Mechanical Safety General Knowledge Questions [One Question per Day 20090408]

Dangers, hazards, and control measures in machining 1. Major dangers and hazards present during metal cutting (1) Mechanical injuries. Injuries such as cuts, lacerations, and entanglement may occur due to the lack of protective devices at the rotating parts of the equipment (gears, couplings, tools, workpieces, etc.), the failure of such devices, or improper operation by personnel ； Injuries can occur when workpieces, tools, or components fly out due to operational errors such as poor equipment maintenance or inadequate clamping of the workpieces; injuries may also result from people being squeezed by moving parts when the distance between equipment units or between them and walls/columns is too small ； Cuts or chipping occur due to undischarded long chips during cutting or inadequate protection against short chips ； In punching, shearing, and pressing operations, hand injuries can occur due to the failure of protective devices or accidental contact with the punching, shearing, or pressing area ； Sharp corners and edges on mechanical equipment can cause scratches ； Inadequate protective measures during maintenance, errors in personnel coordination, and failure to wear appropriate protective equipment can lead to bruises, cuts, and crush injuries. (2) Electric shock. Electric shock to personnel may occur due to equipment leakage, the failure to implement necessary safety measures (such as protective grounding, leakage protection, safe voltage, equipotential bonding, etc.), or the effectiveness of such measures being compromised, as well as as a result of operational errors or violations by the operators. (3) Lifting injuries. Crane accidents can occur due to factors such as quality defects in the lifting equipment, malfunctioning safety devices, operational errors, and management shortcomings. (4) Fire. The lubricants used in mechanical equipment are flammable substances, and they can cause fires in the presence of external sources of fire ； Electrical fires can also be caused by electrical equipment failures, aging insulation of wires, and inadequate inspection and maintenance of electrical equipment. (5) Vehicle injuries. (6) Noise. (7) Vibration. (8) Fall from height. 2. Safety protection devices for metal cutting machine tools (1) Guard shields (to isolate exposed rotating parts) / Protection nets (to prevent human entry). (2) Guard plate: Separates grinding chips, swarf, and cooling lubricants to prevent them from splashing and injuring people. (3) Guardrail: To prevent injury from the back-and-forth movement of the workbench. (4) Safety devices and control devices. Overload protection device: Stops the machine tool from operating in case of an overload during operation. Travel limit device: When the worktable reaches the predetermined position, a stop block or travel limiter presses down on the travel switch, causing the worktable to stop automatically or return. Sequential action interlock device: It controls the various movements to occur in sequence, preventing the next action from starting until the previous one is completed. Emergency stop device, braking device: to shut down the machine quickly and promptly. Protective grounding (neutral) of electrical equipment, etc. 3. Countermeasures to prevent or reduce punch press accidents (1) Equipment, facilities, tools. a. Select stamping equipment with good intrinsically safe performance ； b. Install safety protection devices on the stamping equipment: such as fixed or movable barrier-type guards, safety devices operated with two-hand buttons or handles, optical or sensor-based safety protection systems, and safety interlock devices ； C. Select and install tools and dies appropriately to prevent them from flying out and causing injury. (2) Strictly follow the operating procedures. a. Carefully inspect and conduct a test run before starting work ； b. When the equipment is in operation, it is strictly prohibited to insert hands or fingers into the die to place or remove workpieces; hand tools must be used for handling workpieces inside the die ； c. Warning signs must be placed next to the equipment’s start switch whenever the die is installed or adjusted, the equipment is maintained, or when the machine needs to be shut down to resolve various faults ； d. Turn off the motor at the end of operation until all equipment has stopped ； Clean the work surface of the equipment and move the foot pedal to neutral or lock it. (3) Management. a. Strengthen safety education for operators and raise workers’ safety awareness ； b. Strengthen the inspection, maintenance, and upkeep of mechanical equipment, and repair any issues found promptly.

The hazards associated with woodworking machinery mainly include cutting injuries from tools, impact injuries from wood, and injuries caused by flying objects – these are the common types of hazards in wood processing. Other mechanical injuries, such as contact with moving parts or scratches from protruding parts on the machine, occur less frequently.

