7500×1800×1500mm Bogie Hearth Furnace Heat Treatment Gas Fired Chromium Steel

7500×1800×1500mm Gas fired Bogie Hearth Furnace

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 design body steel structure is made from

12# -18# channel steel and 4-14mm 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℃ 1360type high aluminum 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.

The total thickness of the furnace lining is 325mm. The lining adopts

composite large module structure and stainless steel round steel fixation

technology. The lining at high temperature section adopts aluminum

silicate fiber compression block, the thickness is 300mm.

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 20# I-steel beam and 20# I-steel beam.

The edges of the bogie are made of 20# channel steel. The bogie is

equipped with 10pieces of wheels. Each wheel diameter is 400mm.

The bogie 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.

The sealing of furnace door, furnace body and trolley is the key. The

sealing between the furnace door and the furnace body uses the electric

push rod to press the closed furnace door on the furnace door frame and

the end face of the trolley. In this way, the whole furnace door is tightly

sealed, so as to ensure that the hot gas in the furnace does not leak out

from the furnace door.

2.5 furnace door

The car bottom furnace for sale 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 furnace door has the

feature of simple, practical, reliable and convenient maintenance. The

furnace door is fixed on the bogie.

Driving mode of furnace door: electric hoist is used to move up and down

vertically.

A soft hard contact sealing structure is arranged between the furnace door

and the lining. When the furnace door is closed, the electric push rod

mechanism is used to compress the furnace door to make the sealing fiber

block contact with the furnace mouth for sealing. When the furnace door is

opened, the gap between the furnace door and the steel plate of the

furnace mouth frame is 100 mm by pulling the electric push rod pressing

mechanism, so as to ensure that the furnace door does not scratch or

touch the relevant parts of the furnace lining and trolley during the lifting

process. And ensure smooth movement when opening and closing.

2.6 burning system

The burning system is comprised of Krom technology 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 gas car bottom furnace 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 tempering bogie hearth 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 4 thermal couple and an intelligent temperature controller.

The furnace is controlled by 4 zones.

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.

3.Main Technical Parameters