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  • EMD engine protector

  • Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.
Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.

Moderator: GOLDEN-ARM

 #97778  by EDM5970
 
Could someone explain the workings of the engine protector used on EMDs? I'm up to speed on most of the protection devices used on Alcos and GEs; most of these are electric, but then again, that is the last name of the big locomotive builder from Erie.

The EMD system is more mechanical/fluidic/hydraulic in nature. I'd like to know how it compares to the ALCO and GE systems, and how hard it would be to install on a BC engine. (Or are electric systems, tied in to the ER relay and/or shutdown valve D a better way to go?)
 #97862  by GOLDEN-ARM
 
GREETINGS. I AM JUST CURIOUS. WHICH "ENGINE PROTECTOR" SYSTEM ARE YOU REFERING TO ? THE DIESEL ENGINE OVERSPEED, LOW WATER LEVEL/PRESSURE, OR THE LOW LUBE OIL SYSTEMS ?

 #97886  by EDM5970
 
It's located near the governor, and near number nine cylinder on a 16 cylinder engine. It has a few reset buttons on it. Several tubes run into it, from the governor and airbox, perhaps.

I occasionally work on a shortline unit that doesn't have one, and I think it should have something more than the low oil and hot engine switches.

 #97907  by mxdata
 
There have been several varieties of engine protectors used on EMD 567, 645 and 710 series diesel engines. Some of the 567 engines used a separately mounted protector that just looked at crankcase pressure, these were mounted on a bracket and had a tube to connect to the accessory drive housing. The later type which bolts to the side of the accessory drive housing over the rectangular port (outboard of the main oil pressure relief valve) is built in several variations: One button protectors which just look at crankcase pressure and may either be arranged to alarm or to shut down the engine when they trip; two button protectors which look at crankcase pressure and coolant pressure in one bank of the water system, they shut down the engine when they trip; and three button protectors which look at crankcase pressure and the water pressure on both banks of cylinders, they also shut down the engine when they trip. The ones that shut down the engine have a path built into them which dumps the oil pressure sensing line to the governor, causing the governor to see no oil pressure and shut down the engine.

If an older engine has the rectangular cover plate over the oil pressure relief valve you can probably mount a later type engine protector on it but you may need to change some of the pipe elbows on the water pumps to get connecting points for the sensing lines, and your governor must have the low oil pressure shutdown feature built into it (PG type governor) in order to work with the engine protector.

Best thing would be to call Rail Systems Inc. (RSI) in Houma Louisiana and ask for the parts catalog pages that show the protector and the connecting piping so you can see if you can apply it to your engine.

 #98026  by Clyde
 
Greeting,
You are right. This device is usualy called EPD, (Engine Protecting Device). Typically the EPD has two portions; Crankcase Pressure Detector (CPD) and Low Water Detector (LWD). One version of EPD has a third button/LWD (one per engine bank). Both the CPD and LWD dump engine oil at the governor sensing line if a critical condition is detected in order to shutdown engine.

A new CPD should be triggered if crankcase pressure reaches 0.8 to 1.8" H2O (0.8 to 3" H2O for used detector).

Since the second generation of Low Water Detector is connected to water pump inlet, water pump outlet and air box this device is called "Delta P" EPD. In a nutshell air box pressure works agains water pump inlet and outlet pressure differential. If a low water condition occurs (where air box pressure is ( new: 20@ H2O used: 30" H2O) higher than water pressure differential, air box pressure acting against an internal diaphragm and spool valve assembly trips the detector and dumps engine oil pressure sensing line to the sump which resuts of engine shutdown as previously explained.

Hoping this explanation helpful.
Clyde

 #98105  by mxdata
 
I would like to add to my earlier comments and to the excellent explanation Clyde offered, that if you only require crankcase pressure detection for an older locomotive that is fitted with a governor that uses electric speed setting solenoids, the type of engine protector used on marine and industrial installations can sometimes be the easiest unit to adapt. This type of unit only contains a toggle switch, activated by the crankcase pressure detector, and can be used to control an auxiliary shutdown relay wired into a suitable control circuit to take the feed away from the A, B, and C solenoids in the governor while energizing the "D" solenoid to shut the engine down.

 #98343  by EDM5970
 
Thanks for all the good information. I wasn't aware that crankcase pressure was an issue on EMDs. I'm much more familiar with Alcos and their crankcase exhausters. A different approach to the problem, I guess-

I would imagine a 2 PSI/27" H20 pressure switch could be used to drop out the fuel pump relay, as an alternative to dropping out A, B, C and energizing D. Also, I have a Murphy float switch, which could give me low water level, although not flow. Both of these things would be be an improvement over what this unit has now, which is almost nothing, just the bell and lights for low oil and hot engine.

I saw an interesting low water set up on the Erie Mining (LTV Steel) RS-11s. They had a float switch going to a 12 or 15 second Agastat, which would "debounce" a low water signal. Wire 12 (ESSR2, or B) went through a normally closed contact. When there really was a sustained low water situation, the engine could not be run over fourth notch, and a light came on. I suspect that this was a "limp home, light engine" feature.

 #98509  by mxdata
 
If you are going to apply a pressure switch, I would suggest you look at one with a much lower pressure range. 2PSI is pretty high, it would take a major failure in the engine to trip it. If you can detect crankcase pressure going just slightly above atmospheric your chances are better of catching a problem like a cracked piston before it results in massive damage to the engine.

You might consider the Dwyer Photohelic combination switch/gauge units which are available in very low pressure increments. The A3005 is 5" water column total range with adjustable alarm trip point anywhere from 0" to 5", the A3010 is 10" water column total range, with adjustable alarm trip point anywhere between 0" and 10".

The advantage of a combined gauge/switch is that you can install it and look to see if the normal operation of your elderly engine results in any pressure transients when starting or manipulating the throttle, then set the alarm contacts just above that, so that the switch does not continually interfere with your normal operation. Another option, as you explained regarding the cooling system alarm, is to use a time delay relay in the circuit to filter out transients and only allow an alarm shutdown if the range is exceeded for a set time period.