JB/T 5264-1991 Indirect resistance furnace RF series forced convection pit resistance furnace
Some standard content:
Mechanical Industry Standard of the People's Republic of China
Indirect Resistance Furnace
RF Series Forced Convection Parallel Resistance Furnace
1 Subject Content and Scope of Application
JB5264-91
JB4311.4-87
JB4311.6-87
This standard specifies the requirements for RF series forced convection parallel resistance furnace products (hereinafter referred to as parallel furnaces), including varieties, specifications and technical performance, as well as ordering and supply. This standard applies to forced convection pit resistance furnaces designed according to the requirements of Articles 4.1, 5.1 and 5.2, mainly used for tempering, annealing and normalizing of metal parts in natural atmosphere and controlled atmosphere, as well as carburizing, nitriding, carbonitriding and flangeing of steel parts. This standard also applies to similar forced convection parallel resistance furnaces, and different parts may be specified separately. 2 Reference standards
GB10067.1 Basic technical conditions for electric heating equipment Part 1 General part GB10067.4 Basic technical conditions for electric heating equipment Part 4 Indirect resistance furnace GB10066.1 Test methods for electric heating equipment Part 1 General part GB10066.4 Test methods for electric heating equipment Part 4 Indirect resistance furnace GB10966.3 Indirect resistance furnace Part 3 'ZR series vacuum heat treatment and brazing furnace ZBK60001 Method for compiling product models of electric heating equipment 3 Terms
Except for the following terms, the rest shall be in accordance with the provisions of Chapter 3 of GB10066.4. 3.1 Working area size
The size of the space in the furnace that allows the placement of workpieces specified in the design of a parallel furnace and indicated on the drawing. For a pit furnace with a cylindrical basket, the diameter and height of the working area are equal to the inner diameter and effective height of the basket specified in the design, respectively. 3.2 Maximum loading capacity
The maximum weight of workpieces that can be loaded in each furnace is specified in the design of a parallel furnace. For parallel furnaces with a basket, the weight of the basket is not included. 3.3 Working temperature
The normal operating temperature specified when the parallel furnace is designed is a temperature range. For parallel furnaces with a furnace tank, it generally refers to the temperature outside the furnace tank. However, when the furnace tank is equipped with a main control thermocouple (see Section 5.2.10.1), it refers to the temperature inside the furnace tank. 3.4 Carbon potential (nitrogen potential) uniformity
The uniformity of carbon potential (nitrogen potential) of the parallel furnace when it is in a thermally stable state at the test temperature. The carbon potential (nitrogen potential) uniformity is expressed as: the difference between the highest and lowest carbon potential (nitrogen potential) measured at each specified measuring point 3.5 Carbon potential (nitrogen potential) stability
The stability of the carbon potential (nitrogen potential) in the parallel furnace when it is in a thermally stable state at the test temperature. The carbon potential stability is calculated according to formula (1):
6e=±1
Wherein: 6e carbon potential stability, %C;
Approved by the Ministry of Machinery and Electronics Industry on June 28, 1991 C (C,-Cp)
Implementation on July 1, 1992
JB5264-91
Cp→the arithmetic mean of the carbon potential readings measured multiple times within the measurement time, %C; C; - the carbon potential readings greater than Cp, %C,
n the number of carbon potential readings greater than Cp.
Nitrogen potential stability is calculated according to formula (2):
6%=±1>
Wherein: 6% - nitrogen potential stability, %N2;
(N,-N,)
Np - the arithmetic mean of the nitrogen potential readings measured multiple times within the measurement time, %N2sN; - nitrogen potential readings greater than Np, %N23
n - the number of nitrogen potential readings greater than Np.
4 Product classification
4.1 Varieties and specifications
4.1.1 Parallel furnaces are divided into multiple varieties according to structure, atmosphere and maximum operating temperature, as shown in Table 1. Table 1
Product code
With furnace
Natural atmosphere
Controlled atmosphere
Maximum working temperature
(2)
Other maximum working temperature values are allowed to be used in the enterprise product standards. In this case, the number in the product code (maximum working temperature divided by 100, without decimals) should be changed accordingly.
