ML20043F654

From kanterella
Jump to navigation Jump to search
Training Material for E-111 Emergency Diesel Generator Course, Chapter 3 (3-16), Diesel Engine Construction
ML20043F654
Person / Time
Issue date: 02/12/2020
From:
Office of the Chief Human Capital Officer, Woodard Corp
To:
Gary Callaway
Shared Package
ML20043F634 List:
References
Download: ML20043F654 (84)
v • d • e


Text

Emergency Diesel Generator Diesel Engine Construction 3.0 DIESEL ENGINE CONSTRUCTION properly oriented with respect to each other.

This chapter presents the basic principles of 3.1.1.1 Cylinder Forces (Figure 3-1) - The design and construction methods used to gas pressure created in the cylinder acts to counteract the unbalanced forces created force the piston, and therefore the within the engine, in order to produce crankshaft, away from the cylinder head. As uniform output shaft horsepower and the piston moves away from TDC or BDC, minimize engine vibration. the angularity of the connecting rod generates a lateral force pushing the Learning Objectives crankshaft sideways while thrusting the piston against the wall of the cylinder. The As a result of this lesson, you will be able to: magnitude of these lateral forces varies with the angle of the connecting rod and the

1. Describe the basic construction and pressure of the gas against the piston.

identify the loads imposed on the structural components of a diesel Figure 3-1A shows the magnitude of the engine. vertical and lateral forces in the engine as a result of the pressure acting on the piston,

2. Describe the basic construction and superimposed on the PV diagram shown in function of major rotating and Chapter 2. This is the case of the 8-1/8 OP reciprocating components of a diesel lower piston with similar forces imposed by engine. the upper piston. Note the magnitude of these forces (the vertical up to about 63
3. Describe the basic construction and thousand pounds). The lateral forces are state the function of the cylinder head, small in comparison.

valves, and related components of a diesel engine. The frame or block assembly provides sufficient rigidity to maintain the alignment of

4. Describe the basic construction and the the cylinder to the crankshaft and absorb the purpose of camshafts, cam followers, lateral or sideways forces of the piston and valve operating mechanisms. against the cylinder wall.

3.1 Structural Components 3.1.1.2 Crankshaft Rotation - The power developed by the engine creates a rotating 3.1.1 Structural Loading force or torque output from the crankshaft to the generator rotor. In turn, there is an The engine frame or block assembly forms opposite and equal reactionary force the main structural component of the between the generator and the engine frame engine. During engine operation, it is or block assembly. Therefore, the generator subjected to a complex set of forces. The must be structurally connected to the engine design and construction of the frame or to prevent any relative motion between the block assembly must withstand these forces generator and engine. This can be while keeping the operational components accomplished in one of three ways:

Rev 3/16 3-1 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction The first is to directly mount the generator to design, the crankshaft is supported below the engine frame or block assembly, so they the cylinders by a set of main bearings.

are effectively a single piece of equipment. Internal passages for oil and water are This keeps the reactionary forces within the incorporated in the block.

engine itself.

3.1.2.2 Multi-piece Design (Figure 3-2) -

A second approach involves mounting the With the multi-piece design, the crankshaft engine and the generator on a common is supported in the engine base, which also structural steel frame or base assembly. serves to mount the engine to its basemat.

The rigidity of the frame compensates for the reactionary forces between the engine The engine frame, sometimes called a and generator. The complete assembly is "doghouse", mounts to the engine base and then mounted to the building. With the surrounds the crankshaft. It also provides accessories also attached to the steel base, for mounting of the cylinder blocks.

a somewhat "packaged" configuration is created. The cylinder block or blocks for V-type engines mount to the engine frame and The third method, applied at a generic plant, provides for locating and supporting the involves mounting the engine assembly and cylinder assemblies. These blocks may be generator to a reinforced concrete in groups or banks, or they may be individual basemat that is part of the diesel generator components for each cylinder. Coolant building structure. The mounting scheme is passages are provided as well as provisions Seismic Category I in accordance with NRC for mounting the cylinder heads.

Regulatory Guide 1.29, "Seismic Design Classification." The Category I design 3.1.2.3 Block Construction - Small provides protection from the effects of engines and some medium-sized engines tornados, missile hazards and floods. The use single piece alloy iron castings to form mounting scheme is constructed to their engine block. Alloy castings may also withstand a safe shutdown earthquake be used for the components of the multi-(SSE). piece design.

3.1.2 Engine Block Medium size engines and some larger engines use steel plates welded to specially The engine block or block assembly can be forged sub- components. The welded plate manufactured as either a single piece or design offers good structural rigidity making from several individual components secured it ideal for marine and locomotive by bolts, studs or other such fasteners. applications, as both applications involve a base structure that bends and twists.

3.1.2.1 Single Piece Design - The single piece engine block is manufactured as Typical cylinder blocks for the 12-cylinder either a single casting as in the automotive FM OP and 16-cylinder FM PC engines type engines or as a weldment of steel plate used in EDG service are shown in Figures and forged sub-components. With this 3-3 and 3-4 respectively.

Rev 3/16 3-2 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction 3.1.3 Engine Cylinders On some engines, the water jacket is incorporated as an integral part of the liner.

The bore of each cylinder provides the The General Motors EMD Models 567, 645 enclosure which acts to guide the motion of & 710 2-stroke cycle diesels have the water the pistons. The wall of the cylinder works jacket cast as part of the liner. (Further, in conjunction with the piston rings and EMD engines are designed such that the engine lubricating oil to create a gas- tight cylinder liner, piston, rings, connecting rod, seal to prevent the loss of combustion cylinder head, valves, etc. are replaced pressure. together as a single Power Assembly unit.)

Most diesel engines use replaceable inserts On Fairbanks Morse OP engines a special or cylinder liners rather than boring the sleeve, shrink fitted to the outside of the cylinders directly into the block. In this way, liner, is used to create the water jacket.

the liners may be replaced on an individual Integral type liners offer the same direct heat basis rather than replacing the entire transfer as the wet type liners.

cylinder block.

3.2 Engine Bearings 3.1.3.1 Dry Type Liners (Figure 3-5) - Dry type cylinder liners have a precision ground Engine operation involves relative motion of outside diameter which is fitted into a a vast number of individual components.

machined bore in the cylinder block. Heat Where there is motion and where loads or transfer from combustion is through the forces are being transmitted, some form of cylinder liner with metal-to-metal contact bearing is normally employed.

between the liner and the block and through the cylinder block to the engine coolant. 3.2.1 Journal Bearings Engine coolant does not come into direct contact with the liner. Journal bearings are plain cylindrical-shaped devices which must support the 3.1.3.2 Wet Type Liners (Figure 3-6) - loads and forces imposed on them while With wet type liners, the coolant comes into allowing free movement. Journal bearings direct contact with the outer surface of the must also provide for lubrication of the cylinder liner. This allows for better heat bearing and shaft. Bearing lube is covered transfer than is available with dry type liners in Chapter 5, "Engine Lubrication System.

by conducting heat directly through the liner wall to the engine coolant. The engine main and connecting rod bearings as well as camshaft bearings and Sealing is accomplished at the top of the rocker arm bushings are replaceable, liner by the cylinder head gasket and the fit precision insert journal type bearings. The of the liner into the block. Rubber O-rings or main and connecting rod bearings are split seal rings prevent coolant leakage at the to allow them to be placed around the bottom of the liner. crankshaft journals. OP engine main bearings are illustrated in Figure 3-8, and 3.1.3.3 Integral Type Liners (Figure 3-7) OP crankshafts in Figure 3-24.

Rev 3/16 3-3 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction 3.2.2 Rolling Element Bearings connecting studs, castle nuts and roll pins.

The belville spring pack compensates for With rolling element bearings, a spherical or thermal expansion between the skirt and cylindrical device is placed between the two crown. Seal rings prevent lubrication oil surfaces. As one surface moves, the inside the piston from reaching the element must roll reducing friction and wear. combustion space.

