[Steam-engine] pressure calculations

[Beth]

Hi Jeff,

Yes, Wauseon is quite the gathering place for those from around the states.
We'll look for you next year where the "feature" will be Huber equipment.

Beth
----- Original Message ----- 
From: "Jeff Detwiler" <jdetwiler at detwilerandassociates.com>
To: "Steam-engine mailing list" <steam-engine at lists.stationary-engine.com>
Sent: Thursday, July 01, 2004 1:31 AM
Subject: Re: [Steam-engine] pressure calculations


> Hello Andy and all,
> First let me say I was impressed with the pictures of Wauseon on Ben's
site.  I didn't know there were so many familiar folks there, all 800 miles
from Pawnee... We'll have to make it next year Beth.
>
> Second, let me answer your Working Pressure questions. You've got your
formula correct, and this will calculate the safe pressure to the pound. The
problem lies in the joint efficiency numbers and safety factors.
>
> >From the 2004 Pawnee Steam School at Rushville, and Brian Vaughn of B&B
Steam Restoration:
>
> A double riveted butt and strap joint is 82% efficient.
> A triple riveted butt and strap joint is 87% efficient.
>
> A Double riveted lap garners a 70% efficiency rating, while
> A Triple riveted lap(75Case) offers 75% efficiency.
>
> Now for safety factor.  The NIBC book on boilers as well as the FRA guide
allows safety factors of as little as four, but most states have established
5 as the safety factor, no matter what type of joint you have. Some
states(TN) have even enacted rules that limit all lap seam boilers to 100
pounds, even if they are like new thickness and can support a higher
pressure with the calculations!
>
> With your original thickness of .312 and factor of 5, your boiler would
carry 126.6 lbs safely, thus your original book number is correct.  Return
flue engines presented somewhat of a conundrum in that they were not stayed
surfaces, but rather a firebox in a tube. The forces were exerted on the
fireflue in the same way they they exerted on the shell, but it is a
different dynamic than simply a barrel full of water and steam.
>
> If your ultrasonic testing shows good averages throughout, you should be
able to use a pressure between 100-125 safely. Just do the math, but don't
use a safety factor higher than 5, or the Max drops off in a hurry.
>
> Hope this helps, Andy.  Now a question for the masses.  Does anyone know
of a good 65 Case looking for a new home?  My Keck Gonnerman afflicted
friends are probably going to disown me but I need the perfect complement to
a great side geared engine, and I have run several 65's and have fallen in
hopeless love with a 65 with a 6 bottom plow in tow. Amy ideas?
>
> Thanks,
> Jeff Detwiler
> Oklahoma Steam Threshers
>
>
> --- Andy glines <pioneersop96 at yahoo.com> wrote:
> at the Pawnee steam school Brian Vaughn shared a
> formula used to calculate the safe working pressure of
> a boiler
>
> P= (tensile strength)(thickness)(joint
> efficiency)/(shell radius)(safety factor)
>
> tensile = 55000
> thickness = .3125 (new thickness)
> Joint efficiency = 82% (lap seam)
> radius = 19
> safety factor = 8 (lap seam)
>
> using this formula I get 92.7 psi.  This is on the
> boiler in new condition.  The boiler on my Huber
> originally carried 125 with a 135 pop.  It seams like
> I need a different formula or to adjust this one.
> What do you think?
>
> =====
> Andy Glines
> Evansville, IN
>
>
>
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