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Re: Pneumatic and Electro-Pneumatic Braking
Author: SP5103
Date: 09-14-2008 - 12:22
A few more:
A D-triple is supposed to be in current production, it is a plain diaphragm design.
H triples could be (and I imagine most were) factory updated to a K.
Their are modern K style designs still in use in other locations outside North America.
5ET was just before the 6ET, it had some drawbacks when doubleheading and was quickly replaced by 6ET, most 5ET updated to 6ET.
14EL (very common on early and small diesel switchers) was an updated 6ET design with the independent and automatic brake valves sharing the same pipe bracket.
6BL/6SL/6DL offered self lapping independent, 6BL designed for panel mounting.
8ET/8EL - used on late steam and early diesel or electrics - primarily road units
24RL was an updated 8 system, there was a 24ET for steam locomotives offered. Later 24RL were the first common with factory pressure maintaining, early 24RL could be updated with factory portions or some railroads figured out how to modify older ones to pressure maintaining.
Until 26L was offered (about 1958), 6BL was the common "standard basic" on 1950s diesels, 24RL was the optional "road" rake system. I've seen F units with 6BL, SW1200 with 24RL, GP7s with either. 24RL could not be mu-ed with 6/14 (or vice versa) unless modified.
There was one set of 25 for testing - a failed attempt to convert 24 to diaphragm control.
26 appears to have originated from of the transit side of Wabco, and is pressure maintaining and self lapping independent and automatic. Current engineer's brake valves are the 26B (automatic only for transit), 26C (automatic and independent - most common) and 26E (E-P position brake valve). 26L schedules can be universal (will work with 6 and 24), 26L with 26F control valve (most common), 26NL (designed by NYAB - 6N distributing valve - now discontinued) and a system using a 26D control valve (switchers).
27LA is found on speed swings, track mobiles, cranes, etc. - this is a small low-capacity system. 27LB uses a 26 automatic brake valve and the 27 independent (appears to be export only). 27LV is a combined straight air (engine brakes only) and vacuum system.
30 systems have the same functions and handle postions as a 26, but most of the valving was split from the handles to allow desktop mounting. It can also be mounted vertically (in place of the standard 26) which is starting to be more common.
The first production Wabco electronic brake was the 3101 which used "pneuma cards", a modular plug in system supposed to allow easy maintenance. These "cards" weighed about 50# each and soon discontinued in part due to leakage at the air connections. The current system is 3102 which has numerous variations and panel mounts compenents under the cab. NYAB/Knorr has their own design, and their are rumors of possible compatibility problems between them in DPU service.
The U12 was originally promoted as the "Universal" valve for both passenger and freight, but either New York Central or Pennsy killed the idea. It has a mounting face for optional E-P control, and was common on heavyweight era passenger cars.
The AB also had a factory ABC upgrade, changing the service portion to diapragm control. It did not gain widespread acceptance, and most AB valves remained in their original configuration.
The ABD valves can be factory upgraded to ABDX, I don't know how popular this upgrade is.
The Knorr DB60(L) (comprising DB10 and DB20 portions) are the equivelant of the ABDX(L), the service and emergency portions can be mixed. ABDX still uses slide valves, DB60 uses all rubber seating - but resulting functions are the same.
Previous E-P brake systems have used a variety of methods for controlling the brakes, but the original brake pipe control is always available as a back-up.
Some systems control brake cylinder pressure directly, with standard brake pipe control in parallel operation to control brake cylinder pressure if E-P fails.
Another form of the system instead controls the brake pipe, with magnet valves on each car locally exhausting brake pipe pressure, and locally adds air into the brake pipe during release. In this system, the brake pipe is still controlled normally with the local action of the E-P system providing for a quicker response.
There were several versions of the 24 brake valve for E-P use.
Variations of the PS-68 sytem using the 26E automatic brake valve use a modified ABD valve. The 26E has two release postions, a full release and a holding postion. In either position, the brake pipe is recharged to full pressure. In the holding position, a magent valve is closed to keep the brake cylinder from releasing further while the brake system recharges.