Mechanical injuries are classified as follows: (1) Object impact: This refers to accidents in which objects move due to gravity or other external forces and strike the human body, causing injury or death. It does not include object strikes caused by main mechanical equipment, vehicles, lifting machinery, collapses, etc. (2) Vehicle-related injuries: refer to injury accidents caused by the falling of people, as well as the collapse or falling of objects and crushing, resulting from the operation of an enterprise’s motor vehicles. Accidents that occur during lifting, towing of vehicles, or when vehicles are stationary are not included. (3) Mechanical injuries: refer to injuries such as compression, collision, impact, shearing, entanglement, twisting, ejection, cutting, severing, and puncture caused by the movement (or stillness) of mechanical equipment, as well as by direct contact between its components, tools, and workpieces with the human body. Injuries caused by vehicles and lifting equipment are not included. (4) Lifting injuries: refer to injuries caused by compression, falls, impacts from objects (lifting gear, lifted loads), and other such hazards that occur during various heavy-lifting operations (including crane installation, maintenance, and testing). (5) Electric shock: Includes electric shock from various devices and facilities, electric shock during electrical work, lightning strikes, etc. (6) Burns: Refer to burns caused by flames, hot objects, chemical burns (burns inside or outside the body caused by acids, bases, salts, or organic substances), and physical burns (burns inside or outside the body caused by light or radioactive substances). Burns caused by electrocution and fires are not included. (7) Fire injuries: include burns and deaths caused by fires. (8) Fall from height: refers to injury accidents caused by falling during work at heights. Accidents caused by electric shock or falling are not included. (9) Collapse: refers to accidents that occur when an object, under the influence of external forces or gravity, exceeds its strength limit or experiences a loss of structural stability, such as soil and rock collapses during trenching, scaffold collapses, collapses of piled materials, and building collapses. It does not include roof collapses and slope failures in mines, as well as collapses caused by vehicles, lifting equipment, and blasting. (10) **Explosion**: refers to **explosion accidents that occur during the production, processing, transportation, and storage of** such materials **and their products.** (11) Chemical explosion: refers to an explosion that occurs when flammable gases, dusts, etc. mix with air to form explosive substances, and come into contact with an ignition source (including gas decomposition, spraying, explosions, etc.). (12) Physical explosions: include boiler explosions, container overpressure explosions, etc. (13) Poisoning and asphyxiation: including poisoning, hypoxic asphyxiation, and toxic asphyxiation. (14) Other injuries: refer to injuries other than those mentioned above, such as falls, sprains, contusions, and abrasions. Regarding mechanical parts, the factors that can cause harm to humans include: (1) shape and surface properties ； Cutting elements, sharp edges, pointed corners, rough or overly smooth surfaces. (2) Relative position: Relative motion, with a small relative distance between the moving object and the stationary one. (3) Quality and stability: the potential energy of components that may move under the influence of gravity. (4) Mass, velocity, and acceleration: the kinetic energy of components in controlled or uncontrolled motion. (5) Insufficient mechanical strength: fracture or collapse of parts and components. (6) The potential energy of elastic elements, as well as the potential energy of liquids or gases under pressure or vacuum.

The categories you mentioned are those listed in GB6441-86 \"Classification of Accidents Involving Employees in Enterprises\", and mechanical injuries are just one of these categories.

