scope:

MAXIMUM ALLOWABLE LIFT AND SLEW

Lift: 50mm

Slew: 10mm

Lifts or slews greater than these values require the gold pins to be removed before tamping starts.

Notes

Failure to remove the gold drive pins when required runs the risk of breaking the security-shielded shear pins. A simple visual check that none of the pins have been broken can be made after tamping.

The maximum allowable limits are liable to be breached during the installation of points. After they have been installed on consolidated ballast to the specified design line and level, it is anticipated that there should not normally be any need to breach the limits in subsequent tamping operations.

Purpose

This instruction sets out the maximum allowable lift and slew that may be applied during tamping to points fitted with Hy-Drive without the gold pins being removed beforehand. In effect, the instruction defines the maximum lift and slew that is allowed during 'normal tamping activities' as described in NR/GN/SIG/19808 'The Installation and Set-Up for SO Supplementary Point Drive'.