Rolling element bearings can be found in 3.3.1.2 Floating Skirt Pistons -- A various engine components such as the variation in piston design is the floating skirt jacket water pump, lube oil pump, cam piston shown in Figure 3-11. This type followers and governor drive mechanism. piston is commonly used on 2-stroke cycle engines. The crown and skirt are a single 3.3 Rotating and Reciprocating piece supported by the piston carrier. The Components piston carrier is secured to the skirt by either a lock ring (as shown) or by bolts or studs.

Figure 3-9 shows a view of an OP piston with its connecting rod and other associated Combustion forces are transmitted from the parts that make up the reciprocating piston crown through the thrust washer to components of the power assemblies. the piston carrier, which is linked to the connecting rod by the piston pin.

3.3.1 Pistons 3.3.1.3 Piston Materials -- Pistons must Engine pistons form the lower closure of the be relatively light weight to reduce the cylinder while transmitting the forces of inertial forces acting on the connecting rod combustion to the connecting rod and and crank-shaft, while being strong enough crankshaft. These components are to transmit the forces of combustion.

exposed to temperatures of 3500- 4500oF.

Cast or forged alloy iron and steel are 3.3.1.1 Trunk Type Pistons -- The frequently used for pistons on medium and common type of piston used is the trunk type large diesel engines. These pistons are shown in Figure 3-10. The upper portion or usually multi-piece design as shown in crown absorbs the forces created by Figures 3-10 and 3-11.

combustion and transmits them to the connecting rod through the piston pin boss 3.3.2 Piston Rings and piston pin (see section 3.3.3). The lower portion of the piston or skirt acts to Piston rings may be classified as either guide the movement of the piston in the compression rings or oil control rings.

cylinder while transmitting the side thrust, Compression rings act to seal against the created by connecting rod angularity, to the high pressure combustion gases while wall of the cylinder liner. transmitting heat from the piston to the cylinder wall. Oil control rings prevent For the piston shown in Figure 3-10, the excess lubricating oil from reaching the crown is attached to the skirt with four combustion chamber.

Rev 3/16 3-4 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction 3.3.2.1 Compression Ring Design 3.3.2.3 Compression Ring Material (Figure 3-12) The compression rings are Compression rings are generally made from circular with an uncompressed outer a high quality cast iron or iron alloy. Some diameter slightly larger than the bore of the use a surface treatment such as chromium cylinder and with an inner diameter smaller or molybdenum on the ring face to improve than the piston diameter. An end gap in the ring performance and longevity.

piston ring allows the ring to be expanded to fit over the piston into the ring grooves. The 3.3.2.4 Oil Control Ring Design (Figure 3-end gap also compensates for thermal 16) Oil control rings must prevent excess oil expansion and allows the ring to conform to from reaching the combustion chamber, out-of-round or tapered conditions while still leaving a sufficient film of oil to associated with worn cylinder liners. lubricate and seal the compression rings.

3.3.2.2 Compression Ring Sealing Like compression rings, the oil control rings (Figure 3-13) During operation, combustion are circular with an uncompressed diameter gases pass downward between the piston slightly larger than the cylinder bore. A ring crown and cylinder wall to the compression gap is provided for thermal expansion and to rings as shown. Gas pressure acting on top allow the ring to conform to the liner.

of the ring causes it to seal against the bottom of the ring groove while the pressure The narrow contact face of the ring reduces acting on the back of the ring helps to seal the ring to cylinder wall contact area, against the cylinder wall. The ring end gap, creating a large compressive force between while allowing for thermal expansion of the the ring and the cylinder wall. The ring, acts as a restricting orifice which downward taper of the ring scrapes oil from reduces the pressure acting on each the cylinder wall on the downward stroke subsequent ring by a factor of approximately while spreading a thin film of oil on the 50 percent. upward stroke.

The ring cross-section (See Figure 3-14) is Linear drain slots in the oil control rings generally rectangular with the face being direct oil scraped from the cylinder wall either square, tapered, or barrel shaped. toward the piston skirt where holes or slots Some rings are wedge or "keystone" shaped in the skirt allow oil to return to the which helps prevent the ring from sticking in crankcase by gravity. Several versions of oil the piston. control rings are shown in Figure 3-17.

Various ring joints are used as shown in Compression rings are located in grooves Figure 3-15. The square cut, or butt joint, near the top of the piston (Figure 3-18). The and the angle cut are the most common and uppermost ring is often referred to as the fire economical to produce. Step joints are ring. Location of the oil control rings varies sometimes used to improve piston ring between 2- and 4-stroke cycle engines. On sealing. Their more complex and costly 4-stroke cycle engines, the oil control rings design makes them less desirable for are located just below the compression rings installation on diesel engines. and above the piston pin bore.

Rev 3/16 3-5 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Because 2-stroke cycle engines require The piston pin is linked to the upper end of ports in the cylinder wall, the oil control rings the connecting rod either with a bushing or are positioned in grooves at the bottom of bearing or is bolted or clamped directly to the piston skirt. During operation, the oil the rod. The lower end of the connecting rod control rings do not pass over the liner ports. is split to allow it to be assembled around the If the oil control rings were positioned so crankshaft.

they passed over the cylinder ports, the rings would catch on the ports and break. 3.3.4.1 Conventional Rod (Figure 3-20) -

Even if the rings were designed to pass The crankshaft end of a conventional smoothly over the ports, lubricating oil would connecting rod is split perpendicular to the easily enter the engine air box. This would axis of the rod. High strength alloy bolts or cause excessive oil consumption, smoking, studs secure the cap to the rod. Dowel pins, and possible explosions or fire in the air box. sleeves, alignment pins, shoulders, or serrations are used to ensure alignment of 3.3.3 Piston Pins the cap to the rod.

The piston pins, sometimes called wrist 3.3.4.2 Angle Cut Rod (Figure 3-21) - To pins, transmit the forces acting on the piston pre- vent interference with other engine to the upper end of the connecting rod while components and make disassembly easier, allowing for relative motion (rocking) some engines split their connecting rods at between the two. an angle to the axis of the rod. The rod cap is aligned and secured to the rod in the same Cylindrical in shape with a hollow center, manner as the conventional rod.

piston pins are generally made from high grade alloy steel. The outer surface of the 3.3.4.3 Articulating Rod (Figure 3-22) -

pin is ground and polished. Piston pins are The articulating type connecting rod shown often heat treated or chrome plated to resist is used on the Cooper and Enterprise-wear, as they are highly stressed parts. DeLaval V-type engines to connect two pistons on opposite banks of cylinders to a Piston pins are retained in either the piston single crankpin without having to offset the or connecting rod by retaining rings, bolts, cylinders on one side from the other. (This clamps or special plugs which prevent axial design modestly reduces engine block and movement of the pin. The piston and crankshaft length, at the cost of some connecting rod assembly for the OP engine complexity and an additional highly stressed is shown on Figure 3-19. part.) The assembly consists of a link rod and master rod. The crankshaft end of the 3.3.4 Connecting Rods master rod is split vertically with a serrated joint to maintain alignment. When The connecting rod is the engine component assembled, the lower end of the master rod, which working with the crankshaft, converts including the connecting rod bearing, the reciprocating motion of the piston into surrounds the crankshaft crank pin. The link the rotary motion of the crankshaft needed rod connects to the master rod through a link to run the emergency generators. pin which is similar to a piston pin.