Mechanical hazards can be divided into the following two types based on their mechanism of occurrence: (1) Hazards arising from products or machine parts, or caused by workpieces； (2) Dangers caused by internal energy accumulation in the machinery. Depending on the cause of the injury and the type of hazard it induces: (1) Compression hazard – this can occur when a person or a part of the body ends up between two moving parts that are moving toward each other, or when those moving parts move toward a fixed object. (2) Shear hazard ； (3) Risk of cutting or severing} (4) Wrapping hazard, such as that caused by shaft ends, sprockets, chains, etc ； (5) Risk of being sucked in or entangled, such as entanglement caused by belts or pulleys ； (6) Shock hazard, such as shock caused by the rapid movement of workbenches or slides ； 4.2.2.1 Shape: The shape of machine parts (or workpieces, the same hereafter) is inappropriate. Areas such as sharp protrusions or corners can, even when stationary, lead to dangers such as cutting ； Exposed transmission mechanisms can also cause cuts, abrasions, and pinches. Hazardous areas and related examples: 1. Relative position – A reasonable relative position must be designed; otherwise, hazards such as crushing, shearing, or entanglement may occur as the machine parts move. In particular, the area between the moving parts and the fixed parts, which are easily accessed during human operation or maintenance, is a zone with a high probability of compression hazards. For example, in Yantai, Shandong, there was a tragedy in which a four-in-one folding stroller caused the death of a child aged LJ years, as the spring-controlled folding handle caught the child’s neck; this is an example of inadequate prevention against compression hazards. 2 Quality and stability: The potential energy of components that may move under the influence of gravity is the main factor causing tipping. For example, the \"stroller collapse compensation case\" that attracted widespread media attention concerned the issue of whether the stability of strollers met the required standards. Evening of July 18, 2001, Kunming City, Yunnan Province. Xiaoxiao, a 10-month-old child, was seriously injured after the walking toy she was using overturned and knocked her down. 3 Mass and velocity: The loss of kinetic energy in moving components, whether under control or not, can pose a danger. For example: In February 2002, Sun from Chengguan Town in Huaiyuan County, Anhui Province, purchased a motorcycle of a certain brand model, type 125T 3A. On the afternoon of September 17, Sun drove the motorcycle along with his friend Fang to handle some matters in Heliu Town of the same county. While driving at a normal speed of (50–60) km/h, the engine started making several beeping noises, and the vehicle lost control. Sun was thrown to the side of the road, while Fang fell in the middle of the road and suffered serious injuries. Afterward, a technical inspection by professionals revealed that the accident was caused by the breakage of the crankshaft connecting rod in the vehicle, which led to the engine block being damaged and the vehicle locking up suddenly. This resulted in injuries to people who were in the vehicle at the time. The reducer on it got stuck, causing a mechanical failure; as a result, during rotation the game machine experienced collisions between the compartments, between the compartments and the central column of the machine, and between people and the compartments. Some people suffered minor injuries. One child fainted from shock on the spot. This led to complaints from 7 families, 15 adults, and Xiao Xian against the park operator; this was also an accident caused by a loss of kinetic energy. In both of the above cases, there are issues with the quality of the components. 4 Acceleration: Inappropriate acceleration or failure to meet the required acceleration levels can cause mechanical damage and physical injury. For example, at around 9:30 on September 27, 2002, while driving a bus on Wenzheng Street in the Dongli District of Harbin and turning right from south to east, driver Chao Liang was traveling too fast and his braking system failed, resulting in the vehicle overturning. This accident caused severe injuries to 4 passengers, minor injuries to 5 others, and slight injuries to 12 more people. Liang, while operating a passenger vehicle with a defective braking system, neglected traffic safety and violated transportation regulations; as a result, he was found guilty of traffic accident offenses and sentenced to two years in prison, along with civil liability for compensation, while his employer, the passenger transport company, was held liable for joint and several compensation. It was found that the use of buses with defective braking systems was one of the main causes of this accident. The required braking acceleration cannot be achieved; the resulting damage is severe. 5 Mechanical strength: Insufficient strength may lead to dangerous fractures or ruptures. For example, on August 5, 1997, Zhao, who lived in the Hexi District of Yuanjin, was using the newly installed toilet in his home when it suddenly cracked open; sharp ceramic shards caused a wound about 12 cm long on Zhao’s buttock, with the wound reaching the periosteum. A toilet breaking under the weight of the user is a sign of insufficient strength.

Mechanical injuries include: entanglement, crushing, severing, cuts, entwining, collisions, hazardous areas, points where belts make contact, exposed rotating parts, die openings in stamping equipment, sharp edges and corners of machinery, and the joints of gears

Squeezing hazard, shearing hazard, cutting hazard, entanglement hazard, impact hazard, etc

The part of the body most damaged by machinery is the hand. The area of the body that suffers the most from mechanical injuries is the hand. Because the hands come into contact with machinery most frequently during labor.

