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Tunnel Oven Tunnel Oven


Tunnel Oven

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  • GMS



1.Reference Photo

Tunnel Oven1

1.1.         Description of Machine

1.1.1.    Principle and Purpose of Designing

The Sterilization tunnel is designed for depyrogenation of glass containers under 100Class (Class 5, EN ISO 14644-1) environment of Federal Standard 209.

The circulation of the hot air in the sterilizing tunnel is designed to guarantee a pyrogen reduction as to 3-D in accordance with the following formula:

With the reference trail of E. Coli endotoxins, the D-value is 5 minutes and the Z-value is 46.4 °C. D-value is defined as the time required to reduce 1-log pyrogens at 250°C. The Z-value is defined as the temperature increment to change the D-value by a factor of 10. The containers are transffered to a heating zone for 15 minutes treatment at 250 °C to reach the pyrogen reduction target of endotoxin inactivation by 3-D. (or 5 minutes at 300°C)

1.1.2.    Pre-heating section

The pre-heating section acts as a thermal barrier between the container washing area and the heating section, where containers dried by class 100 hot laminar flow air controlled by differential pressure gauge, Type Magnehelic 2000 (air velocity 0.6-0.7m/s) filtered by H13 HEPA filter (H14 as option) (Dimension 457 × 762 × 150mm).

New sterile air will be maked up by a pre-filter from the washing area.The exhaust fan discharges the moisture out of the tunnel and maintains the air-balance in the tunnel. The air pressure in this section is 28Pa. (Absolute value)

There are three proximity switches at the entrance of the tunnel which control the speed of conveyor belt as per the output of the upstream washing machine. As soon as the container is (almost) full of the pre-heating section,the machine will give a signal to upstream machine to slow down..

Tunnel Oven2

1.1.3.    Heating Section

In the heating section containers are treated by the recirculated cleaning air under H13 HEPA filter (Dimension 762 x 762 x 150mm) for sterilization and depyrogenation with air velocity 0.7-0.8m/s. Air distribution is even.

Heating section equips with ceramic fibers (asbestos-free) insulation and can be heated up to temperature of 350°C (400℃ for temporarily).Heating element is made of nichrome, controlled by SCR (Silicon Control Rectifier). There are more than Eight (standard version) Pressure gauge to monitor the differential pressureof HEPA filters; Environment and Heating inchamber (Ra≤0.4μm); Filling room and Washing room; and etc.(Type Magnehelic 2000).

Five PT100 sensors have been equipped in the heating section, Three for monitoring the temperature of heating section, One above the HEPA filter for alarming and protect the HEPA. One in the center for recording the data.

The temperature distribution is ±5℃ (empty load)The data can be saved and printed out as follows:

Tunnel Oven3

(Smooth Temperature Curve)

Tunnel Oven4

(Heating Section)

1.1.4.    Cooling Section

The Recirculated cooling air (with water cooling function or sterilization function, please refer to the below picture) reduces the containers’ temperature to 25-35ºC. The air velocity is typically 0.6-0.7m/s. The dimension of the H13 HEPA filter is 762 x 762 x 150mm. The air pressure in this section is 30Pa. (Absolute value)


(In Standard version, air is 100% discharged by the blower after reducing the containers’ temperature.)

Tunnel Oven5

(With Water cooling system or sterilizetion function)

1.1.5.    Automatic Balance of Air Over-Pressure

Control and display of overpressure in the cooling section, for stable operation of the sterilizing tunnel in case of pressure fluctuations between the washing room and the filling room. Alarm and machine will stop if overpressure above to 15 Pa from filling room. If surpassed, an additional exhaust system(blower) will be required.

Tunnel Oven6

1.1.6.    Night Mode

Under the circumstance of the positive pressure of the tunnel, we switch off the heating system but keep the fans running at a setting value. This function save the energy and consumptions effectively and can be automatically switch the mode after the duty off.

Tunnel Oven7


1.1.7.    Water Cooling System

The cooling coil is made of silver-painted copper intalled at the out sided of the cooling chamber to avoid potential water leaking in the cooling section.The chilled water (with 8°C optional) worked as the cooling medium. The recirculation water with 12°C returned to the cooling water tank and to be recirculated in the system.

A proportion valve controlled by PLC regulates the flow rate of the cooling water depending on the preseted temperature.

Tunnel Oven8

1.1.8.    Special negative air channel Sealing Design

Solve the problem:”the sealant of HEPA Filter n heating section can not resist high temperature and easy to peel after long time use”

Tunnel Oven9

1.1.9.    Cooling Section Sterilization by Dry-Heating

Cooling Section Sterilization by Dry-Heating is for the purpose that in some relatively moisture area, the bacterium will easily to grow in the cooling section after a certain time not using the tunnel. So we sterilize the section before the machine runs.

When the cooling chamber is ready for sterilizing, all the fans start to run, drain the recirculation loop of the cooling system (cooling coils, piping, etc).

The whole process will last 45minutes at the dry-heating sterile air temperature 180°C.

Once the sterilization is complete, the heating elements will be switched off and the cooling program starts.

By this means, cooling section has the following different function compared to the standard one:

l  Double Chamber excution with insulating

l  Special motor of the fan, resistant to the high temperature

l  HEPA filter temperature resistant up to 250 °C

l  Drainable cooling coils

l  Temperature control and regulation

l  Registration on the recorder for the cooling section temperature

l  Recipe for carry out the sterilization program

1.1.10.Ultrasonic Washing for Converyor belt

In the cooling section, there’s an ultrasonic bath under the conveyor belt to clean-off particles or dusts

which stuck on the conveyor belt.


Wearing Parts

For the standard execution, including electric components, for approx. 24 months or approx. 4000 working hours

1.1.12.Technical Data

Electrical   Power

3   phases,


(Subject to options   selected)

Machine   Net Weight

Approx.   4000kg

Machine   Dimension (L*W*H)


1.1.13. Machine Frame and Housing

Basic structure adopts 2" tubular AISI-304 stainless steel with height adjustable feet. Cavity body and panel are constructed of AISI-304 stainless steel.

Bottle Contact Parts

Bottle contact parts are constructed of AISI-316L stainless steel, as for:

l  Conveyor belt

l  Border plate belt

l  Infeed dead plate

l  Outfeed dead plate

1.1.14.Conveyor Belt

The conveyor mesh belt is 600mm wide and is made of AISI-316L stainless steel with vertical side border plate on both sides. A tensioner automatically adjusts the tension of the belt.

A tachometric dynamo, connected to the motor of the conveyor belt, monitors the speed of the belt and controls the conveyor belt speed within ± 3% deviation.


In order to minimize the generation of the particles inside the chambers, the fans’ motors are all located on the top of the tunnel. Fans are made of AISI-304 stainless steel and the speed is adjustable by the frequency converter. The deviation of the air speed in each chambers can be controlled and maintained within ± 0.2 m/s

clip_image001Tunnel Oven10

1.1.16.HEPA Filter

The HEPA-filter in the pre-heating and cooling section with maximum mean porosity > 99.997 % (H14) and its’s frame is made of stainless steel.

The HEPA-filter in the heating section is able to resist 400℃ temperature and with maximum mean porosity > 99.97 % (H13), and its’ frame is made of stainless steel.

The filter’s integrity and efficiency can be tested in-place by the introduction of DOP/PAO/DEHS, which above the fans via an inlet nozzle.