4.1.2 Each type of parallel furnace is divided into multiple specifications according to the size of the working area. The position of the working area in the furnace should be indicated on the attached drawing in the product manual of the pit furnace.
The working area dimensions (diameter D×height H) of pit-type furnaces newly designed or modified after the release of this standard shall comply with the following specifications 4.1.2.1
Minimum specification: 300mm×375mm
Other specifications: diameter increases by 75mm to 600mm, and then increases by 150mm; height increases by 75mm to 600mm, and then increases by 300mm.
4.1.2.2 The working area dimensions of the four specifications of RF6 and the six specifications of RFG9 listed in Table 2 can be retained for use. Table 2
Working area dimensions
Variety code
JB5264—91
Continued Table 2
Working area dimensions
4.1.3 Each pit furnace manufacturer can choose from the varieties and specifications specified in Articles 4.1.1 and 4.1.2, and formulate their own parallel furnace enterprise product standards accordingly.
4.2 Model
The model of the parallel furnace should be compiled in accordance with ZBK60001, and the technical level code shall be determined in accordance with Article 7.4 of this standard. 4.3 Main parameters
In the enterprise product standards, the following items should be listed for each model of parallel furnace: a.
Power supply voltage, V;
Power supply frequency, Hz;
Number of phases;
Rated power, kW,
Number of temperature control zones;
Connection method of heating elements,
9. Working temperature, °C;
h. Working area size, mm;
Maximum loading capacity, kg;
Heating capacity, kg/h;
Empty furnace heating time, h;
Furnace temperature uniformity, ℃;
Furnace temperature stability, ℃;
Empty furnace loss, kW,.
Surface temperature rise, K;
Empty furnace energy consumption, kW.h;
Applicable atmosphere and gas (or liquid) consumption, Nm/h (or kg/h) (applicable to RFQ and RFG type furnaces); Furnace body weight, t;
Furnace body dimensions, mm.
5 Technical requirements
5.1 General requirements
Parallel furnaces shall comply with the provisions of Chapter 5 of GB10067.4. When there is a discrepancy between the provisions of that standard and this standard, this standard shall prevail. 5.2 Supplementary requirements for design and manufacture
5.2.1 Overall design
The parallel furnace is mainly composed of the furnace body and the control cabinet. 25
JB5264—91
The furnace body is vertical with an open top, which is used to load and unload the charge vertically from above. The furnace body is equipped with a fan to force convection heating of the charge and promote furnace gas circulation.
For a pit-type furnace where the weight of the charge is supported by the furnace bottom, a charging or air guide tube is used according to the different charging methods to guide the air flow. For RF or RFQ parallel furnaces, it is also used to block the direct radiation of the heating element to the workpiece. There should be holes at the bottom of the charging basket, and there should be sufficient ventilation ducts around the lower part of the air guide tube. Pit-type furnaces where the workpiece is suspended by a sling should be equipped with an air guide tube to guide the air flow and block direct heat radiation. For RF and RFQ parallel furnaces, the air flow contacts the heating element when circulating. For RFG pit-type furnaces: the charging basket or air guide tube is located inside the furnace pot. The controlled atmosphere circulates only inside the furnace without contacting the heating elements. The furnace can be ventilated by the exhaust system first and then filled with air, or by gas replacement, or according to the requirements of the buyer (see Article 9.2).
5.2.2 Controlled atmosphere
The controlled atmosphere used for RFQ parallel furnaces is generally a protective atmosphere, which is used to protect the charge to avoid or reduce oxidation and decarburization. The controlled atmosphere used for RFG pit furnaces is an endothermic atmosphere, ammonia nitrogen-based atmosphere, dripping atmosphere, etc. for chemical heat treatment-carburizing, nitriding, carbonitriding, etc.
