Article

All gas phase filter tests are of the single-pass format using a particle challenge, but the methods differ widely, as do the particle formulations used in the challenge and the…

The test circuit used for fatigue tests subjects the filter to start-stop cycles (for evaluating fatigue behaviour under otherwise steady flow conditions), or to cycles of pressure fluctuation (for evaluation…

A range of methods exists for testing various aspects of a filter ’ s performance. These will be briefly discussed here, although a more complete review of test methods and…

A steady flow of fluid through a filter will cause correspondingly steady accumulation of solids and rise in pressure drop. The effect of pulsating flow is to loosen the finer…

The permeability is the reciprocal of the resistance to flow offered by the filter – thus, high permeability represents a low resistance and vice versa. Permeability is usually expressed in…

One especially important case of purification concerns the removal of microbial contaminants so as to produce a sterile fluid. The use of membranes of 0.2 um rating is generally regarded in…

The nominal rating of a filter can be expressed by means of this efficiency figure. Given as a percentage, it can be calculated from the beta ratio, or directly from…

The beta ratio is a rating system introduced with the object of giving both filter manufacturer and filter user an accurate and representative comparison among various filter media. It is…

A mean filter rating is a measurement of the mean pore size of a filter element. It is far more meaningful than a nominal filter rating, and, in the case…

A nominal rating is an arbitrary value for the performance of a filter, determined by the filter manufacturer, and expressed in terms of percentage retention of a specified contaminant (usually…