Engine.Class 60 Mirrlees Blackstone 8MB275T Engine
The engine installed in the Class 60 Locomotive is a Mirrlees Blackstone (now Part of the MAN B&W Group) 8MB275T (8 cylinder - Mirrlees Blackstone - 275 mm cylinder diameter - Traction) diesel engine of 145 litre capacity. It has been designed for easy access and rigidity of components together with compatible stress levels. High cylinder pressures ensure low fuel consumption. This unit is a larger version of the 1800HP 6 cylinder MT275T as fitted to class 37/9s 37901-4 (slugs1-4) in the 1980s.

This engine is an 8 cylinder inline engine producing 3100HP at 1000 RPM. It is turbocharged and is fitted with charge air cooling (intercooling). The cylinders are numbered opposite to the normal method used, i.e., No8 cylinder is the first when looking at the free end of the engine. The firing order of the cylinders is 1,3,2,5,8,6,7,4.

A Woodward governor is employed to control the fuel racks and thus the power output of the unit. This governor is in turn controlled by the micro processor. Should the engine exceed 1100 RPM the engine overspeed trip will operate to disengage the fuel injector pumps from the camshaft so starving the engine of fuel and thus shutting it down before any damage can occur. Because the engine drives alternators, to start the engine two starter motors are provided to start the engine. Should the starter motors become overheated a thermal protection device will prevent them from re - engaging with the starter ring until the temperature has reduced.


Lubricating Oil System.
The system is a full flow type with coarse and fine filtration, pressure regulation, temperature control and low oil level shut down features. An electrically powered priming pump is provided to circulate oil prior to engine startup, following start up a mechanically driven pump takes over and maintains pressure.

System description:
Oil is drawn from the sump via a course filter to the oil pump, on leaving the pump oil flows to the pressure relief valve which protects the thermostatic valve, heat exchanger and a pressure check valve which guards against excessive pressure on cold starts. Oil in excess of 7 Bar returns to the sump. After the pressure relief valve, the lubricating oil passes through the heat exchanger or by - passes it subject to and oil temperature controlled valve. the oil is then passed to a fines filter. This filter is a full flow type, with a filter blocked/restricted visual indicator. Oil passes from the filter to the regulating valve which limits the pressure in the main oil gallery to 4.2 bar with excess oil being returned to the sump. The oil passes around the engine via internally drilled ports and returns to the sump from a hole in the centre of the underside of the piston.

Oil is also supplied to the overspeed trip governor, turbo charger and engine governor. Inside the engine governor the lubricating oil performs two functions, firstly it lubricates the governor drive shaft, and secondly supplies a pressure indication to the low lubricating oil pressure shut down system. In the event of of low pressure this protection system returns the governor to a no fuel position causing the engine to shut down before damage can occur.

Protection Systems.
On the Class 60 Locomotive the engine is shut down is via either the running oil pressure switch or the engine governor. In both cases the engine will stop when oil pressure falls to 1 bar (Normal pressure will be approx 4.2 bar). The governor will detect falling pressure and reduce engine speed (below 3.1 bar) towards idle (1.38 bar), and at 1 bar pressure will after 20 seconds delay return the fuel rack back to the no fuel / shut down position.

The Lubricating Oil Priming System.
An electrically (battery) driven priming pump draws oil from the sump via a course strainer and then around the power unit via the same route as above. A non-return valve is fitted on the output side of the priming pump to keep the system primed and protect the priming pump against excessive pressure. The lubricating oil priming pump runs for 30 seconds prior to the engine start sequence commencing.

Crankcase Extraction and Recuperator.
Ventilation of the crankcase is by DC electric motor and fan, oil is separated out and returns by gravity to the sump. The air and gasses are discharged out of the engine roof via a small grill.

Oil System data.
   •  Capacity: 204.6 gallons 930 litres.
   •  Minimum: 100.8 gallons 413 litres.
   •  Shutdown: 26.8 gallons 131 litres.


