TABLE 3-8. TYPICAL INSPECTION FLASHLIGHTS (Sheet 3 of 5) (Courtesy of McMaster-Carr Supply Company) 1 ° Skinny Probe Inspection Light. PRESE light has 44-inch-long flexible cable and the lamp head can pass through a 7/32-inch-diameter opening.
cable lets you lower the bulb into deep areas and put the flashlight case in your pocket while working.
inch-diameter bulb is mounted on the end of a rigid 10-inch-long stem.
is impact resistant, waterproof and withstands most chemicals.
three D batteries and a number 187 (standard) bulb.
j. Explosion-Proof Inspection Light.
This explosion-proof flashlight has a 14-inch rigid brass or flexible stem that lets you examine fuel tanks and other flammable liquid containers.
uses three D batteries and a number 13 (standard) bulb.
k. Porta-Power Flex Lights. These inspection lights have a black anodized aluminum case with sliding on-off switch. They focus with a twist of the lens head for pinout or broad beam illumination and they are powered by two D batteries; the lamp head fits through a 21/32-inch opening; they use a number 14 (standard) bulb; and they are available with flexible cable lengths of 9, 18, and 36 inches. A combination unit is available that has a 6-inch rigid shaft and a 9-inch flexible cable.
Inspection Light Accessories.
justable illuminating mirrors and magniiers are available for some model in- ›pection lights. The glass mirror is 1 1/4 inch diameter, has a stainless steel back and nickel plated brass extension arm. Overall length is 4 The illuminating magnifier has a straight line viewing 6X lens.
1 1/2 inch diameter with a polished optical glass lens.
Chap 3 Page 98 Par 301
TABLE 3-8. TYPICAL INSPECTION FLASHLIGHTS (Sheet 4 of 5) (Courtesy of McMaster-Carr Supply Company) Illuminating and Magnifying Inspection Kit. All parts of this kit are interchangeable, interlocking and chrome It uses two D batteries and a 1/8-inch and 1/4-inch-diameter bulb.
The kit includes 0.1 inch and 0.3 inch diameter rigid probes in lengths from 3 to 14 1/4 inches, a 0.3-inch-diameter by 14 1/4-inch-long flexible probe, illuminated magnifier; a 10X duplex magand adjustable mirror for use on the rigid probes, 0.9 and 1.5-inchdiameter short stem mirrors; recovery magnet and hook; and accessory handle.
Mini Bench Lights. These lights are the workbench. Lamps can enter a 21/32-inch opening. Each light has a nonsparking aluminum case with a -exiole cable (0, 9, or 12 inches long) that bends and stays electric bench light comes with a 2.5- volt transformer and switch for 110-volt AC outlet. The 5/8-inch-diameter head has a focusing ring for a circle of light or pinpoint beam. The case is shockproof and it uses a number 13 The battery operated bench light uses two AA batteries and a number 222 (standard) bulb.
kit uses a penlight with a Lucite rod and mirror to see around corners. Light Bender Inspection Kit. This uses one or two AA batteries. The kit includes: one and two cell penlight; 6 and 2 1/2-inch-long straight Lucite rods; clip-on mirror; 4-inch curved Lucite rod; and soft plastic case.
Extended Reach Inspection Kit.
kit has up to five-foot reach interchangeable probes, each with its own attached light. The kit includes; a fivefoot flexible cable probe; a 12-inch straight and flexible probe; a five-inch angle probe and two-inch bendable probe;
a 1.2-inch and 0.6-inch diameter mirror;
a 22-mm-diameter mirror; magnifying lens; recovery magnet and hook; shrouded and side aperture lamps; probe adapter;
and case.
Chap 3 Par 301 Page 99
TABLE 3-8. TYPICAL INSPECTION FLASHLIGHTS (Sheet 5 of 5) (Courtesy of McMaster-Carr Supply Company) Twist-Beam Penlights. These flashlights use standard two AA-cell batteries and the beam adjusts from spot to flood.
