A machine shop 100^' ×40^' with a 13^' ceiling will be illuminated for automatic machining and rough grinding. Uniform lighting is required throughout the machine shop. If the luminaries are to be ceiling mounted, all ceilings and walls are to be painted white, and all luminaries are to be cleaned every 24 months

Question

A machine shop [latex]100^{'} imes 40^{'}[/latex] with a [latex]13^{'} [/latex]ceiling will be illuminated for automatic machining and rough grinding. Uniform lighting is required throughout the machine shop. If the luminaries are to be ceiling mounted, all ceilings and walls are to be painted white, and all luminaries are to be cleaned every 24 months, what lighting should be specified?

Accepted Answer

Step 1: Determine the level of illumination. From Table 9.5, a minimum illumination level of 100 footcandles is required.
Step 2: Determine the room cavity ratio. Assume all working surfaces are [latex]3^{'} [/latex] from the floor. Using Equation 9.8 to calculate the RCR results in the following:

[latex]RCR=\frac{(5)(13-3)(100+40)}{(100)(40)}=1.75[/latex]
Step 3: Determine the ceiling cavity ratio. The CCR need not be considered, as the luminaries are ceiling mounted.
Step 4: Determine the wall reflections and the effective ceiling reflectance. According to Table 9.6, the WR and BCR are 80%. Because the luminaries are to be ceiling mounted, the ECR is also 80%.
Step 5: Determine the coefficient of utilization. If fluorescent lamps in uncovered fixtures are to be utilized, the CR may be interpolated in Table 9.8 as being between 0.88 and 0.78. A CU of 0.80 will be utilized.
Step 6: Determine the light loss factor. For fluorescent lamps in uncovered fixtures in a “medium-dirty environment” that are cleaned every 24 months, a lamp luminary dirt depreciation factor of 0.85 may be obtained from Table 9.10. Therefore, the LLF is 0.85.
Step 7: Calculate the number of lamps and luminaries. According to Equation 9.10, the number of lamps required if 60 watt fluorescent lamps are used is

Number of lamps [latex]=\frac{(100)(100)(40)}{(0.8)(0.85)(3300)}=179[/latex]
If two lamps are placed in each luminary, according to Equation 9.11, then 90 luminaries
are required.
Step 8: Determine the location of the luminaries. Table 9.8 indicates that for a mounting height [latex]10^{'}[/latex] above the work surface, the luminaries should be spaced no more than [latex]13^{'}[/latex] apart. Each fluorescent fixture is [latex]4^{'}[/latex] long. By placing nine rows of [latex]10^{'}[/latex] luminaries across the room with the first and last rows [latex]6^{'}[/latex] from the wall and the other rows [latex]11^{'}[/latex] apart, the illumination level within the room will be evenly distributed and will be adequate to perform the tasks within a machine shop. The lighting layout is shown in Figure 9.10.

Table 9.10 Lamp Luminary Dirt Depreciation Factors

[latex]Dirt—Condition^{a}[/latex]
	Clean—Offices, Light Assembly, or Inspection					Medium—Mill Offices Paper Processing or Light Machining					Dirty—Heat Treating, High-Speed Printing, or Medium Machining					Very Dirty—Foundry or Heavy Machining
	Months between Cleaning					Months between Cleaning					Months between Cleaning					Months between Cleaning
Luminaries	6	12	24	36	48	6	12	24	36	48	6	12	24	36	48	6	12	24	36	48
Filament reflector lamps	0.95	0.93	0.89	0.86	0.83	0.94	0.89	0.85	0.81	0.78	0.87	0.84	0.79	0.74	0.70	0.83	0.74	0.6	0.56	0.52
High-intensity discharge lamps	0.94	0.90	0.84	0.8	0.75	0.92	0.88	0.80	0.74	0.69	0.90	0.83	0.76	0.68	0.64	0.86	0.79	0.69	0.63	0.57
Fluorescent lamps in uncovered fixtures	0.97	0.94	0.89	0.87	0.85	0.93	0.90	0.85	0.83	0.79	0.93	0.87	0.80	0.73	0.70	0.88	0.83	0.75	0.70	0.64
Fluorescent lamps in prismatic lens fixtures	0.92	0.88	0.83	0.80	0.78	0.88	0.84	0.77	0.73	0.71	0.82	0.78	0.71	0.67	0.62	0.78	0.72	0.64	0.60	0.57

Table 9.6 Approximate Reflectance for Wall and Ceiling Finishes

Materials	Approximate Reflectance (%)
White paint, light-colored paint, mirrored glass, and porcelain enamel	80
Aluminum paint, stainless steel, and polished aluminum	65
Medium-colored paint	50
Brick, cement, and concrete	35
Dark-colored paint, asphalt	10
Black paint	5

