Re: Leaking packing, CM story, NNG

Typical steam rod type steam locomotive, you have valve packing around the power piston rod and the piston rod for the valve.

Vauclain compound, you have both a high and low pressure power piston rod, plus the valve rod. One cutaway I saw shows it as an outside admission valve, so it would be under constant steam pressure when the throttle is open. So you have three potential leaks due to poor packing on each side on a Vauclain compound versus two on a standard design.

One of the advantages of later piston valve designs is that most built new were inside admission - the packing only subject to exhaust steam. (I believe most conversions - no new cylinder castings - to piston valves retained outside admission for compatibility.