[Steam-engine] pressure calculations

[Ken Majeski]

Well to start with the joint efficiency of 82 % is for a double riveted Butt 
Strap. The efficiency is about 74 % for a double riveted lap seam. Some 
states ( Minnesota for example ) has a formula based on rivet size and 
spacing for lap seam boilers.  Many old boilers were designed for a safety 
factor of about 5. I don't know where you get that 8 from. Here we have to 
have a safety factor of 5 and if we can Prove we have 55,000 tensil strength 
we can go with a SF of 4. According to NBIC apendix C the states can set 
their own safety factor as long as it is not less than 4.

If you think thats Bad figure a boiler with stayed surfaces that has some 
wasting or is constructed of thinner sheets as many early ones were. :(



Ken Majeski, Ellsworth Wis. Case Steam Engine, Minneapolis Steam Engine, 
Rumely Oilpulls H, F, & R. Website, Http://www.pressenter.com/~kmajeski/





>From: Andy glines <pioneersop96 at yahoo.com>
>Reply-To: Steam-engine mailing list 
><steam-engine at lists.stationary-engine.com>
>To: Steam <steam-engine at lists.stationary-engine.com>
>Subject: [Steam-engine] pressure calculations
>Date: Wed, 30 Jun 2004 11:56:21 -0700 (PDT)
>
>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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