Storkwerkspoor Diesel

Formed in 1954 by the merger of Stork and Werkspoor, along with other interests in the Dutch enginebuilding industry, Stork-Werkspoor Diesel (SWD) was acquired in 1989 by the Finland-based multi-national

Wartsila Diesel group, now the Wartsila Corporation. SWD's own-design medium speed engines were gradually phased out of the production programme and replaced by the Wartsila 26 and 38 series (Chapter 27), largely designed by SWD staff and subsequently manufactured in Zwolle, The Netherlands. These models were later assigned for production by Wartsila Italia in Trieste.

Not long after its formation SWD decided to develop a high powered medium speed engine to contest diverse coastal and deepsea propulsion arenas, the resulting TM410 series appearing on the market in the later 1960s. The 410 mm bore/470 mm stroke design (Figure 28.20) was uprated a number of times in its career to a level of 564 kW/ cylinder at 600 rev/min, the series embracing six, eight and nine inline and V12-, 16-, 18- and 20-cylinder versions.

A scaled-up version—the TM620 series—was introduced in the mid-1970s to complement the TM410, the 620 mm bore/660 mm stroke design enjoying a status for many years as the world's largest and most powerful medium speed engine (Figure 28.21). Examples of both types—in in-line and V-cylinder form—remain at sea (Figure 28.22).

The bedplate of the TM410 engine is a U-shaped iron casting in which the main bearing caps are fitted with a serrated joint to form, with the bearing saddles, a rigid housing for the thin-wall steel main bearing shells. For the TM620 engine what is in effect a single tooth serration is used for the main bearing cap joint: the joint faces are inclined towards the abutment.

Bearing shells have copper-lead lining and lead-tin plating. Both upper and lower shells can be removed easily by lifting the bearing cap. Large inspection openings in the bedplate facilitate access to the crankcase, the covers being provided with relief valves. Integrally cast columns in the in-line engine bedplate accommodate alloy steel tierods to connect bedplate and cylinder block tightly together in a rigid construction preventing high tensile stresses from cylinder pressures being transmitted to these major cast iron elements. V-type engines are fitted with two rows of tie-rods. As the rods are in an oblique position, a number of short bolts are additionally fitted to prevent relative movement of cylinder block and bedplate. A thick upper bridge between pairs of cylinders on opposite V-banks also contributes to rigidity.

The crankshaft is a fully machined high tensile continuous grain flow forging in one piece. The large diameter journals and crankpins are provided with obliquely drilled holes for the transmission of lubricating and piston cooling oil. Counterweights fitted on all crankwebs are secured by two hydraulically stressed studs and two keys.

Cross Section Small Diesel Engine
Figure 28.20 Cross-section of in-line SWD TM410 engine

Figure 28.21 Cross-section of in-line SWD TM620 engine

A rigid iron casting cylinder block incorporates the cooling water jackets and the camshaft space. Covers are arranged on the camshaft side of the block to allow inspection of the cams and rollers. Three roller levers are fitted per TM410 engine cylinder: one each for the inlet and exhaust cams, and one for the fuel pump drive. Only two levers per cylinder—for the valves—are arranged on the TM620 engine. The pushrod passages are equipped with seals to prevent any oil leakage from entering the camshaft space.

The camshaft is ground to a single diameter over its entire length, with the hardened steel cams hydraulically shrunk on with the aid of tapered bushes. When necessary, the complete camshaft can be removed sideways; and cams can be exchanged without removing the camshaft from the engine since they can be removed from the shaft at the forward end of the section. The camshaft is driven from the crankshaft by nodular cast iron gearwheels and runs in thin-wall bearings. The direct-reversible engine is provided with double cams with oblique transition faces and a pneumatically controlled hydraulic reversing gear to move the camshaft in an axial direction.

An extremely heavy big end is a feature of the connecting rod, forming a rigid housing for the copper-lead lined lead-tin plated thin-wall steel bearing shells. To allow the rod to be removed through the cylinder liner, the big end is split by serrated joints in two planes. The design fosters a low headroom and easy dismantling. The big end bolts are hydraulically stressed. The TM620 engine connecting rod is similar in principle to that of the TM410 component but uses three pairs of studs, each set normal to the face of the joint it closes rather than bolts at right angles to the axis of the rod.

Lower rated TM410 engines were specified with a light alloy piston with a cast-in top ring carrier and a cast-in cooling oil tube; the higher rated models and the TM620 engine exploited a two-piece piston. Both feature one chrome-plated top ring, three compression rings with bronze insert and an oil control ring above the gudgeon. The TM410 engine additionally uses a second oil control ring at the base of the skirt when the single-piece piston is fitted.

