what does it mean by saying sulzer RND 68 ?

When looking at Sulzer engine’s specifications, there is always some ambiguity. MAN B&W is very clear with its specifications, however Sulzer never gave one. That doesn’t mean MAN B&W is better than Sulzer engines.

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 number given after RND specifies the cy;inder bore. So RND 68 means 68 cm cylinder bore.

You can see the parameters of the engine , mayb asked by the survoyers, in the table given in the end. 

Year	Type of Engine	Cylinder diameter in cm

1967 – 1981

RN (RND, RNF, RNMD)

68,76,90,105

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.’

Parameters for the engines are 

Parameters	RD	RND	RTA	RT-FLEX
Turbocharger	Pulse (No auxiliary Blower)	Constant Pressure	Constant Pressure	Constant Pressure
Scavenging	Loop	Loop and Under piston space	Uni flow	Uni flow
Exhaust valve	Rotary flap valve	Exhaust ports	Hydraulic operated	Hydraulic operated
Stroke Bore Ratio	1.7	1.7	3 to 4.2
Piston	Convex shape	Convex shape	Concave shape	Concave shape
Piston cooling	Water	Water	Oil	Oil
Fuel pump	Suction valve control, no spill valve	Suction valve and spill valve	Suction valve, spill valve and VIT	Common rail system (jerk type)
Drive	Chain	Gear	Gear	Gear
Cylinder Lubrication	Mechanical drive	Mechanical drive	Load dependent, Electric motor driven
Cylinder quills	Quills at upper part	Quills only at upper part	Quills at two level
Cross head bearing	Two piece type	Two piece type	Continues bottom half type	Continues bottom half type
Piston skirt	short	Long	Short	Short
SFOC	208 g/bhp/hr	203 – 208	115	118
MEP	8.6	10.6 – 12.3	17	19.5
Peak Pressure	76 bar	84 – 94 bar	140 bar	150 bar
Power/ cycle	1700 KW	2100 – 2500 KW	3700 KW	2100 – 5720 KW
Piston Speed	6.1 m/s	6.3	8	8 – 8.5