GB 5959.4-2008Safety in electro-heat installations -- Part 4: Particular requirements for safety resistance heating installations (English PDF)

3.1

Direct resistive heating member which contacts with the charge and the current is transferred to the charge.

3.2 The electrical energy into heat for a conductor

Note: The term "heat conductor" often use "heating resistor" alternate.

3.3

The molten glass in the bath the thermal current directly flows generated by the oven to achieve, in which the electrode is immersed in the bath furnace.

3.4 Salt bath furnace is mainly used as the heat transfer fluid

Note: direct heating or indirect heating may be achieved. Direct heating of the heating element assembly (the heater) was placed in a salt bath (the heater or electrodes immersed Salt bath); indirect heating of the heating element assembly (the heater) is placed outside the cylindrical body or the crucible.

3.5

In a metal cylinder or a crucible filled with sodium or potassium nitrite or nitrate salt bath, or a mixture of these salts consisting of a salt bath Bath furnace.

3.8

Has been added so that the melting furnace charge, furnace maintained at a predetermined temperature in the molten state.

3.9

Used to transfer heat from the charge to a liquid or gas heating element assembly (the heater).

3.10

Movable by a user or replaced without removing any other components (e.g., the furnace refractory and insulating material) of the heating element and/or addition Thermal element assembly (the heater).

NOTE: When using movable without interrupting the heating element during operation and/or heating element assembly (the heater) is referred to as "movable in use."

3.11 It refers to disconnect

the power supply device of the heating device when the temperature exceeds a predetermined value.

Note: a resettable thermal cut, and non-resettable fuses, need for replacement after each operation.

3.12 When

the operating temperature of the heating device exceeds a predetermined value, the device is disconnected and maintained at the power supply device power-off state.

Note: Over-temperature limiter can only be set by professionals, lock or reset.

3.13

Furnace temperature control means so as not to exceed a predetermined value or below.

Note: The temperature controller can be set or locked by professionals.

3.14

It refers to the current into the earth or in an outer conductive member during normal operation by the heating means.

Note 1. The leakage current may have a capacitive component, the capacitive component comprising a capacitor using caution due.

Note 2. The leakage current value of the electric hot and cold apparatus may be different.

3.15

The former, when current flows through the one or more accessible parts of the human or animal contact with the electric heating means or electric equipment.

3.17

Heat is transferred to the bath by an electrical heating element insulation and jacketing.

NOTE: immersion heater may be fixed or movable.

6.8 Auxiliary equipment

Deal with operations, transport and handling, and other auxiliary equipment to take protective measures, it does not pose a risk.

Exposed heating conductors 6.9 Typically, the heat conductor exposed so as not to be disposed with the staff handling charge or charge delivery device in contact under normal operating conditions Touch, but in line with the IEC 60364-4-41:2005 Power Safety Extra Low Voltage (SELV) supply is required except for the exposed heating conductors.

6.10 Leakage current

Protective measures should enable staff to the risk of electrical accidents caused by the leak current does not occur under normal operating conditions.

Should take effective measures to ensure that flow through the furnace with a charge or leakage current flowing through the charge does not cause any dangerous electrical accidents.

6.11 Steam, precipitate and scum produced by the charge

Of charge produces steam, precipitate and the like trash, consider physicochemical may have on its staff and/or heating apparatus effect.

6.12 Salt bath furnace and the melting furnace

And 6.12.1 of the salt bath furnace such as galvanized aluminum or other bath furnace was incubated with which immersion heaters allows maximum rated voltage should be 400V.

6.12.2 Should be clearly marked at a temperature controller or a temperature indicator (see 13.9.1) on the maximum allowable temperature of the salt bath.

--- cast aluminum alloy;

---steel.

6.12.3 nitrite salt bath furnace for processing aluminum or wrought aluminum alloys can not be used to process workpieces made from the following materials.

--- unknown elements of aluminum;

--- other light metals and their alloys;

--- Heavy metals and their alloys;

If the furnace temperature may exceed the runtime 550 °C, it should be obvious in the outer furnace shell is marked "not for light metal" warning message.

6.12.4 furnace to heat, disposed immersion heating element assembly (heater) such that it does not produce the deposits.

6.12.5 depth of more than 1.5m bath, unless take other precautions, or should be provided to ensure that no risk when preheating Insurance preheating means for forming vertical channels in the solidified melt in the bath.

6.12.6 External thermal furnace, a heating element assembly (heater) should normally be installed on the furnace wall, in order to avoid local overheating bottom.

6.12.7 large external heating type melting furnace, can not be avoided when heated at the bottom, it should meet the following requirements.

--- bottom surface of unit power should be heated, the manufacturer should make a predetermined value depending upon the particular application lower than the furnace wall;

--- should be able to separately control the heating of the bottom;

--- circuit design should ensure that when the first pre-heating the furnace wall of the crucible;

--- only when the bloom in the crucible was heated by a separate furnace wall and has partially melted, in order to supply heat to the hearth.

Warming body coagulation bath 6.13 When the solidified body in the pre-heat bath, to be noted that part of the surface of the surface should be injected in order to avoid liquefaction.

