Draft:Indian locomotive class HG

The Class HG (Heavy Goods) is one of seven standard classes of broad gauge steam locomotives designed by the British Engineering Standards Association (BESA) for use in the British Raj in the mid-1900s.

This design was used by various railway companies of the British Raj, later passing on to Indian Railways and Pakistan Railways after the partition, the latter of which continued using these locomotives into the 21st century to haul the Khyber Steam Safari on the rugged Khyber Pass Railway.

History
The British Engineering Standards Committee (BESC, later renamed to the British Engineering Standards Association), founded in 1901, envisioned standardised locomotive classes for use in British India, to enable more efficient production and maintenance. In the second edition of the scheme in 1907, the HG class, designed for heavy goods trains, was first mentioned. As with the AP and HP classes of passenger locomotives, the HG was offered with three different tenders: the smaller 3000 gallon and 4000 gallon three-axle tenders, and the larger 4500 gallon bogie tender.

In addition, the 1907 BESA report also catalogued two variants: Variant A with 5 ft diameter driving wheels, which was proposed by the Indian Railways Ministry, and Variant B with 4 ft diameter driving wheels, in common with several other locomotives already in use on various railways, including the Bengal Nagpur Railway. Variant A, however, never saw production, and was excluded from the third edition of BESA's report in 1910.

From 1912, in common with other BESA designs, the HGS class was introduced, fitted with the Schmidt superheater - the S denotes superheated. The saturated HG locomotives that were later retrofitted with a superheater were given the classification of HGC - the C in the designation stands for converted. The superheated locomotives performed better than their saturated counterparts, as the latter were of British designs unsuited for the climate of the Indian subcontinent, due to their narrower fireboxes.

In 1947, after the British Raj was partitioned, 133 HG series locomotives of the North Western Railway ended up in the hands of Pakistan Railways. Indian Railways, who inherited the remainder, still had 168 HG series locomotives on the Central, Eastern, and South Eastern zones in June 1977, and were likely retired in the 1980s.

Pakistan Railways however, despite steam traction being mostly phased out in Pakistan in the 1990s, retained HGS 2216, 2277, and 2306 for use on the Khyber Pass Railway, where two of them worked top and tail on tourist trains to Landi Kotal, until 2006, when the railway suspended operations owing to the damages caused by monsoon rain. At the time, the Khyber Pass Railway was one of the last remaining locations in the world where broad-gauge steam locomotives were still being used on passenger trains.

Preservation
Two of the Indian HG series locomotives have been preserved:
 * HGS 26761 at the Rail Museum, Howrah
 * Ex-NWR HGC 1598 (Vulcan no.2461) at the National Rail Museum, New Delhi

Four of the Pakistani HGS class locomotives are known to have survived, most recently used at a steam event around Attock in April 2020.