Warming up HP steam header
We have a HP steam header through which 4 different plants (plus one power plant)can either export or import HP steam.Many times when one or all
plants r down, the header will be cold(Atmospheric condition).Before any
plant can start using steam from power plant it has to be warmed up to a
perticular temperature.Plug Valves Also for the purpose of venting steam(during
warm up)we are designing a Steam vent Silencer.
Header warm up rate is approximately 50 C per hour.
The question is How do I calculate steam flowrate necessary to get this
warm up rate? Safety ValvesI need this flowrate also to specify my steam vent
silencer.
should be focused on draining the condensate (and venting
noncondensibles).Balance Valves I can't believe that a warmup scenario could be
related to a steam vent sizing basis.
This should be a warm up
valve around the isolation valve for any section of the steam header
which will be brought down.Instrumentation Ball Valves This warmup valve is typically 2" to avoid
an unreasonable condensate slug which could cause a serious hammers if
it can't be drained. The steam traps are typically bypassed straight to
grade via oversized start-up
drains. The purpose is to insure a well drained system. The main valve
is not opened until the header is blowing steam out the trap bypasses.
This is done after the trap bypasses are closed (sometimes these are
closed in sequence as the header warms) and the normal traps are online.
The header will come up to pressure. At that point the main block valve
can be opened to put the header fully and safely on line. There is no
"steam venting" in a normal sense.Needle & Gauge Valves
50C/hr warm up rate seems an
ambiguous basis for design as the header does not warm up uniformly. At
fast warm-up rates (ie imaging just wheeling the steam wide open into a
cold header) the hammer that can occur with a slug of condensate not
well drained can be frightening- I have seen the aftermath of an 8"
blind flange bursting off from exactly this sort of uncontrolled warmup,
but fortunately no injuries.
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