LIGHTING SYSTEMS. Lighting systems are often classified in accordance with their layout or location with respect to the visual task or object lighted (general lighting, localized general lighting, local [supplementary] lighting, and task-ambient ignting). They are also classified in accordance with the CI ype of luminaire used (direct, semi-direct, general diffuse [direct-indirect], semi-indirect, and indirect), as shown in Figure 3-9. Luminaires for general lighting are classified by the CIE in accordance with the percentages of total luminaire output emitted above and below horizontal. The light distribution curves may take many forms within the limits of upward and downward distribution, depending on the type of light source and the design of the luminaire. Light distribution curves for some typical lamp and fixture types that might be used for visual inspection tasks of aircraft and related articles are shown in Figure 3-10. Light distribution curves may be available in technical literature available from manufacturers of light sources.
Horizontal tasks and high, narrow spaces can be most efficiently lighted with fixtures that concentrate most of their light straight down. Such fixtures usually appear to be quite comfortable. However, tasks that are more vertical require light coming from the luminaire at relatively high angles. Luminaires emitting light at high angles are apt to be excessively bright and uncomfortable unless carefully designed. Broad-distribution luminaires are more effective in letting light out of the unit than narrow-distribution ones, but are less effective in getting light to the horizontal work plane in high-bay, narrow spaces since walls absorb a greater portion of the light. Manufacturers generally provide a coefficient of utilization table, which is the ratio between the amount of light or lumens reaching the horizontal task to the lumens generated within the luminaire. The manufacturer's recommended spacing-to-height ratio (or spacing criterion) indicates whether the output of the fixture is broad or General Lighting. General lighting systems provide an approximately uniform illuminance on the work plane over the entire work area. The luminaires are usually arranged in a symmetrical plan fitted into the physical characteristics of the area and therefore blend well with the room architecture. They are relatively simple to install and require no coordination with furniture or machinery that may not be in place at the time of Chap 3 Page 100 Par 301
installation. Perhaps the greatest advantage of general lighting systems is that they permit complete flexibility in task loca-
system consists of a functional arrangement of luminaires with respect to the visual task or work areas. It also provides illumination for the entire room area. Such a lighting system requires special coordination in installation and careful consideration to ensure adequate general lighting for the room.
system has the advantages of better use of the light on the work area and the opportunity to locate the luminaires so that annoying shadows, direct glare, and veiling reflections are prevented or minimized.
Local Lighting. A local lighting system provides lighting only over a relatively small area occupied by the task and its immediate surroundings. The illumination may be from luminaires mounted near the task or from remote spotlights. These an economical means of providing higher illuminances over a small area, and it usually permits some adjustment of the lighting to suit the requirements of the individual. Improper adjustments may, however, cause annoying glare for nearby workers.
cal lighting by itself is seldom desirable. To prevent excessive changes in adaptation, local lighting should be used in conjunction with general lighting that is at least 20 to 30 percent of the local lighting level; it then becomes supplementary lighting.
Task-Ambient Lighting. Task-ambient lighting is a type of lighting arrangement where the lighting is built into the furniture in an open plan office layout. Task lights are located close to work areas (as in local lighting above) and are supplemented by indirect ambient illumination from sources concealed in the furniture and directed to the ceiling (as in general lighting above). These systems usually have extensive ceiling areas almost totally devoid of lighting equipment. Electrical service to the lighting equipment is often through the floor.
e. Direct Lighting. When luminaires direct 90 to 100 percent of their output downward, they form a direct lighting system. The distribution may vary from widespread to highly concentrated, depending on the reflector material, finish, and contour and on the shielding or control media employed.
(1) Direct Glare Control. Direct lighting units can have the highest room utilization factor of all types, but this utilization may be reduced in varying degrees by brightness control media required to minimize direct glare. Direct glare may also be reduced by using area units with minimum number of lamps,
e.g., a two-foot-wide fluorescent unit with just two lamps.
Chap 3 Par 302 Page 101
(2) Veiling Reflections. Veiling reflections may be excessive unless distribution of light is designed to reduce the effect.
(3) Reflected Glare and Shadows. Reflected glare and shadows may be problems unless close spacings are employed.
