Machining safety

Small size, ruggedness, simple cabling and the ability to operate the equipment under adverse conditions in the field has also been design goals. The system should also conform with the regulations necessary for the CE-marking (i. e. standards and directives for EMC, Electrical Safety and Machine Safety). 

Safety at injection moulding machines Safety at blow moulding machines Safety at thermoformmg machines... 

Plastics processing sheet No. 9 safety at compression moulding machines Safety at granulators... 

Fig. 10. Continuous mining machine used in underground mine. As coal accumulates on the mine flixir. the helical screw effect of the culling head constantly moves the pile toward the center of the head, contributing to fast loading and improved productivity and cleanup. Two powerful motors handle all motions of the machine. Safety provisions are incorporated in the design. (National Coal Association)...

Richard Siwek/ M S Managing Director, President, FireEx Consultant Ltd. Member, European Committee for Standardization (CENTC305) Member, Association of German Engineers (VDl 2263,3673) Member, International Section for Machine Safety (ISSA) (Dust Explosions, Preventive Explosion Protection, Explosion Protection through Design Measures)... 

An example of the important dynamic data for workplace design is range of joint mohUity (Table 3) which corresponds to postures illustrated in Figure 1. Very useful anthropometric data, both static and dynamic, are provided by the Humanscale (Henry Dreyfuss Associates 1981). When anthropometric requirements for the workplace are not met, biomechanical stresses, which may manifest themselves in postural discomfort, low back pain, and overexertion injury, are likely to occur (Grieve and Pheasant 1982). Inadequate anthropometric design can lead to machine safety hazards, loss of motion economy, and poor visibility. In other words, the consequences of anthropometric misfits may of be a biomechanical and perceptual nature, directly impacting worker safety, health, and plant productivity. 

Figure 1. Mine machine safety monitoring system.

As an example of standards history and progression, the German ITE safety standard DIN VDE 0805 became EN 60950 (lEC 950), machine safety standard DIN VDE 0113-1 became EN 60204-1 (lEC 204-1), machine EMC standard DIN VDE 0875 became EN 55011 (CISPR 11), and appliance EMC standard DIN VDE 0875-1 became EN 55014 (CISPR 14). Except for EMC immunity, the majority of European product safety, machinery, and EMC standards are traceable back to their German standards origin. Thousands of German standards (DIN, VDI, VDE, VBG, ZH, etc.) form the basis for the newer harmonized standards (EN, lEC, etc.). 

Helpful hint If you have trouble determining whether the Low-Voltage or Machinery Directive applies to your equipment, identify the appropriate product or machine safety standard first. It is then easy to know which safety directive applies since product standards are usually listed under only one of the directives. 

Note If or when a machine safety standard (type C) is published for this machine type, some of the safety standards are then superseded by it. 

Guide limitations. The appropriate product or machine safety... 

Electrical safety is not limited only to products covered by the Low-Voltage Directive (LVD). According to the Machinery Directive, machine designers must also be aware of electrical safety since machines pose electrical hazards and they utilize numerous electrical components and subassemblies. The Low-Voltage Directive, General Product Safety Directive, and Machinery Directive mandate a product s conformity with the relevant electrical, mechanical, component, and other safety standards. To ensure that machinery electrical hazards are addressed by machine manufacturers, EN 60204-1/IEC 204-1 (Electrical Equipment of Machines) was published in both the Low-Voltage and Machinery directives, and, therefore, electrical requirements must also be applied to machinery. EN 60204-1 is a generic safety standard (type B) used in conjunction with the relevant machine safety standards (type C). 

Machines safety circuits sometimes require special components such as relays, contactors, interlocks, and E-stops. Common terms associated with these machine components are control reliable, fault tolerant, aaA fail-safe, which means that they fail to a safe condition after a single fault (not multiple faults). 

Once the product meets all of the applicable design, component, and construction requirements detailed in the previous sections and the relevant safety standards, the electrical safety testing begins. For machinery, the subsequent sections and the relevant machine safety standards should also be met prior to testing. 

The typical electrical safety tests for machinery include, but are not limited to (see also relevant machine safety standard[s]) ... 

The list assumes that all critical and safety components comply with then-individual component safety standards and are acceptable for use in the end equipment. Additional tests may be necessary depending on the complexity of the equipment or components (i.e., specials, lasers, UV/microwave radiation, noise) and the environment where the equipment will be used (residential, industrial, hazardous locations). For test conditions and pass/fail criteria and other tests, refer to the relevant product/machine safety standard(s). 

This section addresses additional requirements according to EN 60204-1 (lEC 204-1) for the electrical safety of industrial machines. The requirements presented in the previous sections are applicable to machines and are for the most part contained in EN 60204-1 or other associated standards. I will point out some of the key electri-cai safety items that are often overlooked by the beginning machine safety inspector. EN 60204-1 does not cover all machine safety requirements for guarding, interiocks, control, and so on that are also applicable and listed in the Machinery Directive. 

Notice. To ensure the machine s conformity with all the electrical safety requirements, a complete assessment according to EN 60204-1 and other applicable standards must be performed by qualified safety persons. Additional requirements may apply depending on the machines use, environment, and machine safety standards. 

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