Pressure resistance and leakage testing is a critical verification procedure that confirms plastic containers, including drums, jerrycans, bottles, and intermediate bulk containers, can safely retain their contents under internal pressure during handling, transport, and storage. Performed in accordance with recognized standards such as ISO 16101, ISO 16467, GB/T 13508, and the UN Recommendations on the Transport of Dangerous Goods, these tests provide essential evidence for regulatory compliance and product safety. This article explains the technical principles, sample requirements, test items, methods, and typical applications of plastic container pressure resistance and leakage testing.
Technical Overview
Pressure resistance and leakage testing evaluates the ability of a plastic container and its closure system to withstand internal pressure without leaking, permanently deforming, or rupturing. During real-world distribution, plastic packaging is subjected to internal pressure from several sources: vapor pressure of the filled liquid at elevated temperatures, air expansion caused by altitude and temperature changes, compressive loads during stacking, and dynamic forces from drops and vibrations. If the container or its seal fails, hazardous contents may escape, creating safety, environmental, and regulatory risks.
The test is particularly significant for packaging certified under the UN Recommendations on the Transport of Dangerous Goods (Chapters 6.1 and 6.5), where the internal pressure (hydraulic) test and leakproofness test are mandatory design-type tests for packaging intended to hold liquids. Supporting standards include ISO 16101 for plastics packaging for dangerous goods, ISO 16104 for transport packaging test methods, ISO 16467 for intermediate bulk containers (IBCs), GB/T 13508 for polyethylene blow-molded containers, and GB 12463 for general technical requirements for dangerous goods transport packaging. For seal integrity verification, methods such as ASTM D4991 (vacuum leakage testing of rigid containers) and ASTM D3078 (bubble emission testing) are widely applied. Testing is typically carried out by accredited third-party laboratories or in-house quality facilities using calibrated pressure control and measurement equipment.
Testing Samples
Blow-Molded HDPE Drums and Jerrycans
High-density polyethylene drums (typically 100 L to 220 L, tight-head or open-head) and jerrycans (typically 5 L to 30 L) used for chemicals, lubricants, solvents, and agrochemicals. These are the most common subjects of internal pressure certification testing.
Plastic Bottles for Consumer and Industrial Liquids
PET, HDPE, and PP bottles ranging from 100 mL to 5 L, tested together with their caps, liners, and induction seals as a complete assembly, for applications such as household chemicals, detergents, paints, and pharmaceutical liquids.
Intermediate Bulk Containers (IBCs)
Composite IBCs of approximately 1000 L capacity, consisting of a plastic inner receptacle within a protective steel or plastic cage, which must pass both leakproofness and internal pressure requirements before UN certification.
Composite and Combination Packaging
Plastic inner receptacles installed within fiberboard, wooden, or metal outer packaging, where the inner container is evaluated for pressure retention and leakage independently of the outer structure.
Samples should be unused, production-representative containers supplied with their intended closures, seals, and gaskets. For design-type certification, multiple identical units (commonly three or more per design) are usually required, and the containers may be tested empty or filled with water or a suitable substitute liquid depending on the selected method.
Testing Items
Depending on the applicable standard and the intended use of the container, the following test items are typically performed:
- Internal pressure resistance (hydraulic pressure test)
- Leakproofness and seal integrity of the closure system
- Burst pressure determination (pressure at rupture or leakage onset)
- Pressure-hold performance and volumetric or dimensional deformation measurement
- Closure torque retention and seal behavior after pressurization
- Combined-sequence evaluation, including drop, stacking, and vibration testing after pressure conditioning
- Complementary assessments such as environmental stress-crack resistance (e.g., ASTM D2561) and compatibility of the plastic with the intended filling substance
Testing Methods
Internal Hydrostatic Pressure Test
The container is filled with water, sealed with its production closure, and connected to a controlled pressure source. Internal pressure is applied gradually and held constant for a defined period. For dangerous goods packaging intended for liquids, common practice follows the UN requirements: a minimum gauge pressure of 100 kPa held for approximately 30 minutes for most plastic drums and jerrycans, with higher pressures (up to 250 kPa or more) for Packing Group I packaging or where the vapor pressure of the contents at 55 °C demands a greater safety factor. The container is inspected for leakage, seepage at the closure, and unacceptable permanent deformation.