Rev 3/16 3-6 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction 3.3.4.4 Fork and Blade Rod (Figure 3-23) on most engines. From there, the oil is The fork and blade rod shown is used on the transmitted to the connecting rod journal General Motors EMD 567, 645 and 710 two- area via tubes or passages machined into stroke cycle diesel engines. The fork rod is the crank throws, as shown in Figure 3-25.

split using a basket assembly rather than a From there, it goes up drilled passages in bearing cap to secure the rod and the connection rods to the piston wrist pin connecting rod bearing to the crankshaft. area and on to the piston crown (in many The blade rod has a lower slipper foot which instances) for cooling of the underside of the rides on the outer surface of the upper piston crown. From the undercrown cocktail bearing shell. This upper surface of the shaker cavity, the oil drains through a hole bearing shell is coated with an appropriate and drops back into the crankcase.

bearing material and grooved for lubricating oil distribution to the slipper surface. 3.3.5.2 Crankshaft Materials - The crankshaft must be strong enough to resist 3.3.4.5 Connecting Rod Materials - the bending action caused by the downward Connecting rods are normally forged from forces of the connecting rod acting on the medium carbon or alloy iron and steel. They crankpins. It must also have enough rigidity are often heat treated and in some cases to withstand the twisting or torsional forces shot peened or stress relieved to improve which occur during engine operation.

ductility and fatigue resistance.

Crankshafts are generally forged from 3.3.5 Crankshaft carbon or alloy steel. They are heat treated to reduce internal stresses created by the The crankshaft accepts the forces acting forging process. Bearing surfaces are often along the axis of the connecting rods and heat treated to increase wear resistance.

converts them into the rotary motion needed for operation. It collects the power from all 3.3.6 Flywheel and Vibration Damper the cylinders and transmits it axially to the crankshaft hub and engine flywheel. The cyclical forces resulting from combustion and the inertial forces due to 3.3.5.1 Crankshaft Design (Figure 3-24) reciprocation, acting on the crankpins, The crankshaft consists of a number of main impart a twisting motion to the crankshaft.

journals and crankpins or rod journals. The This twisting motion combined with the crankpins are connected to the crankshaft natural torsional vibration of the crankshaft by webs. The main journals align with the creates rpm dependent stresses in the rotational axis of the shaft. The crankpins crankshaft. If allowed to go unchecked, are mounted offset to the axis of the these stresses could lead to fatigue and the crankshaft by a distance equal to one-half development of cracks in the crankshaft.

the piston stroke. The crankpins work in conjunction with the connecting rods to The engine flywheel and the vibration convert the linear motion of the piston into damper or harmonic balancer act in a rotary motion of the crankshaft. manner which helps to reduce or dissipate Lube oil is pumped into the main bearings the effects of torsional induced stresses.

Rev 3/16 3-7 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction 3.3.6.1 Flywheel (Figure 3-26) - The the internal spaces of the unit. The flywheel is a large, disk-like inertial mass lubricating oil acts as the elastic element or mounted to the rear or drive end of the viscous fluid between the intermediate ring crankshaft. It stores a portion of the rotating and spider. Oscillating motion of the two or kinetic energy of the engine. It dampens plates and the intermediate ring serves to torsional vibration by resisting the dampen the vibrations.

crankshaft's tendency to accelerate at each power impulse. Both the monofiler and bifiler type dampers (Figure 3-29) are selectively used on the Most engines used on EDGs in nuclear Fairbanks Morse OP engines. As the service do not have or need flywheels. The crankshaft rotates, the individual weights inertia of the generator rotor acts as the oscillate around their respective pins. This flywheel on these units. movement counteracts the torsional vibration in the crankshaft. Figure 3- 29 3.3.6.2 Vibration Damper - Vibration shows a bifiler damper, used on the lower dampers, which are usually mounted to the crankshaft of the 12-cylinder OP engine. A forward end of the crankshaft, function in a monifiler damper is similar but consists of manner similar to the flywheel to reduce only one row of weight assemblies. These torsional vibration. are used on the lower crankshafts of all other OP engines and on the upper There are many different designs of crankshaft of the 12-cylinder engine.

vibration dampers used on diesel engines.

Regardless of design, they all function by 3.4 Cylinder Heads linking an inertial mass to the crankshaft through a flexible or elastic mechanism. On all conventional engine designs, the cylinder head forms the upper closure of the As the crankshaft rotates, the inertia mass combustion chamber. It provides for shifts position in such a way as to counteract installation of valves (2- and 4-stroke cycle).

the acceleration and deceleration of the A port is provided for mounting of the torsional activity. injection nozzle or unit injector and possibly for the installation of a starting air check The spring pack damper is shown in Figure valve. Bolted to the cylinder liner or block, 3-27. The inertia mass is connected to the the cylinder head provides passages for the hub through a set of leaf type springs or flow of engine coolant.

spring packs. The spring packs deflect to allow the inertia mass to move back and 3.4.1 Cylinder Head Construction forth to dampen the vibration.

Cylinder heads (Figure 3-30) are castings of A gear type damper is shown in Figure 3-28. either alloy iron or steel. They may be con-The spider is bolted to the crankshaft. The figured so that each cylinder is provided with inertia mass consists of the front plate, rear a cylinder head (large engines) or so that plate, and intermediate ring. When one head fits several cylinders or an entire assembled, engine lubricating oil is fed to bank.

Rev 3/16 3-8 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction The flat surface or fire deck of the head head or installed as replaceable inserts.

forms the upper closure of the combustion Replaceable valve guides are either bolted space. Seating surfaces are provided in the to or pressed into the head (interference fit).

fire deck for intake and exhaust valves. A gasket surface around the circumference of 3.4.4 Valve Springs and Retainers the fire deck allows for sealing the head to (Figure 3-32) the liner or block.

Valves are held in the closed position by coil 3.4.2 Valves and Valve Seats (Figure 3-31) springs which surround the valve stem and guide. A spring retainer and a pair of Intake and exhaust valves are mounted in keepers or locks transmit the spring force to the cylinder head to allow the flow of air and the valve stem. Some installations include spent gas into and out of the cylinder. When devices which cause the valve to rotate closed, the valve seals against a machined slightly each time the valve is lifted from its valve seat in the fire deck. seat. This movement helps keep the seating surfaces free of deposits and Valve seats may be of the full contact or substantially increases the life of the valve.

interference type (Figure 3-31). With the full contact valve seat, the angle on the face of Engines which use valve rotators must use the valve is exactly the same as that of the full contact valve seats. Use of valve valve seat. With the interference type, the rotators with interference valve seats will valve seat and valve face angle differ by cause improper seating and premature one-half to one and one-half degrees. The valve failure.

angles are such that a line contact is created near the outermost part of the valve face. 3.5 Camshafts and Valve Mechanisms Full contact seats provide the best cooling Engine camshafts function to open intake for the valve while the interference seat and exhaust valves, operate fuel injection offers faster initial seating and has less pumps and in some cases operate starting tendency for carbon deposits to build up. air check valves.

The intake valves (4-stroke cycle) and exhaust valve seats may be machined 3.5.1 Cams (Figure 3-33) directly into the fire deck or installed as separate valve seat inserts. Cams are irregularly shaped circles or ovals which convert the rotating motion of the 3.4.3 Valve Guides (Figure 3-32) camshaft into the linear motion needed to operate valves and injectors. The specific Valve guides are precision passages in the shape of the cam lobe determines the cylinder head in line with the axis of the amount, and duration of, lift for the cam-valve seat. Their purposes is to keep the operated component. Intake and exhaust valve aligned as it opens and closes. valve cam lobes tend have an oval or eccentric shape, while lobes that operate Valve guides may be bored directly into the fuel injection pumps are more circular.

Rev 3/16 3-9 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction 3.5.2 Cam Followers (Figure 3-34) This positive relationship between the crankshaft(s) and camshafts is maintained Cam followers, which mount in or are through the use of gears (Figure 3-35) or connected to the cylinder block, track the chains, with gears being the most common.

contour of the cam along a linear path and transmit this motion to the push rods or Figure 3-36 shows the timing chain drive rocker arms. The three types of cam used on the Fairbanks Morse opposed followers shown in Figure 3-34 are piston engines.

commonly used on diesel engines.

