UK Railways
UK railway companies did not agree on the merits of snifting valves. The London and North Eastern Railway used them very widely. The London, Midland and Scottish Railway did not use them on new locomotives but inherited some locomotives with snifting valves from constituent companies. The Southern Railway used them for a while but later removed them.
The probable explanation for this diversity is that snifting valves were useful as long as steam temperatures were relatively low. As locomotive development proceeded, larger superheaters were fitted and steam temperatures increased. When the locomotive was coasting, the air passing from the superheater to the cylinders became so hot that it oxidised the cylinder oil and interfered with lubrication. At this point, most railways decided to abandon snifting valves.
Read more about this topic: Snifting Valve
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