Occlusion testing checks for blockages (or occlusions) in test parts. Measuring the air flow through the test part determines whether the test part is blocked.
General techniques for identifying occlusions/blockages
Several techniques are used to identify occlusions/blockages in test parts. These techniques include:
- Air flow occlusion testing
- Back pressure occlusion testing
- Pressure drop occlusion testing
Air Flow Occlusion Testing
In this method, the test part is pressurized to a predetermined target pressure. After the target pressure is reached, the flow sensor records the flow rate of air through the part. If the flow rate is below the set limit a blockage is present, and the part fails the test. If the flow rate is greater than the set limit at the desired pressure, the part passes the test.
This technique is often used to identify blockages in open terminal test parts such as medical catheters or refrigeration tubing.
Back Pressure Occlusion Testing
In this method, a test part is pressurized to a specific flow rate and air pressure in the part is measured. Since more pressure is required to force air flow through the test part with a blockage, the test instrument measures this input pressure to determine a blockage. If the required input pressure exceeds the acceptable set limits, the part is occluded and fails the test.
Pressure Drop Occlusion Testing
In this test method, the test part is pressurized and then vented through a downstream port and pressure loss is measured.
The test part is pressurized for a set time to reach a target pressure. After the fill time is complete, the system moves on to the measurement step where the downstream port is opened to vent and there is a drop in pressure. If the pressure drop reaches the predetermined minimum pressure drop value, the test part is considered non-occluded. If the pressure drop is less than the minimum pressure drop value, the part is occluded and fails the test.
The iKit, Isaac HD, Zaxis PD, and Zaxis 7i testers are capable of air flow occlusion testing, back pressure occlusion testing and pressure drop occlusion testing to test parts for occlusions. Zaxis’ line of instruments can be used to reliably detect occlusions in catheters, IV sets, tubing, and check valves.
To find the right occlusion test and the right instrument for your specific application, contact Zaxis to discuss your project.
The figure below illustrates the process of a pressure drop occlusion test:
Figure 1. Zaxis Occlusion Test.