Evaluation of the fall protection of Type I industrial helmets

Data Collection Methods

• Experimental setup
  • Head impact tests were performed using an instrumented manikin.
  • The test manikin was customer-built using the body of an off-the-shelf manikin, a 50th percentile crash test dummy headform, and a 50th percentile Hybrid III neck with a reinforced spine. The height and body mass of the test manikin with all customarily revised elements were close to a standard 50th percentile male.
  • The manikin was fitted with a fall protection harness to facilitate lifting.
  • The accelerations of the head during the impacts were measured using a triaxial, piezoelectric accelerometer.
• Experimental procedure
  • At the start of the test, the manikin was hoisted, by a lifter, to a height of 5 feet.
  • The hanging manikin was released by an electromagnetic release mechanism, such that the instrumented manikin experienced free fall and impacted a flat surface with the manikin’s head back being struck first.
  • The impact surface had one of two different covering materials (concrete or plywood-covered).
  • Four representative helmet models were selected in the study; two of them were basic helmet models and two of them were advanced helmet models.
  • All four selected helmet models were equipped with a suspension tightening ratchet and were provided with a removable chin strap attachment.
  • Two independent factors regarding the proper helmet wearing were considered: (1) chin strap usage (with or without), and (2) tightness of the suspension system (tight, comfortable, and loose).
  • Under each of the test conditions, impact tests were replicated four times.
  • A set of impact tests without a helmet under all other applicable test conditions were applied as the control or reference group.
  • There were a total of 192 trials for the impact tests with helmets and 8 trials for the control group.
• Data processing
  • Peak accelerations (Acc) and Head Injury Criterion (HIC) values were calculated using the time-history data of the head accelerations collected in the experiments.
  • The average values for each of the parameters were calculated by the arithmetic mean of four repetitions for each of the test conditions.
  • The helmet use/type [i.e., no helmet (bare head), and four different helmet types] or helmet type (four different helmet types), the chin strap use (with or without chins strap), the suspension tightness (tight, comfortable, or loose), and the impact surface condition (concrete or plywood-covered) were considered as independent variables, whereas the peak acceleration (Acc) and HIC were considered as dependent variables.