The type of controlled atmosphere used should be agreed upon by the supplier and the buyer according to the requirements of the buyer (see Article 9.1)5.2.3 Furnace shell
The furnace shell is made of steel plates of appropriate thickness welded in an airtight manner and reinforced with steel sections when necessary. The thickness of the steel plates of the furnace bottom and furnace roof should be appropriately thickened to ensure the strength and rigidity of the entire furnace shell. 5.2.4 Furnace cover
The furnace cover should be lined with high-quality insulation material. Refractory fiber should be preferred, and block or granular materials can also be used. The performance and thickness of the insulation material should ensure that the surface temperature rise of the furnace cover does not exceed that of 5.3.6. There should be good sealing between the furnace cover and the furnace shell (or brick body), and for RFG furnaces, the furnace cover and the furnace tank to minimize air leakage. For pit-type furnaces that directly pass ammonia and use the exhaust method to clean the furnace and ventilate, the outer edge of the furnace cover should be sealed with a water-cooled rubber ring or similar reliable sealing facilities. The furnace cover should have a lifting device to lift the furnace cover and move it to the left or right. The force required for manual operation of the furnace cover should not exceed 180N. For RFQ and RFG pit-type furnaces, the furnace cover should be equipped with an air inlet pipe or liquid drip pipe, an exhaust pipe, a thermocouple introduction hole for measuring the uniformity of the furnace temperature, a sample inspection hole (applicable to carburizing furnaces, etc.), etc. 5.2.5 Furnace lining
The material and structure of the furnace lining should meet the performance requirements for pit-type furnaces (see Article 5.3). The lining of RF and RFG Class C pit-type furnaces should be made of refractory fibers except for the load-bearing and collision-prone parts. The furnace lining in contact with the carbon-containing atmosphere should be able to work normally in this atmosphere. The overhaul period of the furnace lining shall comply with the provisions of Table 3.
Furnace Village Type
Brick Furnace Lining
Refractory Fiber Lining
5.2.6 Heating Elements
Overhaul Period
The design and fixation of the heating elements shall meet the working requirements of the parallel furnace. The elements shall be firmly installed and shall not be displaced or loosened under normal working conditions.
The heating elements are made of electric heating alloy. When selecting heating elements for RFQ parallel furnaces, the effect of the atmosphere on the material shall be considered. The service life of the heating elements shall comply with the provisions of Table 4, provided that the input power of the parallel furnace at the rated power supply voltage is 15% less than the rated power.
Maximum working temperature of parallel furnace
5.2.7 Metal parts in furnace such as material basket, air duct and furnace pot JB5264-91
Service life of heating elements》
Material basket, air duct, furnace pot, and other metal parts in the furnace, such as furnace pot base, material basket bottom grid, material basket base, furnace charge hanger, etc., should be cast or welded with suitable steel that can withstand the temperature, load and atmosphere in the furnace. Under normal use conditions, the service life of all these parts for Class A, Class B and Class C furnaces should be not less than one year, two years and three years respectively. 5.2.7.1 Material basket and air duct
The material basket can be a whole or composed of several sections. Each section of the material basket and air duct should have a lifting ring or ear shaft for lifting. The bottom of the material basket should be equipped with a grate and (or) perforated plate, and its design should ensure that there are enough holes for air flow to pass through. The material basket and air guide tube should be equipped with a base to fix their position in the furnace and support the weight on the furnace bottom or the bottom of the furnace. 5.2.7.2 Furnace pot
The furnace pot can adopt two structural types. One is cylindrical with two ends open. When in use, both ends should be sealed. The other is cast or processed into a whole with its bottom and surrounding wall. In the latter case, when the bottom of the furnace pot bears the weight of the furnace charge, a support should be provided between the furnace core and the furnace bottom.
