Western Railroad Discussion > Diesel Locomotive Liquid Cooling System

I was watching a local TV station this morning where a tour was being conducted of the General Electric Transportation Systems Facility in Erie, PA. The gentleman giving the tour took the viewer through the assembly process of how they build a diesel locomotive. During one of the segments, he described the "gull wing" section of the locomotive which houses the radiators and fans for cooling the liquid coolant that circulates through the diesel engine. He made a comment that surprised me unless I misunderstood him. He stated that the cooling fluid runs through the diesel engine and when it reaches a specific temperature, a valve opens and the liquid is then passed through the radiator in the "gull wing" area where it is cooled by fans. Once the coolant has returned to the preset temperature, the fans shut down and the liquid is closed off from the radiator to start the process over again.

This certainly does not make sense to me as we all know that automobiles continualaly circulate their coolant. I would like some information on what I understood was told me by the tour guide. Thanks.

Jim

automobliles only circulate continuously once the thermostat opens. Until the fluid reaches the t-stat temp, it does not circulate or circulates very little.

And most t-stats open to varying amounts, the hotter the liquid the more they open and the more coolant circulates.

I would imagine that locomotive cooling systems work basically the same, although I'm sure details will vary. Internal combustion engines, gasoline or diesel, operate best within a certain temp range.

Sounds like GE is using thermostats just like your automobile. Others may correct me but one of the systems I am familiar with the run of the mill three fan EMDs (pre-computer). There are no thermostats within the engine ... there are three switches in the water line between the engine and the radiators ... the first turns one fan on at 150F, the second turns the second fan on at 175F, the third switch turns the third fan on at 200F and I don't remember the 3-2-1 fan shutoff temps. The average EMD is circulating large volumes of water around in the system so they can get away with this.

The engine should run at a near constant temperature somewhere near 200 deg F. Higher temperatures are generally more efficient but there is a limit to the pressure and temperature that can be used for water based coolant. There are a number of ways that the temperature can be regulated but the coolant does need to circulate thru the engine so that there are no hot spots. If the engine is not up to temp, then it is possible that they use a system similar to the termostat on a car engine where the coolant does not flow thru the radiator until a certain temperature is reached.

I believe that the modern locomotives have electric motor driven variable speed fans to control the air flow thru the radiators but they may also control the coolant flow thru the radiators. However, the older locomotives do not use anti-freeze so if there was no water circulating thru the radiator, the water in the radiator would freeze.

Also, some larger trucks use a shutter arrangement on the radiator instead of a thermostat twhere the air flow thru the radiator is blocked until the engine is up to temperature. The shutters open and close to maintain the correct temperature.

A thermostat controls the circulation of the coolant in an automobile. If the temperature of the coolant is below the preset temperature of the thermostat, usually 195 degrees, the thermostat is closed and the coolant doesn’t circulate. When the coolant warms up to the thermostat setting, the thermostat opens and the coolant circulates. Also many cars have an electric fan, which is also controlled by a separate thermostat with a much higher setting, say 225 degrees. When the automobile coolant gets really hot, the fan turns on to aid in cooling. Sounds to me that the GE locomotive cooling system works exactly like an automobile system.

GE does in fact use a "dry radiator" system, whereas EMD uses a constant flow system. GE also uses one large fan to cool the water where EMD has a temperature manifold that controls the activity of the 3 radiator fans and shutters. Slightly off the topic, but another big difference in the two are the air compressors. EMD compressors are driven by a drive shaft off the prime mover, thereby allowing you to speed up the pumping by going to run 4 or 5. GE compressors are driven by an electric motor, so they pump at the same rate as needed no matter where the throttle is set.

In my car when the engine is running, the water in the block is circulating. The water pump is mechanical, connected to the crankshaft. When the coolant gets hot enough the thermostat begins to divert it to the radiator. I am not sure how newer cars do it, but I think in all engines the coolant is always circulating to prevent hot spots. The cooling system is kicked in one way or another when the temp reaches a certain level.

What we're discussing here is called a "wet/dry" system, and it's found on Amtrak's P32-8BWH's (but not P40's or P42's). I suspect that this very same system is used on GE's other "gull-wing" locomotives.

Follow along in the diagram below. The Engine Water Discharge Temperature Sensor (10) measures the temperature of the cooling water leaving the engine. When the cooling water leaving the engine is below 178 degrees F, water is drained from the radiators and recirculated to conserve engine heat, especially at IDLE and at low ambient temperature. This process eliminates the need for shutters. If the temperature rises to 183 degrees or above, the WFMV -- Water Flow Magnet Valve -- (12) is energized to switch the cooling water from the storage tank to the radiators. If the temperature falls back down to 178 degrees, the WFMV is de-energized to switch the water from the radiators back to the storage tank. (This "switch" is performed physically by a butterfly valve (11) controlled by the WFMV.) If the control system (Aux. Computer) detects that the Water Discharge Temperature Sensor is bad, it will look instead at the Lubricating Oil Temperature to determine cooling requirements (PIck Up Oil Temp. is 193 degrees, Drop Out Oil Temp is 187 degrees). If the control system determines that both of these sensors are bad it will look at Ambient Air Temperature.

GE's also use water temperature to control the fan speed. (As was previously mentioned, GE's use only one radiator fan as opposed to 3 by EMD. EMD uses water temperature to determine how many, if any, of the fans should be turned on. GE uses water temperature to determine how fast the fan should turn.)

With rising water temperature, a GE's radiator fan will turn at 1/4 speed at 192 degrees, 1/2 speed at 196 degrees, and full speed at 200 degrees. With falling water temperature, the fan will drop to 1/2 speed at 190 degrees, 1/4 speed at 186 degrees, and will shut off at 182 degrees.

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Yes, the valve is called a "thermostat".
TH

An interesting aside about the GE system. The U boats used this system where the coolant drained from the radiator when cooling was not needed. I'm sure it seemed like a great idea to the engineers back at Erie but it resulted in some serious problems out in the field. Imagine it is -40F out in the west any you have been sitting in a siding on a coal train at the bottom of a steep grade meeting mtys for hours. The engine cools down and the water drains out of the radiator yet the cooling fan is directly driven by a shaft from the motor. It is blowing -40F air through the radiators all the hours you have been waiting. The signal goes green after the last train passes and, consistent with good train handling, you get into Run 8 asap. Shortly, your engine heats, the magnet valve opens and 240F water heads into the radiator core. The core is at -40F. Imagine the shock to the radiator structure. Imagine trying to keep the core soldered into the headers. There were lots of these types of failures on the GE's and you can sometimes see frozen pink or yellow coolant on sides of these units in photos taken in sub zero conditions. One solution was to set the core tubes into the headers with rubber grommets to better handle the thermal shock.

I believe a thermostat, as is commonly known, is totally self contained, consisting of both the sensor and the actuator. On the loco, there is a separate temperature sensor that then electronically tells the valve which position to assume.