1. Application
The gas fired bogie hearth furnace is mainly used for heat treatment of metal parts.
2.Structural Introduction
2.1 furnace body
The bogie hearth furnace manufacturer body steel structure is made
from 8# U steel and steel plates. The side pillar and back pillars are
made from sectional steel, and are reinforced with sectional steel bracings.
The external wall of the furnace is painted with 2 layers of primers, and 2
layers of coating paint. The key part of the furnace is painted with heat resistant paint.
2.2 lining
The lining material is 1100℃ 1400 type zirconium refractory fibre compacted
block. This refractory lining structure has the advantages of low heat conductivity,
strong anti-shock capacity, and anti-erosion. Aluminum silicate fiber compression
block with thickness of 350mm is designed as the high temperature refractory layer.
2.3 bogie
The car bottom furnace is comprised of heat preservation material, bogie frame
and moving mechanism. The refractory layer is divided into 3 sub-layers, i.e.,
1st top high-alumina brick layer, and 2nd and 3rd layer with both light clay bricks.
The bogie framework is made of 12# U-steel and 12# I-steel. The edges of the
bogie are made of 20mm I-steel. The car bottom furnace supplier is equipped
with 4pieces of wheels. Each wheel diameter is 240mm.
The heat preservation material is divided into 3 layers, the top layer being
high-alumina bricks, and 2nd and 3rd layer being both light clay bricks.
The gas bogie hearth furnace is driven by motor reducer gear driving mechanism.
The moving speed of the bogie is 6-8m/min.
2.4 Sealing System
The sealing between the door and the body of the furnace and the trolley is more critical.
2.5 furnace door
The bogie hearth furnace for quenching door is comprised of all-fiber lining and
steel structure shell. The door is built with silicate aluminum compressed fiber blocks
same as that for the furnace body. The shell is a welding structure from sectional
steel and steel plates. The tempering car bottom furnace door has the feature of
simple, practical, reliable and convenient maintenance. The furnace door is
fixed on the bogie.
2.6 burning system
The burning system is comprised of Krom high speed burners, proportional
combustion control system, gas valve, solenoid valve, burner control box, etc.
The burner has the functions of automatic ignition, flame detection, and flame out
alarm. The burner controller receives the control signal of the temperature controller
and controls the large/small fire status of the burner based on the heat load
requirement so that adjustment of the temperature is realized.
A) The burner has adjustment function and the adjustment rate is 1:10 and the air
efficient is 1-5. The burner could meet the temperature uniformity of the heat
treatment process and effectively control the air-gas ratio so that the fuel
consumption is reduced.
B) When the furnace is working, the burning system could automatically cut off the
electrical gas valve and general safety valve in the case of power failure detected
by the alarm system. When the power supply is resumed, the worker needs to open
the safety valve and restart the ignition program after purging function is confirmed.
The burner is set with a proportional control unit which enables alternative burning
of large and small fire, fire out alarm, and re-ignition. The burner control box has
both manual and self-run modes available. The worker could operate in front of
the furnace or in the control cabinet.
C) The pipe before the burner is equipped with solenoid valve, and manual gas
adjustment valve. The valve system could realize an ideal gas/air supply ratio so
that the air excess efficient is lower than 1.1.
2.6.1 air system
The air piping system is comprised of high pressure centrifugal fan, automatic
regulation valve, pressure gauge and pipes. The air volume is to match the gas
volume, and the air excess rate is lower than 1.20.
2.6.2 gas supply system
The general gas supply pipe is equipped with a pressure regulation device
(equipped with a filter), a low pressure switch and a pressure gauge. For the
sake of safety there is one fast cut-off valve on the general gas pipe.
2.6.3 discharge system
The bogie hearth furnace for heat treatment takes direct fume discharge method.
The fume is directly vented out through the flue pipe to the atmosphere. The fume
conducts heat exchange with the heat exchange before emission to the atmosphere.
2.6.4 Furnace pressure control system
The pressure on the working table in the furnace is kept at (+15 Pa), which is very
beneficial to the uniformity of temperature and the thermal efficiency of the furnace.
When the pressure in the furnace is too high, the hot air in the furnace will escape
from the furnace mouth and other unsealed places, resulting in the heat loss caused
by the escape of the flue gas; because the high temperature flue gas in the furnace
escapes to the outside of the furnace, it will affect the door, the side seal and burner
of the furnace directly, which is related to the overall service life of the furnace; when
the pressure in the furnace is too low, a large number of cold air outside the furnace
will be absorbed into the furnace, as well. The heat loss of off-furnace flue gas is
increased. The low pressure of the furnace causes the diffusion of cold air outside
the furnace into the furnace, and secondary combustion is formed due to the entry
of oxygen-containing cold air, which has adverse effects on the uniformity of furnace
temperature, oxidation of workpiece and thermal efficiency of the furnace. Therefore,
effective technical measures must be taken to control the furnace pressure with full
automatic control. Our method is to control the furnace pressure effectively by using
a system consisting of pressure taking device, pressure transmitter, intelligent
instrument and so on. The furnace pressure is controlled in the optimum state
(the surface of the trolley is in a slightly positive pressure). At this time, the exhaust
gas is in a dynamic equilibrium state, which can not only ensure that the furnace
gas does not overflow, but also ensure that the cold air outside the furnace is not
sucked into the furnace, so as to save energy and maximize the efficiency of the
furnace.