3.5.4 Rocker Arms and Pushrods The flat tappet cam follower is the most (Figure 3-37) economical to produce but also exhibits the greatest rate of wear. As such, flat tappet The location of the camshaft relative to the followers are generally limited to smaller valves is often less than optimum.

diesel engines. Frequently, the camshaft is mounted in the cylinder block or engine frame below the The roller tappet is the most common type cylinder heads. Rocker arms and pushrods for medium and large size diesel engines. are used to transmit the motion of the cam The roller rides on a needle or sleeve type followers to the intake or exhaust valves.

bearing. The rolling contact of the roller on the cam lobe produces the least amount of Pushrods are tubular steel components friction and wear. For both the flat tappet which transmit motion of the cam followers and roller tappet followers, a precision bore to the appropriate end of the rocker arm.

must be provided in the cylinder block to Rocker arms are lever type devices which control the linear motion of the follower. pivot on a fixed axis to change the direction and control the motion of the valve-The hinged follower is a variation of the roller operating bridge. The valve-operating tappet follower. The roller contacts the cam bridge is used to operate two intake or two lobe as before while the hinged arm controls exhaust valves from one rocker arm the motion of the follower limiting it to a shallow arc. .

3.5.3 Camshaft Drive Mechanism (Figures 3-35 and 3-36)

The camshaft must maintain a positive relationship with the crankshaft. On 4-stroke cycle engines, the camshaft rotates once for every two rotations of the crankshaft. On 2-stroke cycle engines, the camshaft and crankshaft operate at the same speed, such that all cylinders produce power during a single engine revolution.

Rev 3/16 3-10 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-1 Cylinder Forces Rev 3/16 3-11 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction 66K 60K VERTICAL FORCES CYLINDER FORCES - POUNDS X 1000 54K 48K 42K 36K 30K 24K 18K 12K HORRIZONTAL FORCE Figure 3-1A Vertical & Lateral Forces during Power Stroke Superimposed on Pressure vs Crank Angle Diagram Rev 3/16 3-12 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-2 Multi-Piece Construction Rev 3/16 3-13 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-3 12-Cylinder OP Engine Cylinder Block Rev 3/16 3-14 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-4 16-Cylinder PC Engine Cylinder Block Rev 3/16 3-15 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-5 Dry Type Cylinder Liner Rev 3/16 3-16 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-6 Wet Type Cylinder Liner Rev 3/16 3-17 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-7 Integral Type Cylinder Liner Rev 3/16 3-18 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-8 OP Engine Main Bearings Rev 3/16 3-19 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-9 OP Piston and Con-Rod Assembly Rev 3/16 3-20 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-10 Trunk Type Piston Rev 3/16 3-21 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-11 Floating Skirt Piston Rev 3/16 3-22 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-12 Piston Ring Nomenclature Rev 3/16 3-23 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-13 Piston Ring Sealing (Compression Rings)

Rev 3/16 3-24 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-14 Compression Ring Designs Rev 3/16 3-25 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-15 Piston Ring Joint Design Rev 3/16 3-26 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-16 Oil Control Ring Rev 3/16 3-27 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-17 Oil Control Ring Designs Rev 3/16 3-28 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-18 Piston Ring Placement Rev 3/16 3-29 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-19 Two-piece Crown Piston with Connecting Rod & Wrist Pin Assembly Rev 3/16 3-30 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-21 Angle-Cut Connecting Rod Figure 3-20 Conventional Connecting Rod Rev 3/16 3-31 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-22 Articulating Connecting Rod Assembly Rev 3/16 3-32 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-23 Fork and Blade Connecting Rod Design - EMD Rev 3/16 3-33 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-24 OP Engine Crankshaft Rev 3/16 3-34 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-25 Engine Crankshaft Oil Passages Rev 3/16 3-35 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-26 Engine Flywheel Rev 3/16 3-36 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-27 Spring Type vibration Damper Rev 3/16 3-37 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-28 Gear Type viscous Damper Rev 3/16 3-38 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-29 Bifiler Type vibration Damper Rev 3/16 3-39 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-30 Cylinder Head Assembly Rev 3/16 3-40 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-32 Valve Seat Assembly Figure 3-31 Valve Seat Angles Rev 3/16 3-41 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-33 Camshaft Lobes Rev 3/16 3-42 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-34 Cam Followers Rev 3/16 3-43 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-35 Gear Type Camshaft Drive Mechanism Rev 3/16 3-44 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-36 Chain Type Camshaft Drive Mechanism - OP Rev 3/16 3-45 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-37 Rocker Arms and Pushrods Rev 3/16 3-46 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-38 Pendulum Torsional Damper Rev 3/16 3-47 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-39 Monofilar Type Torsional Damper Rev 3/16 3-48 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-40 Crankshaft Strain Gauge Readings Rev 3/16 3-49 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-41 Crankshaft Strain Readings Rev 3/16 3-50 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-42 Pielstick Engine Cross Section Rev 3/16 3-51 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-43 Cylinder Head with Rocker Arm Assembly Rev 3/16 3-52 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-44 Rocker Arm Assembly Rev 3/16 3-53 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-45 Sequence and Timing Events Rev 3/16 3-54 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-46 Standard Main Bearing Rev 3/16 3-55 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-47 Lube Oil Distribution - Bearings, Rocker Arm, Piston Cooling Rev 3/16 3-56 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-48 Timing Gear and Auxiliary Drives Rev 3/16 3-57 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-49 Camshaft Bearing Lubrication Rev 3/16 3-58 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-50 Fuel Injection Pump Rev 3/16 3-59 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-51 Flexible Drive Gear Rev 3/16 3-60 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-52 Overspeed Governor and Trip Mechanism Rev 3/16 3-61 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-53 Manual Barring Device Rev 3/16 3-62 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-54 Crank-Lead Timing Viewed from Drive End Rev 3/16 3-63 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-55 Crank-Lead Timing Rev 3/16 3-64 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-56 OP Engine Drive Gears and Timing Chain Rev 3/16 3-65 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-57 Flywheel Coupling Readings Rev 3/16 3-66 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-58 OP Engine Fuel injection Pump Rev 3/16 3-67 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-59 Depth Micrometer for Determining High Point of Cam Rev 3/16 3-68 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-60 Fuel Control Linkage Adjustments Rev 3/16 3-69 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction HANDS-ON SESSION 3A it under stresses that over time, could cause the crankshaft to fail. To eliminate or 3A.0 CRANKSHAFT(S): VIBRATION attenuate this, torsional dampers are added DAMPER, BEARINGS, END to the front end of the crankshaft. There is FLOAT, AND WEB DEFLECTION usually no need to add mass to the drive end of the crankshaft as the generator or Purpose connected load usually adds a great deal of mass to that end of the system.

The purpose of this session is to complement Chapter 3 by providing hands- The torsional vibration damper could be on instruction supplement for better thought of as a soft flywheel. The damper understanding. normally consists of a mass that is connected to a drive hub by springs, or Learning Objectives rubber or viscous fluid or some other pliable element. As the engine accelerates Upon completion of this lesson you will be (torsionally), the mass tends to lag the able to understand: engine, and thus tends to cause the engine to slow down (not accelerate so rapidly).