The design and manufacture of the furnace pot should ensure that the thermal deformation is small and there is no air leakage within the specified service life at the working temperature. 5.2.8 Furnace gas circulation system
The pit furnace should be equipped with a fan and air guide with heat-resistant steel blades for forced circulation of furnace gas. The fan is driven by an electric motor. The fan shaft should have good sealing and reliable cooling. When the fan stops due to a fault, the heating power supply should be automatically cut off. The fan can be installed directly above or below the working area, or in another room connected to the working room. The fan should be calibrated by dynamic balancing test. The noise of the fan should comply with the provisions of relevant national standards. 5.2.9 Exhaust system
The exhaust system for cleaning and ventilation of RFG type parallel furnaces (see Article 5.2.1) should be equipped with necessary valves, vacuum gauges, etc., and should have automatic valves to automatically close in the event of a power outage to prevent vacuum pump oil from entering the furnace. 5.2.10 Measurement, control and recording
The measurement, control and recording of parallel furnaces should comply with Article 5.2.7 of GB10067.4 and the following supplementary provisions. 5.2.10.1. Thermocouple
For RFG type pit furnaces, when it is required to set a control thermocouple in the furnace tank, it can be proposed in accordance with Article 9.2. At this time, the thermocouple in the furnace tank should be used as the main control thermocouple to control the internal temperature of the furnace tank. A thermocouple should also be installed outside the furnace tank as a monitoring thermocouple to prevent the temperature outside the furnace tank from being too high.
5.2.10.2 Temperature instrument
The control type of the temperature control instrument of the parallel furnace should be a time proportion type that controls the contactor through an intermediate relay system, or other technically more advanced types. For RF and RFQ type A-level parallel furnaces, position control is allowed to be retained. For C-level furnaces, a microprocessor digital display temperature control instrument with a temperature setting accuracy of not less than 0.5% and a resolution of not less than 1C should be equipped. The digital height should not be less than 15mm. The instrument should be equipped with an external socket for connecting a recorder or printer. The effective width or diameter of the temperature recorder recording paper should not be less than 150mm. When a printer is required to replace the recorder, it can be requested in accordance with Article 9.2.
5.2.10.3 Atmosphere control instrumentation
JB5264—91
RFG type B and C parallel furnaces used for carburizing or nitriding shall be equipped with instruments and corresponding sensor elements for indicating, controlling and recording the carbon potential or nitrogen potential of furnace gas respectively; if required for A-type pit furnaces, they can be proposed in accordance with Article 9.2. The type and technical performance of the instrument shall be specified in the enterprise product standards of parallel furnaces, or agreed upon by the supply and demand parties (see Article 9.2). The accuracy level of the instrument shall meet the following requirements; A-type furnace shall not be less than level 5
B-type furnace shall not be less than level 3
C-type furnace shall not be less than level 1
RFQ and RFG parallel furnaces using dripping liquid shall be equipped with liquid dripping measurement or control instruments. 5.3 Performance requirements
The performance of parallel furnaces shall meet the requirements of Article 5.3 and the following articles of GB10067.4. 5.3.1 Working temperature
For parallel furnaces with a maximum working temperature not exceeding 750°C, the working humidity is from 300°C to the maximum working temperature; for parallel furnaces with a maximum working temperature exceeding 750°C, the working temperature is from 500°C to the maximum working temperature. Within the working temperature range, the pit furnace shall meet the furnace temperature uniformity and furnace temperature stability requirements of Articles 5.3.4 and 5.3.5. 5.3.2 Maximum loading capacity
Unless otherwise required (see Article 9.2), the maximum loading capacity of the pit furnace with the weight of the workpiece and the inclined basket borne by the furnace bottom and the working area height not exceeding 1.2m, measured by the weight of the steel workpiece, shall be specified in the enterprise product standard according to the requirements of Table 5. V in the table is the volume of the working area. m\. Table 5
Maximum working temperature
Maximum daily load
3000×V
2500×V
For pit furnaces with a working area height exceeding 1.2m, used to process workpieces of other materials or to hang workpieces with slings, the maximum load capacity shall be specified in the enterprise product standards or agreed upon by the supply and demand parties. 5.3.3 Heating capacity
Unless otherwise required (see Article 9.2), the weight of the workpiece and the basket is borne by the bottom of the furnace. Its heating capacity shall be specified in the enterprise product standards according to the requirements of Table 6. The test temperature for assessing the heating capacity is the maximum working temperature of the parallel furnace. The weight of the furnace pot is not included in the weight of the table 6. If the cold furnace pot is heated together with the workpiece to be processed, the weight of the furnace pot shall be added to the weight in Table 6.