All the above systems rely on a multiple conductor train-line operating several magnet valves (most had an additional emergency magnet valve). This has always been the drawback to these systems, maintaining circuit continuity.
From what little I have seen, the "new and improved" proposed/mandated E-P system is similiar as far as control, but very different in the controlling circuits. It appears to use a single conductor (maybe double?) of a substantial voltage that is actually a carrier for a digital electronic signal (and possibly power supply?). The actual circuit connection is part of the gladhand so a separate connector is not required (in part due to unions wanting an electrician to make the trainline connections). In addition to controlling the brakes, there is an expectation that the individual cars are to "talk back" to the controlling unit and report their individual status. I have no idea if prototype testing of this system has been succesful. I have seen what appears to be two variations, one as an add-on filler piece to existing brake valves, another where the E-P is primary and the pneumatic control is greatly simplified to a back-up status (apparently to save cost).
I will not argue that E-P brakes will provide great advantages - graduated release and near instantaneous application and release - if the entire train is equipped with the system and if it works consistently. At this time, I consider this a failed concept at this time based on the following:
1. The problem has always been maintaining circuit continuity. The proposed sytem has not been tested enough to prove its reliability.
2. How well will the individual car systems hold up under real operating conditions and field maintenance?
3. Most of the railroad cars in the US are now privately owned. What economic advantage can be offered to the car owners to justify equipping their cars?
4. Like dynamic brakes, an E-P system is far from a fail-safe design. The touted economic advantages to railroads are based on increased capacities in part to shorter stopping distances. What happens if the E-P sytem fully or partially fails during a stop and suddenly the engineer needs twice the expected distance to get stopped? Take a chance on scattering the train with an emergency application?
5. How well will a new carrier based digital E-P system hold up considering our increasing electronic noise? We are talking about a 10,000'+ cicuit paralleling rails, power lines and communication cicuits also carrying electronic signals for signal and communications, and general em interference.
At this point I think we are about 10 years away from seeing a useable prototype digital E-P system, and another 10-20 years to fully implement it. If there is such an economic advantage to it, why haven't railroads begun to equip their unit trains in captive service on their own?
Understand that on the transit/traction side, there are far too many variations of brake systems to even keep track of.
A D-triple is supposed to be in current production, it is a plain diaphragm design.
H triples could be (and I imagine most were) factory updated to a K.
Their are modern K style designs still in use in other locations outside North America.
5ET was just before the 6ET, it had some drawbacks when doubleheading and was quickly replaced by 6ET, most 5ET updated to 6ET.
14EL (very common on early and small diesel switchers) was an updated 6ET design with the independent and automatic brake valves sharing the same pipe bracket.
6BL/6SL/6DL offered self lapping independent, 6BL designed for panel mounting.
8ET/8EL - used on late steam and early diesel or electrics - primarily road units
24RL was an updated 8 system, there was a 24ET for steam locomotives offered. Later 24RL were the first common with factory pressure maintaining, early 24RL could be updated with factory portions or some railroads figured out how to modify older ones to pressure maintaining.
Until 26L was offered (about 1958), 6BL was the common "standard basic" on 1950s diesels, 24RL was the optional "road" rake system. I've seen F units with 6BL, SW1200 with 24RL, GP7s with either. 24RL could not be mu-ed with 6/14 (or vice versa) unless modified.
There was one set of 25 for testing - a failed attempt to convert 24 to diaphragm control.
26 appears to have originated from of the transit side of Wabco, and is pressure maintaining and self lapping independent and automatic. Current engineer's brake valves are the 26B (automatic only for transit), 26C (automatic and independent - most common) and 26E (E-P position brake valve). 26L schedules can be universal (will work with 6 and 24), 26L with 26F control valve (most common), 26NL (designed by NYAB - 6N distributing valve - now discontinued) and a system using a 26D control valve (switchers).
27LA is found on speed swings, track mobiles, cranes, etc. - this is a small low-capacity system. 27LB uses a 26 automatic brake valve and the 27 independent (appears to be export only). 27LV is a combined straight air (engine brakes only) and vacuum system.
30 systems have the same functions and handle postions as a 26, but most of the valving was split from the handles to allow desktop mounting. It can also be mounted vertically (in place of the standard 26) which is starting to be more common.
