The HydroCorr Water Flow Integrity Test

Description

The HydroCorr test is a highly sensitive, non-alcohol, water flow integrity test for hydrophobic membrane filters.

In the past, hydrophobic filter integrity testing has consisted of diffusion and bubble point tests conducted on filters wet with alcohol or alcohol/water mixtures. Due to contamination concerns, most alcohol integrity tests were conducted off-line, making it impossible to test a filter in place after steaming. Another drawback to alcohol-based integrity testing is its expense. There are high costs associated with purchasing, handling, storing and disposing of alcohol.

The HydroCorr test is water-based, eliminating the costs and limitations associated with alcohol based tests. Because the test uses only water and there is no flow through an integral filter, it can be conducted as a pre-use test, in place, after steaming. This decreases the risk of processing a batch of product with a non-integral filter.

Millipore's water flow integrity test (HydroCorr) meets FDA requirements for integrity tests of sterilizing-grade cartridges. The HydroCorr Test specifications are correlated to the bacterial challenge test.

Theory

The HydroCorr test is based on the fact that liquid is repelled by the pores of hydrophobic filters by surface tension and capillary forces. The minimum pressure required to force liquid into the largest pores is called the water intrusion pressure.

The HydroCorr test is conducted at a pressure below the water intrusion pressure. For integral filters, there is no flow of water through the membrane. This prevents downstream contamination. And, since the membrane does not wet out, the filter can be used immediately after testing, with little or no filter drying required.

A water flow measured in an integral filter during the HydroCorr test is due only to the compression of the pleated filter structure caused by pressurizing the filter. This does not damage the filter.

Water Flow Integrity Test Procedure

Manual Test Procedure

1. Install a dry filter in a housing and fill the filter housing with clean water.
2. Pressurize the system to the appropriate test pressure and maintain a constant pressure on the system until the filter has stabilized. Stabilization takes 20 minutes for most cartridges.
3. After the cartridge has stabilized, take a reading from the flow meter and compare the value with the filter water flow specification.
4. If the filter is integral, drain the water from the upstream of the housing and use the filter immediately. Since the intrusion pressure of an integral filter has not been exceeded, the membrane will not be wet.

Automatic Test Procedure

The HydroCorr test can be conducted on the Integritest Exacta or Integritest II Plus automatic integrity testing systems. All that is required is to use the appropriate HydroCorr Test software (see ordering information).

1. Install a dry filter in a housing and fill the filter housing with clean water.
2. Program the test parameters into the instrument, for the filter system being tested.
3. Connect a compressed air supply to the instrument, and the instrument to the filter system, and run the test.
4. The Integritest systems will adjust to the appropriate test pressure and maintain pressure on the system until the filter has stabilized. It will automatically determine the water flow value and indicate whether the filter passed or failed. The test will take 20 minutes for most cartridges.
5. If the filter is integral, drain the water from the upstream of the housing and use the filter immediately.