Checking the WDM-2 (Alco 251) Turbocharger
Disclaimer: The information presented here is neither complete nor accurate. Complete details on the topics here are available only from Indian Railways and other official organizations. The material here is not a substitute for the official documentation or official training procedures, which are provided to duly authorized personnel. Do not use the information here to design, build, operate, repair, or maintain any equipment.
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!