Large area units are also advantageous in this respect. Highreflectance room surfaces are particularly important with direct ighting to improve the brightness relatlonships, and higher illuminances provided by controlled brightness equipment will alsc tend to improve the brightness relationships throughout the room.
with very concentrated distributions, care should be taken to ensure adequate wall luminances and illuminances on vertical sur- Other Forms of Direct Lighting. Luminous ceilings, louvered ceilings, and large-area modular lighting elements are forms of direct lighting having characteristics similar to those of indirect lighting discussed in later paragraphs. These forms of lighting are frequently used to obtain the higher illuminances. Care should be taken to limit the luminance of the shielding medium to 80 candelas per square foot or less to prevent direct glare if critical, prolonged seeing is involved. Reflected glare may be a problem with systems employing cellular louvers as the shielding medium, since the images of the light sources above the louvers may be reflected by shiny surfaces at the work plane.
f. Semi-Direct Lighting. The distribution from semi-direct units is predominantly downward (60 to 90 percent), but with a small upward component to illuminate the ceiling and upper walls.
The characteristics are essentially the same as for direct lighting, except that the upward component will tend to soften shadows improve room brightness relationships. Care should be exercised with close-to-ceiling mounting of some types to prevent overly bright ceilings directly above the luminaire. The room utilization factor can approach or even exceed that of wellshielded direct units.
g. General Diffuse Lighting. The lighting system is classified as general diffuse when downward and upward components of light from luminaires are about equal (each 40 to 60 percent of total luminaire output). General diffuse lighting units combine the characteristics of direct and indirect lighting. The room utilization factor is somewhat lower than for direct or semidirect units, but it is still quite good in rooms with high reflectance surfaces. Brightness relationships throughout the room are generally good, and shadows from the direct component are softened by the upward light reflected from the ceiling.
(1) Direct Glare Control. Excellent direct glare control can be provided by well-shielded units, but short suspensions can result in ceiling luminances that exceed the luminaire Chap 3 Page 102 Par 302
luminances. Close spacings or layouts that locate units so that they are not reflected in the task result in reductions of reflected glare from the downward component.
_Pendant Mountings. Luminaires designed to provide a general diffuse or direct-indirect distribution when pendant bani direct face ha can note he a cop potector tossecting the upward light back through the luminaire. Photometric data, obtained with the luminaire equipped with top reflectors or installed on a simulated ceiling board, should be employed to determine the luminaire characteristics for such application condi-
special (non-CIE) category within the classification for luminaires which emit very little light at angles near the horizontal. Since this characteristic results in lower luminances in the direct glare zone, direct-indirect luminaires are usually more suitable than general diffuse luminaires which distribute the light about equally in all directions.
i. Semi-Indirect Lighting. Lighting systems which emit 60 to 90 percent of their output upward are defined as semiindirect. The characteristics of semi-indirect lighting are similar to those oi indirect systems, except that the downward component usually produces a luminaire luminance that closely matches that of the ceiling. However, if the downward component becomes too great and is not properly controlled, direct or reflected glare may result. An increased downward component improves utilization of light somewhat over that of indirect lighting. This factor makes somewhat higher illuminances possible with fewer semi-indirect luminaires and without excessive ceiling luminance.
j. Lighting for the Cathode Ray Tube (CRT). Cathode ray tubes are commonplace, with visual display units appearing on the shop floor with ultrasonic equipment, eddy current equipment, video adapters for borescopes and microscopes, etc. Their typically convex surfaces act like curved mirrors that reflect large areas of ceiling, walls, windows, and other room surfaces.
any of these surfaces are intrinsically bright, such as windows and fixtures, or are brightly lighted, their reflected images will reduce the visibility of the information being processed on the screen and annoy the operator. The CRT problem could be solved by turning off all the lights and shading the windows;
however, this is usually not practical. Many of the screen reflection problems can be reduced by the following methods:
(1) Screen Orientation. Proper screen orientation or using hoods or anti-reflection screens or filters.
Chap 3 Par 302 Page 103
(2) Shades. Using blinds, shades, or dark curtains to help eliminate window brightness.
(3) Dark Colors. Finishing walls and other vertical surfaces in darker colors.
(₴) Worker Clothing. Equipping operators with dark smocks.
(5) Luminaires. Using luminaires with dark-tinted lenses, deep parabolic baffles, or parabolic wedge louvers to control fixture brightness. Bright lamp images seen in shiny surfaces directly beneath the fixture can be eliminated by laying a thin plastic diffuser on top of the lens or louver.
(6) Indirect Lighting. When indirect lighting is used to correct CRT reflection problems, leveis should not exceed 30 footcandles; otherwise, vertical surfaces get too bright. Ceiling brightness should be uniform with no hot spots. At this level, supplementary task lighting often will be required.
