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USRA Mikado Steam Engine

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Injectors

 

The injector may be defined as an apparatus for forcing water into a steam boiler in which a jet of steam imparts its energy to the water and thus forces it into the boiler against boiler pressure. Injectors are now universally employed for delivering the feed water to the boiler. Two injectors are always used, either one of which should have a capacity sufficient to supply the boiler with water under ordinary working conditions. They are located one on either side of the boiler. Injectors may be classified as lifting and non-lifting, the former being most commonly used. The lifting injector is placed above the high water line in the tank, therefore in forcing water into the boiler, it lifts the water through a height of a few feet. The non-lifting injector is placed below the bottom of the water tank, hence the water flows to the injector, by reason of gravitation.

(Source: LOCOMOTIVE BOILERS AND ENGINES, A PRACTICAL TREATISE ON LOCOMOTIVE BOILER AND ENGINE DESIGN, CONSTRUCTION, AND OPERATION; LLEWELLYN V. LUDY, M.E.; 1920)

Non-lifting Injectors- Pro & Cons

When surveyed, what eleven railroads in 1922 cited as the the advantages of non-lifting injectors:

  • larger capacity for the same size injector, injector pipes and connections; grades closer, giving a wider ranger for each size of injector;
  • gives less trouble from restricted openings in the feedwater supply pipe;
  • located on the outside of the cab, thus relieving congested conditions inside and making the application and maintenance cost less;
  • more accessible for repairs and repairs can be made on the injector in place without disconnecting from the piping;
  • will work with less water in the tender tank and also operate with the feedwater at a considerably higher temperature.
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    The disadvantages of this type injector are its greater liability to being knocked off by derailment, side swipe, etc. and the liability to freeze in extremely cold weather.

    Source: 1922 Locomotive Cyclopedia of American Practice

     

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    USAR Mikado 3d Render

    Nathan Manufacturing Company

    Non-Lifting Injectors

    for the USRA Locomotives

    Source: 1922 Locomotive Cyclopedia of American Practice

     

    August 23, 2015