Electrodes salt bath furnace, a preheating means should generate sufficient current at the initial stage, in order to avoid the ejection slot thereof.

Vacuum furnace 6.14 Vacuum oven, under vacuum member in a state without the applied voltage to be a breakdown or flashover.

In addition to these additional regulations, according to GB 5959.1-2005 Chapter 7 requirements.

9.5 Protection against direct contact

9.5.1 AC operating voltage exceeds 25V or 60V DC electric conductor having an exposed heating device, which when the door or the like closing After the apparatus (such as a cover or plate) is turned on, the charge in contact with the tool, or heating the exposed conductor can be reliably cut off should be turned on with the door All heating means ungrounded conductor of the power supply.

9.5.2 If the heating device accessible components (e.g., a ceramic member) becomes under normal operating conditions has conductivity, the apparatus can be full The same requirement foot 9.5.1.

9.5.3 to reliably open the contacts, application of mechanical safety switch operating lever.

9.5.4 Design and arrangement of the safety device, so that protection should not be weakened, even when the return spring of the operating mechanism remains fracture Can play a protective role.

9.5.5 When the instantaneous contact when the safety limit switches, there is a separate circuit breaker (e.g., a contactor) to reliably disconnect all the wires (Other than ground). If a plurality of security systems, they may be the operation of the same device.

9.5.6 When it is necessary to use other control means instead of mechanically operated safety switch with normally closed contacts, with the same make sure Level of protection.

Note: When the power supply control device or circuit failure or the relevant control device is interrupted, still play a protective role.

9.5.7 When used in line with IEC 60364-4-41:2005 requirements "safety extra low voltage" (SELV) as protective measures may be waived Additional shock protection measures during normal use of electric equipment.

9.6 Protection against indirect contact

9.6.1 due to operational reasons required to open the door during the continuous power supply of electric equipment, such as enamel pit, a forging furnace, molten light metal bore Furnace, etc., should pay special attention to, to take appropriate protective measures, such as extending into the furnace charge mechanism should be taken insulation or grounding, the operator Personnel should wear appropriate shoes and gloves, the workplace should be kept dry and ensure that these and other measures to improve the protection and reliable. In addition, the establishment of appropriate Hazard warning labels, to draw attention of the staff.

9.6.2 continuous furnace, Ruoyin operation mode can not be provided to prevent contact with the heating conductor exposed electrical protection, it furnace port structure It should prevent the heating conductor when the bare charge out of contact.

9.6.3 Some of the furnace, when the furnace with the ground separable parts will be disconnected before switching off the furnace power through the contactor, it is desirable to take Laid Special protective measures (such as setting danger sign). For example the shaft furnace with a furnace pot the case of this case, which is movable generally in vessel, which itself And as a cover plate of the heating chamber without a special lid.

9.6.4 If the protection line in danger of being broken, it should take appropriate measures, such as.

--- GB 5959.1-2005 measures 9.2 and the 9.3;

--- newly lay a single protection line;

--- using a transformer having separate windings so as to isolate the power supply system;

--- using residual current operated circuit breaker;

--- monitoring the insulation condition.

9.6.5 In normal operation or failure, if possible on the sensor (e.g. a temperature sensor) and the measuring circuit has a shock hazard Contact voltage, then it shall IEC 60364-4-41:2005 to take appropriate protective measures.

9.6.6 electrothermal heater means for heating the immersion liquid, or other conductive medium, allowed as shock protection device class II (See GB/T 17045-2008).

9.6.7 leakage current should be considered, in contact with a suitable current level of security and protection of the line current (see GB/T 12113-2003 and GB/T 13870.1-2008).

9.6.8 leakage current detecting system installation should ensure that any malfunction or failure to detect electrical insulation system and take appropriate action immediately.

13.6 Resistive heating device surface temperature

Design, installation and operation of heating equipment, the device should be considered even when inadvertently left unattended or powered closing, because the equipment is not The generated heat to produce any harm to workers, the environment and charge.

GB 16895.2-2005 and requirements are different, there should be the following requirements.

a) is not required during normal use and accessible within arm's reach parts of electric equipment, the surface temperature can be

GB 16895.2-2005 values given in Table 42A.

b) In this regard, in the instructions for use should be given a warning and a warning flag is set on the appropriate electric equipment.

Special measures 13.7 For failure (e.g., temperature controller failure) may produce dangerous situations when the temperature-limiting safety device should be provided. These assemblies Set in the function and should be electrically independent of each other.

When both electronic power controllers and circuit breakers and off frequently when using an electromagnetic contactor, a separate connection should otherwise Contactor for cutting the supply of electric equipment.

A case where a plurality of furnaces, each furnace control system to be disconnected each furnace supply through respective contacts.

13.8 Temperature safety device

Temperature control circuit is able to ensure the safety when a fault occurs, in Table 1 for different security levels provides heat to be taken with or Respective safety devices and safety measures. These safety devices include.

--- thermal fuses (A);

--- fuse (B);

--- over-temperature limiter (C);

--- temperature controller (D).