Burst Testing Method

A. Introduction

ClassificationDestructive

ObjectiveTo determine the burst strength of a pouch as an indication of correct heat sealing conditions by applying internal pressure.Limit of DetectionDetection Speed

Off-line, > 30 s

B. Operation

PrinciplesBurst 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.Materials

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)

ProcedureUse 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.Results

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.

Diagrams

C. Application

Package Types and Defects

DEFECTSPACKAGE TYPE

Flexible Pouch

Semi-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