(7) Parabolic Lenses. Parabolic lenses can be used to obtain levels up to about 100 footcandles. If higher levels are needed for specific tasks, supplementary lighting can also be
303.-399. RESERVED Chap 3 Pages 104 through 116 Par 302
CHAPTER 4. EQUIPMENT USED IN VISUAL INSPECTION
400. GENERAL. The following chapter describes the various aids to vision used in visual inspection. In general, they consist of mirrors, magnifiers, and various schemes for conveying images from inaccessible sources to where they may be seen.
a. Inspection Mirrors. Inspection mirrors are used to view areas that are not in the normal line of sight. Table 4-1 shows some of the typical types of inspection mirrors that are available for inspection of hidden areas.
TABLE 4-1. TYPICAL INSPECTION MIRRORS (Courtesy of McMaster-Carr Supply Company) (Sheet 1 of 2) Ball-Joint Telescoping Inspection Mirror.
This inspection mirror has tempered spring steel'image or magnifying) to move 360° for double ball-joint links to allow mirror viewing in any position. Nonrotating inner hex rods on telescoping models prevent mirrors from swinging out of alignment. Replacement mirrors are available.
b. Spring-Loaded Inspection Mirror. This inspection mirror has a spring-loaded plunger to tilt the mirror 90°. The mirror is returned to the straight position by tripping a locking device. Single-handed operation allows inspection without removing the mirror from the work area.
Telescoping Inspection Mirror with Magnet.
This inspection mirror can be used to find lost nuts, bolts, and other small parts then pick them up with the magnet in the handali-joint to hold glass mirror at any angle. the telescoping handle has a double Electrical Component Inspection Mirror.
This inspection mirror is extra thin so it can be used to inspect under and around small electrical components. The 90-degree mirrors have beveled edges to match inspection surfaces. Handles are spring-mounted.
Chap 4 Par 400 Page 117
TABLE 4-1. TYPICAL INSPECTION MIRRORS (Courtesy of McMaster-Carr Supply Company) (Sheet 2 of 2)
e. Electrically Insulated Inspection Mirror.
This inspection mirror is electrically insulated to prevent dangerous shocks or shorts when inspecting near sources of electricity.
İ . Adjustable Angle Illuminated Inspection Mirror. This inspection mirror has a light and adjustable mirror at the tip that can be controlled with the thumb.
Magnetic Base Inspection Mirror. This inspection mirror has magnets in a molded nylon base that allows mounting in the work area.
Two ball joints allow adjustment of the glass mirror.
Long Reach Extension Inspection Mirror.
This inspection mirror has a nonconducting handle which extends from five to sixteen feet and it has a nine- by nine-inch glass mirror with light.
Suction Cup Inspection Mirror. This telescoping arm inspection mirror attaches with three suction cups to any hard smooth surface.
The telescoping arm can be extended up thirty inches. The four-inch-diameter unbreakable mirror is true image on one side and magnified image on the other.
Illuminated Inspection Mirror. This penlight inspection mirror has a Lucite rod that directs light on an adjustable plastic frame mirrOr.
b. Simple Magnifiers. A single converging lens, the simplest form of a microscope, is often referred to as a simple magnifier. Magnification of a single lens is determined by the equation M = 10/f, where M is the magnification, f is the focal length in inches, and 10 represents the average minimum distance at which objects can be distinctly seen by the unaided eye.
example, using this equation, a lens with a focal length of 5 inches has a magnification of 2, or is said to be a two-power lens (sometime written 2X). Table 4-2 shows some of the typical types of simple magnifiers that are available.
Chap 4 Page 118 Par 400
TABLE 4-2. TYPICAL SIMPLE MAGNIFIERS (Courtesy of McMaster-Carr Supply Company) Folding Case Magnifiers.
magnifiers single glass or acrylic plastic lenses which can be combined for magnification from 3 to 20 The lenses swing out when needed and the plastic case acts as a Focal lengths vary from 1/2 to 1/2 inches depending on lens combina- Pocket Magnifiers. These magnifiers contain single glass or acrylic plastic lenses mounted in a case that slides open and locks shut to protect the lens when placed in the pocket.
Overall size is 1 5/8 inches by 2 1/4 in 3X and 5X with focal length of 3.3 inches and 2 inches.
