Electrostatic ignition hazards in insulating or dissipative tubes and hoses for pneumatic transfer of powders—Measurements and model calculations

• Measurement of charging current densities during the pneumatic transfer of powders.
• Modeling potential and field distribution in hoses with metal spiral.
• Assessment of occurrence of propagating brush discharges in plastic hoses.
• Requirements for the exclusion of propagating brush discharges in plastic hoses.

When transferring powder through pipes or hoses made from insulating material, propagating brush discharges cannot be excluded. To calculate the limit value of the resistivity of the insulating material, below which no propagating brush discharges will occur, the charging current due to the powder transfer must be known. This charging current has been determined experimentally. Based on analytical calculations and computer models limit values for the resistivity of the hose material are derived from these experiments.