The sources of risk for injury accidents caused by mechanical equipment are often found in the following areas: 1. Rotating parts pose a risk of pulling in human bodies or objects from the outside； The chucks, drills, milling cutters, etc. of machine tools, as well as the protruding parts of transmission components and rotating shafts, pose a risk of catching sleeves, trouser legs, long hair, etc., and pulling people in ； The wind wings and impellers are at risk of being crushed ； Rollers that rotate in relative contact pose a risk of entanglement. 2. There is a risk of bruises and crush injuries in the parts that move back and forth in a straight line. In machinery such as stamping, shearing, and forging machines, components like molds, hammers, and cutting edges are at risk of impact and shear forces. 3. The mechanically swinging parts also pose a risk of collision. 4. There are also various potential risk factors associated with the mechanical control points, operation points, inspection points, sampling points, and material feeding process. Mechanical devices can pose dangers in normal operating conditions, abnormal operating conditions, and even when not in use. I. In its normal operating state while performing its intended function, a machine possesses inevitable motion elements that are necessary for carrying out that function, and these elements may lead to harmful consequences. For example, the relative movement of components, the operation of sharp cutting tools, as well as noise and vibration generated by mechanical operations, create hazards such as collisions, cutting, and environmental degradation under normal operating conditions, all of which pose risks to personnel safety. II. The abnormal operating condition of a mechanical device refers to the unexpected states that occur during its operation due to various reasons, including fault conditions and maintenance states. Equipment failures can not only cause partial or complete shutdown of the machine, but they may also pose a danger to personnel. For example, faults in electrical switches can create a risk of the machine failing to stop operating ； A damaged grinding wheel can cause it to fly out, resulting in object strikes ； A failure in the speed or pressure control system can lead to risks such as loss of control over speed or pressure. Mechanical maintenance is generally carried out when the machine is shut down, but the unique nature of this work often forces maintenance personnel to employ unconventional methods, such as climbing heights, entering narrow or almost enclosed spaces, short-circuiting safety devices, and going into hazardous areas where entry is not permitted under normal operating conditions. This makes the maintenance or repair process prone to hazards that do not exist during normal operation. III. The non-operational state of a mechanical device is the stationary state when the machine has stopped running. Under normal circumstances, a machine in its non-operational state is generally safe, but the possibility of accidents still exists, such as collisions involving people due to insufficient ambient lighting ； Sliding or tipping of outdoor machinery under wind force ； Structural collapse, etc. This post was last edited by lyhh9024 on 2009-4-8 00:29]

These words are appropriate for describing them: involved in, crowded, severed, cut, entangled, collided

Mechanical injuries are generally classified into several forms such as compression, shearing, cutting, severing, entanglement, aspiration, entrapment, and impact

1. Conditions under which machine parts (or components) pose mechanical hazards (1) Shape and surface properties: cutting elements, sharp edges, pointed corners, as well as rough or overly smooth surfaces. 　 (2) Relative position: moving toward each other, with a small relative distance between the moving object and the stationary one. 　 (3) Quality and stability: the potential energy of components that may move under the influence of gravity. 　 (4) Mass and velocity (acceleration): the kinetic energy of components in controlled or uncontrolled motion. 　 (5) Insufficient mechanical strength: Fracture or collapse of parts and components. 　 (6) The potential energy of elastic elements (springs), as well as the potential energy of liquids or gases under pressure or vacuum. 2. Basic types of mechanical injuries (1) Wrapping and entanglement. The cause of such damage is mechanical components that move in a rotational manner (such as shaft components), including couplings, spindles, lead screws, etc ； Protrusions and openings on rotating parts, such as protruding keys on shafts, adjustment bolts or pins, the spokes of wheel-shaped components (sprockets, gears, pulleys), and handles on handwheels, can cause injuries when in motion by entangling a person’s hair, jewelry (such as necklaces), or the sleeves or hems of thick clothing. 　 (2) Entanglement and crushing. The main hazard causing such injuries is the interaction between moving parts; for example, at the points where meshing gears come into contact with each other, as well as between gears and racks. It also includes the tightening areas where belts and pulleys, or chains and sprockets, are in contact, as well as entanglement that occurs between two rollers that are rotating relative to each other ； Compression caused by rotating rolling elements, such as wheels on tracks or wheels on road surfaces. 　 (3) Compression, shear, and impact. Such injuries are caused by components that move in a back-and-forth linear motion, such as squeezing that occurs between two parts in relative motion or between a moving part and a stationary part due to insufficient safety distance, as well as collisions with components moving in a linear path. Linear motion includes horizontal motion (such as the movement of the worktable in large machine tools, the slide in shaper machines, and the movement of components like belts in operating machinery) and vertical motion (such as the movement of the clamping devices and blades in shears, the slider in presses, and the elevation table in large machine tools). 　 (4) Impact from flying objects. Mechanical energy release, such as fracture, loosening, detachment, or elastic potential energy, causes out-of-control objects to fly or bounce away, thereby causing injury to people. For example: Failure of the shaft can cause the pulleys, flywheels, gears, or other moving components mounted on it to fall or fly off ； Loosening or detachment of the bolt causes the moving parts that it secures to fall off or fly out ； The fragments resulting from the breakage of rapidly moving parts are ejected ； Chipping and flying of cutting waste, etc. Additionally, ejection caused by the potential energy of the elastic element. For example: breakage of springs, belts, etc ； High-pressure fluid ejection caused by the potential energy of liquids or gases under pressure or vacuum, etc. 　 (5) Impact from falling objects. Objects at a high position possess potential energy, and when they fall accidentally, this potential energy is converted into kinetic energy, causing injury. For example, parts, tools, or other objects that fall from a height (even if they are very small) ； The suspension components holding the object break, or the clamps fail to hold it tightly, causing the object to fall ； Due to the uneven mass distribution and unstable center of gravity, it tips over or rolls down under the action of external forces ； Injuries caused by derailment due to excessive travel of moving parts, etc. 　 (6) Cutting and abrasions. The cutting edge of cutting tools, burrs on the surface of parts, sharp edges from workpieces or waste material, as well as sharp corners and edges on mechanical equipment ； Rough surfaces (such as grinding wheels, blanks), etc. – regardless of whether the object is in motion or at rest – these shape-related hazards can cause injury. 　 (7) Collisions and scratches. Protrusions and hanging parts in the mechanical structure (such as the legs and jib of cranes, the handles of machine tools, etc.), as well as the parts of long and large workpieces that extend outside the machine tool. These objects, whether stationary or in motion, can pose a danger. 　 (8) Falls, drops. Trips and falls caused by messy debris on the ground or uneven surfaces; slips and falls resulting from insufficient friction at the contact points (such as smooth surfaces, oil, ice, snow, etc.). If secondary injuries occur as a result of a fall, the consequences will be even more severe. 　 A person falls from a height or accidentally steps into a pit and falls ； The elevator suspension mechanism was damaged, causing the car to descend at excessive speed and hitting the bottom of the pit, resulting in injuries to people. 　 Mechanical hazards are largely manifested as injuries resulting from contact between people and moving objects; various forms of mechanical hazards often coexist with other non-mechanical hazards. When identifying hazards, it is necessary to consider the mechanical system as a whole, taking into account the different states of the machine, various manifestations of the same hazard, the relationships and interactions between different hazard factors, as well as the different apparent or potential forms.

