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 Post subject: Injector Location
PostPosted: Mon Nov 09, 1998 6:37 pm 

On some older, but not all, B&M steam, the injectors were located on the engineer's side backhead directed toward the fireman's side where the two boiler checks were located directly over the crownsheet. Apart from neatness of appearance, were there any advantages to dumping the cold water in at the crownsheet rather than the more usual position near the front?<br>


  
 
 Post subject: Re: Injector Location
PostPosted: Mon Nov 09, 1998 8:06 pm 

I can't think of any advantages, but I can think of some disadvantages.<p>The obvious one is the potential for thermal stress in the crown sheet, especially if the water level gets low. <p>The less obvious one has to do with the design of heat exchangers. At the front tube sheet the temperature of the flue gases is (or should be) significantly lower than at the rear tube sheet. Dumping the water in at the front creates a temperature gradient from front to rear of the boiler (in theory at least - measuring it as the boiler rocks along would be a challenge), getting more heat out the flue gases.<p>Now I fully admit this is an esoteric concern in a steam boiler - they weren't steady-state, steady-flow appliances, and so you can't exactly design them down to the fraction of a degree. Exhaust temperatures were still significantly above the saturated temperature at boiler pressure, and it would take a more complex boiler design for all this to really matter. But when a fireman was trying to keep up with steam demands on a steep grade or a heavy train, every little bit helped.<p>JAC<br><br>


  
 
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