Pressure hold tests

Perform and document pressure hold test to determine that the leak rate is within specification. 

Perform pressure hold test or a forward flow test. 

Perform a pressure hold test with the nonsterilized filter. Expose the filter to the chosen sterilization conditions. Repeat the pressure hold test with die sterilized filter. For pressure hold test conditions, follow the recommendations of the filter supplier. 

Filter shall meet the pressure hold test prior to and after sterilization successfully per supplier specification. 

Perform a pressure hold test with the sterilized filter. Perform the filtration of the product to be sterile filtered using normal production conditions. After the filtration step, the filter should be tested again with the bubble point test. 

The filter shall meet the recommendation of filter supplier for pressure hold test. 

Another integrity test referred to as the pressure hold test makes use of the fact that below the transition pressure no bulk flow of the test gas takes place. Therefore, in a pressure hold test, once a filter system is in place and the filter medium wetted, pressure is applied to the system and then shut off and sealed. If there are no leaks in the system or holes in the membrane larger than the corresponding test pressure used, the pressure should remain constant. If the pressure drops, there is a leak somewhere in the system that should be corrected. The pressure hold test is popular in testing filter assemblies and systems in... 

How will the bubble point test be run What will be the conditions of the pressure hold test ... 

The pressure hold test is a variant of the diffusive airflow test. The test set-up is arranged as in the diffusion test except that when the stipulated applied pressure is reached, the pressure source is valved off (Fig. 9). The decay of pressure within the holder is then observed as a function of time, using a precision pressure gauge or pressure transducer. 

An important influence on the measurement of the pressure hold test is the upstream air volume within the filter system. This volume has to be determined first to specify the maximum allowable pressure drop value. The larger the upstream volume, the lower will the... 

The integrity of sterilizing fillers is most often validated and routinely monitored by nondestructive methods. The U.S., European, and U.K. guidelines on sterile filtration refer to four methods of integrity measurement filtration flow rate, bubble point tests, diffusion (forward flow) tests, and pressure hold tests. Each of these has its uses in determining that routinely used filters are per-forming to the same standards as those validated for the particular products and processes. 

Pressure Hold (Pressure Decay) Test . Pressure hold tests require a wetted filter to be pressurized with gas. Further supply of gas is then shut off. The pressure decay in the filter is monitored over time and compared to predetermined standards. 

The pressure hold test can be set up as a variant of the bubble point test by using a pressure slightly below the estimated bubble point. It can be set up as a variant of the diffusion test with the pressure around 80% of the bubble point pressure, or it can be set up at lower pressures around 5-10% of the bubble point pressure. The test can be done over a very short period of time or over a protracted hold time. 

The pressure hold test can be envisaged as a general test to highlight if there is significant leakage. If this is so, the leaks can be located by several methods. 

When a test gas (for example ambient air) is applied over a water moistened filter, just below the pressure level of the bubble point, test gas diffusion will occur through the water in the wetted membrane filter. This diffusion happens in all water filled pores, not only in the largest. This principle is the basis for two tests, which use different approaches to measure gas diffusion the pressure hold test and the diffusive-flow (forward flow) test. Other names for the same principle tests exist. These tests are performed at a pressure of about 80 % of the theoretical bubble point pressure of the filter. It is important that the largest pores are still filled with liquid. In this phase, diffusion occurs more or less linearly with the pressure drop over the... 

In the pressure hold-test, the filter membrane or candle in its tightly closed case is set under test gas pressure. Next, the test gas supply to the filter holder is shut. On the side where the pressure was applied (measured in the filter case) the pressure decrease, as a result from gas diffusion through the wetted membrane filter element, is measured. Very sensitive and calibrated manometers in the testing device are required... 

The execution of this test with a 0.2 pm hydrophobic filter membrane is as follows. The entire filter case is filled with water and brought under a pressure of about 200 kPa using pressurised air. This pressure is not sufficient to fill the pores and cause a liquid flow through the filter this would require around 1,200 kPa. Transport of water due to evaporation does occur. The amount of water that evaporates per time unit is dependent on the pore size. As a result of this evaporation, the pressure in the filter case would decrease. The amount of air that is added to the filter case to maintain the air pressure is measured. This amount should not exceed a value provided by the manufacturer. The method strongly resembles the pressure hold test and can be regarded as the hydrophobic variant of this test. 

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