Assessment of hazard recognition performance of thermal power plant workers: A case study of a combined cycle power plant

Figures & data

Table 1. Hazard categories based on implicit energy sources and typical examples

Hazard categories/energy sources	Definitions	Hazard examples
Gravity	Force due to the attraction of all masses to the earth’s center.	Obstacles on floor causing trip potential; Slippery surface; Humans working at height without fall protection; etc.
Motion	The change in an object or substance’s position.	Movement of mobile equipment: crane, forklift; Human body positioning: lifting, bending, twisting; etc.
Mechanical	The energy contained or transmitted by constituents of a mechanical system or a single piece of machinery.	Compressed springs; Unguarded rotating shafts, gears, pulleys; Vibrating parts of an equipment/structure; etc.
Electrical	The presence and flow of electrical charges.	Overhead power cables; Energized equipment; Broken cable insulation; Uncovered battery terminals; Unearthed equipment; etc.
Pressure	Energy resulting from fluid(liquid/gas) which has been compressed or is under vacuum.	Compressed gas cylinders; piping, hoses; Pneumatic & hydraulic equipment/systems; etc
Temperature	The measurement of thermal energy variations in objects or the environment which is basically sensed by the human body as hot or cold.	Open flame; Hot or cold surfaces; Hot or cold liquids or gases: steam, water, air; Hot or cold weather, etc.
Chemical	The energy contained in chemical substances which inherently or via a reaction can cause physical or health harm to humans, and damage to equipment or the environment.	Low oxygen levels and high carbon monoxide in confined spaces; Volatile organic compounds (VOCs): benzene, methanol; Dust; Flammable liquid, vapours, and gases; etc
Biological	Living organism that can cause physical harm like biting, stinging or diseases.	Animals; Microorganisms: viruses, bacteria, fungi; Contaminated food or water; etc.
Radiation	The energy emitted or transmitted from a radioactive source through space or a medium.	X-rays; Welding arc; Microwaves; Solar rays; etc.
Sound	The energy released when an object is vibrated by a force which is heard by the human ear as a sound	Noise from running engine, elevated pressure relief, impact noise; etc.

(Modified from Albert et al., 2014a)

Table 2. Demographics of participants

Number of participants from operations	Number of participants from maintenance	Average age (years)	Average working experience (years)	Number of male participants	Number of female participants
19	11	32	4.1	30	0

Figure 1. Steam turbine and generator scene photograph before editing.

Figure 2. Sample edited photo used for hazard recognition measurement.

Table 3. Descriptive statistics of HR performance of participants by hazard category

Hazard Category	Mean $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ (%)	Std. Dev. $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ (%)	Minimum $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ (%)	Maximum $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ (%)	% of $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ > 50% (%)
Temperature	14.45	9.52	0.00	33.33	0
Electrical	29.57	22.13	0.00	75.00	17
Gravity	32.22	14.45	6.67	80.00	10
Chemical	30.00	18.89	0.00	71.43	13
Sound	1.67	9.13	0.00	50.00	0
Mechanical	24.00	22.53	0.00	60.00	20
Motion	28.89	19.05	0.00	66.67	10
Pressure	8.33	18.95	0.00	50.00	0

Notes: Participant’s Hazard Recognition index by category = $\mathit{H}{R}_{\mathit{ij}}$, Percentage of $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ greater than 50% = % of $\mathit{H}{R}_{\mathit{ij}}$ > 50%.

Figure 3. Bar graph indicating workers overall hazard recognition performance.

Table 4. Summary descriptive statistics of overall hazard recognition performance of all participants

Number of Subject (N)	Mean$\mathit{H}{\mathit{R}}_{\mathit{iT}}$ (%)	Median$\mathit{H}{\mathit{R}}_{\mathit{iT}}$ (%)	Std. Dev. of $\mathit{H}{\mathit{R}}_{\mathit{iT}}$ (%)	Maximum$\mathit{H}{\mathit{R}}_{\mathit{iT}}$ (%)	Minimum$\mathit{H}{\mathit{R}}_{\mathit{iT}}$ (%)
30	21.24	21.69	7.81	38.18	7.15

Table 5. Kolmogorov–Smirnov and Shapiro–Wilk normality test results

Hazard category	Kolmogorov–Smirnov^a			Shapiro–Wilk
	Statistic	df	Sig.	Statistic	df	Sig.
Chemical	0.197	30	0.004	0.912	30	0.017
Electrical	0.248	30	0.000	0.861	30	0.001
Gravity	0.162	30	0.044	0.918	30	0.024
Mechanical	0.237	30	0.000	0.830	30	0.000
Motion	0.359	30	0.000	0.740	30	0.000
Pressure	0.503	30	0.000	0.452	30	0.000
Sound	0.539	30	0.000	0.180	30	0.000
Temperature	0.359	30	0.000	0.740	30	0.000

Notes: a. Lilliefors Significance Correction.