Round and Rectangular Magnifiers.
These magnifiers have a sculptured plastic handle and lens frame and are available with glass or scratch resistant acrylic plastic lenses. The glass lenses have 2X magnification, lens diameters from 2.75 to 5.32 inches and focal lengths from 6 to 13 inches.
acrylic lens have 2.5% to 3X (with a 5X bifocal insert), lens diameters are from 2 inches and focal lengths from 10 to 2 inches.
d. Attached Case Magnifiers. These magnifiers have an all in one case that protects the lens and serves as a handie. A 2X model has a glass and vinyl case; 3X model has an acrylic lens and plastic case. Lens diameters are 2 inches and 1.5 inches and focal lengths are 5 inches and 2.5 inches.
Working Distance. The focal length of a simple magnifier and its working distance are approximately the same.
example, suppose that it is desired to examine a part without removing it and the magnifier cannot be placed nearer than 3 inches. Therefore, a magnifier with a working distance (focal length) of at least 3 inches is required. From the equation M = 10/f, a three-power lens is required.
(2) Field of View. The field of view is the area seen through the simple magnifier. The diameter of the field of view Chap 4 Par 400 Page 119
of a simple magnifier is less than its focal length. Selection of a magnifier with proper field of view is important. For example, if a large object is to be examined, the time involved using a 20-power magnifier (with a field of view slightly greater than 3/8 inch) would be prohibitive.
(3) Depth of Field. Depth of field is the term used to indicate the distance a magnifier can be moved toward or away from an object, with the object remaining in good focus. At other distances the object is out of focus and not sharply defined. Depth of field varies with the power of the lens and is comparatively greater in lower-power magnifiers, decreasing as the power of the lens increases.
nifiers with single and multiple lenses jeweler's eye loupes, use in conducting visual inspections include: hand-held maii- MAGNIFYING DEVICES. Some magnifying devices recommended luminated magnifiers, pocket/desk type microscopes, toolmaker's nicroscopes, rigid/flexible borescopes, and video imaging systems. These devices are available with numerous features, such as 1 to 2000 power, self-contained illumination, adjustable varible magnification (zoom), stereo viewing, data storage/ trans.
nission, computer generated electronic alignment targets, anc measuring capability.
a. Selecting Magnification Power. Magnification power and field of view are interrelated, and, in general, as magnification power is increased, the field of view is reduced. Therefore, it is important to select a magnification power that will provide the proper field of view for the part being inspected. when inspecting a large area, the time involved could be prohibitive if high power magnification (with a small field of view) is used.
Therefore, the recommended procedure is to first use low power nagnification (with a large field of view), mark questionable areas, and then examine marked areas using high power magnification. The precise relationship between magnification power and field of view of a product is usually specified by the manufac-
nifier depends on its light collecting ability, which depends on its diameter and focal ratio (focal length divided by diameter).
monitor or a photograph allowe inspectors to share analysis, de- cisions, knowledge, and skills when making visual inspections. PHOTOGRAPHIC AND VIDEO SYSTEMS. An image on a video Photographic and video systems are available which attach to the eyepieces of borescopes, fiberscopes, and microscopes for documentation and analysis of visual inspection images. Video systems are also available that have a charge-coupled device (CCD) image sensor at the probe end of the borescope or microscope, which allows wire rather than fiber optic transmission of the image.
Chap 4 Page 120 Par 400
a . System Capabilities. Video systems permit video images to be recorded and stored on print or slide film, video cassette recorders, or computer disks. Microprocessors can be used to digitize video images for storage on a computer disk, or for transfer to other sites by modem and telephone lines. Photographic or video recording provides verifiable data for training purposes and for trend monitoring.
o. lypical Systems. Figure 4-1 shows a typical 35-mm camera and adapter installed on a rigid borescope that has a mounting kit to provide a platform for vibration-free photography. Figure 4-2 shows a typical video adapter system for converting a standard flexible or rigid borescope to a video inspection and documentation system. Figure 4-3 shows a block diagram of a typical video inspection, documentation, storage, and transmission sys- FIGURE 4-1. TYPICAL 35-MM CAMERA AND CAMERA ADAPTER INSTALLATION
ON A RIGID BORESCOPE (Courtesy of Olympus Corporation) Chap 4 Par 402 Page 121