scope:

Collis Point Machine fixing plates, associated with HW and Style 63 point machines mounted on timber S&C Bearers.

NOTE: The Collis fixing plates differ in appearance from other fixing plates and sole plates as they have a close-fitting block on either side of the machine as shown in Figure 1.

Purpose 

The purpose of this SIN is to identify and examine all Collis Point Machine Fixing Plates associated with HW and Style 63 point machines mounted on timber S&C Bearers and undertake a torque check. 

Recent maintenance of HW point machines has revealed that multiple fixing studs had sheared on Collis Point Machine Fixing Plates. The point machine was free to move, compromising the lock and detection of the switch rails. 

The lock and detection are held relative to each other within the point machine. Where the machine is free to move an unsafe relationship between the switch and stock rail could occur during traffic. 

This unsafe state could remain undetected if points are not moved.