[sim-al2]

Hello,

It seems that the emergency function of the triple valve for single pipe air brake systems is not working correctly in recent releases. Service applications still equalize as expected, but when an emergency application occurs with newer OR versions the brake cylinder pressure does not increase beyond full service pressure as expected. Attached are two screenshots, the first showing proper behavior in older versions of OR (U2022.02.23-0951 in this case), and the second that occurs in versions at least as early as U2022.03.31-1852. This bug is still present in the latest unstable release (U2023.03.29-0851) as well. Expected brake cylinder pressures for the 90psi system depicted are 64psi for full service applications and 77psi for emergency applications. As you can see, this condition is achieved in U2022.02.23-0951 but not in U2022.03.31-1852 and later versions. It appears that the emergency portion of the triple valve is not used at all except during brake release.

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[cesarbl]

Yes, the previous implementation was wrong since it switched valves to "Emergency" based on BP pressure. Now it is based on pressure rate, so when a high pressure drop is detected, valve switches to emergency. The default rate was set to 0, but I have just modified it to 15 psi/s so that it works without modifying .wag files. Additionally you will need to set also ORTSEmergencyDumpValveRate() if you want that every wagon discharges BP during emergency, otherwise the emergency application wouldn't be propagated along the full train.

Please test next unstable release to see if it works with the new default value for ORTSEmergencyValveActuationRate.

From recent versions of the manual:

Quote

``Wagon(ORTSEmergencyValveActuationRate`` -- Threshold rate for emergency
brake actuation of the triple valve. If the pressure in the brake pipe
decreases at a higher rate than specified, the triple valve will switch to
emergency mode.
- ``Wagon(ORTSEmergencyDumpValveRate)``-- Rate at which BP is locally discharged
at every wagon during an emergency brake application.

[Weter]

Hello.
What is default rate for the second parameter? Zero?
So, we have now two settings, modifying triple valve's (actually, distributor's) attitude:
ORTSBrakeInsensitivity - for "softness" rate setting, and
ORTSEmergencyValveActuationRate, as it was stated above, right?

[cesarbl]

Quote

What is default rate for the second parameter? Zero?

Yes, it will default to zero unless user feedback requires otherwise.

Quote

ORTSBrakeInsensitivity - for "softness" rate setting, and
ORTSEmergencyValveActuationRate, as it was stated above, right?

Yes, both have been around for a while.

[Weter]

Maybe, to look about some default factor for BP discharge at emergency mode: say 1,5 - for "just silent users"?
OTOH, since some distributor models haven't emergency mode atall, the default zero factor would naturally disable "threshold" parameter.
So, it is indeed up to users' majority to prefer.

Sadly, it's very rare - to look for manual's changes, while among changes list on OR.org that haven't been noticed.

Quote

It seems that the emergency function of the triple valve for single pipe air brake systems is not working correctly in recent releases. Service applications still equalize as expected, but when an emergency application occurs ... the brake cylinder pressure does not increase beyond full service pressure as expected

AFAIK, this may be possible only when additional "emergency" reservoir is present. Because having only one "auxiliary" reservoir, max. BC pressure would be always the same, and equal to (BP pressure times triple valve factor) minus leaks.

[R H Steele]

What is the UoM for ORTSEmergencyDumpValveRate() --- feet per second? I'm confused ( brakes do that to me -- ) because a default of zero would mean there is no rate.

...or does zero mean that the discharge is immediate --- no time delay?

[Weter]

Usually, default UoM for pressure were psi/s. Other are acceptable, being clearly specified just after number (without white space): for me, bar/s would be in favor.
Zero might mean "no addition to discharge rate in emergency mode"
Delay is not about this case: this function only gives en extra opening to atmosphere under given vehicle - for faster BP discharge and avoiding the "reverse brake wave".
The latter can even cause squashing of front cars of the train, if front cars expose harder brake effect, than rear cars, which then would push front cars.