I have been documenting Climax CN 1551. I have recently completed a drawing of the D Valve Part F386. The D Valve has two (2) holes in the top of the valve. One is threaded 5/8" so that it can be closed with a threaded bolt. There is also a smaller one beside it which would not be covered by the bolt head unless an additional part under the bolt head covered the smaller hole.

Can anyone provide an explanation for the two (2) holes?

The separate cast iron strips on top of the D Valve have springs under them to hold the D Valve down on the valve surface until the steam pressure does so.

A 3D pdf may be found at:

https://s3.amazonaws.com/SIMONTON/F386+ ... sembly.pdf

Requires Adobe Acrobat or Acrobat Reader as browser pdf previewers do not properly handle 3D pdfs. View in Solid Outline in Daylight or CADD Optimized Lighting. May be rotated and zoomed.

I can't get the drawing to load but the threaded hole is to use for lifting the valve from the chest. Screw in an eyebolt, etc...... the other hole is the vent from the area above the valve within the balanced area to the exhaust cavity. The metal plates with little single leaf springs is the balancing system - nothing to do with holding the valve against the port surfaces, more to prevent the pressure of the steam from impacting the entire surface atop the valve itself, which would push it against the port surface and make it hard to hook up and wear rapidly in service. Limiting the part of the top of the valve under pressure reduces the amount of shoving down. Check out the Richardson Balanced Valve to find out how one of the most used designs works.

Here's a quick link to Yoder's discussion of the Richardson balanced slide valve:

https://books.google.com/books?id=TKV-AAAAMAAJ&pg=PA16&lpg=PA16&dq=richardson+balanced+valve&source=bl&ots=Duy0buqjqr&sig=dmthasIHGbpaiFx9tDhY8PKgdoE&hl=en&sa=X&ved=0ahUKEwjDkIiBtLTMAhXE6SYKHWveDisQ6AEIHTAA#v=onepage&q=richardson%20balanced%20valve&f=false

(I consider this a good reference book on 'contemporary' practice; people in the United States can download the whole thing from Google Books as a pdf.

Thanks for the info and link. Very illuminating.