I was sent a question the other day, and I did not know the answer, so I forwarded it to Mark Keneford, General Manager for Wartsila, in Montreal, and his excellent reply might interest some of you.
What does the RTA, RND and RT designations on large two stroke engines refer to ?
No direct expansion of these acronyms but they refer to 2 stroke engines as follows:
- Wartsila RTA-series engines are traditional low-speed diesel engines with mechanically-driven camshaft, double-valve controlled fuel injection pumps, exhaust valve actuator pumps and reversing servomotors.
- Wärtsilä RT-flex engines are based on the RTA-series but have electronically-controlled common-rail systems for fuel injection and valve actuation.
The letter 'R' in the engine designations goes back to the Sulzer RSD two-stroke low-speed engine types introduced in 1950. The letter 'R' stood for 'Revidierter', so the RSD types were 'revised' versions of the SD engine types that had been developed since 1930. Built in two bore sizes, 58 and 76cm, the RSD engines were the first two-stroke low-speed engines designed and built by Sulzer that had fully welded structures (columns and bedplates). Turbocharged versions followed in 1956 with the RSAD engine types.
The letter 'R' was then retained over the following years in the RD, RND, RND..M, RLA, RLB, RTA and RT-flex engine types. Yet after the RSD and RSAD designations, the letter lost any connotation of 'revised'. It was simply kept as an easily-recognised identifier for Sulzer low-speed engines. When electronically-controlled common-rail systems were applied in 1998, the designation RTA was adapted to RT-flex to emphasise the key feature of flexibility given by the new technology.'