External reducing valves

NW Mailing List nw-mailing-list at nwhs.org
Tue Feb 12 18:52:57 EST 2019


You are right in that you mentioned the intercepting value, but it included the reducing valve as well.  The intercepting and reducing valves both were located in the saddle of the high pressure cylinders and both gave considerable trouble by getting stuck due to carbon deposits.  They were very difficult to reach for maintenance and required frequent cleaning and attention.  Engineers had to service and exercise them at starts, and when out on the road he had to check to see if they remained operable.  This required kerosene followed by oil being poured into a tube to keep these valves serviceable during long runs.  If the reducing valve got stuck and the kerosene and oil treatment didn't work, the engineer had to physically work on the reducing valve to correct this before using simple.  Because of this, Bob Pilcher sought a way to improve dependability and accessibility of these parts and while increasing power of the Mallet compound.

The externally-located reducing valve allowed greater access and it could be used to add some steam to the front LP cylinders when in compound through the use of the booster operating valve or “booster valve” in short.  The simpling valve in the cab allowed the engineer to control the intercepting valve directly for compound or simple operation.  The new components gave much better service and greatly increased power at the lower speeds while in compound mode.  The new Y6b valve travel (which was also added to the 80 older modern Mallets) increased the maximum drawbar horsepower by more than a 1,000 at a higher optimum speed.

All of these improvements were done in the 1950s when all other railroads were dieselizing.

Bud Jeffries

-----Original Message----- 
From: NW Mailing List 
Sent: Monday, February 11, 2019 1:28 PM 
To: NW Mailing List 
Subject: Re: External reducing valves 

On 2/11/2019 11:55 AM, NW Mailing List wrote:

> External reducing valve (relocated from the HP steam saddle and to 
> above the right HP cylinder)
This was because they were having trouble keeping the intercepting valve 
lubricated down there in the middle of the saddle.

Jimmy Lisle

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