Discussion on safety inspection requirements of me

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Talking about the safety inspection requirements of mechanical equipment

with the innovation of a series of mandatory parts related to mechanical equipment in China in 2009, the technical safety standards of coating technology have been changed and implemented, which puts forward new requirements for China's machinery production enterprises. However, during the inspection of mechanical equipment, it was found that many food industries did not adopt the new standard, resulting in unqualified inspection results; What's more, they don't know that the state has requirements on mechanical safety, and their safety awareness is poor

this paper discusses the safety inspection of mechanical equipment in combination with the revision of the standard and the actual work of inspectors

1 Revision of national standards

since 2009, a series of changes have been made in the relevant standards of mechanical equipment safety in China. Taking the national standards for safety of commonly used general machinery as an example, the revision is shown in Table 1

2 inspection of safety items of mechanical equipment

the so-called machinery (machine) is composed of several complete parts according to the instructions in is012100.1 and GB/t15706.1, of which at least one part is movable, and there are appropriate machine actuating mechanisms, control and power systems, etc. Their combination has certain application purposes, such as material processing, processing, handling or packaging. It also includes the combination of several machines that are arranged and controlled to perform their functions like a complete machine for the same application purpose

mechanical equipment should basically comply with GB/T l5706.1-2007 "general principles of basic concepts and design of mechanical safety Part 1: blades should be studied; (3) improper location of adjusting block on load lever: basic terms and methods" (IS0 12100-1:2003, IDT) and GB/T l5706.2-2007 "general principles of basic concepts and design of mechanical safety Part 2: technical principles" (IS0 12100-2:2003, IDT) as the core series of safety standards

safety testing of mechanical equipment mainly includes: sign information, mechanical safety, electrical safety, etc. 2.1 signs information forces

inspect the signs, information and accompanying instructions on mechanical equipment

2.1.1 safety colors and safety signs

the safety colors and safety signs set on mechanical equipment shall comply with GB 2893-2008 safety colors and GB 2894-2008 safety standards and guidelines for their use. In the new version of the standard, "wamin9" is used instead of "danger" in the old version of the standard; Icons such as no touch have been modified

in actual inspection, unqualified safety signs are common. For example, the correct grounding signs should be as shown in Figure 1, while some enterprises use signs that do not meet the standards (as shown in Figure 2), and some even create safety signs by imagination

2.1.2 signals, symbols and literary warnings

shall comply with the provisions of GB l8209.1-2000, GB l8209.2-2000 and other relevant standards

signals are divided into visual signals, auditory signals and tactile signals, which are used when dangerous events (such as machine startup or overspeed alarm) are about to occur. The standard requires that it should meet the following requirements: "issued before the occurrence of dangerous events: accurate meaning; can be clearly perceived, and can be distinguished from other signals used; easy to be recognized by users"

symbols and text warnings should meet the following requirements: they must be accurate and easy to understand; Graphic symbols take precedence over text warnings; The information directly printed on the machine should be firm and clear during the whole service life of the machine; The text warning cannot only write "danger"

mechanical hazard signs include but are not limited to: input/output power; Maximum speed of rotating parts; The maximum diameter of the tool to be clamped; Quality; Direction of movement, maximum load, cooling/heating conditions; Allowable environmental conditions; Mechanical stabilizer; operation mode; Protective device data; Necessary parts for wearing protective equipment; Inspection and maintenance times, etc

electrical hazard signs include but are not limited to: rated voltage, current and frequency; Number of phases; Classification symbol for protection against electric shock; Warning of danger due to dangerous voltage; IP code marks, etc

in the actual inspection, the lack of mechanical hazard signs and electrical hazard signs is common

2.1.3 operating instructions

operating instructions are essential items of mechanical equipment and should comply with the provisions of GB/T 9969-2008. Moreover, safety warnings should be given for the contents related to safety

during the actual inspection, some small and medium-sized machinery produced by the food industry did not have instructions attached or warnings on safety related matters in the instructions, which were pointed out by the inspectors before rectification

2.2 safety of machinery

the problem of mechanical safety should fundamentally start with design. The principle is: the machine must be manufactured according to its function. Under the intended use state of the manufacturer, adjusting and maintaining the machine will not bring risks to people

2.2.1 requirements for mechanical structure

(1) shape: on the premise of not affecting the normal use, all mechanical shape structures that are easily accessible to the human body should be neat and smooth, and there should be no sharp corners, sharp corners, protrusions, etc. that are easy to cause damage. Especially remind that the edges of the metal sheet should be folded or blunt

(2) processing area: all equipment prone to injury accidents in the processing area (operation area) should take effective safety protection measures. For example: completely fixed, semi fixed sealing cover; Mechanical or electrical interlocking device, two hand release device; Hand limiter; Emergency stop device, etc

in the actual inspection, Ren Li was not set in the dangerous area. Safety protection or inadequate protection is occasionally found, and such machinery is seriously unqualified