1. Where the crankshaft is located and how When the engine slows (between torque it is supported in the engine on its pulses), the mass tends to continue at its bearings and their support structures. average speed and puts energy back into the crank in trying to keep it from slowing.
2. Functions of engine bearings including their assembly, disassembly, and The engine tends to accelerate in the basis measurements.

of once per revolution (called the first order),

but since it has a multiple number of

3. Crankshaft loading, motion, and proper alignment. cylinders, it also has a frequency that is related to the number of cylinders and
4. Torsional vibration and how vibration orders of frequency related to the primary dampers work. (first order) and multiple of that. Therefore, the torsional vibration damper assembly 3A.1 Vibration Damper needs to be able to take care of the primary (first order) frequency as well as multiple As each cylinder of the engine fires it orders of the primary frequency. (Usually creates a pulse on the crankshaft. This odd orders are of most interest: 3rd, 5th, etc.)

pulse of torque causes the crankshaft to want to accelerate. In between these There are a number of examples of torsional pulses, the crankshaft tends to decelerate vibration dampers available in the work as a result of the load from the generator (or area. The instructor will point these out to whatever else the engine may be driving). the students. This exercise will involve These torque pulses result in a torsional primarily the damper system used on the vibration within the engine. This tends to Fairbanks Morse Opposed Piston engines.

twist and untwist the crankshaft, which puts Rev 3/16 3-70 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction There are basically three types of dampers. Disassemble the damper by removing the On older engines, the pie damper was lock wire and the bolts that hold the cover used, as shown in Figure 3-38. This damper plates in place. Remove the cover plates on was used on the lower crankshafts of the one side. This gives access to the pins.

earlier 4- through 10-cylinder engines. On When the pins are removed, the weights the newer engines, the monofiler damper is may then be removed radially. Note that used, as shown in Figure 3-39. The lower each set of weights is marked with its weight damper on 12-cylinder engines is actually or position as are the pins and the locations two sets of dampers on a single hub on the hub.

assembly and is called the bifiler damper.

The 12-cylinder uses a monofiler damper on Examine the pins, the bushings in the hub, the upper crankshaft as well as the bifiler on the bushings in the weights, as well as the the lower crankshaft. We will disassemble weights. There should not be any significant and examine parts of the monofiler damper. wear on the pins, and certainly no ridges, galling, or excessive scratches. There The principle of the monofiler damper can should be no wear in the bushings in the be explained as follows: There are a series hub. Excessive wear occurs at the radial of doughnut (toroid) shaped parts that are outside of these bushings if wear exists.

suspended in the damper hub (spider) on These should be no wear in the bushings in pins. The diameter of the pin, in the weights and no signs of galling on the combination with the inside diameter of the edges of the weights, or other signs that the doughnut determines the radius of gyration weights are binding in the hub, etc.

and thus the frequency at which the pendulum thus formed vibrates. The mass Reassemble the damper, including installing of the doughnut ring determines the the cover plates, bolts and lock wire. Be magnitude of the oscillation. The two factors certain that the proper pins and weights are determine the energy that can be absorbed installed in the proper locations in the hub.

or given up. It is particularly important that the pins and weights on the opposite sides of the hub are In the damper assembly, there are pairs of matched as to weight and order. If this is not weights with the same pin diameters and done, it can lead to vibration of the engine, weight inside diameters and mass such that as the damper is only physically balanced various frequencies can be handled. In when the same order weights are opposite.

operation, centrifugal force causes the pins and the weights to go to the most radially 3A.2 Engine Bearings, Crankshaft End outward position in the spider. As the Float, and Web Deflection engine accelerates or decelerates, the pins and weights oscillate within the bore to The main bearings of the engine support the absorb or give up energy to the spider, and crankshaft and control the longitudinal thus to the crankshaft. This motion tends to position of the crankshaft. Most of the main hold the crankshaft speed constant, and bearings in the engine are of the same thus attenuate the effect of the torque pulses design and may be interchanged. That is, from the cylinder firings. any bottom half may be put in any bearing of Rev 3/16 3-71 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction the engine, as can any top half. However, are 4 inches wide by about 3/8 inches thick the bottom and top halves may not be and 6 3/4 inches inside diameter.

interchanged. There are also a number of special bearings which should not be There are a number of special bearings in interchanged or mixed with others of the the engine, as described below:

main bearings. Although most main bearing halves may be interchanged, it is the custom 1. Each crankshaft has a thrust bearing (in to mark all main bearing halves as to their two halves) immediately in front of the location in the engine. This is so that upon vertical drive gear flange location on the disassembling the engine for inspection or crankshaft (see Figure 2-30). The repair, it is evident where a failed bearing vertical drive causes the crankshaft to thrust toward the forward end of the was located, and so forth.

engine and the thrust bearing has a considerable area on the associated side The main bearings in the Opposed Piston of the bearing. The other thrust face is engine are made of a special aluminum considerably smaller in area. The thrust alloy. It has been observed that since bearing also limits the travel of the having switched the engine to aluminum crankshaft longitudinally and positions bearing, a bearing failure does not cause a the crankshaft within the engine failure of the crankshaft. After a failure, any assembly. It is important, when the unit aluminum material adhering to the is connected to a generator, that the generator bearing(s) permit enough free crankshaft can be removed chemically travel that the engine thrust bearing and / or by lapping the crank journal. retains control of crankshaft position.

A bearing failure is easily detected by either 2. The last bearing in the engine has to an opening up of the clearance / gap at the support about half of the load of the ends of the bearing halves, or by a pimpling generator rotor assembly. For this of the bearing material, usually evident on reason its a special bearing and has a the edges of the bearing. There have been section cut out to provide more cases of bearings that failed, then healed clearance. Upon starting the engine, and ran on for some time without a failure of especially after not running for some time, the bearings may have little oil in the engine to operate.

them. This can cause excessive bearing wear. For that reason, this bearing is The main bearings for the OP engine are provided with a bearing booster. The located Figure 3-8. They are 3 inches wide booster fills with oil while the engine is in by approximately 3/4 inches thick and the operation and remains full when the inside diameter, free, is 8.5075 inches. The engine is shut down. Upon the next start, bearing has a groove on the inside diameter starting air in put into this booster that conducts oil from the oil inlet (at the top cylinder, driving its piston toward the oil of the bearing) to the cross drilling in the outlet end. This oil is forced into the last main bearing and helps lubricate that crankshaft throw that takes oil to the heavily loaded bearing as it begins to connection rod bearing and on up to the rotate when the engine is started. The piston. The connecting rod bearings are of oil enters the bearing with enough the same material as the main bearings and pressure to slightly lift the crankshaft.

Rev 3/16 3-72 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction

3. As the engine fires, the main bearing on relatively simple but must be carried out to both crankshafts are forced away from ensure proper assembly. It consists of the the cylinders. In the case of the upper following steps:

crankshaft, the crankshaft is forced upward. However, the blower end main

1. Install a dial indicator on the cylinder bearing does not see this firing load and block with the stylus on either the end of the crankshaft at that location would ride the upper crankshaft or on the blower in the center of that bearing. This drive gear mounted on the crankshaft to actually causes the crankshaft to be bent measure longitudinal motion. In the case slightly at the last crank throw. To of the lower crankshaft, install the compensate for this effect, the blower indicator between the cylinder block and end main bearing is intentionally bored the flywheel in the longitudinal direction.

and installed off center. For that reason This bearing cannot be interchanged

2. Thrust the crankshaft forward using a bar with other bearings between a crank cheek and the cylinder block bearing frame.
4. The forward end of the upper crankshaft on 12-cylinder engines supports the
3. Set the dial indicator to zero.

torsional damper. The damper is heavy and tends to bend the crankshaft

4. Thrust the crankshaft in the aft direction.

downward at the first throw. Therefore, the 12-cylinder engines are provided with a special bearing, installed into the 5. Read the dial indicator, which will be front cover of the engine to help support indicating the thrust clearance. Repeat that end of the crankshaft. the procedure at least once more to be sure the number recorded is consistent.

The instructor may have students remove 3A.4 Checking Crank Web Deflection, and reinstall the thrust bearing on the upper Crankshaft Alignment crank-line of the 6-cylinder engine unit.

