As I read and mull over my Westinghouse No.6 ET brake books, I have a couple questions involving the "turning on and off" the two gov. tops. The "low" pressure head contols the pump while the automatic's handle is in release, running, and holding. The "high" pressure head likewise controls the pump, but in lap and application positions. Herein lies the questions,

1) Once one side is "turned off" due to handle position, and it's pin is up allowing air to seat the gov., how does the other side's pin valve then being seated cause the gov. to open allowing steam to the pump? In other words, how does one side not cancel out the other?

and

2) With the "main res." side being the "high" side and seemingly always in communication, how does the "low" side allowed to govern at all?

Ray

> As I read and mull over my Westinghouse No.6
> ET brake books, I have a couple questions
> involving the "turning on and off"
> the two gov. tops. The "low"
> pressure head contols the pump while the
> automatic's handle is in release, running,
> and holding. The "high" pressure
> head likewise controls the pump, but in lap
> and application positions. Herein lies the
> questions,

> 1) Once one side is "turned off"
> due to handle position, and it's pin is up
> allowing air to seat the gov., how does the
> other side's pin valve then being seated
> cause the gov. to open allowing steam to the
> pump? In other words, how does one side not
> cancel out the other?

> and

> 2) With the "main res." side being
> the "high" side and seemingly
> always in communication, how does the
> "low" side allowed to govern at
> all?

> Ray

I'm surprised you've had no response, so here goes

The high pressure head is always connected to the Main res. so in the absence of any other control, it will limit the MR pressure. In all positions other than release, running,and holding the low pressure head is connected to the MR and will cut in before the High pressure head.

It's all in how you look at it!

> 1) Once one side is "turned off"
> due to handle position, and it's pin is up
> allowing air to seat the gov., how does the
> other side's pin valve then being seated
> cause the gov. to open allowing steam to the
> pump? In other words, how does one side not
> cancel out the other?

You may be confused in that when the LP head is turned off, its pin drops down and is seated which takes that side out of the equation.

The MR head is always set at the higher pressure, and never lifts until the high pressure setting is reached. And that never happens until the brake valve is lapped which turns off the LP.

> As I read and mull over my Westinghouse No.6
> ET brake books, I have a couple questions
> involving the "turning on and off"
> the two gov. tops. The "low"
> pressure head contols the pump while the
> automatic's handle is in release, running,
> and holding. The "high" pressure
> head likewise controls the pump, but in lap
> and application positions. Herein lies the
> questions,

> 1) Once one side is "turned off"
> due to handle position, and it's pin is up
> allowing air to seat the gov., how does the
> other side's pin valve then being seated
> cause the gov. to open allowing steam to the
> pump? In other words, how does one side not
> cancel out the other?

> and

> 2) With the "main res." side being
> the "high" side and seemingly
> always in communication, how does the
> "low" side allowed to govern at
> all?

The HP side is always connected to the MR. The LP side is connected to the MR only in certain brake valve handle positions (as you have mentioned above). When the LP side is connected, it overrules the HP side because it's set for a lower opening pressure.

When the brake valve handle is placed in a position which shuts off the air supply to the LP side (any postition other than the ones you have mentioned), the LP side still continues to operate (i.e the pin will go up before the HP one does) because of common passageways inside the governor. But it's been disconnected from the large supply of MR air coming from the brake valve, without which it can't close the steam valve.

When the automatic brake valve in returned to any of the three releasing positions, the MR air supply to the LP side is re-established, and it regains its dominane over governor operation. The HP side still receives air, those passageways again, but being set to a higher cut-out pressure, it returns to non-operation.

Thank you for answering my questions clearer than Westinghouse did.