Posted by Sombe Longwani

Zambia Railways embarked on the rehabilitation of its railway infrastructure and needed to improve train speeds.

The  purchase of the Duomatic machines for rail track rehabilitation came at the right time.

The poor state of the railway infrastructure during the nine year concession period contributed to customers switching to road transport.

The speed of freight trains at the time were running at 15km/hr while passenger trains were running at 20km/hr. More than 269km of the track out of 1,248km total net work was on temporal speed restrictions (TSR) which constituted about 22%.

The two tamping machines which were commissioned in May 2015 have been working on the track ever since.

In order to operate the machine efficiently, some employees had to undergo training on how to operate the machines and maintaining them. If handled properly, the machines have a life span of up to 20 years.

These machines are called ‘duomatic’ because of their ability to tamp two sleepers at the same time. They are designed to tamp and align a total of 25 sleepers per minute, which translates to 18 meters per minute. If given sufficient block time given, one tamping machine can cover a total of 3.5km without any problem.

The trained machine operators are now tamping 20 sleepers per minute which translates into 14.4 meteres  per minute and this is a great achievement for ZRL

I wish to mention that other tamping machines are designed to tamp only one sleeper at a time. So our tamping machines have that extra capability as compared to other tamping machines.

In addition, each tamping machine has two air conditioned cabins fitted with comfortable seats for operators where one operator sits in the front cabin and his responsibility is to feed data into the computer while the other operator sits in the rear cabin doing the actual tamping and lining of the track. The two operators are in constant communication with each other via an in built communication system.

The other issue to note is that these tamping machines are so sophisticated that any slight malfunctioning of any part of its system will cause the tamping machine to stop and this prevents damage to the machines.

When working the track the tamping machines perform three functions simultaneously. They lift the track to the required levels and then consolidate the ballast around the sleepers by dropping the vibrating tamping tines into the ballast. This helps to achieve the required vertical alignment of the track. At the same time the tamping machine will clamp the rails and slew the track either left or right in order to achieve the desired horizontal alignment of the track. When working on a curvature, depending on the radius of the curvature, super elevation and the length of the transitional curve that have been fed into the computer, the tamping machine will lift the outer rail to the required millimeters to provide the exact super elevation and align the track into a perfect circular curve.

From June 2015 a total 117km of track has been tamped and lined covering sections from Karubwe to Lukanda North and 5km of track between Fubela and Kashitu. The section between Kafue to Lilayi has also been tamped and lined.

Speeds in the tamped areas have improved significantly up to 50km per hour for passenger train and up to 45km per for freight train. Also there has been a substantial reduction in the occurrence of derailments especially those attributed to poor track in the tamped areas.

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