Burst Testing Method

A. Introduction 

DestructiveTo determine the burst strength of a pouch as an indication of correct heat sealing conditions by applying internal pressure.Off-line, > 30 s> $5,000

B. Operation 

Burst testing is conducted by introducing air (or other gas) into the package at a controlled rate, maintaining the internal pressure for a specific length of time, and inspecting for material failure. The entire package is subjected to uniform stress and failure generally reveals the weakest point. Burst testing provides an indication of the ability of a package to withstand internal pressure and the maximum internal pressure required to cause failure of the package seal. It also provides information on package reliability against material or seal failure during manufacture, distribution, and storage.

Both restrained and unrestrained burst testing may be used. Restraint limits expansion by minimizing the angle of the package seal, which becomes greater as a package is inflated. With restraint, packages with strong seals fail at greater internal pressure than do packages with weak seals. Thus, use of a restraining device during burst testing permits noticeable separation between packages having strong or weak seals.

Conventional burst tests have two basic controllable parameters: the rate of pressurization and the lid restraint height. The first parameter is the rate at which the internal pressure of the test package is increased, while the latter is the maximum distance above the package flange that the lid is allowed to expand. The lid restraint height is not meaningful in aseptic package testing, but it is applicable when retort processed packages are tested. 

Dynamic burst testing involves a steady increase of internal pressure until failure occurs. Static burst testing involves a steady increase in internal pressure to a pressure less than failure, followed by a 30-s hold. Both methods are used for packages with fused seals. Peelable seals are weaker than the walls of a flexible package, and less pressure and a longer time increment is needed to induce pressure failure. Peelable seals are burst-tested by inflating at a steady rate to a point less than failure pressure and held for 30 s, followed by a 0.5 psig pressure increase and another 30-s hold. Pressure and time indexing is continued with observation of the seal area for seal separation (peeling) until failure occurs.

  • Compressed air 
  • Regulation valve
  • Needle with gasket and pressure tubing
  • Solenoid with timer(s)
  • Pressure indicator(s), digital or gauge with sweep hand
  • Restraining device (optional)

Use empty sealed package, or cut and remove contents of a filled package. Place package in restraining fixture (if used). Pierce package with gasketted needle(s) and inject air or water. Inflate at 1 psig/s.

Dynamic method 

  1. Continue inflation at 1 psig/s until failure occurs.
  2. Record internal pressure at failure.
  3. Observe peelable seal separation. 
  4. Report internal pressure at failure.

Static method 

  1. Inflate at 1 psig/s to specified internal pressure, and hold at specified pressure for 30 s. 
  2. Record as pass or fail.
  3. Observe peelable seal separation. 
  4. Report internal pressure at failure.

Indexed method 

  1. Inflate to 5 psig and hold for 30 s, inflate additional 0.5 psig and hold for 30 s. 
  2. Continue increase and hold sequence until failure occurs. 
  3. Observe peelable seal separation. 
  4. Report internal pressure at failure.

Positive

Pressure failure occurs below specified level of performance, indicating a hole in the package.

Negative

No pressure failure occurs below specified level of performance.

False positive

A leak is present at point where air or water is injected into package and pressure cannot be maintained.

False negative

A small leak occurs, but is not sufficient to reduce pressure noticeably.

C. Application 

PACKAGE TYPES AND DEFECTS

 PACKAGE TYPE
DEFECTSFlexible PouchSemi-rigid and
Rigid plastic container
Plastic Can (Double-seam Metal End)Paperboard
Abrasion
Corner Dent   
Crushed 
Cut (Fracture)
Delamination 
Double Seam Defects*   
Flexcracks 
Foreign Matter Inclusion  
Gels  
Hotfold   
Label Foldover   
Leaker   
Leaker (Channel) 
Leaker (Corner)   
Leaker (Notch)   
Leaker (Perforation)   
Leaker (Pulltab)   
Leaker (Seal)   
Loose Flap or Ear   
Malformed  
Puncture (Pinhole)
Seal Defects (Blister)   
Seal Defects (Blocked)   
Seal Defects (Burnt)   
Seal Defects (Compressed)   
Seal Defects (Contaminated)  
Seal Defects (Convolution/Embossing)   
Seal Defects (Creep)   
Seal Defects (Crooked)   
Seal Defects (Incomplete)   
Seal Defects (Misaligned/Deformed)  
Seal Defects (Nonbonding/Weak)   
Seal Defects (Plastic Lumps)   
Seal Defects (Seal-width Variation)   
Seal Defects (Stringy)   
Seal Defects (Uneven Impression)   
Seal Defects (Uneven Juncture)   
Seal Defects (Wrinkle)  
Swell (Swollen Package)
Waffling   

D. Source 

  • TM Electronics, Inc. 45 Main Street , Boylston, MA, 01505. TEL (508)-869-6400 (http://www.tmelectronics.com/)Pro-Pack Testing Laboratory, Inc. 2385 Amann Drive, Belleville, IL, 62220. TEL (618)-277-1160 (http://www.propacktestlab.com/Forms/Home.htm)Moncon. 7500 Mendelssohn Ave N., Minneapolis, MN 55428 USA. TEL (763)-493-6370 (http://www.mocon.com/index.php)ARNDT., G.W. JR. 1998. Chapter 22C Examination of Flexible and Semirigid Food Containers for Integrity. FDA Bacteriological Analytical Manual (8th Ed)
  • ASTM F1140 - 07 Standard Test Methods for Internal Pressurization Failure Resistance of Unrestrained Packages
  • ASTM F2054 - 07 Standard Test Method for Burst Testing of Flexible Package Seals Using Internal Air Pressurization Within Restraining Plates
  • Canadian Food Inspection Agency. 2002. Flexible Retort Pouch Defects Manual - Identification and Classification. (http://www.inspection.gc.ca/english/fssa/fispoi/man/pousac/pousace.shtml)