SIA Rigas Satiksme is a publicly owned body that operates public transport and vehicle hire in the Latvian capital Riga and its surrounding areas, which has over 700,000 inhabitants. It is the largest provider of public transport in Riga, operating buses, trolleybuses and trams. Trams are one of the city's principal modes of transport, with Rigas Satiksme operating 252 trams on 11 routes across the city with a length of 120 km. In 2010 they will start using modern, low-floor trams on one city route, for which the infrastructure is now being prepaired.

New track is embedded on noise reducing rubber pads, which also give better electro isolation and less vibration. One disadvantage with concrete embedded rails is that they are not so easily re-placed as rails embedded in cobblestones or tarmac.

In Riga, tramways last 20 to 25 years, depending on the intensity of traffic. Tramway curves wear faster than straight track because of side-wear, depending on the radius and frequency of use.

Tramtrac™ II
For Rigas Satiksme, the ESAB Tramtrac II welding tractor provides a cost-efficient solution for repairing curves embedded in either concrete or tarmac, avoiding more costly total replacement. In addition, other parts susceptible to wear, such as tram stops and switches, can be repaired efficiently with this portable system based on the FCAW process using self-shielded wires. The FCAW process allows Tramtrac II to be small and ultra lightweight. It is easily stored and used from, for example, a pick-up truck, together with a petrol/diesel generator and welding power source. The tractor can be hand-carried and is easily installed and removed from the rail, allowing welding to take place between successive trams.

The FCAW process gives Tramtrac™ II a high deposition rate and a high duty cycle, due to quick installation and easily removed slag. Tramtrac II is operator friendly with a four-wheel drive carriage that rides the single rail, a wire feeding unit for 1.2 or 1.6mm ø wires and adjustable traction wheels to fit most worn flanges and railheads. The control box, on top of the feeder encasement, features clearly marked symbols for wire feed speed, travel speed and start and stop welding functions, as well as wire inching.

The curved slide on which the welding head is located enables easy and exact positioning of the wire extension between 0 to ± 65°, while the horizontal and vertical slides enable positioning in the x- and y-planes. Tramtrac II takes a 42V AC control voltage from an Origo™ Mig 320 or 410 power source featuring 40 voltage settings. Control and welding cables - 10 metres in length - allow the tractor to travel a distance of up to 17m when the power source is positioned close to the rail.

Consumables
The need to weld embedded grooved rails in cities makes preheating of rails impossible. With rail grades ranging from 700A (R220) to 900A (R260), consumables for difficult to weld steels are recommended with a weld deposit that can accommodate high carbon migration without cracking. ESAB OK Tubrodur 15.65 and OK Tubrodur 14.71 are two wires that have been successfully used by tramway repair contractors for many years. Once the beads have been there is no need to grind to the final profile of the rail. Rigas Satiksme uses 1.6mm diameter OK Tubrodur 15.65 (Table 1) for the repair of the Russian T62 type tram rails, which are very common in Riga. The rutile, self-shielded cored wire has a very good weldability and excellent slag detachability.

Rigas Satiksme uses 1.6mm diameter OK Tubrodur 15.65 for the repair of the Russian T62 type tram rails, which are very common in Riga. The rutile, self-shielded cored wire has a very good weldability and excellent slag detachability.

The weld metal is austenitic-martensitic work-hardening, with excellent metal to metal abrasion and impact resistance.

By Maris Zvirbulis, Country manager, ESAB Latvia and Janis Cerbulis, Chief Track Department,  Rigas Satiksme.