The gudgeon pin is fully floating and the small end bearings have different widths in order to provide a greater area to withstand better the combustion loads. The small end bearing material is of the same specification as the large end. The small end and piston cooling oil supply passes through drillings in the connecting rod; the spent oil from the pistons and gudgeon pins is expelled from the piston. In the case of the one-piece piston, however, cooling oil passes through a separate drilling to the bottom of the big end. Both engines deploy restrictors in the big end oil passages incorporating non-return valves. Despite the three-part large end configuration, both engines use horizontally split two-part big end shells. The V-engine big ends run side-by-side on the crankpin.

The special cast iron cylinder liner is provided with cooling water passages drilled to a hyperboloid pattern in its thick upper rim. This feature was designed to secure intense cooling of the upper liner part and also to ensure, by equalizing the temperatures of the connected liner rim and the cylinder block, a perfectly circular liner when the engine is operating.

Two holes for cylinder lubrication are drilled in each liner from the bottom, thus avoiding oil pipes through the cooling water spaces. Each hole feeds one lubricating oil quill arranged halfway along the liner length. A normal Assa cylinder lubricator is provided. There are four holes per cylinder in the case of the TM620 engine.

Both engine types are equipped with four-valve cylinder heads with an unusual two-bearing exhaust rocker design. In the case of the

TM620 the inlet valve is shorter than the exhaust valve and two fulcrum shafts are used with different lengths of Y-shaped rockers to operate each pair of valves.

Cooling water is directed over the flameplate of the head by the intermediate deck which also serves the function of a strength member so that the flameplate itself can be thinner and thus better able to withstand thermal load. The exhaust valves work in water-cooled cages and are Stellited on the seating face. Careful cooling of the seat area, and hence of the sealing face, reportedly gave the valves a lifetime between overhauls when burning heavy fuels not greatly inferior to that experienced by valves in marine diesel-burning engines. The inlet valves seat on hardened cast iron inserts mounted directly in the cylinder head.

Cam profiles were designed to avoid rapid acceleration changes and thus to minimize noise and dynamic stresses. The valve rockers are fitted with needle bearings that require no oil supply; all other contact faces within the cylinder head covers are lubricated by separate impulse oiling equipment. The associated lubricator is driven, in parallel with the cylinder lubricator, from the camshaft gear. The oil used for these purposes is drained separately to prevent contamination of the crankcase oil should a fuel leak occur.

A dedicated fuel injection pump serves each cylinder. The injector is equipped with an easily replaceable nozzle which is water cooled to prevent carbon deposits forming when handling residual fuels. The TM410 fuel pump is actuated by a spring-loaded pushrod which itself follows a lever-type cam follower similar to those that actuate the valve pushrods. On the TM620 engine the pump has an integral roller.

The mechanism for the starting air pilot valves is also used to stop the engine at overspeed. In such an event the mechanical overspeed trip actuates a pneumatic valve to allow air pressure into an auxiliary cylinder which then keeps every fuel injection pump plunger lifted with the roller free of the cam (Figure 28.23). Safety devices for low lubricating oil pressure and for low cooling water flow are integrated in the engine systems and are thus independent of the external electrical alarm system.

A more modern smaller bore design, the SW 280 engine, was introduced by SWD in 1981 to fill a gap between the TM410 and the SW 240 models and remained in the Stork-Wartsila Diesel production programme until 1997 when the Wartsila 26 series was launched (see Chapter 27). The 280 mm bore/300 mm stroke design (Figure 28.24) developed 300 kW/cylinder at 720-1000 rev/min and found favour as a genset drive in deepsea tonnage as well as a propulsion unit for smaller ships. It was available in six, eight and nine in-line and

Figure 28.23 Fuel pump drive and cutout on SWD TM410 engine

V12-, 16- and 18-cylinder versions to cover power demands up to 5400 kW.

A short and compact engine was sought by the Dutch designers, with power available from both ends of the crankshaft. Engine-driven pumps could be installed on a sideways-mounted gearcase. The design allowed for combustion pressures up to 150 bar and associated high fuel injection pressures. Well-controlled wall temperatures in the combustion space addressed heavy fuel operation.

A reduced number of overall components was achieved by replacing most pipes for water and oil passage with drillings through the structure. This, and other measures, lowered the risk of fluid leakages and eased maintenance procedures. A rigid design was secured by incorporating the air duct, water and lubricating oil galleries in the cylinder block casting.

The cylinder liner features a high collar and drilled cooling channels. The piston comprises a pressed aluminium alloy body and a forged steel crown which is cooled by lubricating oil and provided with hardened ring grooves. The cylinder head is relatively high and very rigid, its stiffness largely achieved by a special shaped intermediate deck. The head incorporates four valves whose seats are detachable; the exhaust valve seats are water cooled.

A separate lubricating system serves the fuel pumps to prevent contamination of the main system oil. Pulse turbocharging was specified to secure the maximum air supply over all loads. The scavenge air is heated for starting and low-load operations on heavy fuel.

Raining All Over The World
Figure 28.24 Stork-Werkspoor Diesel SW 280 design
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  • valerio
    Why obliquely drilled jacket cooling water bores?
    3 years ago

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