1. The hazards of winding and twisting. Mechanical components that move in a rotating motion are the cause of such damage. Such as shaft components, including couplings, spindles, lead screws, etc ； Protruding shapes on rotating parts, such as protruding keys, bolts, or pins mounted on shafts, and handles on pistols, etc ； The open parts of mechanical components that undergo rotational motion, such as the teeth of sprockets, gears, pulleys, and the spokes of circular components, as well as the hollow sections of rotating cams. The mechanical components of rotational motion can wrap a person’s hair, accessories such as necklaces, gloves, or the sleeves and hems of thick coats around the rotating parts, thereby causing injury to the person. 2. Dangers of extrusion, shearing, and impact. Components that move back and forth in a straight line are the cause of such damage. Its path of movement may be lateral, such as the moving worktable of large machine tools, the slide of a headstock planer, or chains in operation ； It can also be vertical, such as the clamping device and blades of a shear machine, the slider of a press, and the lifting table of large machine tools. The relative motion state of the two objects can be approaching type, with the distance between them decreasing gradually, until they eventually come together ； It could also be a passing type, where they move past each other slightly when they are relatively close. Linear motion, especially relative motion between two components, can cause crushing, collision, or shear injuries to people between the moving components and the stationary ones. 3. Risk of being introduced into or involved in rolling. The main hazard causing such damage is the interaction between moving components; for example, between meshing gears and between the teeth of gears and racks, at the points where belts and pulleys, or chains and sprockets come into contact, as well as at the junctions between two rollers that are in relative rotational motion, which can lead to entanglement or being pulled in ； Rolling and rotational movements such as those between wheels and tracks, or between wheels and the road surface, can cause crushing effects. 4. Risk of impact from flying objects. Mechanical energy release, such as fractures, loosening, detachment, or elastic potential energy, causes out-of-control objects to fly or bounce, thereby injuring people. For example, the failure of the shaft can cause moving components such as pulleys and flywheels mounted on it to fall or fly out ； Due to the loosening or detachment of bolts, the fastened moving components are ejected as a result of the potential energy stored in elastic elements, such as the breakage of springs, belts, etc ； High-pressure fluid ejection caused by the potential energy of liquids or gases under pressure or vacuum, etc. 5. The risk of injury from falling objects. Objects at a high position possess potential energy, and when they fall accidentally, this potential energy is converted into kinetic energy, causing injury. For example, parts, tools, or other objects that fall from a height (even if they are very light in weight) ； The falling of the suspended object is caused by damage to the suspension components or insufficient clamping force by the fixture ； Due to uneven mass distribution and unstable center of gravity, it tips over or rolls down under the action of external forces ； Injuries caused by the guide rails exceeding their operating range due to moving parts. 6. Risk of cutting and abrasions. The cutting edge of cutting tools, burrs on the surface of parts, sharp edges from workpieces or waste material, as well as the sharp corners, points, and rough surfaces of mechanical equipment (such as grinding wheels and blanks), all pose potential hazards due to their shape – whether the object is in motion or at rest. 7. Risk of collisions and scratches. Protruding or hanging parts of the mechanical structure, such as the legs and boom used for lifting, the handles of machine tools, and the parts of large or long workpieces that extend outside the machine tool. These objects, whether stationary or in motion, can pose a danger. 8. Risk of falling and dropping. Trips and falls caused by disordered debris on the ground or uneven surfaces ； Excessively low friction at the contact surface (smooth surfaces, oil, ice, snow, etc.) leads to slipping and falls ； People fall from heights, accidentally step into pits or wells and fall, etc. If secondary injuries occur as a result of the fall, the consequences will be even more severe.

Mechanical injuries include: entanglement, collision, crushing, severing, cutting, entwisting, and compression.

To prevent or reduce stamping machine accidents, the following countermeasures can be taken: (1) Stamping equipment with good intrinsically safe properties should be selected. (2) Install safety protection devices on the stamping equipment: fixed barrier-type or movable barrier-type guards ； Safety devices operated using two-hand button or two-hand lever controls ； Safety protection devices such as light-based and sensor-based types ； Safety interlock devices, etc. (3) Select and install tools and dies appropriately to prevent them from flying out and causing injury. (4) Stamping workers must strictly follow the operating procedures: carefully inspect and conduct a test run before starting work ； When the equipment is in operation, it is strictly prohibited to insert hands or fingers into the die to place or remove workpieces. Manual tools must be used to pick up and place workpieces inside the die ； When installing and adjusting die sets, performing equipment maintenance, or when it is necessary to shut down the equipment to resolve various faults, a warning sign must always be placed next to the equipment’s start switch ； Turn off the motor at the end of work until all equipment has stopped, clean the work surface of the equipment, and move the foot pedal to neutral or retract it. (5) Strengthen the inspection, maintenance, and upkeep of mechanical equipment; address any issues found with such equipment promptly. (6) Strengthen safety training for operators to raise workers’ safety awareness. 3. Briefly describe the countermeasures to prevent electric shock? Answer: The main measures to prevent electric shock are: (1) Neutral and grounding protection systems ； (2) Leakage protection ； (3) Insulation ； (4) Safe voltage ； (5) Shielding and safety distance ； (6) Cascading protection.