Class 60 Fuel TankFuel System.
The fuel system on the Class 60 Locomotive is similar to that used on many other diesel-electric locomotives. For standard locomotives a single underslung tank, is fitted. This tank is provided with a contents gauge and associated mechanical float. Fillers are an integral part of the tank with one provided at each side of the locomotive. The fuel system is a full flow type with the rate of flow being three times the amount required at maximum load. The return fuel line is also pressurised and excess fuel being returned to the suction side of the fuel transfer pump.

Fuel Circuit Description - Low Pressure.
Fuel is drawn from the main underslung fuel tank via a strainer by an electrically driven fuel transfer pump, it is then delivered from the pump to a pressure relief valve, any fuel in excess of 2.4bar regulated fuel pressure is returned to the suction side of the transfer pump. Fuel from the pressure relief valve passes through a fine filter to the supply manifold and then onto to the injector pumps. The injector pumps have fuel flowing through them at ail times the pump is running. The return manifold being pressurised at 1.7 bar, any fuel in excess of this pressure being returned to the suction side of the transfer pump. Because this manifold has a pressure within it, shock waves and turbulence at the injectors is prevented.


Class 60 Engine - Fuel System
Fuel Circuit Description - High Pressure.
Each cylinder of the Mirrlees Blackstone MB275T Engine has it's own fuel injector pump and injector. Fuel from the injector pump is passed to the injectors at 5,570 PSI (380Bar). Any excess fuel flows to the return manifold and eventually back to the fuel transfer pump. The fuel injectors are similar to others used on many other large Diesel engines except they are very long (700mm) 28 inch.

Fuel System Data.
   •  Fuel Tank Capacity: 1000Gal - 4540Ltrs
   •  Low Pressure Flow: 1660 Litres per Hour.
   •  Max High pressure: 17,200PSI (1170 bar).
   •  Fuel Tank Capacity: 1000Gal - 4540Ltrs







Engine Governor.
A Woodward Governor is fitted to the engine at the alternator end of the engine, directly above the main alternator. This governor controls the fuel rack and thus engine speed by controlling the amount of fuel supplied by the injectors to the cylinders. The governor is nominally set to produce,

   •  Idle speed of 400 rpm.
   •  Max speed of 1000 rpm.

The engine speed is in 8 steps, but as drivers power controller is 'notchless' variable power can be selected. The governor has protection devices for low lubricating oil pressure, charge air failure and excessive fuel, incorporated within it. An externally fitted engine run control valve performs the normal functions of stopping and running the engine. As the driver opens the power controller towards maximum a variable differential transducer inputs signals to the microprocessor which then determines the engine rpm and alternator excitation to match the demanded power. By increasing and decreasing excitation in step with the diesel engine a 'stepless' increase in power can be obtained. Engine RPM is controlled by four solenoids within the governor.

Overspeed Trip.
Should the engine governor fail to prevent the engine RPM from exceeding 1100RPM the overspeed trip will operate and cause a cam under the fuel injectors to operate and disengage the pumps from the camshaft, the engine stops with no fuel.


Engine Charge Air and Exhaust System.
The 8MB275T engine as fitted to the locomotive is provided with a very much traditional charge air system and exhaust system however more attention is given to air cleaning, exhaust noise levels and the use of a single unit high performance turbocharger, than has been commonplace with older diesels.

System Description.
Air enters the locomotive via primary centrifugal inertia filters located in the bodyside, and passes into the clean air compartment. Combustion air is taken from the clean air compartment to the secondary filter box then by ducting to the turbocharger. Compressed combustion air is passed through the intercooler to the air manifold and the cylinder heads. Exhaust gasses pass from the cylinders via the outlet manifold to the turbocharger and then out to atmosphere via a large roof mounted silencer..

Charge Air Data.

Turbocharger RPM: 23,400.
Charge Air Pressure: 2.37 bar.

Air Filters.

The primary filters are a self purging (cleaning) type, a motor driven dump fan discharges the dirt from the bottom of the locomotive and on to the track.

Silencer.
To meet modern stricter noise emission levels the silencer is a larger unit than is normal for older locomotives, it is mounted on the roof of the clean air compartment and is designed to follow the roof curvature line.




Page Last Updated: December 2008