The first production Wabco electronic brake was the 3101 which used "pneuma cards", a modular plug in system supposed to allow easy maintenance. These "cards" weighed about 50# each and soon discontinued in part due to leakage at the air connections. The current system is 3102 which has numerous variations and panel mounts compenents under the cab. NYAB/Knorr has their own design, and their are rumors of possible compatibility problems between them in DPU service.
The U12 was originally promoted as the "Universal" valve for both passenger and freight, but either New York Central or Pennsy killed the idea. It has a mounting face for optional E-P control, and was common on heavyweight era passenger cars.
The AB also had a factory ABC upgrade, changing the service portion to diapragm control. It did not gain widespread acceptance, and most AB valves remained in their original configuration.
The ABD valves can be factory upgraded to ABDX, I don't know how popular this upgrade is.
The Knorr DB60(L) (comprising DB10 and DB20 portions) are the equivelant of the ABDX(L), the service and emergency portions can be mixed. ABDX still uses slide valves, DB60 uses all rubber seating - but resulting functions are the same.
Previous E-P brake systems have used a variety of methods for controlling the brakes, but the original brake pipe control is always available as a back-up.
Some systems control brake cylinder pressure directly, with standard brake pipe control in parallel operation to control brake cylinder pressure if E-P fails.
Another form of the system instead controls the brake pipe, with magnet valves on each car locally exhausting brake pipe pressure, and locally adds air into the brake pipe during release. In this system, the brake pipe is still controlled normally with the local action of the E-P system providing for a quicker response.
There were several versions of the 24 brake valve for E-P use.
Variations of the PS-68 sytem using the 26E automatic brake valve use a modified ABD valve. The 26E has two release postions, a full release and a holding postion. In either position, the brake pipe is recharged to full pressure. In the holding position, a magent valve is closed to keep the brake cylinder from releasing further while the brake system recharges.
All the above systems rely on a multiple conductor train-line operating several magnet valves (most had an additional emergency magnet valve). This has always been the drawback to these systems, maintaining circuit continuity.
From what little I have seen, the "new and improved" proposed/mandated E-P system is similiar as far as control, but very different in the controlling circuits. It appears to use a single conductor (maybe double?) of a substantial voltage that is actually a carrier for a digital electronic signal (and possibly power supply?). The actual circuit connection is part of the gladhand so a separate connector is not required (in part due to unions wanting an electrician to make the trainline connections). In addition to controlling the brakes, there is an expectation that the individual cars are to "talk back" to the controlling unit and report their individual status. I have no idea if prototype testing of this system has been succesful. I have seen what appears to be two variations, one as an add-on filler piece to existing brake valves, another where the E-P is primary and the pneumatic control is greatly simplified to a back-up status (apparently to save cost).
I will not argue that E-P brakes will provide great advantages - graduated release and near instantaneous application and release - if the entire train is equipped with the system and if it works consistently. At this time, I consider this a failed concept at this time based on the following:
1. The problem has always been maintaining circuit continuity. The proposed sytem has not been tested enough to prove its reliability.
2. How well will the individual car systems hold up under real operating conditions and field maintenance?
3. Most of the railroad cars in the US are now privately owned. What economic advantage can be offered to the car owners to justify equipping their cars?
4. Like dynamic brakes, an E-P system is far from a fail-safe design. The touted economic advantages to railroads are based on increased capacities in part to shorter stopping distances. What happens if the E-P sytem fully or partially fails during a stop and suddenly the engineer needs twice the expected distance to get stopped? Take a chance on scattering the train with an emergency application?
5. How well will a new carrier based digital E-P system hold up considering our increasing electronic noise? We are talking about a 10,000'+ cicuit paralleling rails, power lines and communication cicuits also carrying electronic signals for signal and communications, and general em interference.
At this point I think we are about 10 years away from seeing a useable prototype digital E-P system, and another 10-20 years to fully implement it. If there is such an economic advantage to it, why haven't railroads begun to equip their unit trains in captive service on their own?
Understand that on the transit/traction side, there are far too many variations of brake systems to even keep track of.
