## 1 Introduction
[PERSON] and [PERSON] [12] carried out vibration measurements of the roller shell installed on a test stand. By comparing the results from analyses of new and worn rollers at further stages in their studies, the authors determined limit levels for vibroacoustic phenomena, after exceeding which, the roller needs to be replaced. [PERSON] et al. [13] measured the noise and vibration in a rubber conveyor belt when not loaded. Their research results make it clear that the noise and vibration in the conveyor belt structure were reduced using rollers made of precision tubes. [PERSON] et al. [14] used driven rollers on a test stand, which reduced the load on a conventional actuator of the pipe conveyors. Thus, the actuator can be smaller, which leads to energy and cost savings. Another crucial factor that affects pipe conveyors' reliable operation is the dynamics of the conveyor belts (dynamic characteristics of the belt conveyor). These are determined by the belt's properties. Several authors are engaged in this area. [PERSON] et al. [15] investigated a belt's frequency and dynamic stress using digital simulation. The results showed that the belt conveyor's frequency decreases when its throughput increases. [PERSON] and [PERSON] [16] carried out experiments to determine a conveyor belt's dynamic properties. They measured the dynamic modulus of elasticity, viscous damping, and rheological constants of the belt. They investigated longitudinal vibrations, natural vibration frequency in the transverse direction, and response to impulse actuating. They found that the speed of stress wave propagation increased with a tensile load, and the tensile load was the main factor influencing the longitudinal vibration. [PERSON] et al. [17] investigated the axial elastic response of the conveyor belt with the help of performed simulations when starting unloaded belt conveyors with various numbers of actuators. For each simulation case, they assessed linear starting. The simulations revealed that using multiple actuators reduced the maximum stress on the conveyor belt in both non-stationary and stationary conditions. [PERSON] and [PERSON] [18] proposed an energy-efficient model for a conveyor system that controls several actuator units, thereby increasing its efficiency. [PERSON] et al. [19] dealt with the causes of dynamic stress during the movement of a conveyor belt with material load. They defined the main factors of dynamic resistance in the transport system and found that the speed of failure propagation depends on the level of material load on the conveyor belt. [PERSON] et al. [20] analyzed belt vibrations, which provide information on the conveyor's operation. They measured the frequency of a belt's transverse vibrations along the entire length of its route without the presence of material on the conveyor belt and with the belt loaded using a specially made device located on the conveyor belt. This paper deals with research on issues for online diagnostic needs during a pipe conveyor's operation. This research aims to verify the possibility of identifying selected pipe conveyor failures in its straight section during operation (a missing roller in the idler housing, absent material on the conveyor belt) with the use of a discrimination method. Discrimination, in this case, is an estimate that the device is in a failure-free state or an estimate for the type of device failure, based on continuous measurement and evaluation of measured contact forces for given positions of the rollers in the hexagonal idler housing. Until now, most of the presented papers have dealt with the detection of various failures in continuous transport systems, for example, [21; 22; 23; 24; 25]. Their common feature is the use of specific methods to identify various types of failures in continuous transport systems. However, within the research they present, their effort is to identify failures using quantifiable measurable parameters, i.e., so that the undesirable state of a continuous transport system can be identified using digital measurements.