Particularly when main bearings have been After any main or connecting rod bearing is disturbed, replaced, etc., or the generator replaced in the engine, or after bearings are has been removed and replaced, it is removed for inspection, the engine should necessary to check to see that the engine is be run-in. This consists of gradually properly aligned. This is down by measuring bringing the engine up to speed and load in the crank web deflection. If the crank is several steps. In between steps, bearings straight, then as the crankshaft is rotated, a are inspected for opening of the parting line, dial indicator located between the adjacent pimpling, or running hot.

webs of the crank journal will not change the distance between them. If the crankshaft is 3A.3 Checking Crankshaft End Float bent at the throw, then as the crankshaft is rotated, the webs get closer together or Particularly after the thrust bearings have further apart. This is due to the fact that the been removed for inspection or replaced, it crank pin (journal for the connecting rod) is necessary to check the end float of the does not change in length. If the crank is crankshaft to ensure thrust bearings have bent at the throw, the webs then wobble.

been properly installed. This procedure is Rev 3/16 3-73 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction This is detected by putting a dial indicator in 5. Rotate the crankshaft until the indicator the prick marks provided on the crank webs again approaches the connecting rod (on and rotating the crank. Since the connecting the opposite side). Record the reading.

rods are in the way, it is only possible to take 5 readings. As shown in the diagram on 6. The readings in step 1 and 5 should be very close to the same, if not the same.

Figure 3-40. Record the values on a chart The difference between the reading at similar to that shown in Figure 3-41.

step 3 and steps 1 and/or 5 should fall within the limits set for crank strain given It is normally only necessary to do this check in the data book (or the instructors on the last throw of the OP engine, as the direction). If they are not within the limits, block is rigid enough that the other bearings it may be necessary to adjust the are normally well aligned. On the Pielstick generator position as required to bring engine, however, it is recommended that all the strain within the limits.

the throws be checked periodically (at refueling periods, or every 5 years). Also, 7. The difference between the readings in any time that a generator is disturbed, on steps 2 and 4 should also be within the lateral limits for strain. If they are not, it any engine, the crankshaft alignment should indicates that the generator needs to be be checked. moved sideways to bring the engine into alignment.

At the instructors direction, place a dial indicator (strain gage) between the crank cheeks as shown in the figure, using the prick marks provided in the crank web. Do the following steps:

1. Rotate the crankshaft in the opposite normal direction until the dial indicator is almost touching the connecting rod.

Take a reading or zero the dial indicator at that point. Record the reading.

2. Rotate the crankshaft (in the direction of normal rotation) until the indicator is 90 degrees from the vertical position (horizontal position). Record the reading.
3. Rotate the crankshaft until the indicator is at the bottom (vertically down).

Record the reading.

4. Rotate the crankshaft until the indicator is at the other horizontal position (opposite side to step 2). Record the reading.

Rev 3/16 3-74 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction HANDS-ON SESSION 3B We will now look in some detail at parts used on the Pielstick 4-stroke cycle 3B.0 PIELSTICK ENGINE CYLINDER engine. It is also very similar to the ALCO HEADS, VALVE OPERATING engine design, such that much of the MECHANISMS, CYLINDER discussion and items observed are WATER JACKET, MAIN applicable in general to the typical 4-stroke BEARINGS, PISTONS, AND cycle engines, regardless of manufacturer.

CONNECTING RODS Figure 3-42 shows a cross section of the Pielstick V type engine, typical of those Purpose used in nuclear applications.

The purpose of this session is to The cylinder head becomes a very complement classroom instruction on 4- important component of most diesel stroke cycle components and their engines. It acts to close one end of the functions with hands-on instruction utilizing cylinder with the piston closing the other the actual components. end. It usually contains the valves that admit combustion air into the cylinder and Learning Objectives allow the exhaust to be expelled. The fuel injection nozzle is normally housed in the Upon completion of this lesson you will be cylinder head. If the engine is air over able to understand: piston started, the air start admission/

check valve is also mounted in the cylinder

1. The 4-stroke cycle PC cylinder head head.

assembly including its intake and exhaust valves. Because the cylinder head is exposed to the pressures and temperatures of the

2. The PC engine cylinder and water combustion process, it must be strong jacket assembly. enough to contain the high pressure and yet thin enough to quickly conduct the heat
3. The PC main bearing assembly.

away from the surfaces subject to the high temperature. It is usually a rather intricate

4. The PC piston and connecting rod assembly. high strength cast iron part.

3B.1 Pielstick Cylinder Heads, Valves, Figure 3-43 shows a view of the cylinder and Valve Operating Mechanism head complete with the valve operating mechanism and its housing, ready to be In the previous sessions, we have studied installed in the engine. The cylinder head primarily the Opposed Piston engine. This is held down to the top of the cylinder liner engine is unique in that it has two and water jacket assembly by a number of crankshafts, two pistons in each cylinder, studs with nuts. These studs are very no cylinder head and no valves (the air is strong and are torqued to a very high let in and the exhaust let out through ports). value, using a special process, as follows:

Rev 3/16 3-75 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction It is impossible to manually torque these 2. Remove the nuts on the studs that heads properly. Therefore, the studs are retain the exhaust valve cages and hydraulically stretched and then the nuts remove the exhaust valve assemblies.

are tightened hand tight, and the hydraulic pressure relaxed. This ensures the studs 3. Remove the spring keepers from the are loaded uniformly and to the proper top of the intake valves using the spring compressor assembly. Remove the stretch required to hold the cylinder head keepers, retainers and springs.

tight to the cylinder liner. This seal must Remove the intake valves from the withstand 1300 - 1500 psig pressure cylinder head.

resulting from the combustion process.

4. On the exhaust valve cages, use the Figure 3-44 shows an exploded view of the spring compressor to depress the valve cylinder head assembly with the valve pushrods to the point that the keepers rocker mechanism. The valves of the can be removed. Remove the keepers, engine must be operated at the proper time retainers and springs. Remove the in the engines cycle in order for the engine exhaust valves from the cage assemblies.

to operate properly. Figure 3-45 gives a quick review of the engine cycle and shows 5. Inspect the parts as required/directed.

when the valves are operated during the engines operation--taking two complete 6. Reassemble the valves and valve revolutions of the crankshaft to accomplish cages to the cylinder head.

the 4-stroke engine cycle. Reassemble the valve rocker mechanism and torque the nuts and A mock-up of the cylinder head with its studs as required/directed.

valves and the associated section of the cam shaft will be used to demonstrate the The instructor will also cover valve lash operation of the valves and the injection adjustments and other checks using the pump during engine operation. Figure 3- operational display model of the cylinder 46 shows a diagram of the relationship of head and valve mechanism.

the crankshaft, connecting rods, pistons, camshaft and valve operating mechanism 3B.2 Cylinder Liner-Jacket Assembly of the engine, and how lube oil is supplied to these operating components. Using the Pielstick 2-cylinder engine, the students will be shown how the cylinder Students will disassemble a cylinder head liner and jacket assembly fits into the assembly at the direction of the instructor. cylinder block and how cooling water The primary steps required for this are: enters the liner jacket at the bottom outside edge and proceeds up through the jacket

1. Remove the nuts on the studs that and out into the cylinder head assembly retain the valve rocker arm support. through jumpers. The student will observe Remove the rocker arm support and its a cylinder liner and water jacket parts attached mechanism. disassembled.

Rev 3/16 3-76 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction See engine cross section shown in Figure is held to the engine bearing saddle block 3-42. Note that the liner jacket sits in a by studs and nuts, as shown. These studs seat on the top of the cylinder block. The are very strong and are tightened to the liner in turn sits in a seat at the top of the point they will not yield / deflect / stretch any jacket. The cylinder head sits on top of the further due to firing loads from the cylinders liner and the cylinder head studs, properly plus the crush pressure from loading of the tightened holds all of these parts together bearing cap.

in the engine cylinder block.

