My maternal grandfather Herbert Mavor belonged to the United Association of Journeymen and Apprentices of The Plumbing and Pipefitting Industry, Local Union 608 in Montreal. He was a Steamfitter for the Canadian National Railway in Montreal, and a Union member for over 30 years.
You may also look in the government Sessional Papers for pipefitter names, and other railroad employees. Here it shows the wages of the employees at the Moncton Shop.
Steamfitter (or Pipe fitter) information is found under Plumbing.
Plumbers, gas and steam fitters journal 1919
Plumbers, gas and steam fitters journal (several years)
Official organ of the United Association of Journeymen Plumbers, Gas Fitters, Steam Fitters and Steam Fitters Helpers of the United States and Canada, 1907
The Illinois plumbing license law 1924-1968
Montreal Brass Foundry: plumbers, gas & steam fitters, brass founders, copper smiths and silver platers - 1890
Illustrated catalogue of James B Clow & Son - USA 1886
The Metal worker, plumber and steam fitter (several years)
Plumber and Steam Fitter - 1920-1921
Hayden, Gere & Co brass founders, 1877
Charles Millar & Son, Utica NY - 1894
Group portrait of Southern Pacific Railroad Sacramento Shops employees: pipers and steam fitters 1899