The most common areas affected by mechanical injuries are the hands, followed by the face, feet, etc

1. Mechanical injuries resulting from the use of inappropriate cutting tools: In a residential building construction site, an electric saw operator attached a toothless saw blade meant for use with a cutting machine to the power shaft of the electric saw, and then used that saw blade to file material; this caused the toothless saw blade to break apart, with fragments flying and hitting the operator, resulting in injuries. 2. Mechanical injuries caused by illegal operations Case: At two construction sites, operators improperly secured the fall prevention devices when using material lifters; they did not connect them to the power supply and used their feet to release the brake on the winch, causing the material tray to fall at an accelerated rate. When they removed their feet from the brake, the brake wheels shattered, hitting the operator on the spot and resulting in one death and one serious injury. Such actions constituted a serious violation of the operating procedures for machinery, i.e., illegal operations. 3. Injuries caused by problems with the machinery itself. Example: At a construction site, a very inexpensive tower crane was newly purchased. During the process of lifting the crane, the lower crossbeam of the lifting frame suddenly cracked, causing the crane to lose its balance and collapse. Expert evaluations confirmed that there were serious quality issues with the crane itself; it was indeed an unqualified product.

Mechanical equipment can cause various types of injuries such as collisions, pinching, shearing, and entanglement. Its main hazardous areas are as follows: (1) the points of engagement between rotating components and components moving in a tangential direction, such as power transmission belts and pulleys, chains and sprockets, racks and gears, etc. (2) Rotating shafts, including connectors, spindles, chucks, lead screws, and rods, etc. (3) At the rotating protrusions and holes. Rotating components with protrusions or cavities are very dangerous, such as fan blades, cams, flywheels, etc. (4) The mating surfaces of counter-rotating components, such as gears and mixing rollers. (5) The junctions between rotating and fixed components, such as spoke handwheels or flywheels and machine tool beds, as well as rotary mixers and mixing devices with unprotected open enclosures. (6) Near-type, such as the hammer head of a forging hammer and the ram of a power press. (7) By type, such as the worktable and bed of a metal planer, the cutting blade of a shear machine, etc. (8) Unidirectional sliding components, such as the teeth on a band saw blade, the grinding particles in a belt sander, and convex moving belts. (9) Between rotating components and sliding parts, such as the mechanisms found on certain flatbed printing presses, textile machinery, etc.

1) The interfaces between rotating components and those moving in a tangential direction, such as power transmission belts and pulleys, chains and sprockets, racks and gears, etc. 2) Rotating shafts, including connectors, mandrels, chucks, lead screws, circular mandrels, and rods, etc. 3) At the rotating protrusions and holes. Rotating components with protrusions or cavities are very dangerous, such as fan blades, cams, flywheels, etc. 4) The meshing points of counter-rotating components, such as gears, rolling mills, mixing rollers, etc. 5) The junctions between rotating and fixed components, such as in rotary mixers and mixing devices with unprotected open housings. 6) Proximal types, such as the ram of power presses and the hammer head of forging hammers, etc. 7) By type, such as the cutting blade of a shear machine, the worktable and bed of a metal planer, etc. 8) Unidirectional sliding components, such as the teeth on a band saw blade, the grinding particles in a belt sander, and convex moving belts. 9) Between rotating components and sliding parts, such as the mechanisms found in certain flatbed printing machines and textile machinery. 10) Sharp corners and edges of equipment and metal sheets can also cause employees to suffer cuts and bruises.