Leak Testing PET Bottles


Leak Testing PET Bottles

ALPS has become a global leader in the leak testing of PET bottles, testing over 25 billion PET bottles annually. ALPS has tested both One-Step Injection Stretch Blown and Two-Step Stretch Blown PET containers.  ALPS is capable of testing a variety of bottles in different shapes, sizes, and at different production speeds. ALPS' wide array of machines can test containers produced as slowly as 10 BPM or as fast as 1200 BPM.

Common Bottle Types & Speeds

The majority of clear bottles are produced on high speed PET blow molders.  Common bottle types include carbonated soft drinks, water, sports drinks, juices, specialty beverages, ready-to-drink teas, dressings, sauces, food oils, wide mouth jars produced at high volumes, and cleaners, among others.  The process is ideal for high speed and efficient production of clear containers with precise neck finishes.

Key Reasons for Leak Testing PET Bottles

Leak testing of PET bottles has evolved to become a best practice by providing the following benefits:

  1. Functional Test that verifies that each bottle will seal and hold pressure
  2. Detection of the Most Critical Defects using the most straightforward method
  3. Protection from random quality issues through 100% inspection. Sampling will not guarantee

  4. Monitoring the blow molding process. Typically the leak tester is positioned as the first machine after
    the blow molder, to detect and alert operators quickly to initiate corrective action.

  5. Protection of inventory and prevention of costly return

A main complementary technology, or in some cases a competing technology based on customer budgets, is Vision inspection of bottles. Vision technology has its own value to consider in providing visual checks of each container, but Vision is not a reliable approach for leak testing plastic bottles because leaks are not consistent in their location and appearance. Leak Testing offers a more straightforward technology, typically at a lower capital and operating cost, at 1-step PET production rates.

Common Defect Types in PET Bottles

  • Sealing Related Defects (Short Shots, Nicks, Cocked Necks, etc.)
    • The ALPS leak test provides a functional test of every seal surface, by sealing and pressure checking
      every container. ALPS specifically uses the lowest test pressure in the industry, to enable low sealing
      forces and the ability to tune the Seal Surface inspection. Alternate probe seals (softer or harder) and
      probe designs (fixed, tilting, etc.) can be provided to ensure the integrity of the most critical sealing related defects for a given container.

  • Holes (Gate Leaks, Gate Cracks, Contamination Defects, Misformed Bottles)
    • Pressure-based leak testing will detect leakage regardless of its location or appearance. The most
      common weak points for small leaks in a PET container is the Gate, which is the injection point on
      the bottom of the container. Leaks can occur anywhere in the bottle if there are material issues (e.g.
      contamination from recycled material) or process issues affecting the proper formation of the bottle.

  • Height and Topload
    • Auxiliary inspections can be added to ALPS leak testers to detect tall and short containers, and to
      verify that the container does not deform at a specific sealing force (topload).

Common Defect Types

Gate pinhole or crack in PET bottles

Gate Crack

Laser hole in PET bottle

Laser Coding Hole

Contamination hole in PET bottle

Contamination Hole

Short shot in PET bottle

Short Shot

Cocked neck in PET bottle

Cocked Neck

Seal Surface nick in PET bottle

Seal Surface Nick

Other PET Leak Testing Resources

For more information on Leak Testing different types of PET containers, see our below application notes pages: