Surely one can use torque figures to infer bolt stress if one uses a standard bolt ( ASTM A 193 GR B7 with ASTM A 194 Gr 2H nuts)in a clean condition and lubricated?
Where it gets dodgy is when the bolts are dirty, galvanised or from an unknown source. Also 316 ss bolts may give you a problem if you dont use "never sieze" and galling occurs.
To do determine the bolt torque you can get some freeware from the Klinger website.
As far as Belleville washers are concerned I have used these successfully on an LPG cold box where the piping was aluminium with MSS stub flanges and 316 ss backing rings. All the bolts were torqued up. We made damn sure that the threads were to specification using QC gauges, lubricant/"never sieze" was applied and they werent dropped in the desert before they were assembled.
Most problems experienced with bolting come from lack of QC. If one considers the bolt to be equally as important as the weld on the WNRF flange, the gasket and the pipe support then there will be less problems.
<tt>
Does this mean that API publishes a torque value without considering<BR>
external forces, moments and material of gasket etc.,?sure would like to<BR>
know how they arrive as such values. <BR>
<BR>
how many do use a calibrated torque wrench to tighten flange joint (OK<BR>
b16.5, 24 NPS and under)? all ive seen so far both in construction and<BR>
maintenance are impact wrenches (ok mallet and box wrench also. hydraulic<BR>
torque wrench and bolt tensioner are reserved for the big boys handling big<BR>
equipment). How many inspector do check the ocnodition of the bolt -<BR>
lubricated, markings, pitch, troque values, etc? Yet all (wuth the
exception<BR>
of very few) flange that are properly fitted remains tight. One more thing,<BR>
near the creep range how does one factor in the bolt torque to ensure that<BR>
flange joint remain leak free? well i bet you you do hot ..... by the way<BR>
ever heard of the superbolt? and how about the belleville spring washers -<BR>
live loading? all ive heard from these guys are bolt tensions.<BR>
<BR>
section viii div 1 flange calc yes. determining torque values not sure.<BR>
there are only very few instance where ive look up section viii as far as<BR>
flange analysis is concerned (aided by codecalc since doing it manually is
a<BR>
pain the neck). 1. when i do refacing to ensure that i dont skimmed a lot<BR>
and 2. when the joint keeps leaking to determine if the bolt as spec out is<BR>
ok and possibility of replacing the gasket with other type (m and y
values).<BR>
for routine flange bolt tightening, the values published by gasket mfr such<BR>
as flexitalic and garlok is a-ok.<BR>
<BR>
-----Original Message-----<BR>
From: s_v_s_phanikumar@ltcis.ltindia.com<BR>
Please note that<BR>
API Spec 6A, recommends only maximum Flange Bolt Torque value, however it<BR>
don't consider any external forces, moments and material of gasket etc.,<BR>
while calculating maximum flange bolt torque values.<BR>
<BR>
Phani<BR>
<BR>
<BR>
</tt>
<br>
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