Checking the WDM-2 (Alco 251) Turbocharger
I have with me a handwritten operational manual of the WDM-2 locomotive.
I wish to share with you a quaint procedure used to check whether the huge turbocharger of the Alco 251 engine is defective or not.
This test is to be conducted if the Booster (Turbocharger in WDM-2 pidgin) is not developing proper pressure during a run.
In my profession, I am near a lot of large diesel engines but I have never heard of such a crude procedure. I think it offers a glimpse of the diesel engine technology of 1950s and 1960s.
Turbo Rundown Test
- Secure the loco: Keep the A9 (Train Brake lever) in released condition; keep the SA9 (Loco brake lever) in an applied condition; switch off the GF (Generator Field); keep the reverser in neutral condition; and put the ECS (Engine control switch) in the run mode.
- Ensure that the water temperature is higher than 49 degrees Celsius.
- The driver should climb on top of the hood and sight the turbine of the turbocharger through the 'chimney' (their term, not mine!)
- The assistant should raise the engine to 4th notch rpm and allow the engine to stabilize in speed.
- The assistant should now shut the engine down by operating the MUSD (Multiple Unit Shut Down) breaker on the control stand.
- As the engine begins to stop turning, the assistant must quickly get down and come to the hood door to the 'Expressor' [exhauster and compressor].
- He must give a signal to the driver as to the instant the huge engine stops rotating by looking at the crankshaft of the engine coupled to the expressor.
- The driver must count the number of seconds the exhaust turbine takes to come to a stop, from the instant the engine has come to a standstill.
- If the turbine (which revolves at 18,000 to 19,000 rpm) takes more than 90 seconds then it is a good turbocharger, any reduction in the period of spinning down is an indication of a faulty turbo.
- As simple as that!