2.6.5 Heat exchange and flue system
A flue is set at the back of the furnace, and it is carried out with the heat exchanger
(according to the national standard GB3486-83). The flue leads to the outside of the
factory building. The cold air is exchanged with the heat exchanger to preheat the
combustion-supporting air before entering the burner, so as to improve the heat efficiency
of the furnace.
Heat exchangers and flue gas exhaust pipes are insulated by internal insulation
(using fiber castables) to ensure the service life of heat exchangers and flues.
2.6.6 fault detection and alarm system
The furnace has a complete fault detection, alarm, diagnosis, and safety protection
system. On the control cabinet there is an alarm lamp.
2.7 control system
control system has the following parts: Ⅰ. Burning control system; Ⅱ. Electrical power
control system; Ⅲ.temperature control system .
Measures taken for burning control system:
K type thermal couple gets mV signal and sends it to temperature PID controller
(SHIMADEN brand). The temperature controller calculates the signal and outputs 4-20mADC
control signal to the electrical actuator. The actuator further sends a signal to the burner
controller after calculation.
The burner controller is mainly responsible for ignition and flame detection. When the terminal
receives the ignition signal, the burner controller carries out flame simulation and self
testing stage. If during this simulation and self-test stage the burner couldn’t detect the flame
signal. The burner controller would open the gas solenoid valve and convert the voltage
220VAC to 5KV for ignition (ignition time about 3S). If the burner detects the flame signal
in the safe time period (about 8S), the yellow indication light of the burner would be on
(ignition successful). If the burner couldn’t detect the flame signal, the red light would be on
(ignition failed). The burner controller is locked and the gas solenoid valve is cut off.
B) electrical power control system: The electrical power control system mainly controls
ON/OFF of the fan, and IN/OUT of the bogie.
C) temperature control and record system
The system has the functions of temperature setup, control and digital display. And also
there is an audible and visual alarm at over-temperature situations.
Temperature control zone arrangement
A:temperature control system
The furnace is equipped with 1 thermal couple and an intelligent temperature controller.
The furnace is controlled by 1 zone.
B: instrument temperature control
The temperature controller allows setup of heating time, holding time, and cooling time.
It has self-tuning and self-adjustment function, and displays SV and PV.
4. Furnace Design Standards Referred To
4.1 "Technical Management Principles for Rational Use of Heat in Enterprises" stipulated in
GB/T3486-93 should be rationally optimized and reduced heat losses.
4.2 GB50211-2004 Standard for Construction and Acceptance of Industrial Furnace
Masonry Engineering.
4.3 GBJ87-85 "Noise Standards for All Kinds of Locations in Factories".
4.4 Environmental Pollution Discharge reaches GB3095-1996 standard.
4.5 The temperature of the effective heating zone of the furnace is measured by GB/T9452-2003,
and the temperature uniformity is±10℃.
4.6 The energy consumption level is up to ZBJG1004-87 level of the special furnace stipulated
in the standard of heat treatment furnace energy consumption classification.
4.7 Implement the main material standards of furnace body: heat-resistant steel (GB/T8492-87),
heat-resistant steel plate (GB4238-92), clay refractory brick (YB/T5106-1993), amorphous
refractory (GB4513-84), clay refractory and high alumina refractory castable (YB/T5083-1997);
4.8 GB985-86 basic forms and dimensions of manual arc welding joints.
4.9 JB/ZQ4000.3-86 general specification for welds.
4.10 GB/T5000.9-1998 general technical requirements for chip processing parts;
4.11 GB/T1804-1992 "tolerance of shape and position, general tolerance, linear dimension".
4.12 GB1801-79 "tolerance and fit size to 500mm hole, shaft tolerance belt and cooperation";
4.13 GB/T1801-1999 basic size to 500mm priority is used to match extreme clearance and
limit interference.
4.14 GB8923-1998 "corrosion grade and derusting grade of steel surface before painting";
4.15 GB/T1182-96 symbol and its standard;
4.16 JB/T13384-21992 general technical conditions for packaging;
4.17 GBJ55-1983 code for design of electrical installations for industrial and civil installations.
4.18 GB420-1984 "electrical control equipment Part 1 low voltage electrical appliance
electrical control equipment".