Table 6. Levene’s homogeneity of variances test results

Levene’s Test of Equality of Error Variances ^a,b
Type of Levene Statistic (F)	F	df1	df2	Significance
F Based on Mean	6.984	7	232	0.000
F Based on Median	4.866	7	232	0.000
F Based on Median and with adjusted df	4.866	7	180.602	0.000
F Based on trimmed mean	7.210	7	232	0.000

Notes: df₁ = group degree of freedom; df₂ = total degree of freedom.

Table 7. Kruskal–Wallis test summary of hazard recognition performance by category

Independent-samples Kruskal–Wallis test summary
N	240
H	82.618^a
Degree Of Freedom	7
Asymptotic Sig. (2-sided test), p-value	0.000

Notes: a. The test statistic is adjusted for ties; N = total number of observations; H = test statistic value.

Table 8. Pairwise comparisons of hazard recognition performance levels across the eight hazard categories

S/N	Pairwise comparison	Mean difference $\left({\bar{\mathit{\mu }}}_{\mathit{i}}-{\bar{\mathit{\mu }}}_{\mathit{j}}\right)$	Standard error	Confidence interval
				LL	UL
1	Temperature-Electrical **	−15.12	4.529	−25.234	−6.665
2	Temperature-Gravity **	−17.78	3.200	−23.775	−11.985
3	Temperature-Chemical **	−15.56	3.866	−23.679	−7.799
4	Temperature-Sound **	12.78	2.464	7.538	17.206
5	Temperature-Mechanical **	−9.56	4.596	−18.541	−1.120
6	Temperature-Motion **	−14.44	3.702	−21.872	−7.126
7	Temperature-Pressure	6.11	3.792	−1.723	13.194
8	Electrical-Gravity	−2.66	4.930	−11.535	7.156
9	Electrical-Chemical	−0.44	5.323	−11.517	10.550
10	Electrical-Sound **	27.90	4.417	19.655	36.995
11	Electrical-Mechanical	5.57	5.867	−5.391	16.571
12	Electrical-Motion	0.68	5.231	−9.324	12.249
13	Electrical-Pressure **	21.23	5.268	10.992	32.701
14	Gravity-Chemical	2.22	4.415	−7.125	11.988
15	Gravity-Sound **	30.56	3.184	24.201	36.692
16	Gravity-Mechanical	8.22	4.970	−1.357	16.819
17	Gravity-Motion	3.34	4.235	−5.064	11.963
18	Gravity-Pressure **	23.89	4.231	16.073	32.296
19	Chemical-Sound **	28.34	3.800	21.095	35.320
20	Chemical-Mechanical	6.00	5.356	−4.232	15.711
21	Chemical-Motion	1.11	4.733	−8.218	10.410
22	Chemical-Pressure **	21.67	4.739	12.758	29.910
23	Sound-Mechanical **	−22.33	4.537	−30.443	−14.072
24	Sound-Motion **	−27.22	3.678	−34.564	−19.877
25	Sound-Pressure	−6.67	3.809	−14.471	1.190
26	Mechanical-Motion	−4.89	5.353	−15.593	6.159
27	Mechanical-Pressure **	15.67	5.455	3.532	27.272
28	Motion-Pressure **	20.56	4.774	10.375	29.999

Notes: ** indicates pairwise comparison revealed a statistically significant difference in hazard recognition performance levels; LL = lower limit; UL = upper limit.

Table 9. Summary of pairwise comparisons

Group 1		Group 2
Hazard category	Mean $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ (%)	Hazard category	Mean $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ (%)
Electrical	29.58	Sound	1.67
Gravity	32.22	Pressure	8.33
Chemical	30.00	Temperature	14.44
Motion	28.89
Mechanical	24.00
Mean Group HRP	28.94	Mean Group HRP	8.12

Notes: $\mathit{H}{\mathit{R}}_{\mathit{ij}}$ = mean hazard recognition performance by category, HRP = hazard recognition performance.

Albert, A., Hallowell, M. R., & Kleiner, B. M. (2014a). Enhancing construction hazard recognition and communication with energy-based cognitive mnemonics and safety meeting maturity model: Multiple Baseline study. Journal of Construction Engineering and Management, 140(2), 04013042. https://doi.org/10.1061/(asce)co.1943-7862.0000790

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Data availability statement

Data associated with this study will be made available upon request.