The dust explosion course in pipes of pneumatic conveying systems is discussed. A high number of large scale tests was carried out and the influence of pipe diameter, dust concentration, conveying velocity, location of the ignition source and powder specific parameters was taken into account. The concentration of the ignited dust/air mixture is measured and controlled by an opto-electronic measuring system. The flame propagation time, the flame front velocity and the explosion pressure depending on the distance of the flame front from the ignition source are shown as well as the explosion pressure as a function of the flame front velocity. The experimental results give important hints concerning the explosion course in pipes, the strength of pipes and location of disengagement systems under practical operating conditions.