NR NR/GN/MTC/00011 ISSUE 1 PDF

This guidance note concentrates primarily on stock rail bolts specifically (see illustration 1). The principles for effective torque application can also however be adopted for some other switch and crossing bolts.

Purpose

We have levels of torque prescribed in Standards, which we are to apply and maintain in order to achieve effective clamping load on bolts. Whilst it is difficult to accurately and consistently apply torque to meet specific target levels, we have an obligation to apply torque as effectively as practicable at installation and to ensure it is maintained. This is in parallel with undertaking other maintenance and improvement activities (e.g. voiding rectification).

We have a number of instances of points failure due to loose or broken stock rail bolts. One contributory factor is ineffective torque application and maintenance. There are a number of references to torque application and checking for switch and crossing bolts in Standards and Guidance. However it is not clear from these, which torque target applies specifically to stock rail bolts. This Guidance Note seeks to clarify target torque and gives some advice on technique for applying and maintaining effectiveness.