebar installation for structural upgrades and anchor bolt installation. This drilling task can expose workers to respirable silica dust and noise. The aim of this pilot study was to evaluate the effects of bit wear on respirable silica dust, noise, and drilling productivity.
Test bits were worn to three states by drilling consecutive holes to different cumulative drilling depths: 0, 780, and 1560 cm. Each state of bit wear was evaluated by three trials (nine trials total). For each trial, an automated laboratory test bench system drilled 41 holes 1.3 cm diameter, and 10 cm deep into concrete block at a rate of one hole per minute using a commercially available hammer drill and masonry bits. During each trial, dust was continuously captured by two respirable and one inhalable sampling trains and noise was sampled with a noise dosimeter. The room was thoroughly cleaned between trials.
When comparing results for the sharp (0 cm) versus dull bit (1560 cm), the mean respirable silica increased from 0.41 to 0.74 mg m-3 in sampler 1 (P = 0.012) and from 0.41 to 0.89 mg m-3 in sampler 2 (P = 0.024); levels above the NIOSH recommended exposure limit of 0.05 mg m-3. Likewise, mean noise levels increased from 112.8 to 114.4 dBA (P < 0.00001). Drilling productivity declined with increasing wear from 10.16 to 7.76 mm s-1 (P < 0.00001).
Increasing bit wear was associated with increasing respirable silica dust and noise and reduced drilling productivity. The levels of dust and noise produced by these experimental conditions would require dust capture, hearing protection, and possibly respiratory protection. The findings support the adoption of a bit replacement program by construction contractors.
在商业建筑中，锤钻被广泛用于在混凝土中钻孔，用于包括钢筋安装在内的各种任务，以进行结构升级和锚固螺栓安装。这项钻孔任务可能使工人接触到可吸入的二氧化硅粉尘和噪音。本初步研究的目的是评估钻头磨损对可吸入二氧化硅粉尘、噪音和钻孔生产率的影响。
通过连续钻孔至不同的累计钻孔深度（0、780 和 1560cm），将测试钻头磨损至三种状态。通过三个试验（总共九个试验）评估每种钻头磨损状态。在每个试验中，使用市售的锤钻和砖石钻头，一个自动化的实验室测试台系统每分钟钻一个孔，直径为 1.3 厘米，深度为 10 厘米，在混凝土块中钻 41 个孔。在每个试验中，通过两个呼吸采样器和一个吸入采样器连续采集粉尘，并用噪声剂量计采集噪声。在每个试验之间彻底清洁房间。
将锋利（0cm）钻头与钝钻头（1560cm）进行比较时，采样器 1 的可吸入二氧化硅均值从 0.41 增加到 0.74mg m-3（P=0.012），采样器 2 的均值从 0.41 增加到 0.89mg m-3（P=0.024）；均超过 NIOSH 推荐的 0.05mg m-3 暴露限值。同样，平均噪声水平从 112.8 增加到 114.4dBA（P<0.00001）。随着磨损的增加，钻孔生产率从 10.16 下降到 7.76mm s-1（P<0.00001）。
钻头磨损的增加与可吸入二氧化硅粉尘和噪声的增加以及钻孔生产率的降低有关。在这些实验条件下产生的粉尘和噪声水平需要进行粉尘收集、听力保护，可能还需要进行呼吸保护。研究结果支持建筑承包商采用钻头更换计划。
