  This paper focuses on multiscale dynamics occurring in steam supply systems.
The dynamics of interest are originally described by a distributed-parameter
model for fast steam flows over a pipe network coupled with a lumped-parameter
model for slow internal dynamics of boilers. We derive a lumped-parameter model
for the dynamics through physically-relevant approximations. The derived model
is then analyzed theoretically and numerically in terms of existence of
normally hyperbolic invariant manifold in the phase space of the model. The
existence of the manifold is a dynamical evidence that the derived model
preserves the slow-fast dynamics, and suggests a separation principle of
short-term and long-term operations of steam supply systems, which is analogue
to electric power systems. We also quantitatively verify the correctness of the
derived model by comparison with brute-force simulation of the original model.
