Quality requirements of tin box - Expansion tank

- Jun 09, 2018-

Expansion tank: For various reasons, the tank is in a positive pressure state and exceeds the strength limit that the container can withstand. The top and bottom lids will encourage outward, that is, expansion tanks. Swelling cans are divided into three categories: physical, chemical, and bacterial.


Physical expansion tank

       A. Features: Only changes in appearance, the top cover or bottom cover is convex, but the seal is good, the content sensory quality, PH value, no change, is a commercial aseptic, the tank was slightly positive pressure or very low The degree of vacuum.

       B. Main reasons:

           a. The top clearance is small: too much can loading;

           b. There are many residual air in the tank: insufficient exhaust gas, low canning temperature, and low degree of vacuum sealing;

           c, top and bottom cover elastic volume lack of: iron thickness, improper hardness or improperly designed cover shape;

           d. Improper sterilizing and cooling operations, large pressure difference between the inside and outside of the tank: no back pressure during pressurization and sterilization, or bucking too quickly during cooling.


 chemical expansion tank

       A. Features: Caused by excessive corrosion of the tank wall due to excessive hydrogen; occurs in acidic foods with strong corrosion. The degree of protrusion of the top or bottom cover of this type of expansion tank will increase with the extension of storage time; the content of the expansion tank has a serious iron smell.

       B. Main reasons:

           a. Many weld burrs, thin coating or poor curing;

           b. Low tin plating amount of tinplate;

           c. The performance of the inner coating film is poor, including thin film coating, insufficient curing, and mechanical damage.


bacterial expansion tank

      A、Characteristics: Due to the residual bacteria breeding gas production in the tank, it is common in low-acid food and beverage cans that require high temperature sterilization; this can be divided into two cases: a. Insufficient bactericidal strength; b. Contamination caused by sterilization.

     B. Main reasons:

◆ Insufficient sterilization strength:

a. The initial bacterial contamination of the raw and auxiliary materials is serious; b. The bacteria has not been sterilized in time after canning;

c. The heat distribution of the sterilizing pot is not uniform or the operation of the genial misfortune is not standardized. The exhaust and local sterilizing are not sufficient.

◆ Recontamination after sterilization:

a. The rate of sealing and the lack of tightness;

b. The curl thickness (T value) is too high, and the deviation of the same hemming or the curl of the cans is too large.

c, sealant performance: bad adhesion, not high temperature resistance, influx or external extrusion plastic after sterilization; lack of glue; improper glue location, poor uniformity, film is too wide or broken plastic glue phenomenon;

 d, cooling water pollution: lack of residual chlorine, excessive number of bacteria in water;

 e. Improper enveloping: Due to the incompatibility between the indenter and the cover, the cover is markedly indented and deformed, the surface of the cover is sunken, and the head pressure is equal, and it cannot withstand the pressure change during sterilizing and cooling.


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