Blow pressure standard

The pressure standard of the air compressor in the bottle blowing process needs to be comprehensively set according to the bottle type, material and process requirements. The specific specifications are as follows:

1. Core pressure range

1. Conventional PET bottles
   • standard range: The blowing pressure is usually between2.5 to 4.0 MPa (25 to 40 bar)between, among them3.5 to 4.0 MPa (35 to 40 bar)It is the most commonly used range and is suitable for standard containers such as carbonated beverage bottles and mineral water bottles.
   • process justificationPET material needs to be heated and inflated, and the pressure needs to match the temperature to ensure that the preform fully fits the mold to avoid overpressure cracking or incomplete under-pressure molding.
2. glass bottle
   • pressure range: blowing pressure is low, about0.2 to 0.5 MPa (2 to 5 bar), molten glass is blown and formed by compressed air, and is suitable for beer bottles, daily glass containers, etc.
3. Special bottle type
   • Thick-walled or large industrial drums: Higher pressure is needed (close to30 bar and above) to ensure that thick-walled materials are completely blown up and are suitable for chemical drums, liquid storage tanks, etc.
   • High-performance engineering plastic bottles: Due to the high hardness of the material, it is requiredPressure above 30 bar, such as special containers used in the aerospace or automotive industries.
   • High-precision bottle shape(such as pharmaceutical packaging): need to stabilize high pressure (35 to 40 bar) to ensure size accuracy, wall thickness uniformity and appearance quality.

2. Pressure setting basis

1. preform characteristics
   • PET preform needs to be heated (usually above 200℃) and then blown, and the pressure needs to be adjusted in conjunction with the heating temperature. Imported PET raw materials are more likely to blow up than domestic raw materials. When the production dates of the same batch of preforms are different, the process parameters need to be fine-tuned.
2. device capability
   • High-capacity equipment requires higher pressure to maintain efficiency, but needs to balance energy consumption and stability. For example, equipment with a production speed of 100 bottles per minute needs to be matched with a compressor with sufficient displacement.
3. industry standards
   • GB/T 3853-2018: Prescribing the energy efficiency level of air compressors indirectly affects the selection of blowing pressure, and giving priority to Level 1 energy efficiency equipment to reduce long-term costs.
   • JB/T 13963-2020: Clarify the technical specifications and rated exhaust pressure of reciprocating piston air compressors for bottle blowing3.0 to 6.0 MPa (30 to 60 bar), covering indicators such as mechanical performance, safety protection and noise control.
   • GB/T 44359-2024: For lightweight PET bottle molds, core indicators such as blowing pressure are stipulated to optimize energy consumption and quality and promote green transformation of the industry.

3. Key points of practical adjustment

1. Pre-blowing pressure control
   • Adjust according to bottle specifications: Large capacity bottles require lower pre-blowing pressure, and high-capacity equipment requires higher pressure. For example, when producing carbonated beverage bottles (with pressed bottles), the pre-blowing pressure is close to 4.0 MPa (40 bar); ordinary non-pressed bottles can be appropriately reduced.
2. Adapting materials to environment
   • Special materials (such as glass fiber reinforced PET) require a small pre-blowing pressure to be formed, while bottles that are stored exceeding the standard or are reheated need to reduce the heat input and reduce the pressure accordingly.
   • The production environment needs to be constant (room temperature, low humidity) to avoid temperature fluctuations affecting pressure stability.
3. Balancing safety and efficiency
   • Risk of excessive stress: It may cause bottle breakage and mold wear to accelerate. The maximum pressure needs to be limited through a pressure regulating valve and the pressure sensor must be checked regularly.
   • Effect of insufficient stress: resulting in uneven thickness of the bottle wall and incomplete molding. It is necessary to ensure that the compressor discharge volume meets production needs (considering margin and pipeline loss).
   • energy consumption optimization: Adopt variable frequency motors or three-stage compression technology to reduce power consumption while meeting pressure requirements. For example, three-stage compression can improve volumetric efficiency and reduce heat generation.

IV. Summary

Bottle blowing pressure standards need to be comprehensively set based on specific bottle types, materials and equipment capabilities. Industry specifications provide the basic framework (such as GB/T 3853-2018, JB/T 13963-2020). In actual production, process debugging (such as pre-blowing pressure adjustment), environmental control (constant temperature and low humidity) and equipment selection (such as oil-free compressors, frequency conversion technology) are needed to achieve the best balance to ensure product quality and production efficiency.