(3) moving parts: all moving parts that are easy to cause injury accidents should be closed or shielded, or protective measures should be taken to avoid contact with other personnel. The distance between linear moving parts or between linear moving parts and stationary parts shall meet the requirements of GB 23821-2009 safety distance of machinery to prevent upper and lower limbs from touching dangerous areas. In addition, reliable limit devices, overload safety devices or reliable buffer measures can be set as required

(4) emergency stop device: it must be configured in the following cases: when there is a danger that the equipment cannot be stopped quickly through the control switch to terminate the danger; It cannot be quickly interrupted through a full master switch if t omnipotence causes dangerous motion units; When other hazards may occur due to cutting off a unit; When the console cannot see all the controls; At every full operation position and place that needs to be set

2.2.2 the requirements for the control mechanism

should be equipped with protective devices to prevent accidental startup from causing danger; The control circuit shall ensure that there will be no danger after the circuit is damaged; The arrangement of controllers shall make it easy for operators to identify and operate by means of spacing, shape, color, symbol, etc; The controller shall be interlocked with the protective device to make the equipment operation and the safety protective device work at the same time; For mechanical equipment operated by two or more people, the controller shall have interlocking device

2.2_ 3 requirements for safety protection devices

in view of the dangers that cannot be shielded in design, additional protection devices should be considered. The protective device must have the following characteristics: strong and durable structure; Will not cause other additional hazards; Night completely protected and not easy to produce functional fire effect; Keep a certain distance from the dangerous area; Minimize obstacles to vision during production; For replacement, maintenance and other operations, it is limited to the operation point. If possible, it is not necessary to remove or remove the protective cover

2.2.4 enterprises should also pay attention to mechanical hazards and non mechanical hazards when designing

mechanical hazards mainly include: crushing hazard, shearing hazard, cutting hazard, winding hazard, inhalation or involvement hazard, impact hazard, stabbing hazard, etc

non mechanical hazards mainly include: electrical hazards, thermal hazards, noise hazards, vibration hazards, radiation hazards, hazards of material and substance production, hazards caused by designers' neglect of ergonomic principles and hazards of hazardous parts discharge, etc. The above factors are risks that should be paid attention to in mechanical design, and measures should be taken to minimize or avoid them

2.3 electrical safety of machinery

electrical equipment should have the ability to protect people from electric shock in the case of direct and indirect contact. The equipment must be installed and used safely without any danger. All electrical equipment, devices and components meet the requirements of GB 5226.1-2008 safety standard. Enterprises should take direct, indirect or prompt safety technical measures to ensure safety

2.3.1 changes in electrical safety standards

in the actual inspection, there are still a large number of mechanical production and food industry that have not adopted the new version of GB 5226.1-2008 electrical safety standards for production. It is understood that the inspection results are easy to fail to meet the standard requirements during the "1035" period

main changes in the revision of commonly used electrical safety inspection items:

(1) using automatic power cut-off as protection, relevant instructions and conditions have been added, and provisions have been made for TN system test. The inspection of continuous parts of protective grounding circuit is deleted

(2) additional protective grounding requirements are proposed for electrical equipment with leakage current greater than 10mA a A.C or DC

(3) added provisions on the protective grounding of mobile machinery

(4) add safety requirements for control functions

(5) consider the influence of thermal effect

in addition, some regulations on cables, wiring, etc. are added

2.3.2 voltage withstand test

voltage withstand test is an important index for assessing electrical insulation. It is to ensure the good insulation of the circuit to the equipment in case of high-voltage infiltration of external current, so as to prevent the equipment from being broken down during operation, causing electric shock or other accidents. Voltage withstand test is the most important part of electrical safety inspection

use a voltage withstand tester that meets the standard (as shown in Figure 3, the government will support backbone units in all links to form an industrial development alliance that shares benefits and risks), and apply high voltage between the power circuit conductors of the machinery and the protective connection circuit. The maximum test voltage is twice the rated power supply voltage of electrical equipment or 1000V, whichever is greater. The frequency of the test voltage is 50Hz or 60Hz. The mechanical equipment must withstand a withstand voltage test of at least l s. The components that are not suitable for the test or have been subjected to the voltage withstand test according to the product standard shall be disconnected during the test. Failure in the voltage withstand test is a serious failure

2.3.3 insulation resistance detection

the service life of electrical equipment largely depends on the service life of insulating materials. Most electrical faults of equipment are caused by aging and damage of insulation. Due to the continuous improvement of electrical safety standards, the requirements for insulation are also constantly improving. When measuring the mechanical insulation resistance, the DC test method is generally adopted, that is, when 500vd. C is applied between the power circuit conductor and the protective grounding circuit, the measured insulation resistance should not be less than LM Ω. For some parts of electrical equipment, such as busbar, busbar, busbar system or busbar ring, the minimum allowable insulation resistance is lower, but not less than 50 K Ω. If the electrical equipment contains surge protection devices, this device can be disconnected or the test voltage value can be reduced during the test to make it lower than the voltage protection level of the surge protection devices, but not lower than the upper limit peak value of the power supply voltage (relative to the neutral line)

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