Diesel Loco Primer, Spirax and other sound help

[ProjectRedcar]

Hello. First time posting after a very long time. I'll try my best to make my questions clear. These are regarding sounds you'd hear from diesel locos.

 

Primer: What is it used for? When would it be used and for how long?

Spirax valve: When would you hear this sound? Is it when the engine is off or on?

 

There are also sounds listed in the Hornby HM DCC sound lists that I don't understand the meaning behind.

These are the Class 47's 'Triple Pump' (I assume this is just another name for the Primer?) and the Class 50's 'Lift Pump' (Might be the compressor? Not sure)

 

 

[Davexoc]

Class 47 triple pump is a motor driven pumpset that comes in at the beginning of the starting sequence. It is triple because it provides lube oil to allow the governor to work and prime the crank and camshafts, diesel from the tanks to the fuel galleries, and starts circulating cooling water.

 

Class 50 lift pump is the fuel pump used to prime the fuel galleries, like the class 47 triple pump. I don't recall it being quite as noticeable. EE provided a manual pump to prime the oil, something which was less likely to be used, resulting in the start windings turning the engine over for longer as the governor will not open the fuel racks until the oil pressure rises. Probably why 50s seemed to frequently suffer flat batteries on the Waterloo-Exeter in the winter....

 

Normally both would run for a several seconds before the engine was turned over on the start windings.

 

Spirax valves are air system drain valves, and when water has accumulated at the valve a float lifts and the valve expels the water. They are important to keep the brake system dry(ish) and avoid freezing in the winter. Operation is whenever there is water present, which is all the time, but more likely when air is not being used and the loco static. They will operate more frequently on days when the air is more humid.

 

Hope that explains things for you,

 

Dave

[25901]

On 06/05/2024 at 22:04, Davexoc said:

 

Normally both would run for a several seconds before the engine was turned over on the start windings.

Dave

The Sulzer triple pump has to run long enough to reach starting pressures or the pressure relays will not let you start

[Luke Piewalker]

I always think of the Spirax valve as a characteristic of locomotives parked in the sidings at Carlisle station, ticking away.

[pheaton]

On 08/05/2024 at 21:20, 25901 said:

The Sulzer triple pump has to run long enough to reach starting pressures or the pressure relays will not let you start

im trying to resist but im gunna have to be pedantic Robin :)

 

The pressure switches are shorted via an interlock when S1 and S2 (contactors that connect the generator start windings to the battery) are energised because on a sulzer type 2/3 and a sulzer type 4 the voltage drop across the batteries during engine cranking slows the pump down to the point the water pressure switch will usually not hold. In reality, (as dave ex OC pointed out :) ) the fuel racks wouldn't open if the governor hasn't seen oil pressure but that would be achieved within several revolutions of the engine via its own oil pump.

 

EEs seem to be a lot more phinicky than a sulzer and they will just crank and crank until the pressure is hit 

 

once S1 and S2 drop out (start button is released) the engine run solenoid is maintained via the action of the pressure switches but even then...the discharge resistor means it will discharge slower and make it less prone to a shutdown in the event of letting go of the start button immediately after firing.....unless...its a 47 which has an additional "run oil pressure" switch (set to higher pressures), which is why you have to wait for the engine stopped light to go dim before you can let go of the start button.

 

 

Edited May 14 by pheaton

[25901]

8 hours ago, pheaton said:

im trying to resist but im gunna have to be pedantic Robin :)

 

The pressure switches are shorted via an interlock when S1 and S2 (contactors that connect the generator start windings to the battery) are energised because on a sulzer type 2/3 and a sulzer type 4 the voltage drop across the batteries during engine cranking slows the pump down to the point the water pressure switch will usually not hold. In reality, (as dave ex OC pointed out :) ) the fuel racks wouldn't open if the governor hasn't seen oil pressure but that would be achieved within several revolutions of the engine via its own oil pump.

 

EEs seem to be a lot more phinicky than a sulzer and they will just crank and crank until the pressure is hit 

 

once S1 and S2 drop out (start button is released) the engine run solenoid is maintained via the action of the pressure switches but even then...the discharge resistor means it will discharge slower and make it less prone to a shutdown in the event of letting go of the start button immediately after firing.....unless...its a 47 which has an additional "run oil pressure" switch (set to higher pressures), which is why you have to wait for the engine stopped light to go dim before you can let go of the start button.

 

 

I stand well and truly corrected but must point out that on most Sulzer type twos relays were packed out with match sticks while in BR service lol