Each half of the main bearing is generally 3B.3 Main Bearing Assembly referred to as the bearing shell. In order for the main bearing shells to be retained Using the 2-cylinder Pielstick engine and a in the bearing bore formed by the cap and section of the crankcase, the student will saddle, they must be installed with a very observe how the main bearing are installed high loading. The bearing shell is made into the engine. The main bearing is an too long for the half of the bearing bore it assembly of two parts, the upper and lower is to occupy. When two shell are installed, halves. Each half is a steel backed tri- if the cap and saddle were not tightly held metal unit. The steel backing has a layer together, there would be a gap between of copper material plated onto the backing. them due to the bearing shells being too The copper in turn has a layer of lead / tin long. To close the gap, the bearing cap is material which is the bearing surface. pressed down by a special cap nut Properly lubricated, there is no metal to assembly so that the clearance between metal contact between the crankshaft the cap and saddle is closed. This creates journal and the bearing surface. The softer enough stress in the bearing shells to lead / tin material helps the bearing wear cause them to adhere to the bore wall such in and accommodate the crankshaft that they will never turn in the bore.

surfaces. The copper material is primarily there to conduct away the heat generated The special cap nut assembly used to load in the bearing and to become a bearing the cap is a combination of a nut and stud material should the lead / tin layer be worn which contains a piston. There is a port in away. Lube oil is vital not only to lubricate the nut assembly that is connected to a this and other bearings but also to conduct hydraulic pump. Hydraulic pressure is heat away from them. See Figure 3-47. pumped up to about 8000 to 10,000 psi.

This causes the nut assembly, the cap and The bearing bore is made such that it can the cathedral section of the bearing cap to be taken apart. Otherwise, there would be be compressed against the engine saddle no way to install the crankshaft into the block. A nut on the assembly is then engine. The bearing bore in the block tightened finger tight plus one flat. The consists of two parts, as shown in Figure hydraulic pressure is then relieved but, 3-46. The bottom half of the bearing bore because the nut is now holding the is called the saddle. The top half of the assembly in the loaded condition, the load bearing bore is called the cap. The saddle on the cap remains. Interestingly, this Rev 3/16 3-77 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction special nut assembly also acts to 5. Examine the fits on the piston and in the communicate lube oil from the lube oil crown. Examine the O seal ring.

header into the main bearings. Examine the oil feed holes in the piston to be sure they are clear.

Because of the tremendous load on the

6. Reassemble the piston to the crown cap assembly in the main bearing system, and tighten and torque the nuts.

it has been noted that if a bearing fails, it usually results in a gap developing at either

7. Reassemble the connecting rod into the bearing shell parting line or the parting the piston and install the wrist pin and line between the cap and the saddle. One retaining clips. See that the piston method of bearing inspections is to moves freely on the connecting rod.

determine that a 0.001 inch feeler gauge will not go into the parting line between the Note that the piston rings (piston ring cap and saddle, or between the saddle and grooves) on this piston are all at the top of the engine saddle block. If a feeler can be the piston. The three compression rings inserted, the bearing is probably failed and install into grooves of the crown portion of the assembly should be taken apart for the piston. The oil control rings install in further inspection. the grooves on the piston skirt portion.

3B.4 Pielstick Piston and Connecting 3B.5 Pielstick Power Output Shaft Rod Assembly - (See Figure 3-19) GearDrive Support Systems The students, with the assistance and The Pielstick engine power output shaft direction of the instructor, will disassemble gearing provides power to engine support a PC piston and connecting rod assembly. systems as shown in Figure 3-48. The The following steps are involved: (With the camshafts are driven through the flexible piston crown sitting on the floor) drive gears to dampen oscillations caused by engine cylinder firing and camshaft

1. Remove the keeper rings from the ends action of its loads. The camshaft bearing of the wrist pin, in the piston wrist pin is illustrated in Figure 3-49.

bore.

The cam shaft is driven by a series of gears

2. Remove the wrist pin and pull the mounted at the rear of the engine (power connecting rod out of the piston.

take off end). The gear train for this engine is shown in Figure 3-48. The gear on the

3. Examine the wrist pin, the wrist pin bushings in the connecting rod and the camshaft is a flexible drive gear intended wrist pin bores in the piston. to remove the torsional oscillations created both by the firing of the cylinders and by
4. Remove the nuts from the studs that the torque oscillations created by the hold the piston skirt to the piston crown. operation of the injection pumps on the Pull the piston skirt from the piston camshaft. The camshaft drive at full power crown. is shown in Figure 3-50.

Rev 3/16 3-78 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction Figure 3-51 shows an exploded view of the parts of this flexible drive gear arrangement. The flexible drive gear assembly is hydraulically dampened by the entrance of engine lubricating oil in the assembly. The gear train of the engine not only drives the cam shaft, but also provides power to drive the water pump(s), lube oil pump, fuel pump, over-speed governor and the speed regulating governor.

Figure 3-52 shows the parts of the over-speed governor assembly. Similar to the OP engine over-speed governor, this governor / trip mechanism consists of a flyweight that is acted upon by centrifugal force. When the engine is at normal operating speed, a spring holds the flyweight against the shaft to which it is mounted. If the engine experiences an over speed condition, the centrifugal force on the flyweight overcomes the spring force and the flyweight moves out and hits a pawl. When the pawl moves off center, it allows a spring to push a plunger which operate a switch and/or a hydraulic valve which then causes the shutdown control cylinder to operate, shutting off the fuel to the cylinders.

Rev 3/16 3-79 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction HANDS-ON SESSION 3C The crank-lead establishes the point at which the air intake ports open with respect to the lower crankshaft position by changing 3C.0 ENGINE CRANK-LEAD AND FUEL the angular relationship between the upper INJECTION TIMING FOR THE OP and lower crankshaft. The connecting ENGINE vertical drive gear coupling hub assembly can be used to change their relationship Purpose between the two crankshafts. Refer to Figure 2-30.

This session will complement classroom instruction of Chapter 3 and 4 by providing The vertical drive is connected to the hands-on instruction for measuring and crankshaft by sets of bevel (miter) gears at setting crank-lead in the OP engine thereby each end. Large changes in the crank-lead proper intake combustion and exhaust can be made by changing the tooth of the timing. In addition, it will provide hands-on pinion gear that is engaged with the gear on instruction for measuring and setting fuel the crankshaft, but this does not allow for injection pump timing. small changes (less than about 5 degrees).

Therefore, the joint at the coupling hub is Learning Objectives used to allow the vertical drive to be adjusted.

Upon completion of this lesson you will be able to: On some vertical drive designs, this is done by having a cone on the mating parts, the

1. Understand the reason for crank-lead in cone being locked up by bolts that hold the the OP engine. parts of the cone tightly together. On another design, there are 23 bolts in the
2. Understand how crank-lead is measured lower coupling joint. By a combination of the and reset by means of the vertical drive number of teeth on the vertical drive pinions gears. and the number of bolts, it is possible to find a position within one-half degree, where the
3. Check and set fuel injection pump height 23 bolts can be installed when the crank-for proper fuel injection timing lead is as desired.

(applicable to all engines).

With directions from the instructor, students 3C.1 Checking/Setting the Crank-lead will check or set the crank-lead by using the following procedure:

These exercises use the 6-cylinder OP engine unit in the work area. This engine 1. Locate the flywheel and flywheel pointer assembly is complete with the crankshafts, at the rear of the engine block. Locate connecting rods, pistons, cylinders, the barring drive and use the ratchet camshaft with its gear drive mechanism, and wrench provided to turn it. See Figure 3-injection pumps. 53.