Pneumatic (Air Pressure) Leak Test — Bubble Emission Method
The sealed container is pressurized with air and submerged in water, or its closure area is covered with a surfactant solution. A continuous stream of bubbles indicates a leak path through the body, seam, or closure. This method is highly sensitive and well suited to locating leak positions rather than merely confirming pass or fail.
Vacuum Decay and Vacuum Immersion Methods
For rigid containers, vacuum methods such as ASTM D4991 evacuate the container and monitor for pressure change or liquid ingress, detecting micro-leaks that pressure testing alone may miss. These techniques are frequently used for empty container quality control and for packaging with critical sealing requirements.
Pressure Decay Method
The container is pressurized to a specified level, isolated from the pressure source, and the internal pressure is monitored over time. A pressure drop beyond the acceptance threshold indicates leakage through the body or closure interface. This method is easily automated for production-line quality control.
Burst Pressure Test
Internal pressure is increased at a controlled rate until the container leaks, deforms catastrophically, or ruptures. The recorded burst pressure characterizes the safety margin between the rated working pressure and the ultimate strength of the container, and is valuable for design validation of products such as carbonated beverage PET bottles.
Conditioning and Test Environment
Unless otherwise specified, samples are conditioned at 23 ± 2 °C and 50 ± 5 % relative humidity in accordance with ISO 291 or ISO 2233 before testing. For certain certification schemes, additional conditioning such as low-temperature exposure or prolonged stacking at elevated temperature precedes the pressure test to simulate realistic worst-case service conditions.
Applications
Pressure resistance and leakage testing supports a wide range of industries and regulatory scenarios:
- UN performance certification of drums, jerrycans, and IBCs for the transport of dangerous goods, enabling manufacturers to apply UN design-type markings
- Chemical, petrochemical, and agrochemical packaging qualification for solvents, acids, and formulated liquid products
- Lubricant, fuel additive, and automotive fluid container validation
- Paint, coating, and adhesive packaging development and incoming inspection
- Carbonated beverage and food bottle evaluation, including internal pressure and burst resistance
- Pharmaceutical and cosmetic packaging validation, including seal integrity studies
- Research and development of new container designs, materials, and closure systems by converters and fillers
FAQ
What pressure level is applied during the internal pressure test?
The required pressure depends on the standard and the packing group of the intended contents. For most plastic drums and jerrycans intended for Packing Group II or III liquids, a minimum of 100 kPa gauge is typical, while Packing Group I packaging and containers for high vapor-pressure liquids may require 250 kPa or higher, calculated with an appropriate safety factor relative to the vapor pressure at 55 °C.
How long is the pressure maintained?
Common hold times range from 10 to 30 minutes depending on the specification. IBC leakproofness testing, for example, typically applies approximately 20 kPa for 10 minutes, whereas design-type hydraulic tests for drums often specify a 30-minute hold. The exact duration is defined by the applicable standard or the certification scheme.
How many samples are required for testing?
For design-type certification, several identical containers (commonly three or more per design variant) are tested to account for material and process variability. Production quality control testing may use smaller statistical sampling plans defined by the manufacturer or the customer specification.
Is the test destructive?
Internal pressure and burst testing are generally considered destructive because pressurization may permanently deform or damage the container and closure. Samples subjected to these tests should not be returned to service or filled for commercial distribution.
Who can perform this testing?
Testing can be conducted by accredited third-party laboratories or by manufacturers' own qualified laboratories equipped with calibrated pressure, temperature, and flow instrumentation. Using accredited laboratories with experience in dangerous goods packaging standards is recommended when results support UN certification or regulatory submission.
What are the typical acceptance criteria?
A container passes when it exhibits no leakage of the test liquid, no continuous bubble stream in air-based leak tests, no pressure decay beyond the specified limit, and no permanent deformation or rupture that would compromise handling, stacking, or transport safety.