Proofers and furnaces are a structure consisting of a proofer and oven, united by a common conveyor. The units are designed to produce tin bread from rye and wheat flour and provide complete mechanization of production processes at the proofing section - baking.
The PSNUMX-XPM proofing and furnace unit (Fig. 6) consists of the 3.31 auto-landing machine, the 7 proofing conveyor cabinet and the 2 furnace combined with a common chain conveyor with cradles to which the molds are attached.
In total, 119 cradles are placed on the conveyor of a baking unit made from wheat flour, of which 47 workers are in the oven and 38 ... 47 are in the proofing cabinet. For baking bread from rye flour on the conveyor of the unit, 98 cradles are located, including 47 workers - in the oven and 31 - in the proofing cabinet.
Figure 3.31. Proof - oven unit PNNUMX-ХРМ
In the proofing cabinet the conveyor with the cradles is located vertically. The conveyor consists of a roller chain with an 140 mm pitch, two upper 3 and two lower 9 pull-off units and a 5 mobile carriage with two 6 blocks for changing the length of the proofing. The 11 drive shaft with sprockets is located outside the cabinet where the drive mechanism of the unit is located. In case of emergency power outage, you can use the manual drive.
At the extreme upper position of the 5 carriage, the 38 cradles are located in the cabinet, which corresponds to the minimum duration of the proofing. At the bottom position of the carriage, the 47 cradles are located in the cabinet, which ensures maximum proofing that is longer than the baking time by 22%. Moving the carriage is carried out manually with the handle of a screw mechanism or an 10 electric motor.
To create an appropriate temperature and humidity inside the cabinet, a tubular radiator and steam humidifier are provided.
Unloading of bread from the forms onto the 7 belt conveyor is performed automatically by the 8 roller cam. The baking time is regulated by a time relay within 10 ... 100 min.
The proofing furnace with the HPA-40 oven (fig. 3.32) consists of the 2 final proofing cabinet, the 4 conveyor-and-dead-end blind furnace and 7 mechanisms for loading the dough into molds. The dough is loaded into the forms at the end of the cabinet.
On the general 3 conveyor, the kiln-proofing unit houses 225 cradles, of which 82 workers and 43 are idle in the cabinet and 100 in the furnace. On the cradles installed 16 bread baking molds weighing 1 kg. The chain conveyor in the proofing cabinet is horizontal. It consists of a roller chain with a pitch 140 mm and cradles with forms attached to them.
The duration of the proofing is controlled by the carriage 7, moving in the horizontal plane along the rails of the frame.
Figure 3.32. The proofer furnace with HPA-40 furnace
When moving the carriage in the direction of the furnace, the working branch of the conveyor in the proofer is extended and the duration of proofing increases accordingly; when moving the carriage in the opposite direction, the duration of proofing decreases. Thus, the duration of proofing can be changed within 35..50 min.
The duration of baking can be changed within 38..65 min speed variator. Baked bread is unloaded from the molds in the 6 connecting chamber, where stops are placed on the path of the cradles from the oven. The cradles with their copiers slide along the stops, overturn and then fall on the combs - curved metal strips. When copiers interact with combs, the moving cradle is repeatedly shaken, and the bread from the molds gets onto the 5 conveyor belt of the finished product located in the lower part of the chamber.
Upon further movement of the cradle with the forms return to its original position. Before loading the molds are lubricated with an automatic lubricator installed in the proofing chamber.
Cabinet-type furnaces, as a rule, are electrically heated, operate in intermittent mode, and are used in small-scale enterprises.
Cupboard type three-chamber level stump (fig. 3.33) consists of three 9 baking chambers and a welded 5 stand. Each chamber is heated by 8 tubular electric heaters (heating elements) installed horizontally: six from the bottom (bottom group) and seven from the top (top). The lower heating elements are closed with the 11 flooring, on which the pans or pastry sheets 10 are placed. A window closed by the 2 valve is provided in the 4 door of the chamber for removal of vapors formed during operation from the chamber. On the back and sides, the oven is covered with 7 liners. An 3 roof is attached to the side cladding on top. To reduce heat loss there is heat insulation.
In the lower part of the furnace, there is the 1 control panel, to which the knobs of the switches, the limbs of the temperature sensors-relays and the warning lights are displayed.
Each group of electric heaters has an independent switching on and regulation of the intensity of heating, which is carried out by setting the knob of the corresponding switch to the position of weak, medium or strong heating.
The oven for 20 ... 30 minutes before the start of the product heat treatment is turned on to warm up the chambers by setting the switch knobs to the high heat position. Limb sensor-temperature switch us-
Fig. 3.33. Cabinet type three-chamber oven
tant on the value corresponding to the desired process. The warning lights come on. When the lamps go out (which means that the desired temperature in the chamber is reached), the product is loaded and the desired mode is set using the mode dial.
To moisten the environment of the baking chamber, water is supplied to the steam humidification cascade using the “Water” button switch. The opening of the water supply solenoid valve is controlled by a signal lamp built into the push-button switch.
While the furnace is operating in automatic mode, the drives of the recirculation fan and the container rotation mechanism are turned on when the door is closed, and the shutdown is on when it is opened. In this case, the mechanism of rotation of the container stops in a strictly oriented position, convenient for rolling out the container.
