• Deep Dive Into The Elesco Type T.P. 502 Exhaust Steam Injector Used On UP Big Boy No. 4014

  • Discussion of steam locomotives from all manufacturers and railroads
Discussion of steam locomotives from all manufacturers and railroads

Moderators: Typewriters, slide rules

  by Fan Railer

Deep dive into the Elesco Type T.P. 502 Exhaust Steam Injector used on UP Big Boy No. 4014, and Challenger 3985.

For water supply to the boiler, UP 4000-class Big Boy No. 4014 employs a Nathan Type 4000 Size C "Special" automatic restarting live steam injector on the engineer's side, and an Elesco Type T.P. 502 Exhaust Steam Injector on the fireman's side. The Nathan injector is sized for 12,500 gallons per hour while the Elesco injector used on Big Boy* is sized for 14,076 gallons per hour maximum operation.

*Size 18 nozzles were used on Challenger locomotives, giving 12,360 gallon/hour capacity, while size 19 nozzles were used on Big Boys, giving 14,076 gallon/hour capacity.

In this deeper dive video about the exhaust injector, you will first see a series of photos, including a diagrammatic view of the injector, followed by still shots of the injector on Challenger 3977 in Cody Park, North Platte, Nebraska. To round off the photo section, I've included the article from the Enginemen's Magazine in June 1942 detailing how the type TP injector is laid out and functions. I suggest pausing here and reading the article, particularly the last two pages that detail operation of the changeover valve that allows the injector to switch between live and exhaust steam.

In the next section, there are a few clips of the injector running on live steam (locomotive throttle closed, no exhaust steam available). You will see the process of operation, which starts with pulling the starting valve into the priming position. This supplies steam to the cold water turbine pump located under the cab on the fireman's side, which then pumps water from the tender up to the injector located next to the smokebox on the same side. The exhaust for the cold water pump can be seen as a plume of white smoke on top of the turret ahead of the cab. Once the injector is primed, the starting valve is moved into the full open position, live steam is supplied into the injector, and the water is injected into the boiler. Overflow is a normal part of the starting process, and its drainage can be seen just ahead of the cylinder for the rear engine unit. Water supply to the injector is regulated with an indexed dial control in the cab. After the proper water level is reached in the boiler, the operating valve is shut off. Any remaining water within the system that was not injected into the boiler drains from the overflow.

In the final section of the video, you will see operation of the injector while the locomotive throttle is open and the engine is working steam. The operation is much the same as described above, with the added step of changing over from live steam to exhaust steam, which takes place approximately 10 seconds after the injector is initially started. The changeover process is completely automatic, with no input from the fireman needed. Note the overflow of water that occurs when the changeover happens, and the darkening of the stack exhaust plume while the injector is operating on exhaust steam. The darkening of the stack exhaust occurs because there is less exhaust steam from the cylinders to the stack (it is being diverted to the exhaust injector) to dilute the oil smoke from the firebox, flues, and tubes.

For more information on how injectors work (and more info on the Elesco type TP), here are some useful links:
https://utahrails.net/flebbe-papers/UP_ ... papers.pdf (Official UP test report on the type TP injector, as tested on CSA Challenger 3911)

Table of contents:
0:00 - Intro and diagrammatic view of type TP injector 0:10 - Injector body on UP 3977
0:35 - Pyle National cold water turbine pump on UP 3977
0:50 - Exhaust steam supply pipe to injector on UP 3977
0:55 - Changeover relay valve on UP 3977
1:05 - Water regulating dial in cab on UP 3977
1:15 - Article on type T and TP injectors
1:30 - Operation on live steam (throttle closed)
4:07 - Operation on live & exhaust steam (throttle opened)
4:12 - Starting valve to priming position
4:17 - Starting valve to open position, injector starts on live steam, note overflow
4:28 - Automatic changeover process to exhaust steam starts, injector briefly stops, causing overflow
4:31 - Injector restarts on exhaust steam, causing darkening of stack exhaust
5:13 - Injector is shut off
5:18 - Residual water drains from overflow