The Missabe Road (DM&IR) purchased two steam-generator equipped SD-9s in the mid-fifties. They were geared as freight engines. At first they were as back-up power on passenger runs, but later became standard power on shipper's special trains and such. In the 1970's, the engines were leased to Amtrak for a time and used on the North Star (Twin Cities to Twin Ports train).
GM designed the early GPs and SDs to be able to be used in passenger service, with a steam generator in the short high hood. Passenger GPs were more common than SDs. I know Great Northern, Soo Line, and New York Central used passenger GPs in regular passenger service.
Nile; The Southern Pacific purchased 43 SD-7s, or 23% of the total of 188 units built. Of these units, twenty were steam generator equipped for use system-wide as reserve passenger power. The slow passenger trains were disappearing in the 1950s and the SD-7s wound up on branch lines and local freights. Eventually, they became heavy switchers, confined to yard and transfer duties in California.
Southern Pacific's 150 SD-9s or, about 32% of all SD-9 production was the largest fleet of any purchaser. The next largest buyer, the Burlington, took 80 units and the Duluth, Missabe & Iron Range was third with 74. The SP had steam generator equipped SD-9s that they used on secondary passenger trains as well as in San Francisco commuter service. They would also pull office car extras when the brass hats went out on the road. Like the SD-7s, their domain was not the Sunset Limited or, the Daylights.
The SD-7s were delivered in SP's "tiger stripe" switcher paint scheme while, the SD-9s arrived wearing "black widow" colors. All finished their days in the "bloody nose" paint. It should be noted the last two SD-9s with serviceable steam generators, nos. 4450 and 4451 lasted at least into the late 1980s, if not longer, as they were protection power for the San Francisco commute pool. That doesn't mean they never got out on the road. I saw 4450 in Sanderson TX in 1986, on an eastbound freight and it was definitely contributing tractive effort!
The SD-9 roster in the September/October 1969 issue of " Extra 2200 South: The Locomotive Newsmagazine" (now-defunct) lists the units delivered with steam generators besides the first 47 on the SP as:
CB&Q 325-374 and 430-459 80 units
C&NW 1701-1710, 1721-1724 14 units
I hope this answers some of your questions.
'
I'll mention the one railroad that I'm sure about, the Bessemer & Lake Erie, which had three steam generator-equipped SD7s built in October of 1952. The Bessemer had a moderate passenger business between Erie, Pennsylvania (with trackage rights) and Pittsburgh.
Proto 2000 made a model of the steam generator SD7s.
Regards, Ed
I'm interested in railroads or instances where SD-7s or SD-9s were used in passenger service. Were these engines steam heater equiped? What railroads used them? Were there railroads that used them on an as needed or to "pitch hit" when they were short on power?