Hi Chris
Condensate hammer is often caused by opening valves which isolate portions
of a circuit. This is a very real problem withe distributed heating systems.
At one time branch mains were normally left on which kept everything hot.
However standing losses are often enormous, so it makes more sense from an
energy conservation perspective, to isolate the entire mains. However
sometimes the branches are not returned to service with any care. Bang.
Grid type systems and multilevel systems are especially exposed to this type
of problem.
Many steam traps are connected via an uninsulated drop leg with them. This
reduces cycling and air binding, and also improves valve seat life. The drop
leg is "designed" to subcool the condensate a little.
Boiler priming is also a killer.
Thats 3 ways.
Cheers
Steve
>From: Christopher Wright <chrisw@skypoint.com>
>Reply-To: PipingDesign@yahoogroups.com
>To: PipingDesign@yahoogroups.com
>Subject: [PipingDesign] NYC steam line rupture
>Date: Sat, 21 Jul 2007 11:13:03 -0500
>
>
>I'm surprised there's been so little comment about the pipe that
>ruptured in New York. Does everyone realize what happened and that
>it's serious damn business?
>
>Anyway one thing puzzles me. The cause of the rupture has been
>postulated as 'condensate hammer'--condensate slammed around which
>overloads the pipe. That's the first time I've ever run into, and I
>don't understand it. Supposedly the line runs at about 200 psi. The
>only way you can have any significant amount of condensate is if the
>steam is saturated--at a temperature of about 381F. If it cools even
>a little you get condensation and if the temperature goes up even a
>little the condensate flashes to steam. It's not apparent to me that
>you can have condensate and steam in the same line for any
>appreciable time. Can anyone explain how this happens?
>
>OTOH, given that the line is about 80 years old, it seems a lot more
>likely that corrosion or settlement is the cause.
>
>Christopher Wright P.E. |"They couldn't hit an elephant at
>chrisw@skypoint.com | this distance" (last words of Gen.
>.......................................| John Sedgwick, Spotsylvania
>1864)
>http://www.skypoint.com/~chrisw/
>
>
This archive was generated by hypermail 2.1.8 : Mon Oct 27 2008 - 20:24:13 EDT