Author Topic: Hancock Inspirators vs Sellers Injectors Part 2  (Read 3572 times)

Roger Whitney

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Hancock Inspirators vs Sellers Injectors Part 2
« on: December 01, 2011, 08:21:21 PM »

   In the last blog Superintendent Morrill changed his mind on what type of feed water injection system he wanted on the new Vulcan No. 3 which was near completion in Pennsylvania.   He chose the Sellers Injectors over the Hancock Inspirators due to frequent cronic problems with the Hancocks.  But what was wrong with the Hancocks? What’s the difference between an injector and an inspirator?
   This gets a little technical, which probably only the steam crew will love…..    
        An injector has a single chamber with a combined suction and delivery nozzle that creates a vacuum and then discharges a jet of water at high velocity(into the boiler).
        An inspirator has two chambers which are individually adjustable. One chamber has a nozzle for suction, which feeds a second chamber with a nozzle for discharge. The steam supply to each chamber is individually adjustable, although usually “tied” together on the same handle.
         I found several forums where engine crews who have actually used the Hancocks commented on them.
         One of the advantages of the Hancock Inspirator they claimed, is that it delivers water at a higher temperature than an injector.
         However they seem a little harder to get started than an injector but once you “get used to them it is no problem”.
         In their experience with the Hancock, the problem was the mechanical overflow valve. On the Sellers, the overflow either uses a check valve or relies on a gap and fluid flow principles. On the Hancock, the overflow is closed by a linkage to the handle, and it frequently closed before the inspirator had developed a good vacuum and flow. Also when worn, the linkage introduces lost motion. Was this the real trouble with the Monson Hancocks?  Design flaws? According to those in the know, the operator had to be really sensitive with the handle to develop a good flow before completing the handle movement.
         Superintendent Morrill solved the problem in his no-nonsense manner by switching to the Sellers.  Trivia….are the Sellers still on the Monson Vulcans today? Many thanks to Keith Taylor for his assistance on this topic.