Tier two-chamber oven (fig. 3.34) provides more uniform product baking and improved steam humidification, which is achieved by having the front baking chamber 5 and the rear heating chamber 3 with steam humidification system, 2 fan, around which 7 electric heaters are installed in the oven design and perpendicular to the 10 partition with a central opening 9. The 10 partition forms its upper and lower edges with
Fig. 3.34. Tier two-chamber furnace
the walls of the baking chamber 5 are air ducts 4 and the side edges adjoin the side walls of the baking chamber 5, along which there are vertical 8 racks with guides for baking trays mounted on 7 brackets located on the top and bottom along the sides of the 5 chamber and having holes for fixing racks 8. The 5 steam relief valve is installed in the ceiling of the 6 chamber.
The furnace operates as follows. Before starting work, it is aired and heated to the required baking temperature (100 ... 290 ° C), which is installed and maintained by the thermostat. Then open the door of the baking chamber 5, load the trays or bread forms with dough pieces along the guides on the vertical racks of 8 and close the door. Set on the timer the time required by the technology for baking products. The steam humidification system and the 2 fan are activated.
The baking chamber 5 is heated by air that circulates in it in a closed loop. The 2 fan draws air from the 5 baking chamber through the central 9 opening in the vertical 10 partition into the rear 3 convective heating chamber, directs it to the 1 electric heaters and heats up there. The heated air through the 4 air ducts enters the baking area of the baking chamber 5. There the air washes the trays or molds, heats the dough pieces and is sucked off again by the 2 fan. This allows you to create a strong directional air flow through two channels formed by the edges of the partition with
the upper and lower walls of the baking chamber, which ensures uniform blowing of dough pieces, and hence the high quality of baked products.
The fan operates in reverse mode: 3 min in one direction, 30 s - pause and 3 min in the other direction, 30 s - pause during the whole baking time. This creates a time-uniformly uniform airflow throughout the baking process in the baking chamber.
The steam for humidifying the air environment of the baking chamber 5 is produced by a steam humidification system. At the same time, water is sprayed through a nozzle onto the rotating impeller of the 2 fan. The amount of steam is determined by the time of water supply. Excess steam accumulated in the 5 baking chamber is removed to the 6 steam trap valve.
After baking is completed, a beep sounds, the 2 fan and 7 electric heaters are turned off. Open the door and unload the finished products.
Rules of operation of furnaces
When servicing furnaces, personnel should have a good understanding of their design, the principle of operation of instrumentation and automation equipment, and the rules for starting and stopping the drive.
Operation and ignition of furnaces of furnaces must be carried out strictly in accordance with the approved instructions. Fuel inserts are loaded, the grate is cleaned and the grate is cleaned with the blast off and in protective glasses.
Heating of electric heaters from cold to operating temperature should be done gradually. For this, with remote (manual) switching on, the current is given to only one group of electric heaters. When the temperature in the baking chamber 100 ... 120 ° С is reached, the second and subsequent groups of electric heaters are turned on. The duration of the warm-up of the furnace from a cold state must be at least 2,5 h, since if this condition is not observed, the density of the joints of the sections and units of the furnace and the unacceptable deformation of its parts may be disturbed. After heating the furnace, the control system is transferred from the manual mode to the automatic mode.
The operation of baking ovens with steam-water heating devices has its own characteristics, due to the fact that the tubes operate at high pressure. Water may be released from the furnace end of the tube and impaired circulation of steam and water in the tube, as a result of which an accident may occur (overheating of the tube and burning of its combustion end). To prevent this, the temperature rise in the baking chamber to 150 ° С should continue no less than 10 h. After the temperature is
the baking chamber reaches 150 ° C, normal operation of the firebox is allowed.
In the process of servicing furnaces when burning solid fuel, special attention should be paid to the proper management of fuel combustion and measures for the safe maintenance of furnaces.
For normal operation of the solid fuel baking oven, periodically clean the heating channels of the oven from soot and ash using special metal brushes (ruffs), starting from the upper channel. At the same time stop the casting of fuel into the furnace, turn off the blast and cover the gate thrust. During cleaning use goggles and mittens. For inspection of the channels, a portable electric tube with voltage 36В is used.
During operation, the oven monitors the complete combustion of the fuel, the temperature of the heating gases and the baking chamber, controls the vapor pressure, maintains purity.
During the operation of baking ovens equipped with tubular electric heaters, there are cases of burn-through of the steel tube (body) of the heating element, if the filler in the tube for any reason has been moistened. To prevent this, the heaters are dried before installation in the furnace.
Furnace maintenance personnel are responsible for damage and accidents that occurred during operation from non-compliance with operating rules and safety measures.
When gas heating stoves, special attention should be paid to security measures: complete tightness of gas pipeline systems, strict compliance with the established rules of ignition and burners, careful monitoring of instrumentation and strict adherence to safety measures.
When operating steam generators and hot water boilers installed on furnaces, one should be guided by the rules for the design and safe operation of steam boilers; for electric heated furnaces, the instructions for electrical equipment should be followed.