Indian locomotive class SP

4 ft 8+1⁄2 in (1,435 mm) • Tube plates11 ft 4+1⁄4 in (3.46 m) • Small tubes1+3⁄4 in (44 mm) × 236 offBoiler pressure180 lbf/in² (1.24 MPa)Heating surface:​ • Firebox120 sq ft (11 m²) • Tubes1,229.5 sq ft (114.22 m²)CylindersTwo, insideCylinder size18+1⁄2 in × 26 in (470 mm × 660 mm)Valve gearRotary Lentz valve gearValve typeSlide valve

Performance figures
Tractive effort	11.2 bar boiler pressure: 87 kN 9.3 bar boiler pressure: 72 kN

Career
Operators	Indian Railways, Eastern Bengal Railway, East Indian Railway Company Oudh and Rohilkhand Railway
Locale	Eastern Railway zone and Northern Railway zone
Disposition	At least one preserved in the United Kingdom.

The Indian locomotive class SP (Standard Passenger) is a class of Indian 4-4-0 passenger steam locomotives which was built around 1905. It was one of the BESA locomotives developed by the British Engineering Standards Committee, later called the British Engineering Standards Association (BESA).

The SP class was catalogued in the first edition (1903) of the BESA report on standard locomotives for the railways of the British Raj. 4-4-0 (American) locomotives were preferred in India as they had good riding qualities, even on poor track conditions.^{[citation needed]} The SP class used the same boiler as the SG class standard goods locomotives, which had a diameter of 4 feet 8+1⁄4 inches (1,429 mm). In the 1910 BESA report, a variant with a larger boiler was developed, which had a diameter of 5 feet 1+1⁄4 inches (1,556 mm), as used in the PT class passenger tank locomotives.^[2]

The locomotives were delivered to different railways, but only the Indian States Railways (ISR)-operated railways referred to them as the SP class. Beyer Peacock delivered 10 locomotives to the North Western Railway (NWR), which operated lines around the modern-day border of India and Pakistan.^[3]

The locomotives were designed with two cylinders, a Belpaire firebox, and used saturated steam. The grate was arranged between two driving wheels. Between the frames were the two cylinders and the Walschaerts valve gear. A small pilot was fitted to the locomotive's buffer beam. The cab was completely enclosed, with the cab's rear wall being formed by the tender.

A later version was designed with a superheater and designated SPS (Standard Passenger, Superheated); SP locomotives retro-fitted with superheaters were usually reclassified as SPC (Standard Passenger, Converted).

An SPS locomotive, most recently operated by Pakistan Railways under road number 3157, is preserved in the Museum of Science and Industry (MOSI) in Manchester. The exterior of the locomotive is practically identical to that of the SP class.

• Indian Railways
• Rail transport in India#History
• Locomotives of India
• Rail transport in India

• Hughes, Hugh (1990). Indian Locomotives: Part 1 – Broad Gauge 1851–1940. Harrow, Middlesex: The Continental Railway Circle. ISBN 0-9503469-8-5. OCLC 21871114.