The Importance of Choosing the Correctly-Sized PET Air Compressor for Your PET Bottling Operations

When it comes to PET bottling, selecting the right air compressor is crucial to ensuring efficient production while maintaining the quality of the bottles and minimizing operational costs. An incorrectly sized compressor can result in inefficiencies, either by overloading the system or under-delivering the required air pressure and flow. This can lead to downtime, equipment damage, and increased energy costs. In this post, we will explore how to calculate the ideal size for your PET bottle blowing compressor and common mistakes to avoid.

Key Factors to Consider When Sizing a PET Air Compressor

1. Pressure Requirements

The pressure needed for PET bottle blowing is critical for achieving the right bottle shape and integrity. The amount of pressure required depends on several factors, including bottle size and type of filling process. Here’s a breakdown of the pressure needs for different types of PET bottling:

Bottle Size: For standard 500ml to 1L PET bottles, a pressure of 26-27 bar is typically required.
Hot Filling Bottles: For hot-fill applications (where the liquid is heated before being bottled), the required pressure increases to 32-33 bar to maintain bottle integrity during the hot-filling process.

These pressure values can be easily monitored through a pressure meter at a blowing machine during the bottling process to ensure the system is delivering the right pressure at all times.

2. Flow Requirements (Free Air Delivery – FAD)

Flow, also known as Free Air Delivery (FAD), refers to the amount of compressed air the compressor can provide in a given time period. This is crucial because a bottling system that lacks sufficient air flow will result in slower production rates or even system shutdowns.

To estimate the required air flow, it is important to consider how many bottles you plan to produce per hour. For instance, a Gairs PET compressor OGWBE60S/F-6m³/min @ 30 bar can blow around 12,000 1L bottles per hour.

3. How to Calculate the Right-Sized Compressor

When determining the right-sized PET air compressor for your production line, calculating compressed air consumption is essential. Below are two possible formulas depending on the type of blow molding machine you’re using:

1. Rotary Blow Molding Machine with Gas Recovery System
For machines equipped with a gas recovery system, the recycled air reduces the overall demand for compressed air, improving system efficiency. The formula for compressed air consumption (Nm³/min) is:

Compressed air consumption (Nm³/min)=(Bottle volume (L)+0.146)×Number of bottles per hour×40/60/1000×1.3

2. Blow Molding Machine without Gas Recovery System
For machines without a gas recovery system, additional air is required to compensate for the air loss during the molding process. The formula for compressed air consumption (Nm³/h) is:

Compressed air consumption (Nm³/min)=(Bottle volume (L)+0.146)×Number of bottles per hour×40/60/1000×1.4

For instance, you are considering buying a blowing machine with gas recovery system that has a capacity of blowing 14,000 500ml-bottles per hour for your production line, here is how you calculate the right sized PET compressor: (0.5+0.146)×14,000×40/60/1000×1.3=7.8m³/min. Thus, a PET air compressor with FAD of 7.8m³/min is an appropriate choice.

Formula Breakdown:

• Bottle Volume + 0.146 L: This accounts for the total compressed air required per bottle, which includes both the bottle’s nominal volume and a fixed residual volume (0.146 L) that arises from the pre-blow or mold exhaust process.

• Number of Bottles per Hour: Represents the total production capacity, which is a crucial factor in determining how much air the compressor will need to provide.

• 40/60: Converts the blowing time per cycle (which is typically around 40 seconds) into a fractional hourly value. In this case, 40/60 ≈ 0.667.

• /1000: Converts the result from liters to cubic meters (Nm³).

• 1.3 or 1.4: The safety factor compensates for system inefficiencies, leaks, or pressure drops:

  • 1.3 is used for rotary blow molding machines with gas recovery systems, which recycle some of the air during the molding process.
  • 1.4 is used for machines without gas recovery, as these systems experience higher air losses and require more compressed air.

Common Mistakes to Avoid When Sizing PET Compressors

1. Undersizing the Compressor

One of the most common mistakes is choosing a compressor that’s too small for the required output. Undersized compressors can’t maintain the required air pressure and flow, leading to inconsistent bottle quality, slower production rates, and even system shutdowns.

2. Oversizing the Compressor

While it might seem like a good idea to over-size the compressor for future growth, choosing an oversized compressor can lead to excessive energy costs. Compressors that operate below their capacity waste energy and result in unnecessary wear and tear.

3. Ignoring the Compressed Air System as a Whole

It’s important to consider your entire compressed air system when sizing the PET compressor. Factors such as air storage, piping, and pressure regulation can all affect the performance of your system. Focusing only on the compressor without evaluating the entire system could result in suboptimal performance.

4. Not Factoring in Peak Demands

PET bottling lines experience variations in air demand throughout the day. These fluctuations may arise due to changes in the bottle size, speed of the production line, or the type of product being filled. Ensure that your compressor can meet peak demands without compromising performance.

How Gairs’ PET Compressors Help Your Bottling Line?

GAIRS offers specialized solutions for the PET bottling industry, with our OGWBE series being the ideal compressor for high-pressure requirements. The OGWBE model provides efficient and reliable air delivery at pressures of up to 40 bar, tailored to meet the demands of PET bottling operations. Here’s why you should choose Gairs compressors:

High Pressure Capability: Capable of achieving up to 40 bar, perfect for hot filling and high-pressure applications.
Energy Efficient: Equipped with variable frequency drive (VSD) and permanent magnet (PM) motor, our OGWBE series uses water-injected technology to provide clean, class zero oil-free air while reducing energy consumption.
Easy Maintenance: Minimal maintenance includes water filter element, air filter element, water softener filter replacement and daily valves check.
Customized for PET Bottling: Designed specifically to meet the unique air demands of PET bottle blowing, offering the right balance of pressure and flow for your production needs.