GB 4793-2024Safety technical specification for electrical equipment for measurement,control and laboratory use (English PDF)

5.1 Marking

5.1.1 General The equipment shall be marked with markings in accordance with the provisions of 5.1.2 ~ 5.2.In addition to the markings on internal parts, these markings shall be visible from the outside, or, if the cover or door is intended to be removed or opened by the operator, these markings shall be visible from the outside after the cover is removed or the door is opened without tools. Marks applicable to the entire equipment shall not be marked on parts that can be removed by the operator without tools.

5.1.2 Identification The equipment shall be marked with at least the following.

5.1.3 Power supply The equipment shall be marked with the following information.

5.1.4 Fuse Any fuse that can be replaced by the operator shall be marked next to its fuse holder, to enable the operator to identify the correct replacement fuse.

5.1.5 Terminals, connectors and operating devices

5.1.6 Switches and circuit breakers If a power switch or circuit breaker is used as a disconnect device, the "off" position shall be clearly marked.

5.1.7 Equipment protected by double insulation or reinforced insulation Equipment that is only partially protected by double insulation or reinforced insulation shall not be marked with the symbol of No.10 in Table 1.

5.1.8 Field wiring terminal box Under normal conditions, at an ambient temperature of 40 °C, or at the maximum rated ambient temperature (if higher than 40 °C), if the temperature of the terminals or enclosure of the field wiring box or junction box exceeds 60 °C, there shall be a sign to warn the installer to refer to the installation instructions when determining the temperature rating of the cable connected to the terminal. The sign shall be visible before or during connection; or the sign shall be marked near the terminal.

5.2 Warning signs Warning signs are visible when the equipment is in normal use. If a warning sign applies to a specific part of the equipment, it shall be marked on or near that specific part. The dimensions of the warning sign shall be as follows:

5.3 Durability of markings The required markings shall remain legible under normal conditions of use and shall withstand the effects of cleaning agents specified by the manufacturer.

5.4 Documentation

5.4.1 General For safety purposes, the following documentation shall be provided with the equipment as required by the operator and responsible personnel. It shall be ensured that the service personnel authorized by the manufacturer have access to the safety-related documents they need.

5.4.2 Equipment rating The documentation shall contain the following.

5.4.3 Equipment installation The documentation shall include installation and specific commissioning instructions, and, if necessary for safety, warnings of hazards arising during the installation and commissioning of the equipment or due to improper installation or commissioning of the equipment. Such information (if applicable) includes.

5.4.4 Equipment operation The instructions for use shall include, where applicable.

6.3 Limits for accessible parts

6.3.1 Limits under normal conditions If the measured voltage exceeds the limit in a), meanwhile the other measured values are greater than the limits in

c) below, it is considered to be hazardous live.

6.4 Primary protection measures

6.4.1 Enclosure and protective shield If the enclosure or protective shield is provided by insulation, they shall meet the requirements of basic insulation.

6.4.2 Basic insulation The electrical gaps, creepage distances, solid insulation that form basic insulation shall meet the requirements of 6.6.

6.4.3 Impedance The impedance used for primary protective measures shall meet all of the following requirements.

6.5.1 Protective connections

6.5.1.1 General Accessible conductive parts shall be connected to the protective conductor terminals if they could become hazardous live in the event of a single fault in the primary protective measures specified in 6.4, or they shall be isolated from hazardous live parts by a conductive protective screen connected to the protective conductor terminals.

6.5.2 Additional insulation Gaps, creepage distances and solid insulation forming additional insulation shall meet the applicable requirements of 6.6.

6.5.3 Reinforced insulation Gaps, creepage distances and solid insulation forming reinforced insulation shall meet the applicable requirements of 6.6.

6.5.4 Protective impedance The protective impedance shall limit the current and voltage to the limits of

6.3.1 under normal conditions and to the limits of

6.3.2 under single fault conditions.

6.6.1 Nature of insulation

6.6.3 Insulation of secondary circuits supplied by a mains power circuit of overvoltage category II not exceeding 300 V

6.6.3.1 General In this document, the isolation of secondary circuits from the mains power circuit is achieved by a transformer. Inside the transformer, the primary and secondary windings are separated by reinforced insulation, double insulation or a shield connected to the protective conductor terminal.

7.3 Moving parts

7.3.1 General The hazard caused by moving parts shall not exceed the permissible level except as specified in 7.3.2.The conditions specified in

7.3.5 are considered to be permissible limits.

7.3.4 Limits of pressure The following limits shall be met under normal conditions and single fault conditions. The maximum permissible continuous contact pressure is 50 N/cm2 and the maximum pressure is 150 N.

7.3.5 Gap limits between moving parts

7.3.5.1 Gap limits between moving parts - Normal access allowed If a body part can be inserted between moving parts and the forces and pressures of the moving parts exceed the limits of 7.3.4, the width of the gap shall not be reduced from greater than the minimum gap value for the body part in Table 9 to less than the minimum gap value under normal conditions and single fault conditions.

7.4 Stability Equipment and components of equipment that are not fixed to the building structure before operation shall be physically stable during normal use. If measures are provided to ensure that the operator can maintain the stability of the equipment after operations such as pulling out a drawer, these measures shall be automatic or shall be marked with a warning sign to use the measures.

7.5 Lifting and carrying devices

7.5.1 General Equipment or parts with a mass greater than or equal to 18 kg shall be equipped with lifting and carrying devices or shall be described in the manufacturer's documentation.

7.5.2 Handles and handlebars If handles or handlebars for carrying are installed on or provided with the equipment, they shall be able to withstand a force of 4 times the weight of the equipment.

7.5.3 Lifting devices and supporting parts Parts of lifting devices and parts supporting heavy objects shall have a rated maximum load or be tested to pass 4 times the maximum static load.

7.6 Wall mounting For equipment intended to be mounted on a wall or ceiling, the bracket shall be able to withstand a force of 4 times the weight of the equipment.

7.7 Flying parts If a part fails and flies apart, the equipment shall be able to control or limit the energy of the part that may cause a hazard.

9.3 Once a fire occurs, contain the flame within the equipment

9.3.1 General The possibility of the flame spreading outside the equipment is considered to be reduced to an acceptable level, if the equipment meets one of the following structural requirements.

9.3.2 Structural requirements Comply with the following structural requirements.

9.4 Energy-limited circuits Energy-limited circuits are circuits that meet all of the following criteria.

9.6 Overcurrent protection

9.6.1 General Equipment intended to be powered by the mains supply shall be protected by fuses, circuit breakers, thermal cut-outs, impedance limiting circuits or similar devices, to prevent excessive energy from being drawn from the mains, in the event of a fault in the equipment.

9.6.2 Permanently connected equipment Overcurrent protection devices in permanently connected equipment are optional. If the equipment is not equipped with overcurrent protection devices, the characteristics of the overcurrent protection devices required in the building facilities shall be specified in the equipment installation instructions.