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Glossary of Terminology - TM Electronics, Inc. Leak, Flow and Package Testing Products

Pressure Decay Test: an inflation leak test in which a non-porous package or product is pressurized to a preset level. After the package has stabilized, the decay in pressure over a preset test time is evaluated to determine if a leak is present.

Vacuum Decay Test: similar to the Pressure Decay Test, except that a preset vacuum is established inside the product or package, and the decay in the vacuum over a preset time is evaluated to determine if a leak is present.

Decay: refers to the change of pressure ( P) inside a pressurized containment during a pressure decay leak test. Decay can refer to either positive or negative (vacuum) pressure

Pressure/Vacuum Decay Test Cycle graphPressure/Vacuum Decay Test Cycle:
Consists of five consecutive steps:

  1. Load (attach the test item to the test system)
  2. Charge (pressurize the test item to a preset pressure, or create a predetermined vacuum level)
  3. Settle (time allowed for the volume of the test item to stabilize to minimize the effects of material stretching, adiabatic heating, etc.)
  4. Test (the time during which the decay in the pressure or vacuum is measured
  5. Unload (removal of the test part from the test system).

 

Decay Curve: In a pressure decay leak test, the graph of the drop in pressure (Y axis) over time (x axis) is called the decay curve. TME uses the decay curve in its "Test Plot" graphic display and in its "Memory Reference Curve" technology, in which the decay curve for an acceptable test part is determined and reject decisions are made by the test instrument by comparing the test decay curve to the acceptable "memory reference curve" for the test part.

Resolution vs. Sensitivity:
Resolution is the least significant digit that an instrument is capable of measuring; for example, the TME Solution Leak Tester has a resolution of 0.0001 psi.
Sensitivity is the smallest volume leak rate your test system (including the air lines, fixtures, etc.) can detect.

Units of Measure:
Pressure units of measure include: psig (pounds per square inch gauge), Pascals, kg/cm2 and many others.
Flow rate units of measure include: liters/min, sccm (standard cubic centimeter per minute), sccs (standard cubic centimeters per second) - where standard refers to atmospheric pressure.

Transducer: Any sensor that converts a physical parameter (for example, pressure) into an electronic signal that can be utilized by an instrument.

Leak Rates:
Volume Leak Rate: change in volume per unit of time (measured in Flow Rate units of measure, see above)
Pressure Leak Rate: change in pressure per unit of time (measured in Pressure units of measure, see above)

Operating Test Parameters: the descriptive factors defining a leak, flow or package test.
These may include:
Charge, settle, and test times for pressure or vacuum decay tests;
Test pressure;
Flow rate into the test item (very important in burst testing);
Maximum acceptable volume leak rate.

Sequential vs. Concurrent Testing:
Concurrent testing enables leak tests to be performed simultaneously on more than one and up to four test items in a Solution tester, with one test item connected to each port on the instrument. The tests must have identical test parameters (test time, pressure, decision point etc.), and the test results are discrete and identifiable to a specific test part. An instrument of this type has individual transducers for each test port.
Sequential testing involves performing a series of like tests on a test item through a single port. An example is a leak test followed by a flow occlusion test on a test item and/ or a series of leak and flow tests on multiple ports. An instrument of this type may have one port or multiple ports that are tested one at a time.

Occlusion Testing: An occlusion is a partial blockage of a flow path. An example is a crimp in a catheter. Occlusion testing can be done in several ways, including:
1. mass flow rate
2. back pressure measurement
3. pressure drop measurement.

Back pressure: the pressure forcing air through a leak path.

Package Testing: Based on international standards and FDA guidelines, thorough package testing should consist of both seal strength testing and leak integrity testing.

Seal Strength Testing: a destructive test that provides a measurement of the strength of a package seal of a porous or non-porous package. Seal strength testing can also identify the area of weakest seal. Seal strength testing can be done using inflation tests or tensile tests, but TME recommends using one or more of the following inflation seal strength tests:
1. Burst testing (recording the peak or ultimate strength of a package seal);
2. Creep Testing (measuring resistance to seal peel) - result is pass/fail only;
3. Creep-to-Failure (measuring resistance to seal peel) - result is variable statistic (time).

Integrity Testing: a measure of the quality of the package or product in general, including the seal areas and the package or product materials themselves. Leak Integrity Testing generally refers to product or package leakage measured by a leak test.

Fixtures: Fixtures are used to enable the test instruments to perform specified leak, flow or package tests on a variety of products or packages. Examples of fixtures commonly used by TME include: Open Package Test Fixtures, Closed Package Test Fixtures, Restraining Plate Fixtures, Package Probe Assembly, Radial Sealing Fixtures. Fixtures are often custom designed to accommodate a customer's very specific testing need.

Closed Package Entry System: a method to obtain a leak tight measuring path between the package interior volume and the instrument's pressure transducer. TME uses the patented Package-Port System, which consists of the following disposable items:
1. Package-Port - a reusable plastic entry port which accommodates the pressurizing sensor probe, and
2. Adhesive Disks that adhere the Package-Port to the surface of the test item which are supplied in rolls of 1000.


Non-Destructive (Chamber) Testing: a method to non-destructively test a sealed, non-porous package or product for leaks. It is necessary that the test item contain some air or other gas inside - this is called the "head space". The package or product is enclosed in a surrogate chamber that provides an interstitial air space around the test item. This air space is then pressurized and stabilized, and decay of the pressure in this air space (indicating air leaking into the head space of the package or product) is measured. A chamber test can also be done using vacuum.

Surrogate Chamber: the test chamber used in non-destructive chamber leak testing is called a "surrogate chamber" because the actual pressure or vacuum decay leak test is done on the air contents of the chamber surrounding the test item rather than on the test item itself.

NEMA-4: A designation in the USA which indicates that an item (such as case, components, or an assembly) can withstand damage from harsh industrial environments, including water or dust. The NEMA-4 designation corresponds to the IP-65 designation.

Verification/Qualification/Validation: These terms describe a process that is helpful when evaluating a new product or package manufacturing process:
1. Verification refers to the test and inspection results for each individual component and/or step involved in the manufacture and packaging of a medical device.
2. Qualification is a combination of verifications to determine how well equipment, materials, and a process can work together.
3. Validation is the combination of various qualifications and other objective evidence that the processes consistently produce product meeting predetermined specifications.

IQ/OQ/PQ: Installation Qualification, Operation Qualification, Performance Qualification. These protocols are part of the validation process addressed above.