A) Powder Volume Resistivity (PVR)

The test is performed at two controlled relative humidity conditions, an upper humidity of 50% and a lower humidity of 15%, in order to see the changes in resistivity as humidity falls. In pharmaceutical production many of the processes operate at low humidity.

The resistivity value will determine whether a material is conductive, static dissipative or insulating. With the latter case, care must be taken during movement of the powder to minimise charge accumulation which could increase the risk from electrostatic spark discharges.

B) Charge Relaxation Time

The Charge Relaxation Time compliments the Powder Volume Resistivity measurement as it indicates how long a material can retain its electrostatic charge. This is especially important with materials that are found to be insulating so as to minimise the risk from electrostatic spark discharges. Again the tests are performed at two relative humidity’s.

This test data is useful for operations that involve powder movement or storage such as pneumatic conveying, blending, milling, big bag storage etc.