10 locomotives from W1 class were later fitted with new engines and renumbered as W3 class.
Sri Lanka Railways W1 is a class of Sri Lankan diesel-hydraulic locomotive that was built by Rheinstahl Henschel in 1969 for use by Sri Lanka Railways (SLR). This is the first diesel-hydraulic locomotive to run on Sri Lankan rails.
Forty-five W1s were imported to Sri Lanka in 1969, which made the W1 the most numerous class of SLR locomotive that time. During that time period, the only operational diesel locomotives were the Class M1 and M2. Most other services were carried out by steam locomotives. But with the introduction of W1s, most steam locomotives were taken out of service and the services operated by them were taken over by the diesels.
The W1 along with the M6 classes were used to operate Main Line trains such as the Udarata Menike and Podi Menike for about 25 years until 1995.
The Class W1 locomotive can be operated on any of Sri Lanka's railway lines.[2][4]With the declination of the W1s, two locomotives (Nos. 650 & 657) were fitted with new Paxman VEGA SE/RP 160[1] prime movers with a power output of power 1250hp.
By the 1990's, most of W1s were out of service owing to problems in the prime mover. Some units were afflicted serious damages due to accidents; these condemned locomotives were scrapped.[2] By 2011, only 2 units were in running condition; these were used for light duties. By 2012, none of the W1s were operational excluding No. 657, which was a yard shunter at Dematagoda in 2016.
In 1997, 10 Class W1 locomotives were extensively refurbished. Sri Lanka Railways and Adtranz were involved in this process. During this refurbishment, the locomotives were fitted with new power plants, power transmission systems and electronic engine control systems, and given a new Blue and silver livery.
These extensively modified W1s were classified as the Class W3. All of these locomotives are still in active service today.