Other uses, with basket
Other uses, without basket
When there is a basket, the weight includes the weight of the basket. Table 6
Heating capacity ≥
250×D×H
500×D×H
300×D×H
For pit furnaces with hanging equipment for charging, the heating capacity shall be specified in the enterprise product standards or agreed upon by the supply and demand parties. kg/h
5.3.4 Furnace temperature uniformity
5.3.4.1 For RF and RFQ types: as well as RFG type parallel furnaces with main temperature control thermocouples in the furnace core, the furnace temperature uniformity should not exceed the following specified range:
A-level furnace ±10℃
B-level furnace ±8℃
C-level furnace ±5℃
JB5264—91
5.3.4.2 For RFG type pit furnaces without main temperature control thermocouples in the furnace tank, the furnace temperature uniformity shall be based on the highest temperature value a in the furnace tank. The difference (a-b) from the minimum value b indicates that the following provisions shall be met: For parallel furnaces with a maximum operating temperature not exceeding 650°C: Class A furnace (ab) ≤ 15°C
Class B furnace (ab) ≤ 10°C
Class C furnace (ab) ≤ 6°C
For parallel furnaces with a maximum operating temperature exceeding 650°C: Class A furnace
Class B furnace
Class C furnace
(ab) ≤ 20°C
(ab) ≤ 15°C
(ab) ≤ 10°C
5.3.5 Furnace temperature stability
For RFG pit furnaces equipped with master thermocouples in the furnace tank, the furnace temperature stability shall not exceed the following specified range: Class A furnace
Class B furnace
Class C furnace
The furnace temperature stability of other parallel furnaces shall not exceed the following specified range: Class A furnace
Class B furnace
±10℃
±4℃
Class C furnace±1℃
5.3.6 Surface temperature rise
When the parallel furnace is in the thermally stable state at the highest operating temperature, the surface temperature rise of the furnace shell, furnace cover and furnace roof shall comply with the provisions of Table 7. The surface temperature rise of the operating handle, etc. shall not exceed 25K.
Maximum working temperature
5.3.7 Empty furnace heating time
Furnace shell surface
Furnace cover and furnace top surface
Furnace shell surface
Furnace cover and furnace top surface
Surface temperature rise
Unless otherwise required (see Article 9.2), the empty furnace heating time of a pit furnace with a working area volume not exceeding 1m\ shall comply with the provisions of Table 8. When the working area volume is greater than 1m\, the empty furnace heating time shall be separately specified in the enterprise product standard or agreed upon by the supply and demand parties. 5.3.8 Empty furnace loss
The empty furnace loss of the following specifications of parallel furnaces shall comply with the provisions of Table 9. Other specifications shall comply with the provisions of the enterprise product standards. 5.3.9 Empty furnace energy consumption
The empty furnace energy consumption of the following specifications of pit furnaces shall comply with the provisions of Table 10, and other specifications shall comply with the provisions of the enterprise product standards. 5.3.10 Empty furnace exhaust time and pressure rise rate
For RFG pit furnaces equipped with an exhaust system for furnace cleaning and ventilation, the empty furnace exhaust time (from atmospheric pressure to 100Pa) should not exceed 20min, and the pressure rise rate should not exceed iPa/min. 5.3.11 Others
The other performances of parallel furnaces should comply with Article 5.2 of this standard, as well as the corresponding provisions in the enterprise product standards and supply contracts. 5.4 Requirements for complete sets
Maximum working temperature
Product code
Product code
JB5264—91
Working area volume V
Working area size
Working area size
Air protection heating time
Air furnace loss
Energy consumption of empty furnace
Product code
JB5264-91
Continued Table 10
Working area size
Energy consumption of empty furnace
5.4.1 The complete set supply scope of parallel furnace specified by the supplier should be listed in the enterprise product standards. The following items should be mainly included: a. Parallel furnace body (including material basket, furnace tank, etc.); b. Control cabinet;
Temperature instrument; Www.bzxZ.net
Thermocouple
Compensation wire;
Carbon potential (or nitrogen potential) controller and corresponding sensor elements (applicable to RFG class B and C pit furnaces); exhaust system (applicable to RFG pit furnaces that use the method of exhausting first and then filling to clean the furnace); g.
