[Steam-engine] Safety valves

Bruce & Marlene Babcock babcock2 at gte.net
Tue Sep 21 07:10:54 PDT 2004


Ken,

        I was looking through my notes on safety valves and noticed that
between 1983 and 2001 ASME dropped the requirement that the blowdown be
indicated on safety valves.  Maybe Jeff can check to see if this change was
made at the same time they increased the maximum blowdown to 6%.

    In the 1983 Code, stamping of safety valves is specified in PG-110 .
"B.D. ____lb (blowdown ---difference between the opening and closing
pressure.)"

    In the 2001 Code, blowdown is not mentioned in PG-110.

    It appears that the only way of determining the blowdown on a new safety
valve is by observing the steam gauge.

Sincerely,

Bruce E. Babcock






----- Original Message ----- 
From: "Ken Majeski" <fuller_johnson1 at msn.com>
To: <steam-engine at lists.stationary-engine.com>
Sent: Monday, September 20, 2004 11:28 AM
Subject: RE: [Steam-engine] Safety valves


> Well Bruce, I geuss the next time I am out there I will look and see what
> the tags say. I believe the specified blowdown is 6 PSI. I believe it is
PSI
> not %...???
>
>  >
> Ken Majeski, Ellsworth Wis. Case Steam Engine, Minneapolis Steam Engine,
> Rumely Oilpulls H, F, & R. Website, Http://www.pressenter.com/~kmajeski/
>
>
>
>
>
> >From: "Bruce & Marlene Babcock" <babcock2 at gte.net>
> >Reply-To: Steam-engine mailing list
> ><steam-engine at lists.stationary-engine.com>
> >To: "Steam-engine mailing list"
<steam-engine at lists.stationary-engine.com>
> >Subject: [Steam-engine] Safety valves
> >Date: Mon, 20 Sep 2004 08:21:53 -0400
> >
> >Ken,
> >
> >     You said your safety valves blow down 5 or 6 psi.
> >
> >     At 5 psi your 140 psi safety valves would blow down 3.6% and your
145
> >psi valve 3.4%.
> >
> >     At 6 psi the figures would be 4.3% and 4.1%.
> >
> >     If you were to  purchase new valves that blow down 6% the 140 psi
> >valve would blow down 8.4 psi and the 145 valve would blow down 8.7 psi.
> >
> >     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%.   I suspect
> >you purchased your valves before that change occurred.   If you simply
> >replaced your existing valves and did not specify 4% blowdown and
received
> >valves set at 6% you might be disappointed in their performance.
> >
> >     Your satisfaction with valves set at 3.4% to 4.3% blowdown is
> >consistent with what owners and operators have reported.  Your experience
> >certainly supports the idea that safety valves with lower blowdowns are
> >more satisfactory.   I hope others will report their experiences just as
> >you have.
> >
> >     Thanks,
> >
> >Bruce E. Babcock
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