Table 9.8 Coefficients of Utilization for Standard Luminaries

Luminaire	Spacing Not to Exceed	RCR	ECR
			80%				50%				10%				0%
			WR				WR				WR				WR
			80%	50%	30%	10%	80%	50%	30%	10%	80%	50%	30%	10%	0%
Filament reflector lamps	1.5× mounting height	1	1.11	1.09	1.07	1.03	1.04	1.02	1.00	.98	.96	.95	.94	.93	.91
		2	1.04	1.00	.95	.92	.99	.95	.92	.88	.92	.90	.87	.85	.83
		3	0.95	.92	.88	.82	.92	.88	.84	.80	.85	.83	.80	.77	.75
		4	0.90	.85	.76	.73	.86	.81	.76	.71	.79	.77	.73	.70	.68
		5	.82	.77	.71	.65	.80	.75	.69	.64	.75	.71	.67	.63	.61
		10	.58	.50	.43	.38	.54	.49	.43	.38	.51	.47	.42	.38	.36
High-intensity discharge lamps (mercury, metal halide, or sodium)	1.3×mounting height	1	.89	.87	.84	.82	.81	.80	.78	.77	.74	.73	.72	.71	.70
		2	.82	.79	.75	.72	.77	.74	.71	.68	.70	.68	.66	.64	.63
		3	.76	.72	.67	.63	.72	.68	.64	.61	.65	.63	.60	.58	.56
		4	.7	.66	.61	.57	.67	.63	.58	.55	.57	.55	.54	.53	.51
		5	.64	.60	.55	.51	.62	58	53	49	56	54	52	49	46
		10	.45	.40	.34	.30	.42	.38	.34	.30	.40	.36	.41	.20	.28
Fluorescent lamps in uncovered fixtures	1.3×mounting height	1	.88	.85	.82	.79	.79	.65	.72	.71	.65	.64	.63	.62	.59
		2	.78	.75	.70	.65	.71	.67	.63	.59	.60	.57	.55	.52	.50
		3	.69	.66	.60	.55	.63	.59	.54	.50	.54	.51	.48	.45	.42
		4	.61	.59	.52	.46	.56	.52	.47	.43	.48	.45	.41	.38	.36
		5	.53	.51	.44	.39	.51	.46	.40	.39	.43	.40	.36	.33	.30
		10	.35	.30	.23	.19	.32	.27	.21	.18	.26	.23	.19	.16	.14
Flourescent lamps in prismatic lens fixtures	1.2×mounting height	1	.56	.63	.61	59	.60	.59	.58	.56	.56	.55	.54	.53	.52
		2	.6	.57	.54	.51	.56	.54	.51	.49	.51	.50	.49	.47	.46
		3	.54	.51	.48	.44	.51	.49	.46	.43	.47	.46	.44	.42	.41
		4	.49	.46	.42	.39	.48	.44	.41	.38	.44	.42	.39	.37	.36
		5	.45	.42	.37	.34	.44	.40	.36	.34	.40	.38	.35	.33	.32
		10	.31	.26	.21	.18	.29	.25	.21	.18	.27	.24	.20	.18	.17

Table 9.5 Minimum Illumination Levels for Specific Visual Tasks

Task	Minimum Illumination Level (footcandles)
Assembly
Rough easy-seeing	30
Rough difficult-seeing	50
Medium	100
Fine	500
Extra fine	1000
Inspection
Ordinary	50
Difficult	100
Highly difficult	200
Very difficult	500
Most difficult	1000
Machine Shop
Rough bench and machine work	50
Medium bench and machine work, ordinary automatic machines,rough grinding, medium buffing and polishing	100
Fine bench and machine work, fine automatic machine, medium grinding, medium buffing and polishing	500
Extra-fine bench and machine work, fine grinding	1000
Material Handling
Wrapping, packing, labeling	50
Picking stock, classifying	30
Loading	20
Offices
Reading high or well-printed material; tasks not involving critical 30 or prolonged seeing, such as conferring, interviewing, and inactive files	30
Reading or transcribing handwriting in ink or medium pencil on good-quality paper; intermittent filing	70
Regular office work; reading good reproductions, reading or transcribing handwriting in hard pencil or on poor paper; active filing; index references; mail sorting	100
Accounting, auditing, tabulation, bookkeeping, business machine 150 operation; reading poor reproductions; rough layout drafting	150
Cartography, designing, detailed drafting	200
Corridors, elevators, escalators, stairways	20
Paint Shop
Dipping, spraying, rubbing, firing, and ordinary hand painting	50
Fine hand painting and finishing	100
Extra-fine hand painting and finishing	300
Storage Rooms and Warehouses	2
Inactive	5
Active
Rough bulky	10
Medium	20
Fine	50
Welding
General illumination	50
Precision manual arc welding	1000

Question 9.4: A machine shop 100^' ×40^' with a 13^' ceiling will be illum...

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