RCA

Gauge-adjustable RCA mounted on the chassis of a rail grinder

The RCA is a train-mounted instrument that has been designed to measure the longitudinal rail profile to accuracies that are sufficient to approve grinding work and to determine whether rail should be ground. The RCA equipment comprises a measuring head for each rail, signal conditioning electronics, and an industry-standard Personal Computer loaded with application software to perform the measurements and provide the data analysis.

The “classical” design of RCA that has been fitted to many rail grinders is shown here.  The equipment is also available as a self-contained measuring bogie (below) and in a more compact design, similar to our MSRCA, that can be attached to either the chassis or a bogie.

Self-contained RCA measuring bogie

Simultaneous measurement of both rails is possible at moderate speeds (typically 5-10km/h) with an accuracy that is only slightly poorer than that of the CAT. Measurement at higher speeds (up to 20km/h) is possible with slightly reduced accuracy.

Validation of RCA

The RCA is typically calibrated by using both it and the CAT to measure the same length of track, as shown below.  For a 500m test site there is typically a difference of less than a micron in RMS levels measured with CAT and RCA in the most critical 10-30mm, 30-100mm and 100-300mm wavelength ranges. The following graphs show a comparison of RCA and CAT, 300-1000mm wavelength range and one-third octave, left and right rails:

Use of RCA for approval of reprofiling work

The most common use of the RCA is for approval of reprofiling work, usually rail grinding.  Accurate measurements can be made during grinding, so that operators know whether more work is required at a site.  An example of measurements of rail that has been finished to standard and from three grinding passes previously, when irregularities were still too high, is shown below.  There are few other pieces of measuring equipment, if any, that not only measure rail to this accuracy but can also be used to take a continuous measurement from a train during the reprofiling operation.

RCA measurements of finished rail and from three passes previously; note irregularities around axle counter on left rail at 9.00km

Use of RCA for routine corrugation surveys

The self-contained RCA measuring bogie is an ideal piece of equipment for making corrugation surveys.  The equipment can be used with a hi-rail vehicle (as shown above) or attached to a more normal railway vehicle, such as a reprofiling train.  An example is shown below of measurements made over more than 10km of a metro line on which surveys are made routinely using this equipment at a speed of 15-20km/h. These measurements are used to assess where track should be reprofiled and whether reprofiling has been undertaken to standard.

An example of RCA output from a corrugation survey

Further information on the accuracy and repeatability of our corrugation measurement products is given here, whilst a comparison of our product specifications and use is available here.