[Steam-engine] Safety valves

[Bruce & Marlene Babcock]

Jeff,

    The blowdown specifications are found in PG-72.1. of both the 1983 and
2001 editions of the ASME Boiler Code.

    The 1983 Code specifies:  "After blowing down, all valves shall close at
a pressure not lower than 96% of their set pressure, ... ."

    The 2001 Code includes a table that specifies that for set pressures
between 67 psi and 250 psi the maximum blowdown is 6% of the set pressure.

      Ken's satisfaction with his modern safety valves with 4% blowdown
supports the idea that the increased blowdown may be a factor.  If we can
narrow down the date when the change from 4% to 6% took place, we may be
able to get a better sense of whether or not the change is responsible for
some of the problems owners and operators are reporting.

    I'm sure that it is not realistic to think that simply setting the
blowdown at 4% will solve all of the problems attributed to modern safety
valves.

 I look forward to any information you can find.

Thanks,

Bruce E. Babcock



----- Original Message ----- 
From: "Jeff Smith" <steamenginesmitty at yahoo.com>
To: "Steam-engine mailing list" <steam-engine at lists.stationary-engine.com>
Sent: Monday, September 20, 2004 11:49 AM
Subject: Re: [Steam-engine] Safety valves


> Give me the approx. code section numbers you are
> looking for and I will try and look it up for you.  I
> have a few of my father's code books from the 1980's
> and maybe the 90's, but I will have to dig them out
> first.
>
> Jeff Smith
>
> "--- Bruce & Marlene Babcock <babcock2 at gte.net> wrote:
> >     I wish I had copies of the ASME codes published
> > between 1983 and 2001 so I could determine when they
> > increased the blowdown to 6%.   "
>
>
>
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