The Steam Engine Safety Valve: New Valves Require Knowledge of Old Boilers

What you need to know before buying a valve for your hand-fired boiler

A possible safety valve arrangement; the new valve satisfies the code requirements, while the old-style valve performs the function for which it was designed. Notes: The ASME code valve must not be installed on the branch of the tee. Nipples between the valves and the boiler must be scheduled 80 and short as possible. Elbow and tee between valves, and the boiler must be at least 300 psi. No other fittings may be installed between the valves and the boiler.
Figures courtesy of Bruce E. Babcock