Analysis of Geodetic Control Results for the Plan Position of Overhead Crane Tracks in a Machine-Building Workshop

Abstract

A statistical analysis of the results of geodetic surveys of crane tracks carried out in one of the workshops of a machine-building plant over four years of operation was performed. The purpose of the study was to assess the deviations of overhead crane tracks from their design plan position and to analyse the changes in these deviations over time.

The investigated workshop is a multi-span single-storey building with overall dimensions of 168 × 96 m, equipped with overhead cranes with lifting capacities of 10–30 tf. Geodetic surveys of the plan position of the crane rails were performed using a theodolite or a laser sight installed on the braking platforms of the crane girders. Based on the survey results, deviations of the distances between the crane rail axes from the design value of 22,500 mm were calculated in the plane of each transverse frame. Over four years of measurements, 28 samples of deviations were obtained in seven spans. According to regulatory documents, these deviations at the time of installation should be within ±10 mm, and during operation should not exceed ±15 mm.

Analysis using Pearson's chi-squared test showed that the vast majority of the obtained samples do not contradict the normal distribution, which was therefore used to describe the random variable representing deviations of the distance between the crane rail axes from the design value. Analysis of variance indicated that the differences between deviation samples in different spans, as well as in different years of observation, are statistically significant.

The probability of the measured deviations of the distances between the crane rail axes exceeding the permissible limit of ±15 mm specified by standards was used as a generalised indicator of the crane tracks condition. For different spans and different years of observation, these probabilities vary from fully acceptable values below 0.1 to clearly unacceptable values reaching 0.4–0.45. Temporal changes in this probability and in the span-averaged deviations are largely random; however, analysis of the observed trends made it possible to determine the average rates of change of the deviations of the distances between the crane rail axes over time. Assuming an allowable increase in deviations of 5 mm after installation or subsequent alignment of the crane rails, appropriate intervals for geodetic surveys of 1.5–3 years were established for different spans of the workshop.