Steve, isn't this why there are small bore bypasses around block valves
- i.e., to warm-up the downstream piping prior to opening the main valve?
Paul
Steve McKenzie wrote:
> 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: <a href="/group/PipingDesign/post?postID=udNDQM9K3fp6M2EWqnHq1-ON7j-OeMIHPciMJxg_NxNeaisghBjM3Xq0y10Or_1Sr8pnIvRfKKrhMIOE_Sj5ya8yC7Q5">PipingDesign@yahoogroups.com</a>
>> To: <a href="/group/PipingDesign/post?postID=udNDQM9K3fp6M2EWqnHq1-ON7j-OeMIHPciMJxg_NxNeaisghBjM3Xq0y10Or_1Sr8pnIvRfKKrhMIOE_Sj5ya8yC7Q5">PipingDesign@yahoogroups.com</a>
>> 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.
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