Spare parts,
Product manual, including necessary drawings. The above items can be supplemented as necessary in the enterprise product standards, and the specific contents of each item should be listed, including model, specification and quantity.
If the demander has different requirements for the items specified by the supplier, it can be proposed in accordance with Article 9.2. When the following accessories or devices are required to be provided, they can be proposed in accordance with Article 9.2. The necessary technical requirements shall be agreed upon by the supply and demand parties. 5.4.2
Cooling barrel or blowing device with cooler; a.
b. Electric energy meter and (or) other measuring instruments, program controller;
Control gas generating device and (or) its accessories (applicable to RFQ and RFG pit furnaces); d.
Carbon potential (or nitrogen potential) control instrument and corresponding sensor element (applicable to RFG Class A pit furnace). 6 Test method
The test of parallel furnace shall be carried out in accordance with the corresponding provisions of GB10066.1 and GB10066.4 and the following supplementary provisions. If necessary, it shall be supplemented in the enterprise product standard.
When conducting the empty furnace test, the components such as the material basket, furnace pot, and air guide tube that play the role of air guide shall be placed in the furnace so that the furnace gas can circulate according to the design requirements.
6.1 The test temperatures for the measurement of furnace temperature uniformity and furnace temperature stability are the highest working temperature and the lowest working temperature respectively. The test is carried out under the condition that the furnace is in natural atmosphere. For RFG type pit furnaces equipped with main control thermocouples in the furnace tank, the furnace temperature uniformity and furnace temperature stability should be determined based on the reading of the main control thermocouple.
For pit furnaces with multiple temperature control zones. The set temperature of each zone should be the same. For RF and RFQ pit furnaces, the arithmetic mean of the temperature measured at the temperature control points in each zone should be used as the reference value to determine the furnace temperature uniformity. 6.2 Measurement of carbon potential (or nitrogen potential) uniformity and stability JB5264-91
The test method is specified in the enterprise product standard or agreed upon by the supply and demand parties. The chemical composition of the raw gas or dripping liquid should be strictly specified. 6.3 Measurement of surface temperature rise
The position of the measuring point is specified as follows:
The measuring point shall be at any point of the furnace shell, furnace cover, furnace roof and operating handle, except within 75mm from the edge of the heating element and the thermocouple lead-out hole and the center of the furnace lining penetration fastener. The exhaust pipe wall and its vicinity are also excluded. 6.4 Heating capacity test
a. Direct method
When the pit furnace is in a thermally stable state at the highest operating temperature, a batch of cold steel materials (including cold material baskets when there are material baskets) is loaded into the furnace. Its weight should be equal to the heating capacity value specified for the parallel furnace of this specification (see Section 5.3.3). After loading, immediately turn on the power for heating. The furnace temperature should be able to return to the highest operating temperature within 1 hour. For RFG pit furnaces equipped with a main control thermocouple in the furnace tank. The furnace temperature is based on the temperature measured by the main control thermocouple in the furnace tank. b. Indirect method
According to item b of Article 6.17 of GB10066.4. The weight of the charge G is the heating capacity value specified for the parallel furnace of this specification or agreed upon by the supplier and the buyer, kg (see Article 5.3.3), and the test time is 1h. 6.5 Loading and running test
Unless otherwise arranged by the manufacturer, the loading and running test is carried out at the user's site. The material, shape, size and placement of the charge are agreed upon by the supplier and the buyer. The charge is provided by the user. Load a batch of workpieces with a weight equal to the maximum load into the furnace, and run it at the maximum operating temperature for more than 8 hours cumulatively. Then stop the furnace and inspect it according to Article 7.2.8 of GB10066.1. 7 Inspection rules and classification
The inspection and classification of parallel furnaces shall be carried out in accordance with Chapter 7 and the following articles of GB10067.1. 7.1 The factory inspection items of parallel furnaces should include the following: a. General inspection;
safety inspection;
durability test of label writing;
inspection of furnace size and working area size; d..
