Discussion on vacuum packaging of heavy export machinery (1)

Heavy-duty export machinery often experiences shocks, vibrations, drops, and severe environmental changes in the shipping process. Among them, the temperature and humidity in environmental factors are particularly severe, and the performance requirements of packaging materials are very high. Therefore, the packaging materials must be studied. The performance of the bottle to identify the factors that affect its performance is targeted for protection. Whether the sealing performance of the main packaging and packaging material meets the requirements, whether the fixing of the product in the packaging box affects the sealing performance, and the influence of the environment on the sealing performance of the material. This article focuses on the sealing properties of packaging materials, and discusses the effects of heat sealing properties, heat sealing strength, and environmental temperature and humidity on the packaging materials.

The principle of vacuum packaging is to extract the air inside the package and then seal it with a non-permeable packaging film. The purpose is to keep the sealed space in a state of low oxygen and low humidity, thereby preventing corrosion of the surface of the metal product. Vacuum packaging requires the use of high barrier and strength composites and desiccants. Due to the vacuum packaging, the shape, size, and material of the packaged products are not limited, and the operation method is simple: it is convenient and convenient to use, and it is widely used in practical operations.

The vacuum packaging materials currently used are mostly aluminum-plastic composite materials, and their greatest advantages are high barrier properties and high strength.

Vacuum packaging process

(1) Cleaning and Drying of Packages: Cleaning and drying of packages are the preparation process for vacuum packaging. Cleaning is to clean condensate, dust, perspiration, and other foreign materials on the surface of metal products. The choice of cleaning fluid depends on the nature of the metal product and the degree of protection. Drying is a necessary process after the metal products are cleaned. Commonly used drying methods include: compressed air drying, heating and drying, infrared drying, dehydration in a bath, and wiping.

(2) Bottom protection: Two layers of polyvinyl alcohol bubble film are tiled on the basis of the waterproof material on the bottom of the wooden box to prevent the composite material from contacting the bottom surface of the wooden box to damage the sealing property, and then leveling on the blister plastic film. Laying composite materials.

(3) Fixing of the machine: The machine is lifted to the base of the wooden box and fixed on the wooden box sleeper.

(4) Fixation of attachments: After the mechanical attachments or parts have been properly packaged, they are fixed in position on the base of the wooden box.

(5)Calculation and selection of drying utilization: Because the mechanical products to be protected are usually of more volume and different shapes, the composite material cannot completely adhere to the surface of the machine after vacuum, so the space inside the vacuum packaging is very human. A large amount of air remains, so the placement of the desiccant is particularly important, as far as possible in the entire transportation and storage of mechanical products to maintain the air in the sealed space. Scrape: The type of dry agent can be selected based on the value of the packaged mechanical product or the material of the machine. The amount of desiccant can be calculated according to the empirical formula recommended by CH 4879:

Empirical formula calculation:

(W=K1ARM ten K2D)

In the formula:

W——Required amount of desiccant, kg
A—surface area of ​​the packaging surface that is permeable to moisture m2
R - moisture permeability of packaging materials, g/m224h

M - packaging time, month
D - Buffer material quality, kg
K1 - coefficient of temperature and humidity, 0.12 - 0.0007
K2 - buffer material type coefficient, 0.84 a (). 04 (can check standard)

The desiccant is packed in air-permeable paper bags, cloth bags or fine-pore metal containers and placed inside the envelope to seal it.

(6) Making envelopes: Cover the products to be packaged with composite materials, seal the long sides, make envelopes, and then vacuum.

(7) Pumping and sealing: Extract the air in the jacket with a suction device and finally seal the suction port.

(to be continued)