Crane rail welding

Table of Contents

Crane rail welding is a specialist process that must be undertaken by fully trained and competent engineers. Rapid rail supply welding engineers, supervision and /or training in either mma (puddle arc) or thermit/thermic welding

Puddle arc welding

MMA Puddle Arc Welding is the process of joining carbon steel crane rails.

Preparation for Crane Rail Welding

The rails to be joined together are aligned leaving a prescribed gap between their ends. Rail ends shall be smooth and free from defects and grease.

The rails are set with a slight camber at the joint to allow for weld contraction and copper moulds are placed around and under the joint.

Heat Treatment

Joints are pre-heated to prescribed temperature and confirmed using temperature indicators prior to welding.

The Welding Process

Welding is carried out using low hydrogen electrodes to an approved working procedure by competent certified welders.

Thermit welding

Preheat

Using a specially designed burner, the moulds and the enclosed rail ends are pre-heated for a time, dependent upon the rail section, to achieve the correct welding temperature of 900 – 1000°C

Ignition

When the correct degree of preheat has been achieved reaction is initiated in the crucible using a special igniter. Superheated molten steel is produced by an Aluminothermic reaction (the Thermit® reaction).Weld Forming

At the correct time the tapping system at the base of the crucible discharges the superheated molten Thermit® steel followed by the slag into moulds via the pouring cup.

After solidification, surplus Thermit® steel is removed from the rail head and following an appropriate cooling period, the railhead is ground to profile and the rail aligned and fastened.