inspection of furnace lining quality;
inspection of manufacturing quality of heating elements;
measurement of cold DC resistance of metal heating elements; inspection of short circuit of heating elements to furnace shell;
insulation resistance measurement (applicable to pit-type furnaces for baking before leaving the factory); insulation withstand voltage test (applicable to pit-type furnaces for baking before leaving the factory); calibration of temperature instruments;
cold inspection of movement mechanism operation or action 1. Inspection of interlock alarm system;
inspection of water, gas, hydraulic and exhaust systems (when these systems are available), n.
inspection of accessories. Including inspection of models, specifications, and factory certificates; scope of supply, including inspection of the completeness of factory technical documents; and packaging inspection.
JB5264—91
7.2 The type inspection items of parallel furnaces shall include the following: all factory inspection items (under type inspection conditions); a.
circuit test;
measurement of empty furnace exhaust time and pressure rise rate (applicable to RFG type pit furnaces equipped with exhaust system); measurement of empty furnace heating time;
measurement of rated power;
measurement of maximum working temperature,
measurement of empty furnace loss;
measurement of empty furnace energy consumption;
measurement of furnace temperature uniformity;
measurement of furnace temperature stability;
measurement of surface temperature rise;
heating capacity test;
furnace shell leak detection (applicable to RFQ type pit furnaces); hot inspection of the operation or action of moving machinery; inspection after hot test.
When required (see Article 9.2), a charging operation test should be carried out. 7.3 After the process inspection or industrial operation inspection of the pit furnace is completed, the following two tests should be carried out again; a.
Measurement of surface temperature rise
b. Measurement of furnace temperature uniformity;
The retest results should comply with the provisions of this standard, and the measurement value of item b shall be used as the basis for the technical classification of pit furnace products (see Article 7.4). 7.4 The technical classification of parallel furnaces shall be in accordance with Table 11. Parallel furnaces of various technical levels shall fully meet the requirements listed in the table and other provisions of this standard.
Technical level
Heating elements
Heat-resistant steel parts
Control instruments
According to the requirements of Article 5.2.5
According to the requirements of Article 5.2.6
According to the requirements of Article 5.2.7
According to Article 5.2.7.3 of GB1C057.4 and Article 5.% of this standard. 10.2 and 5.2.10.3 requirements can be provided in accordance with the requirements of Articles 5.3.4, 5.3.5, 5.3.7 and 7.3. Can provide complete sets of equipment in accordance with the requirements of Articles 5.4.1. Can provide complete sets of equipment in accordance with the requirements of Articles 5.4.1 and 5.4.2. 7.5 National-grade superior products of parallel furnaces shall technically meet the requirements of Class C above. 8 Marking, packaging, transportation and storage. Can provide complete sets of equipment in accordance with the requirements of Articles 5.4.1 and 5.4.2, as well as the requirements for supporting parts in Article 9.2. 8.1 The marking, packaging, transportation and storage of parallel furnaces shall comply with the provisions of Chapter 8 of GB10067.1. 8.2 The following items shall be marked on the nameplate of the pit furnace: a. Model and name of the product;
Power supply voltage, V,
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