RailMeasurement’s HSRCA is a development of equipment that was originally supplied to Australian National railways (AN) in 1989 to provide a routine way for AN to measure both rail corrugation and discrete irregularities (particularly bad welds) and thereby prioritise grinding and weld straightening. This equipment, which uses axlebox accelerometers mounted on a service vehicle, ran reliably for more than a decade. A paper that describes the work undertaken to understand the cause of AN’s corrugation problem, provide a solution to this and a means of measuring it is contained here. This is not the only system available that is based on axlebox accelerometers, but we would be surprised if many other suppliers could accept the challenge of providing the comprehensive validation that we are happy to provide for our systems.
Validation of HSRCA
The HSRCA has been validated in two ways. The more basic tests have been of repeatability and reproducibility, assessing the effects of speed and direction of travel. Graphs are shown below that demonstrate minimal effect of speed on irregularities in both short and longer wavelength ranges (30-100mm and 300-1000mm).
The influence of measuring speed on measured one-third octave spectra is also relatively small, as shown below. This is a site with a relatively low level of roughness throughout the wavelength range, but with the residue of grinding marks apparent at a wavelength of about 30mm and the effects of sleeper spacing at about 650mm.
A more challenging validation is to compare one-third octave spectra measured with the HSRCA and with a datum instrument (both the CAT and a straight-edge device have been used for this). Two sets of results are shown below, demonstrating excellent correlation of spectra on both rails at one site and slightly poorer correlation of spectra at a second site. These results come from a comprehensive test with French railways (SNCF) whose objective was to compare commercially available systems that could provide the means to undertake “noise mapping” of the French railway network. A paper that describes these tests is available here.
Use of HSRCA
The first version of our HSRCA was used for many years by AN to schedule rail grinding and straightening of welds. A version has recently been supplied for a measuring car to undertake routine monitoring for essentially the same purpose. The tests with SNCF, described in this paper, were undertaken to provide a system for “noise mapping” of the French network.
The HSRCA is compact and can be rapidly attached to and removed from a service vehicle. In the SNCF tests, for example, the equipment was carried to site by two people using public transport and installed on a vehicle in less than a day. Three days were then spent on the test programme and the equipment was removed from the vehicle at the end of the fourth day. Similar surveys of less than a week’s duration have been undertaken by RailMeasurement staff using the HSRCA system on railways elsewhere.