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It isn't a big secret that I am an engineer who employs dynamic braking a great portion of the time during normal train handling (I can, however, also go the air and throttle `blood and guts work' route too). So when it comes to this technique, along with equipment operation, I have been on both the inquirer and the receiver of inquiries about these topics.
This month's feature will begin by a response to a question from a yard conductor concerning the axle count factor used for determining the dynamic braking effort output of, in particular, locomotives of a rating of 3800 horsepower and higher. In a later outline, I'll touch on a dynamic braking rule which has some variations you need to be aware of.
The Answer The on-property arrival of the AC Traction model locomotives prompted the issuance of two general orders which revised Air Brake Rules 31.5.1, 31.8.2, and 31.8.4; also affected was Item 4 of UP Timetable No. 2 special instructions.
The changes for calculations of equivalent dynamic braking axles output, along with equivalent axles power output are included with the new Item 4 table.
These changes were necessary in order to facilitate the use of AC Traction locomotives for conventional, manned helper or Distributed Power services by going to powered axles restrictions versus using amperage outputs. By going this route, it will allow for maintaining in-train forces within normal safety margins.
The general orders contain an important statement; that being, you must have copies of them available for reference while on-duty.
RULE 31.5.6: HOW THE EQUIPMENT INVOLVED FUNCTIONS
The current edition of UP's air brake rulebook has among its contents Rule No. 31.5.6; it is called Continuous Dynamic Braking. There are two different arrangements which fall under this category; they are called:
The maintaining version is in use on any UP dynamic brake equipped locomotives which are not of previous CNW, SP, SSW or DRGW heritage. It is a more simple, straightforward arrangement than the dynamic beake holding system.
Upon activation, the maintaining system allows the DBI-MV (dynamic brake interlock magnet valve) to remain energized, allowing backup protection for preventing locomotive brake cylinder pressure buildup from the automatic brake to be retained (Why the DBI-MV is named a backup device is explained by Rule 31.5.4, called Locomotive Brake).
Prior to the full absorption into the UP system, the CNW retrofited their dynamic brake equipped locomotive with the dynamic brake holding system. The key difference this format has from the maintaining system arrangement:
Upon activation, the DBI-MV is de-energized, and a device called a BCPS (Brake Cylinder Pressure Switch) comes into active status. Should BCPS detect buildup of 20 lbs or more of air pressure from either an automatic or independent brake application, the dynamic brake output will be reduced to zero.
Once BCPS detects 18 lbs or less of air pressure, dynamic braking will be reinstated; however, due to the time window between air pressure decrease and dynamic brake output buildup, this event sequence could result in a train separation. Therefore, the adherence to Rule 31.5.4 is a must.
TO ALL CONCERNED
Not all of the former SP, SSW, and DRGW locomotives, prior to merger implementation, had been retrofited with the dynamic brake holding system.
The Maintenance Operations group in Omaha is presently conducting an audit to determine the locomotives which are not. Your input from the field will provide help in locating those particular locomotives.
Should you incur this during operations, notify the Mr. Goodwrench folks at the HDC by the first available means of communication; they can log a referral maintenance note for the locomotive.
Any locomotives which do not have either of the following ID tags posted in the cab is a likely candidate for this modification:
Q. From a Fort Worth South engineer: What condition(s) would cause the brakes to set up undesireably on a dead in consist locomotive?
A. On a running locomotive, the locomotive brake cylinders are "fed" by the main reservoirs. If you should lose either the air compressor or the diesel engine, you will lose main reservori pressure. When the main reservoir pressure drops to below the level whereby it cannot charge the brake pipe, the reverse effect of the reservoirs "feeding" off the brake pipe will occur. This circumstance can lead to the development of brake cylinder pressure, thus an application of the brakes on the dead locomotive.
A LOOK AHEAD
I'll be taking more of your questions, along with taking a look into cold weather protection techniques used for locomotives.
UPDATE FROM LAST MONTH
Subject: The 15 Min. Flange Lube Disable Switch In regards to the UP locomotives: The flange lube circuit breaker is a reset-only device. This reset-only circuit breaker is a spring loaded device that does not allow for manual shut off of power to the device(s) it protects.
The intent is to have a reset function in case the circuit breaker detects an excessive amount of current flow. If and when this occurs, the circuit breaker will trip. The circuit is restored by moving the toggle lever portion of the circuit breaker.
On some UP C40-8 locomotives, this switch is a method employed to provide continuous power to the flange lubrication system, unless the circuit breaker detects an excessive amount of current flow. Moving the reset lever on the front of the circuit breaker does not provide a temporary shutoff method.
This same reset-only circuit breaker can be found in other applications on other newer locomotives in the UP fleet. For example, the BCCB (Battery Charge and Computer circuit breaker) on the C60AC locomotives is a reset-only device. There is no method to manually turn off this circuit breaker.
MY CLOSING THOUGHT
During this time of exchanging gifts, keep in mind...the greatest gift of all is provided to us through Jesus Christ (See John 3:16).
Have a wonderful, prosperous holiday season.