Rev 3/16 3-80 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction

2. If not already removed, remove the top end), until the timing flat on the number cover from the upper crank-line (or one throw of the upper crankshaft (aft remove the inspection covers from the web) is vertical using the bubble control side of the top cover). Remove protractor. Reference Figure 3-55.

the lower crankcase inspection covers from both sides of the engine (at least for 8. Read the position of the flywheel pointer the No. 1 cylinder). (on the lower crankshaft) when the upper crankshaft is so positioned. The pointer

3. Locate the timing flats on the crankshaft should read 12 degrees (or a number set throw counterweights. See Figures 3-54 by the instructor).

and 3-55. These should be evident when the crankshaft is rotated to a 9. If the flywheel pointer is not at the correct position where the flywheel pointer reads reading, then the crank-lead is not (or is near) zero. correct. If not correct, depending on the type of vertical drive coupling, do one of

4. Using a bubble type protractor, the following:

determine that the crankcase is level by placing the protractor on one of the air a. Loosen the bolts that hold the taper receiver compartment flanges. If not cone together and using the bar level, set the protractor so that the provided to break the cone loose, bubble is level when the protractor is flat OR, on the flange (vertical surface). b. Undo and remove the 23 cap-screws Remember the direction in which the on the lower hub flange coupling.

protractor is being used for reference in future use. 10. Once the coupling is loose, continue to turn the lower crankshaft until the

5. Rotate the engine until the protractor on flywheel pointer is at the correct crank-the timing flat on the lower crankshaft lead. If it was necessary to turn the shows the lower crankshaft is at the crankshaft clockwise, then turn it too far inner dead center position (IDC). and come back to the correct position in the counter-clockwise direction.
6. Read the flywheel pointer. It should read zero. If not, recheck the bubble 11. Once the lower crankshaft is in the protractor to be certain it is set properly correct crank-lead position, lock up the (per Step 4 above) and that the vertical drive coupling by either:

crankshaft is in the correct position. If the pointer still reads other than zero, a. Tightening and torquing the bolts on then loosen and reset the pointer to read the ring that locks the taper cones exactly zero. together, OR.

b. Installing the 23 bolts in the lower
7. Rotate the engine in normal direction of coupling hub flange.

operation (counterclockwise on the lower crankshaft as viewed from the flywheel NOTE: It may be necessary to turn the Rev 3/16 3-81 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction lower crankshaft through several 1. If not already removed, remove the high rotations (always CCW) in order to find pressure tubing line between the the position at which the 23 bolts can be injection pumps and the nozzles on the inserted at the correct crank-lead (plus or No. 1 cylinder (both sides).

minus 1/2 degree). Tighten and torque the bolts. 2. Remove the discharge fitting, check valve and spring on the No. 1 injection This completes the check and/or setting of pumps (both sides).

the crank-lead.

3. Install the stroke gage on the #1 OCS 3C.2 Checking High Point of CAM pump. In some cases, the stroke gage may be equipped with a dial indicator. In It is necessary to complete the crank-lead the following steps, the gage will be check before this procedure. The injection aligned or matched when the dial timing is always referenced back to the indicator reading is the same as the lower crankshaft, but the camshafts are previous reading. Refer to Figure 3-58.

driven off the upper crankshaft. Therefore, any change in the crank-lead will result in a 4. Turn the flywheel in the normal direction change in the injection timing. of rotation until the stroke gage lines align with the plunger line going in a The injection timing consists of two steps. downward stroke. STOP when the lines First, the camshaft must be properly timed. are aligned.

Then the point at which injection starts as the injector plunger moves up the cam flank 5. Record the flywheel pointer reading at must be set. Before injection timing can be which alignment was found.

set, cam position must be checked/set.

6. Continue to turn the engine (in direction The cam has two flanks which are of normal rotation) until the stroke gage symmetrical about the center of the high goes all the way down and comes back point of the cam. Tramming the cam, as up until the lines are again aligned.

described in the procedure below, will STOP when the lines are aligned.

determine the location of the high point on the cam. This high point is used to set the 7. Record the flywheel pointer reading at cam to the correct position with respect to which this second alignment was found.

the crankshaft. Only the cams for the No. 1 cylinder are used for this. The other cams 8. If the first number is between say 340 are located, during manufacture and and 360 degrees, first subtract the assembly of the camshaft, to align properly number of degrees between 360 and the with the cam for the No. 1 cylinder. first reading from the second reading.

Then divide the resulting number by 2 to The following steps are required to obtain the high point of the cam. If the check / set the high point of the cam. Refer first number is greater than zero, then to Figures 3-56 through 3-59. add the two numbers together and divide Rev 3/16 3-82 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction the result by 2 to find the average, which Turn the nut counterclockwise to will be the high point of cam. This advance timing, (making the high cam procedure is illustrated by the example number lower). Turn the nut clockwise shown in Figure 3-57. to retard the timing, (making the high cam number higher). NOTE: One turn

9. Move the stroke gage to the No.1 Control on the timing nut equals 1.5 degrees of Side (CS) pump and repeat steps 1 rotation.

through 8 above.

3C.3 Setting the Injection Pump Timing

10. If the CS cam does not match the OCS cam, slip the CS cam sprocket the The above steps put the high point of cam in number of degrees to match up with the the correct position, which influences the OCS cam. If the CS cam is too far timing on all of the cylinders. It is also advanced, this means that the CS high necessary to check the point of port closure cam figure is a lower number than the on the injection pumps to time each cylinder OCS high cam figure. To change, as follows:

loosen the four (4) nuts or capscrews one turn on the CS sprocket and turn the 1. Using the same stroke gage as used in flywheel in rotation to number of degrees the steps above, turn the engine in change desired. Re-tighten the nuts or rotation to the point of high cam for the capscrews. respective cylinder in its firing order.

11. Repeat Steps 4 through 8 as required to 2. With the cam for that cylinder at high match the figures. point, the end of the stroke gage plunger should be flush with the end of the gage.
12. If the CS cam is too far retarded, this means the CS high cam number reads 3. Measure the amount of protrusion or higher than the OCS high cam figure. To amount of recess of the gage plunger. If change, loosen the four (4) nuts or there is a protrusion, then additional fuel capscrews one turn on the CS sprocket, pump shimming is required. If the gage and turn the flywheel against rotation the plunger is recesses, then shims must be number of degrees change desired. Re- removed.

tighten the capscrews or nuts.

4. Remove the injection pump assembly
13. Repeat Steps 4 through 8 as required to from the tappet assembly.

match the figures.

5. Determine the thickness of the present
14. With both camshafts reading the same shim pack and add or subtract the shims high cam number, you now have to set as determined in Step 3. Always try to the high cam to agree with the technical obtain the minimum number of shims manual setting. To do this, rotate the that will result in the desired shim pack external timing device to get 43 degrees thickness. Refer to Figure 2-39.

high cam after Inner Dead Center (IDC).

Rev 3/16 3-83 of 84 USNRC HRTD

Emergency Diesel Generator Diesel Engine Construction

6. Reinstall the injection pump and again check the stroke gage. If the exact number of shims cannot be obtained, it is better that the plunger be slightly recessed at high cam.

Since this is an exercise only, it is only necessary to demonstrate this technique on one injection pump. In actual practice, this must be done for each injection pump on both sides of each cylinder on the OP engine.

Similar procedures are applicable to other engines. First, the cam must be timed to the crankshaft and then the pump must be timed to the individual cylinder cam.

One other setting on the injection system needs to be check / set. On the Control Side (CS) injection pump of the number one (1) cylinder, set the distance from the injection pump control rod collar to the pump body to 2-3/16 inches, as shown on Figure 2-36.

Figure 3-60 shows the fuel control system from the governor output shaft to the fuel pumps pinion gear for each cylinder.

Once No. 1 CS pump is set as shown, set all other pumps on both sides of the each cylinder so that they have the same rack reading on each pump. These settings are to assure each cylinder receives the same amount of fuel during each injection, to produce balanced power output. This is very important when the engine is running at rated load, so that no cylinders are subject to overload due to others not carrying their share.

Rev 3/16 3-84 of 84 USNRC HRTD

Retrieved from "https://kanterella.com/w/index.php?title=ML20043F654&oldid=2521207"